Name: alternate immersion in glucose to produce prolonged hyperglycemia in zebrafish
Uploaded: 2021-05-05T15:00:00
Description: Watch this Scientific Journal Video about Alternate Immersion in Glucose to Produce Prolonged Hyperglycemia in Zebrafish at JoVE.com

We would like to acknowledge VPC, CJR, and MCP for the development of this protocol. EMM received financial support from the American University College of Arts and Sciences Graduate Student Support to carry out this research.&#160;This work was also supported by an American University Faculty Mellon Award and funding through the American University College of Arts and Sciences (both to VPC).

All procedures were approved by the Institutional Animal Care and Use Committee at American University.
1. Preparing the Solution Tanks
<ol>
	<li>Obtain six tanks, two for each experimental group (glucose, mannitol, and water). Label one of the two tanks &#8216;housing tank&#8217; (it will house the fish) and label the other &#8216;solution tank&#8217; (it will hold the solution). 
	NOTE: The mannitol treatment group is the osmotic control, and the water treatment group is a handling/st...

<ol>
	<li>Rubinstein, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish:+from+disease+modeling+to+drug+discovery.">Zebrafish: from disease modeling to drug discovery.</a> Current Opinion in Drug Discovery and Development. 6 (2), 218-223 (2003).</li><li>Gerlai, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Associative+learning+in+zebrafish+(Danio+rerio).">Associative learning in zebrafish (Danio rerio).</a> Methods in Cell Biology. 101, 249-270 (2011).</li><li>Goldsmith, J. R., Jobin, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Think+small:+zebrafish+as+a+model+system+of+human+pathology.">Think small: zebrafish as a model system of human pathology.</a> BioMed Research International. , (2012).</li><li>Moss, J. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regeneration+of+the+pancreas+in+adult+zebrafish.">Regeneration of the pancreas in adult zebrafish.</a> Diabetes. 58 (8), 1844-1851 (2009).</li><li>Connaughton, V. P., Baker, C., Fonde, L., Gerardi, E., Slack, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternate+immersion+in+an+external+glucose+solution+differentially+affects+blood+sugar+values+in+older+versus+younger+zebrafish+adults.">Alternate immersion in an external glucose solution differentially affects blood sugar values in older versus younger zebrafish adults.</a> Zebrafish. 13 (2), 87-94 (2016).</li><li>Etuk, E. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+for+studying+diabetes+mellitus.">Animal models for studying diabetes mellitus.</a> Agriculture and Biology Journal of North America. 1 (2), 130-134 (2010).</li><li>Agardh, E., Bruun, A., Agardh, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+glial+cell+immunoreactivity+and+neuronal+cell+changes+in+rats+with+STZ-induced+diabetes.">Retinal glial cell immunoreactivity and neuronal cell changes in rats with STZ-induced diabetes.</a> Current Eye Research. 23 (4), 276-284 (2001).</li><li>Carmo, A., Cunha-Vaz, J. G., Carvalho, A. P., Lopes, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitric+oxide+synthase+activity+in+retinas+from+non-insulin-dependent+diabetic+Goto-Kakizaki+rats:+correlation+with+blood-retinal+barrier+permeability.">Nitric oxide synthase activity in retinas from non-insulin-dependent diabetic Goto-Kakizaki rats: correlation with blood-retinal barrier permeability.</a> Nitric Oxide. 4 (6), 590-596 (2000).</li><li>Ramsey, D. J., Ripps, H., Qian, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+electrophysiological+study+of+retinal+function+in+the+diabetic+female+rat.">An electrophysiological study of retinal function in the diabetic female rat.</a> Investigative Ophthalmology &amp; Visual Science. 47 (11), 5116-5124 (2006).</li><li>Biessels, G. J., Gispen, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+of+diabetes+on+cognition:+what+can+be+learned+from+rodent+models.">The impact of diabetes on cognition: what can be learned from rodent models.</a> Neurobiology of Aging. 26 (1), 36-41 (2005).