This work was supported by the National Institute for Mental Health, and National Science Foundation. Special thanks to Dr. Jen Gutzman, Dr. Amanda Dickinson and other Sive lab members for many useful discussions and constructive criticism, and to Olivier Paugois for expert fish husbandry.

1. Preparing Microinjection Needles and Cell Tram
<ol>
	<li>Fill Eppendorf CellTram oil microinjector apparatus with mineral oil according to manufacturer's instructions.</li>
	<li>Prepare microinjection needles by pulling capillary tubes using Sutter instruments needle puller.</li>
	<li>Mount needle on micromanipulator connected to Eppendorf CellTram.</li>
	<li>Carefully break the tip of the needle. For uniform tip size, measure with a micrometer, or compare to a reference needle.</li>
	<li>Fill the length of the needle with oil, using the CellTram to push oil down the length, being careful to avoid any bubbles.</li>
</ol>
2. Preparing the Embryos
<ol>
	<li>Poke holes in a 1% agarose coated dish with a 1-200 &mu;l pipette tip, and remove agarose plugs. Fill dish with embryo media (made according to Westerfield25).</li>
	<li>Using forceps, dechorionate embryos under stereomicroscope.</li>
	<li>Transfer dechorionated embryos into agarose coated dish.</li>
	<li>To anesthetize embryos, add Tricaine (0.1 mg/ml) to agarose dish until embryos stop moving (made according to Westerfield25).</li>
</ol>
3. Draining the eCSF
<ol>
	<li>Orient the embryos with their tails in the holes of the agarose and their posterior sides closest to the micromanipulator, allowing for visualization of the dorsal side of the brain.</li>
	<li>Position the needle at the rhombomere 0/1 hinge-point or the widest point of hindbrain ventricle (Figure 1A).</li>
	<li>Carefully pierce roof plate of hindbrain ventricle being sure not to go through the depth of the brain into the yolk.</li>
	<li>Drain the eCSF using the CellTram and collect fluid in microinjection needle. Be careful to avoid any cells.</li>
</ol>
4. Collecting the eCSF for Composition Analysis
<ol>
	<li>Once the eCSF is collected in the needle, carefully stop suction from the CellTram.</li>
	<li>Move the dish out from under the needle and carefully position the needle into a tube containing the desired buffer.</li>
	<li>Using the CellTram, drain the eCSF out of the needle into the buffer trying to avoid contaminating the solution with oil.</li>
	<li>In order to remove cells that you have aspirated along with the eCSF, spin eCSF at 10,000 x g. Collect uncontaminated eCSF (supernatant) and store at -80 &deg;C until ready for further analysis.</li>
</ol>
5. Reintroduction of Selected Factors
<ol>
	<li>Drain the eCSF every 2 hr during desired time interval, since the fluid is replenished within that time period. Between drainage time-points, remove the needle and store the embryos at 28.5 &deg;C or desired temperature.</li>
	<li>Load second micropipette needle with test factor.</li>
	<li>Place needle into micromanipulator attached to microinjector.</li>
	<li>Adjust injection volume to 1 nl by measuring the drop size in oil and adjusting injection time and pressure.</li>
	<li>Inject 1-2 nl into brain ventricles as described previously26.</li>
</ol>