</li><li>Intine, R. V., Olsen, A. S., Sarras, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+zebrafish+model+of+diabetes+mellitus+and+metabolic+memory.">A zebrafish model of diabetes mellitus and metabolic memory.</a> Journal of Visualized Experiments. (72), e50232 (2013).</li><li>Sarras, M. P., Intine, R. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+zebrafish+as+a+disease+model+provides+a+unique+window+for+understanding+the+molecular+basis+of+diabetic+metabolic+memory.">Use of zebrafish as a disease model provides a unique window for understanding the molecular basis of diabetic metabolic memory.</a> Research on Diabetes. , (2013).</li><li>Gleeson, M., Connaughton, V., Arneson, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+hyperglycaemia+in+zebrafish+(Danio+rerio)+leads+to+morphological+changes+in+the+retina.">Induction of hyperglycaemia in zebrafish (Danio rerio) leads to morphological changes in the retina.</a> Acta Diabetologica. 44 (3), 157-163 (2007).</li><li>Capiotti, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperglycemia+induces+memory+impairment+linked+to+increased+acetylcholinesterase+activity+in+zebrafish+(Danio+rerio).">Hyperglycemia induces memory impairment linked to increased acetylcholinesterase activity in zebrafish (Danio rerio).</a> Behavioural Brain Research. 274, 319-325 (2014).</li><li>Capiotti, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Persistent+impaired+glucose+metabolism+in+a+zebrafish+hyperglycemia+model.">Persistent impaired glucose metabolism in a zebrafish hyperglycemia model.</a> Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology. 171, 58-65 (2014).</li><li>Capiotti, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperglycemia+alters+E-NTPDases,+ecto-5'-nucleotidase,+and+ectosolic+and+cytosolic+adenosine+deaminase+activities+and+expression+from+encephala+of+adult+zebrafish+(Danio+rerio).">Hyperglycemia alters E-NTPDases, ecto-5'-nucleotidase, and ectosolic and cytosolic adenosine deaminase activities and expression from encephala of adult zebrafish (Danio rerio).</a> Purinergic Signaling. 12 (2), 211-220 (2016).</li><li>Ali, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoreceptor+Degeneration+Accompanies+Vascular+Changes+in+a+Zebrafish+Model+of+Diabetic+Retinopathy.">Photoreceptor Degeneration Accompanies Vascular Changes in a Zebrafish Model of Diabetic Retinopathy.</a> Investigative Ophthalmology &amp; Visual Science. 61 (2), 43 (2020).</li><li>Wiggenhauser, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+Retinal+Angiogenesis+in+Hyperglycemic+pdx1-/-+Mutants.">Activation of Retinal Angiogenesis in Hyperglycemic pdx1-/- Mutants.</a> Diabetes. 69 (5), 1020-1031 (2020).</li><li>Chen, X. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Involvement+of+HMGB1+mediated+signalling+pathway+in+diabetic+retinopathy:+evidence+from+type+2+diabetic+rats+and+ARPE-19+cells+under+diabetic+condition.">Involvement of HMGB1 mediated signalling pathway in diabetic retinopathy: evidence from type 2 diabetic rats and ARPE-19 cells under diabetic condition.</a> Journal of Ophthalmology. 97, 1598-1603 (2013).</li><li>Costa, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+light+exposure,+pH,+osmolarity,+and+solvent+on+the+retinal+pigment+epithelial+toxicity+of+vital+dyes.">Effects of light exposure, pH, osmolarity, and solvent on the retinal pigment epithelial toxicity of vital dyes.</a> American Journal of Ophthalmology. 155, 705-712 (2013).</li><li>Alvarez, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predominant+cone+photoreceptor+dysfunction+in+a+hyperglycemic+model+of+non-proliferative+diabetic+retinopathy.">Predominant cone photoreceptor dysfunction in a hyperglycemic model of non-proliferative diabetic retinopathy.</a> Disease Models and Mechanisms. 3, 236-245 (2010).</li><li>Fletcher, E. L., Phipps, J. A., Wilkinson-Berka, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dysfunction+of+retinal+neurons+and+glia+during+diabetes.">Dysfunction of retinal neurons and glia during diabetes.</a> Clinical and Experimental Optometry. 88, 132-145 (2005).</li><li>Fletcher, E. L., Phipps, J. A., Ward, M. M., Puthussery, T., Wilkinson-Berka, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+and+glial+abnormality+as+predictors+of+progression+of+diabetic+retinopathy.">Neuronal and glial abnormality as predictors of progression of diabetic retinopathy.</a> Current Pharmaceutical Design. 13, 2699-2712 (2007).</li><li>Agardh, E., Bruun, A., Agardh, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+glial+cell+immunoreactivity+and+neuronal+cell+changes+in+rats+with+STZ-+induced+diabetes.">Retinal glial cell immunoreactivity and neuronal cell changes in rats with STZ- induced diabetes.</a> Current Eye Research. 23, 276-284 (2001).</li><li>Barber, A. J., Antonetti, D. A., Gardner, T. W., Group, T. P. S. R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+expression+of+retinal+occludin+and+glial+fibrillary+acidic+protein+in+experimental+diabetes.">Altered expression of retinal occludin and glial fibrillary acidic protein in experimental diabetes.</a> Investigative Ophthalmology &amp; Visual Science. 41, 3561-3568 (2000).</li><li>Lieth, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+reactivity+and+impaired+glutamate+metabolism+in+short-term+experimental+diabetic+retinopathy.">Glial reactivity and impaired glutamate metabolism in short-term experimental diabetic retinopathy.</a> Diabetes. 47, 815-820 (1998).</li><li>Rungger-Brandle, E., Dosso, A. A., Leuenberger, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+reactivity,+an+early+feature+of+diabetic+retinopathy.">Glial reactivity, an early feature of diabetic retinopathy.</a> Investigative Ophthalmology &amp; Visual Science. 41, 1971-1980 (2000).</li><li>Zeng, X. X., Ng, Y. K., Ling, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+and+microglial+response+in+the+retina+of+streptozotocin-induced+diabetic+rats.">Neuronal and microglial response in the retina of streptozotocin-induced diabetic rats.</a> Visual Neuroscience. 17, 463-471 (2000).</li><li>Mizutani, M., Gerhardinger, C., Lorenzi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Muller+cell+changes+in+human+diabetic+retinopathy.">Muller cell changes in human diabetic retinopathy.</a> Diabetes. 47, 445-449 (1998).</li><li>Tanvir, Z., Nelson, R., DeCicco-Skinner, K., Connaughton, V. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One+month+of+hyperglycemia+alters+spectral+responses+of+the+zebrafish+photopic+electroretinogram.">One month of hyperglycemia alters spectral responses of the zebrafish photopic electroretinogram.</a> Disease Models and Mechanisms. 11, (2018).</li><li>Hancock, H. A., Kraft, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oscillatory+potential+analysis+and+ERGs+of+normal+and+diabetic+rats.">Oscillatory potential analysis and ERGs of normal and diabetic rats.</a> Investigative Ophthalmology &amp; Visual Science. 45, 1002-1008 (2004).</li><li>Layton, C. J., Safa, R., Osborne, N. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oscillatory+potentials+and+the+b-wave:+partial+masking+and+interdependence+in+dark+adaptation+and+diabetes+in+the+rat.">Oscillatory potentials and the b-wave: partial masking and interdependence in dark adaptation and diabetes in the rat.</a> Graefe's Archives for Clinical and Experimental Ophthalmology. 245, 1335-1345 (2007).</li><li>Li, Q., Zemel, E., Miller, B., Perlman, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+retinal+damage+in+experimental+diabetes:+electroretinographical+and+morphological+observations.">Early retinal damage in experimental diabetes: electroretinographical and morphological observations.</a> Experimental Eye Research. 74, 615-625 (2002).</li><li>Kohzaki, K., Vingrys, A. J., Bui, B. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+inner+retinal+dysfunction+in+streptozotocin-induced+diabetic+rats.">Early inner retinal dysfunction in streptozotocin-induced diabetic rats.</a> Investigative Ophthalmology &amp; Visual Science. 49, 3595-3604 (2008).</li><li>Phipps, J. A., Yee, P., Fletcher, E. L., Vingrys, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rod+photoreceptor+dysfunction+in+diabetes:+activation,+deactivation,+and+dark+adaptation.">Rod photoreceptor dysfunction in diabetes: activation, deactivation, and dark adaptation.</a> Investigative Ophthalmology &amp; Visual Science. 47, 3187-3194 (2006).</li></ol>