<ol>
	<li>Chodobski, A., Szmydynger-Chodobska, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Choroid+plexus:+target+for+polypeptides+and+site+of+their+synthesis.">Choroid plexus: target for polypeptides and site of their synthesis.</a> Microsc. Res. Tech. 52, 65-82 (2001).</li><li>Redzic, Z. B., Preston, J. E., Duncan, J. A., Chodobski, A., Szmydynger-Chodobska, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+choroid+plexus-cerebrospinal+fluid+system:+from+development+to+aging.">The choroid plexus-cerebrospinal fluid system: from development to aging.</a> Curr. Top. Dev. Biol. 71, 1-52 (2005).</li><li>Brown, P. D., Davies, S. L., Speake, T., Millar, I. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+of+cerebrospinal+fluid+production.">Molecular mechanisms of cerebrospinal fluid production.</a> Neuroscience. 129, 957-970 (2004).</li><li>Praetorius, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water+and+solute+secretion+by+the+choroid+plexus.">Water and solute secretion by the choroid plexus.</a> Pflugers Arch. 454, 1-18 (2007).</li><li>Speake, T., Whitwell, C., Kajita, H., Majid, A., Brown, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+CSF+secretion+by+the+choroid+plexus.">Mechanisms of CSF secretion by the choroid plexus.</a> Microsc. Res. Tech. 52, 49-59 (2001).</li><li>Garcia-Lecea, M., Kondrychyn, I., Fong, S. H., Ye, Z. R., Korzh, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+analysis+of+choroid+plexus+morphogenesis+in+zebrafish.">In vivo analysis of choroid plexus morphogenesis in zebrafish.</a> PLoS One. 3, e3090 (2008).</li><li>Welss, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secretory+activity+of+the+inner+layer+of+the+embryonic+mid-brain+of+the+chick,+as+revealed+by+tissue+culture.">Secretory activity of the inner layer of the embryonic mid-brain of the chick, as revealed by tissue culture.</a> The Anatomical Record. 58, 299-302 (1934).</li><li>Saunders, N. R., Habgood, M. D., Dziegielewska, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Barrier+mechanisms+in+the+brain,+II.+Immature+brain.">Barrier mechanisms in the brain, II. Immature brain.</a> Clin. Exp. Pharmacol. Physiol. 26, 85-91 (1999).</li><li>Zheng, W., Chodobski, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The blood-cerebrospinal fluid barrier. , (2005).</li><li>Salehi, Z., Mashayekhi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+cerebrospinal+fluid+on+neural+cell+survival+in+the+developing+chick+cerebral+cortex:+an+in+vivo+study.">The role of cerebrospinal fluid on neural cell survival in the developing chick cerebral cortex: an in vivo study.</a> Eur. J. Neurol. 13, 760-764 (2006).</li><li>Parada, C., 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=Embryonic+cerebrospinal+fluid+collaborates+with+the+isthmic+organizer+to+regulate+mesencephalic+gene+expression.">Embryonic cerebrospinal fluid collaborates with the isthmic organizer to regulate mesencephalic gene expression.</a> J. Neurosci. Res. 82, 333-345 (2005).</li><li>Mashayekhi, F., Salehi, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+importance+of+cerebrospinal+fluid+on+neural+cell+proliferation+in+developing+chick+cerebral+cortex.">The importance of cerebrospinal fluid on neural cell proliferation in developing chick cerebral cortex.</a> Eur. J. Neurol. 13, 266-272 (2006).</li><li>Martin, C., 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=FGF2+plays+a+key+role+in+embryonic+cerebrospinal+fluid+trophic+properties+over+chick+embryo+neuroepithelial+stem+cells.">FGF2 plays a key role in embryonic cerebrospinal fluid trophic properties over chick embryo neuroepithelial stem cells.</a> Dev. Biol. 297, 402-416 (2006).</li><li>Martin, C., 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=Early+embryonic+brain+development+in+rats+requires+the+trophic+influence+of+cerebrospinal+fluid.">Early embryonic brain development in rats requires the trophic influence of cerebrospinal fluid.</a> Int. J. Dev. Neurosci. 27, 733-740 (2009).</li><li>Gato, A., 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=Embryonic+cerebrospinal+fluid+regulates+neuroepithelial+survival,+proliferation,+and+neurogenesis+in+chick+embryos.">Embryonic cerebrospinal fluid regulates neuroepithelial survival, proliferation, and neurogenesis in chick embryos.</a> Anat. Rec. A Discov. Mol. Cell Evol. Biol. 284, 475-484 (2005).</li><li>Desmond, M. E., Levitan, M. L., Haas, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Internal+luminal+pressure+during+early+chick+embryonic+brain+growth:+descriptive+and+empirical+observations.">Internal luminal pressure during early chick embryonic brain growth: descriptive and empirical observations.</a> Anat. Rec. A Discov. Mol. Cell Evol. Biol. 285, 737-747 (2005).</li><li>Alonso, M. I., Martin, C., Carnicero, E., Bueno, D., Gato, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebrospinal+fluid+control+of+neurogenesis+induced+by+retinoic+acid+during+early+brain+development.">Cerebrospinal fluid control of neurogenesis induced by retinoic acid during early brain development.</a> Dev. Dyn. 240, 1650-1659 (2011).</li><li>Miyan, J. A., Zendah, M., Mashayekhi, F., Owen-Lynch, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebrospinal+fluid+supports+viability+and+proliferation+of+cortical+cells+in+vitro,+mirroring+in+vivo+development.">Cerebrospinal fluid supports viability and proliferation of cortical cells in vitro, mirroring in vivo development.