Diabetes is a nationwide problem. Studies show that by 2030, an estimated 400 million people will have some form of diabetes. In rodent models, Type 2 DM is studied using genetic manipulation. In rats, the Zucker diabetic fatty rats (ZDF), and the Otsuka Long-Evans Tokushima fatty rats (OLETF), are providing more information on the effects of Type 2 DM10. In addition, high fat diets have been used in rodent to induce hyperglycemia. This mirrors the noninvasive procedure proposed in this paper. Usi...

Zebrafish (Danio rerio) are quickly becoming a widely used animal model to study both disease and cognition1. The ease of genetic manipulation and embryonic transparency through the early developmental stages, make them a prime candidate to study human diseases with a known genetic basis. For example, zebrafish have been used to study Holt-Oram syndrome, cardiomyopathies, glomerulocystic kidney disease, muscular dystrophy, and diabetes mellitus (DM) among other diseases1. In addition, the zebrafish model is ideal because of the species&#8217; small size, ease of maintenance, and high fecundity2,3.
The zebrafish pancreas is both anatomically and functionally similar to the mammalian pancreas4. Thus, the unique characteristics of size, high fecundity, and similar endocrine structures make zebrafish a suitable candidate for studying DM-related complications. In zebrafish, there are two experimental methods used to induce the prolonged hyperglycemia that is characteristic of DM: an influx of glucose (modeling Type 2) and cessation of insulin secretion (modeling Type 1)5,6. Experimentally, to stop insulin secretion, pancreatic &#946;-cells can be chemically destroyed using either Streptozotocin (STZ) or Alloxan injections. STZ has been used successfully in rodents and zebrafish, resulting in complications associated with retinopathy7,8,9, cognitive impairments10, and limb regeneration11. However, in zebrafish, &#946;-cells regenerate after treatment, causing &#8220;booster injections&#8221; of STZ to be necessary to maintain diabetic conditions12. Alternatively, the pancreas of the zebrafish can be removed6. These are both highly invasive procedures, due to the multiple injections, and extensive recovery time.
Conversely, hyperglycemia can be induced noninvasively through exposure to exogenous glucose. In this protocol, fish are submerged in a highly concentrated glucose solution for 24-hours5,13 or continually for 2-weeks14,15,16. Exogenous glucose is taken up transdermally, by ingestion, and/or across the gills resulting in elevated blood sugar levels. Since this non-invasive technique does not directly manipulate insulin levels, it cannot claim to induce Type 2 DM. However, it can be used to examine complications induced by hyperglycemia, which is one of the main symptoms of Type 2 DM.
Recently, the zebrafish mutant pdx1-/- was developed by manipulating the pancreatic and duodenal homeobox 1 gene, a gene linked to the genetic cause of Type 2 DM in humans. Using this mutant, researchers have been able to replicate pancreatic development disruption, high blood sugar, and study hyperglycemia-induced diabetic retinopathy17,18.
In this paper, we describe a noninvasive hyperglycemia induction method that uses an alternating immersion protocol. This protocol maintains hyperglycemic conditions for up to 8 weeks with subsequent complications observed. In brief, adult zebrafish are placed in a sugar solution for 24 hours and then a water solution for 24 hours. As opposed to continuous immersion in external glucose solutions, alternating days between sugar and water mimics the rise and fall of blood sugar in diabetes. An alternating glucose protocol additionally allows hyperglycemia to be induced for longer periods of time, as the zebrafish are not as able to compensate for the high external glucose conditions. As proof of principle, we provide data showing that hyperglycemia induced using this protocol alters retinal chemistry and physiology.

<table>
	<tbody>
		<tr>
			<td>Airline Tubing</td>
			<td>petsmart</td>
			<td>5291863</td>
			<td>This can be used in the tank to circulate air</td>
		</tr>
		<tr>
			<td>Airpump</td>
			<td>petsmart</td>
			<td>5094984</td>
			<td>This can be used in the tank to circulate air</td>
		</tr>
		<tr>
			<td>Airstones</td>
			<td>petsmart</td>
			<td>5149683</td>
			<td>This can be used in the tank to circulate air</td>
		</tr>
		<tr>
			<td>D-glucose</td>
			<td>Sigma</td>
			<td>G8270-5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>D-mannitol</td>
			<td>Acros Organics</td>
			<td>AC125340050</td>
			<td></td>
		</tr>
		<tr>
			<td>Freestyle Lite Meter</td>
			<td>Amazon</td>
			<td>B01LMOMLTU</td>
			<td></td>
		</tr>
		<tr>
			<td>Freestyle Lite Strips</td>
			<td>Amazon</td>
			<td>B074ZN3H2Z</td>
			<td></td>
		</tr>
		<tr>
			<td>Net</td>
			<td>petsmart</td>
			<td>5175115</td>
			<td></td>
		</tr>
		<tr>
			<td>Tanks</td>
			<td>Amazon</td>
			<td>B0002APZO4</td>
			<td></td>
		</tr>
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</table>

alternate immersion in glucose to produce prolonged hyperglycemia in zebrafish

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This alternate immersion protocol is a noninvasive, step-wise method of inducing hyperglycemia for up to eight weeks. Adult zebrafish are alternately exposed to sugar (glucose) and water for 24 hours each. The zebrafish begin treatment in a 1% glucose solution for 2 weeks, then a 2% solution for 2 weeks, and finally a 3% solution for the remaining 4 weeks. Compared to water-treated (stress) and mannitol-treated (osmotic) controls, glucose-treated zebrafish have significantly higher blood sugar levels. The glucose-treated zebrafish show blood sugar levels of 3-times that of controls, suggesting that after both four and eight weeks hyperglycemia can be achieved. Sustained hyperglycemia was associated with increased Glial Fibrillary Acidic Protein (GFAP) and increased nuclear factor Kappa B (NF-kB)&#160;levels in retina and decreased physiological responses, as well as cognitive deficits suggesting this protocol can be used to model disease complications.

Using this protocol (Figure 1), blood sugar values are significantly elevated after both 4-weeks and 8-weeks of treatment (Figure 2A), with hyperglycemia defined as 3x the control averages from both water-treated and mannitol-treated groups. Water-treated controls are transferred in and out of water daily, providing a stress/handling control. Mannitol serves as an osmotic control in in vitro glucose studies19,...

Watch this Scientific Journal Video about Alternate Immersion in Glucose to Produce Prolonged Hyperglycemia in Zebrafish at JoVE.com

Alternate Immersion in Glucose to Produce Prolonged Hyperglycemia in Zebrafish

This protocol noninvasively induces hyperglycemia in zebrafish for up to 8 weeks. Using this protocol, an in-depth study of the adverse effects of hyperglycemia can be made.

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This ...

This protocol induces hyperglycemia in zebra fish in a rise and fall pattern that mimics the hyperglycemia that is seen in type two diabetes. The main advantage of this technique is that it is a noninvasive technique that makes it possible to ensure that hyperglycemia is the cause of any alterations observed in the hyperglycemic fish. This protocol could potentially be used to explore therapeutic avenues or pharmaceuticals that target complications of hyperglycemia.This protocol has a lot of steps, but when the steps are followed correctly and with care, it should quickly become second nature. Remember however, to always treat the animals gently and humanely throughout the entire protocol. Begin by setting up six tanks, two for each experimental group.Use two liter tanks, if the total number of fish is less than 20 and four liter tanks if the total number of fish is more than 20. Label one of the two tanks, housing tank and the other solution tank. Keep the tanks in a water bath at 28 to 29 degrees Celsius to maintain water temperature.On day one, place the fish into their respective treatment solutions for 24 hours. On day two, transfer the fish from their treatment solutions to water for 24 hours. On day three, transfer the fish from water to treatment solutions.Continue this alternating exposure for the remainder of the experiment. Transferring water treated control fish from water-to-water daily. Ensure that the fish are fed and transferred within the same two-hour window each day throughout the duration of the experiment.Transfer fish in each treatment group from the housing tank to the corresponding solution tank using a standard fish net. Place the tank containing the fish back in the water bath and replace the air stone and tank lid. This tank is now the housing tank and the tank that previously held the fish is now the solution tank.Discard the old solution and clean the tank along with the tank lids, air lines, air stones and nets to prevent buildup of glucose and mannitol. Use water and a dedicated sponge for each treatment condition to properly clean the tanks. Dry the newly cleaned solution tanks with a paper towel and prepare the solutions for the following day using this tank.Ensure the other items are dried and separated by appropriate treatment groups. To prepare the sugar solutions, fill each solution tank with two or four liters of system water. Measure the correct amount of glucose and mannitol using a top-loading scale and separate weigh boats for each chemical.Add the weighed glucose or mannitol aliquot to the appropriate clean solution tank. Stir the solutions with separate glass stir rods until the sugars are completely dissolved. Then return the solution tanks to the water bath and cover them with their corresponding lids.To prepare the water solution, fill experimental tanks with system water Return these solution tanks to the water bath and cover them with their corresponding lids. Blood sugar values were significantly elevated after both four-week and eight-week glucose treatments. With hyperglycemia defined as three times the control averages from both water treated and mannitol treated groups.Retinal tissue collected after four weeks of hyperglycemia had an increase in glial fibrillary acidic protein or GFAP levels. GFAP expression is observed in Mueller glial cells in the retina, which are altered in diabetic retinopathy. This increase in GFAP was associated with an increase in nuclear factor kappaB levels.Suggesting that the induced hyperglycemia triggers an inflammatory response and reactive gliosis. ERG recordings after four weeks of treatment identified a decreased response in glucose treated retinas compared to mannitol treated controls. Amplitudes of both photoreceptor and bipolar cell components were decreased in hyperglycemic fish.This procedure can be supplemented by other tests of hyperglycemia. For instance, a memory assay can be used to look at cognitive deficits or record visual based responses such as the optomotor response to assess vision-based complications. Once this technique was established, our lab was able to use it to study hyperglycemia induced complications in the zebra fish model.We observed these complications relatively quickly, after four weeks of treatment.

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JoVE Journal

Neuroscience

Human Fear Conditioning Conducted in Full Immersion 3-Dimensional Virtual Reality

Fear conditioning is a widely used paradigm in non-human animal research to investigate the neural mechanisms underlying fear and anxiety. A major challenge in conducting conditioning studies in humans is the ability to strongly manipulate or simulate the environmental contexts that are associated with conditioned emotional behaviors. In this regard, virtual reality (VR) technology is a promising tool. Yet, adapting this technology to meet experimental constraints requires special accommodations. Here we address the methodological issues involved when conducting fear conditioning in a fully immersive 6-sided VR environment and present fear conditioning data.
In the real world, traumatic events occur in complex environments that are made up of many cues, engaging all of our sensory modalities. For example, cues that form the environmental configuration include not only visual elements, but aural, olfactory, and even tactile. In rodent studies of fear conditioning animals are fully immersed in a context that is rich with novel visual, tactile and olfactory cues. However, standard laboratory tests of fear conditioning in humans are typically conducted in a nondescript room in front of a flat or 2D computer screen and do not replicate the complexity of real world experiences. On the other hand, a major limitation of clinical studies aimed at reducing (extinguishing) fear and preventing relapse in anxiety disorders is that treatment occurs after participants have acquired a fear in an uncontrolled and largely unknown context. Thus the experimenters are left without information about the duration of exposure, the true nature of the stimulus, and associated background cues in the environment1. In the absence of this information it can be difficult to truly extinguish a fear that is both cue and context-dependent. Virtual reality environments address these issues by providing the complexity of the real world, and at the same time allowing experimenters to constrain fear conditioning and extinction parameters to yield empirical data that can suggest better treatment options and/or analyze mechanistic hypotheses.
In order to test the hypothesis that fear conditioning may be richly encoded and context specific when conducted in a fully immersive environment, we developed distinct virtual reality 3-D contexts in which participants experienced fear conditioning to virtual snakes or spiders. Auditory cues co-occurred with the CS in order to further evoke orienting responses and a feeling of "presence" in subjects 2 . Skin conductance response served as the dependent measure of fear acquisition, memory retention and extinction.

Classical fear conditioning paradigm was adapted for human participants in a fully immersive virtual reality setting. Using a discrimination paradigm, conditioned fear, cue and context memory retention, and extinction was measured with skin conductance response to dynamic virtual snakes and spiders (the conditioned stimuli) in two distinct virtual contexts.

Fear conditioning is a widely used paradigm in non-human animal research to investigate the neural mechanisms underlying fear and anxiety. A major ...

Time-lapse Live Imaging of Clonally Related Neural Progenitor Cells in the Developing Zebrafish Forebrain

Precise patterns of division, migration and differentiation of neural progenitor cells are crucial for proper brain development and function1,2. To understand the behavior of neural progenitor cells in the complex in vivo environment, time-lapse live imaging of neural progenitor cells in an intact brain is critically required. In this video, we exploit the unique features of zebrafish embryos to visualize the development of forebrain neural progenitor cells in vivo. We use electroporation to genetically and sparsely label individual neural progenitor cells. Briefly, DNA constructs coding for fluorescent markers were injected into the forebrain ventricle of 22 hours post fertilization (hpf) zebrafish embryos and electric pulses were delivered immediately. Six hours later, the electroporated zebrafish embryos were mounted with low melting point agarose in glass bottom culture dishes. Fluorescently labeled neural progenitor cells were then imaged for 36hours with fixed intervals under a confocal microscope using water dipping objective lens. The present method provides a way to gain insights into the in vivo development of forebrain neural progenitor cells and can be applied to other parts of the central nervous system of the zebrafish embryo.

The present video demonstrates a method which takes advantage of the combination of electroporation and confocal microscopy to perform live imaging on individual neural progenitor cells in the developing zebrafish forebrain. In vivo analysis of the development of forebrain neural progenitor cells at a clonal level can be achieved in this way.

Precise patterns of division, migration and differentiation of neural progenitor cells are crucial for proper brain development and function1,2. To ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

Multi-unit Recording Methods to Characterize Neural Activity in the Locust (Schistocerca Americana) Olfactory Circuits

Detection and interpretation of olfactory cues are critical for the survival of many organisms. Remarkably, species across phyla have strikingly similar olfactory systems suggesting that the biological approach to chemical sensing has been optimized over evolutionary time1. In the insect olfactory system, odorants are transduced by olfactory receptor neurons (ORN) in the antenna, which convert chemical stimuli into trains of action potentials. Sensory input from the ORNs is then relayed to the antennal lobe (AL; a structure analogous to the vertebrate olfactory bulb). In the AL, neural representations for odors take the form of spatiotemporal firing patterns distributed across ensembles of principal neurons (PNs; also referred to as projection neurons)2,3. The AL output is subsequently processed by Kenyon cells (KCs) in the downstream mushroom body (MB), a structure associated with olfactory memory and learning4,5. Here, we present electrophysiological recording techniques to monitor odor-evoked neural responses in these olfactory circuits.
First, we present a single sensillum recording method to study odor-evoked responses at the level of populations of ORNs6,7. We discuss the use of saline filled sharpened glass pipettes as electrodes to extracellularly monitor ORN responses. Next, we present a method to extracellularly monitor PN responses using a commercial 16-channel electrode3. A similar approach using a custom-made 8-channel twisted wire tetrode is demonstrated for Kenyon cell recordings8. We provide details of our experimental setup and present representative recording traces for each of these techniques.

Multi-unit Recording Methods to Characterize Neural Activity in the Locust Schistocerca Americana Olfactory Circuits

We demonstrate variations of the extracellular multi-unit recording technique to characterize odor-evoked responses in the first three stages of the invertebrate olfactory pathway. These techniques can easily be adapted to examine ensemble activity in other neural systems as well.

Detection and interpretation of olfactory cues are critical for the survival  of many organisms. Remarkably, species across phyla have strikingly similar ...

Direct Intraventricular Delivery of Drugs to the Rodent Central Nervous System

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses specifically on antisense oligonucleotides (ASOs), though the techniques shown in the video here can also be used to deliver a plethora of other drugs to the CNS. Antisense oligonucleotides (ASOs) have the capability to knockdown sequence-specific targets 1 as well as shift isoform ratios of specific genes 2. To achieve widespread gene knockdown or splicing in the CNS of mice, the ASOs can be delivered into the brain using two separate routes of administration, both of which we demonstrate in the video.
The first uses Alzet osmotic pumps, connected to a catheter that is surgically implanted into the lateral ventricle. This allows the ASOs to be continuously infused into the CNS for a designated period of time. The second involves a single bolus injection of a high concentration of ASO into the right lateral ventricle. Both methods use the mouse cerebral ventricular system to deliver the ASO to the entire brain and spinal cord, though depending on the needs of the study, one method may be preferred over the other.

We describe a method to target drugs to the central nervous system by either implanting a catheter or performing a bolus injection into the right lateral ventricle in mice. We focus specifically on the delivery of antisense oligonucleotides. This technique is readily adaptable to other drugs and to rats.

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses ...

Fast Micro-iontophoresis of Glutamate and GABA: A Useful Tool to Investigate Synaptic Integration

One of the fundamental interests in neuroscience is to understand the integration of excitatory and inhibitory inputs along the very complex structure of the dendritic tree, which eventually leads to neuronal output of action potentials at the axon. The influence of diverse spatial and temporal parameters of specific synaptic input on neuronal output is currently under investigation, e.g. the distance-dependent attenuation of dendritic inputs, the location-dependent interaction of spatially segregated inputs, the influence of GABAergig inhibition on excitatory integration, linear and non-linear integration modes, and many more.
With fast micro-iontophoresis of glutamate and GABA it is possible to precisely investigate the spatial and temporal integration of glutamatergic excitation and GABAergic inhibition. Critical technical requirements are either a triggered fluorescent lamp, light-emitting diode (LED), or a two-photon scanning microscope to visualize dendritic branches without introducing significant photo-damage of the tissue. Furthermore, it is very important to have a micro-iontophoresis amplifier that allows for fast capacitance compensation of high resistance pipettes. Another crucial point is that no transmitter is involuntarily released by the pipette during the experiment.
Once established, this technique will give reliable and reproducible signals with a high neurotransmitter and location specificity. Compared to glutamate and GABA uncaging, fast iontophoresis allows using both transmitters at the same time but at very distant locations without limitation to the field of view. There are also advantages compared to focal electrical stimulation of axons: with micro-iontophoresis the location of the input site is definitely known and it is sure that only the neurotransmitter of interest is released. However it has to be considered that with micro-iontophoresis only the postsynapse is activated and presynaptic aspects of neurotransmitter release are not resolved. In this article we demonstrate how to set up micro-iontophoresis in brain slice experiments.

In this article we introduce fast micro-iontophoresis of neurotransmitters as a technique to investigate integration of postsynaptic signals with high spatial and temporal precision.

One of the fundamental interests in neuroscience is to understand the integration of excitatory and inhibitory inputs along the very complex structure of ...

Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light

The nervous system has the remarkable ability to adapt and respond to various stimuli. This neural adjustment is largely achieved through plasticity at the synaptic level. The Active Zone (AZ) is the region at the presynaptic membrane that mediates neurotransmitter release and is composed of a dense collection of scaffold proteins. AZs of Drosophila melanogaster (Drosophila) photoreceptors undergo molecular remodeling after prolonged exposure to natural ambient light. Thus the level of neuronal activity can rearrange the molecular composition of the AZ and contribute to the regulation of the functional output.
Starting from the light exposure set-up preparation to the immunohistochemistry, this protocol details how to quantify the number, the spatial distribution, and the delocalization level of synaptic molecules at AZs in Drosophila photoreceptors. Using image analysis software, clusters of the GFP-fused AZ component Bruchpilot were identified for each R8 photoreceptor (R8) axon terminal. Detected Bruchpilot spots were automatically assigned to individual R8 axons. To calculate the distribution of spot frequency along the axon, we implemented a customized software plugin. Each axon&#39;s start-point and end-point were manually defined and the position of each Bruchpilot spot was projected onto the connecting line between start and end-point. Besides the number of Bruchpilot clusters, we also quantified the delocalization level of Bruchpilot-GFP within the clusters. These measurements reflect in detail the spatially resolved synaptic dynamics in a single neuron under different environmental conditions to stimuli.

Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light

Here we show how to quantify the number and spatial distribution of synaptic active zones in Drosophila melanogaster&#160;photoreceptors, highlighted with a genetically encoded molecular marker, and their modulation after prolonged exposure to light.

The nervous system has the remarkable ability to adapt and respond to various stimuli. This neural adjustment is largely achieved through plasticity at ...

A Revised Surgical Approach to Induce Endolymphatic Hydrops in the Guinea Pig

Endolymphatic hydrops is an enlargement of scala media that is most often associated with Meniere&#39;s disease, though the pathophysiologic mechanism(s) remain unclear. In order to adequately study the attributes of endolymphatic hydrops, such as the origins of low-frequency hearing loss, a reliable model is needed. The guinea pig is a&#160;good model because it hears in the low-frequency regions that are putatively affected by endolymphatic hydrops. Previous research has demonstrated that endolymphatic hydrops can be induced surgically via intradural or extradural approaches that involve drilling on the endolymphatic duct and sac. However, whether it was possible to create an endolymphatic hydrops model using an extradural approach that avoided dangerous drilling on the endolymphatic duct and sac was unknown. The objective of this study was to demonstrate a revised extradural approach to induce experimental endolymphatic hydrops at 30 days post-operatively by obliterating the endolymphatic sac and injuring the endolymphatic duct with a fine pick. The sample size consisted of seven guinea pigs. Functional measurements of hearing were made and temporal bones were subsequently harvested for histologic analysis. The approach had a success rate of 86% in achieving endolymphatic hydrops. The risk of cerebrospinal fluid leak was minimal. No perioperative deaths or injuries to the posterior semicircular canal occurred in the sample. The presented method demonstrates a safe and reliable way to induce endolymphatic hydrops at a relatively quick time point of 30 days. The clinical implications are that the presented method provides a reliable model to further explore the origins of low-frequency hearing loss that can be associated endolymphatic hydrops.

This article demonstrates an extradural approach to obliterate the guinea pig endolymphatic sac and injure the endolymphatic duct with a fine pick in order to induce experimental endolymphatic hydrops.

Endolymphatic hydrops is an enlargement of scala media that is most often associated with Meniere&#39;s disease, though the pathophysiologic mechanism(s) ...

Combining Behavior and EEG to Study the Effects of Mindfulness Meditation on Episodic Memory

Although there has been recent interest in how mindfulness meditation can affect episodic memory as well as brain structure and function, no study has examined the behavioral and neural effects of mindfulness meditation on episodic memory. Here we present a protocol that combines mindfulness meditation training, an episodic memory task, and EEG to examine how mindfulness meditation changes behavioral performance and the neural correlates of episodic memory. Subjects in a mindfulness meditation experimental group were compared to a waitlist control group. Subjects in the mindfulness meditation experimental group spent four weeks training and practicing mindfulness meditation. Mindfulness was measured before and after training using the Five Facet Mindfulness Questionnaire (FFMQ). Episodic memory was measured before and after training using a source recognition task. During the retrieval phase of the source recognition task, EEG was recorded. The results showed that mindfulness, source recognition behavioral performance, and EEG theta power in right frontal and left parietal channels increased following mindfulness meditation training. In addition, increases in mindfulness correlated with increases in theta power in right frontal channels. Therefore, results obtained from combining mindfulness meditation training, an episodic memory task, and EEG reveal the behavioral and neural effects of mindfulness meditation on episodic memory.

Here we present a protocol for combining mindfulness meditation training, an episodic memory task, and EEG to understand the behavioral and neural effects of mindfulness meditation on episodic memory.

Although there has been recent interest in how mindfulness meditation can affect episodic memory as well as brain structure and function, no study has ...

A Scalable Model to Study the Effects of Blunt-Force Injury in Adult Zebrafish

Blunt-force traumatic brain injuries (TBI) are the most common form of head trauma, which spans a range of severities and results in complex and heterogenous secondary effects. While there is no mechanism to replace or regenerate the lost neurons following a TBI in humans, zebrafish possess the ability to regenerate neurons throughout their body, including the brain. To examine the breadth of pathologies exhibited in zebrafish following a blunt-force TBI and to study the mechanisms underlying the subsequent neuronal regenerative response, we modified the commonly used rodent Marmarou weight drop for the use in adult zebrafish. Our simple blunt-force TBI model is scalable, inducing a mild, moderate, or severe TBI, and recapitulates many of the phenotypes observed following human TBI, such as contact- and post-traumatic seizures, edema, subdural and intracerebral hematomas, and cognitive impairments, each displayed in an injury severity-dependent manner. TBI sequelae, which begin to appear within minutes of the injury, subside and return to near undamaged control levels within 7 days post-injury. The regenerative process begins as early as 48 hours post-injury (hpi), with the peak cell proliferation observed by 60 hpi. Thus, our zebrafish blunt-force TBI model produces characteristic primary and secondary injury TBI pathologies similar to human TBI, which allows for investigating disease onset and progression, along with the mechanisms of neuronal regeneration that is unique to zebrafish.

We modified the Marmarou weight drop model for adult zebrafish to examine a breadth of pathologies following blunt-force traumatic brain injury (TBI) and the mechanisms underlying subsequent neuronal regeneration. This blunt-force TBI model is scalable, induces a mild, moderate, or severe TBI, and recapitulates injury heterogeneity observed in human TBI.