</a> Cerebrospinal Fluid Res. 3, 2 (2006).</li><li>Mashayekhi, F., Bannister, C. M., Miyan, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failure+in+cell+proliferation+in+the+germinal+epithelium+of+the+HTx+rats.">Failure in cell proliferation in the germinal epithelium of the HTx rats.</a> Eur. J. Pediatr. Surg. 11, S57-S59 (2001).</li><li>Lehtinen, M. K., 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=The+cerebrospinal+fluid+provides+a+proliferative+niche+for+neural+progenitor+cells.">The cerebrospinal fluid provides a proliferative niche for neural progenitor cells.</a> Neuron. 69, 893-905 (2011).</li><li>Zappaterra, M. D., 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=A+comparative+proteomic+analysis+of+human+and+rat+embryonic+cerebrospinal+fluid.">A comparative proteomic analysis of human and rat embryonic cerebrospinal fluid.</a> J. Proteome. Res. 6, 3537-3548 (2007).</li><li>Parvas, M., Parada, C., Bueno, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+blood-CSF+barrier+function+controls+embryonic+CSF+protein+composition+and+homeostasis+during+early+CNS+development.">A blood-CSF barrier function controls embryonic CSF protein composition and homeostasis during early CNS development.</a> Dev. Biol. 321, 51-63 (2008).</li><li>Parada, C., Gato, A., Bueno, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mammalian+embryonic+cerebrospinal+fluid+proteome+has+greater+apolipoprotein+and+enzyme+pattern+complexity+than+the+avian+proteome.">Mammalian embryonic cerebrospinal fluid proteome has greater apolipoprotein and enzyme pattern complexity than the avian proteome.</a> J. Proteome Res. 4, 2420-2428 (2005).</li><li>Gato, A., 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=Analysis+of+cerebro-spinal+fluid+protein+composition+in+early+developmental+stages+in+chick+embryos.">Analysis of cerebro-spinal fluid protein composition in early developmental stages in chick embryos.</a> J. Exp. Zool. A Comp. Exp. Biol. 301, 280-289 (2004).</li><li>Westerfield, M., Sprague, J., Doerry, E., Douglas, S., Grp, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Zebrafish+Information+Network+(ZFIN):+a+resource+for+genetic,+genomic+and+developmental+research.">The Zebrafish Information Network (ZFIN): a resource for genetic, genomic and developmental research.</a> Nucleic Acids Res. 29, 87-90 (2001).</li><li>Gutzman, J. H., Sive, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+Brain+Ventricle+Injection.">Zebrafish Brain Ventricle Injection.</a> J. Vis. Exp. (26), e1218 (2009).</li><li>Parada, C., Gato, A., Bueno, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=All-trans+retinol+and+retinol-binding+protein+from+embryonic+cerebrospinal+fluid+exhibit+dynamic+behaviour+during+early+central+nervous+system+development.">All-trans retinol and retinol-binding protein from embryonic cerebrospinal fluid exhibit dynamic behaviour during early central nervous system development.</a> Neuroreport. 19, 945-950 (2008).</li><li>Parada, C., Escola-Gil, J. C., Bueno, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-density+lipoproteins+from+embryonic+cerebrospinal+fluid+are+required+for+neural+differentiation.">Low-density lipoproteins from embryonic cerebrospinal fluid are required for neural differentiation.</a> J. Neurosci. Res. 86, 2674-2684 (2008).</li><li>Kramer-Zucker, A. G., 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=Cilia-driven+fluid+flow+in+the+zebrafish+pronephros,+brain+and+Kupffer's+vesicle+is+required+for+normal+organogenesis.">Cilia-driven fluid flow in the zebrafish pronephros, brain and Kupffer's vesicle is required for normal organogenesis.</a> Development. 132, 1907-1921 (2005).</li><li>Lowery, L. A., Sive, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Initial+formation+of+zebrafish+brain+ventricles+occurs+independently+of+circulation+and+requires+the+nagie+oko+and+snakehead/atp1a1a.1+gene+products.">Initial formation of zebrafish brain ventricles occurs independently of circulation and requires the nagie oko and snakehead/atp1a1a.1 gene products.</a> Development. 132, 2057-2067 (2005).</li><li>Lowery, L. A., De Rienzo, G., Gutzman, J. H., Sive, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+and+classification+of+zebrafish+brain+morphology+mutants.">Characterization and classification of zebrafish brain morphology mutants.</a> Anat. Rec. (Hoboken). 292, 94-106 (2009).</li></ol>

No conflicts of interest declared.

Use of this technique to manually drain eCSF from zebrafish brain ventricles will be useful for determining the requirement for eCSF during development. In addition, this technique will allow description of the eCSF protein profile over the course of embryonic development. Identification of different proteins during this time will enable further investigation into the function of the CSF and its potential role during brain development. In amniotes, some factors identified in eCSF (IGF2, FGF2, retinoic acid, and apolipop...

<table border="1">
 <tbody>
 <tr>
 <td>Name of Reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 </tr>
 <tr>
 <td>Eppendorf CellTram Oil</td>
 <td>Eppendorf</td>
 <td>516 000.025 </td>
 </tr>
 <tr>
 <td>Mineral Oil </td>
 <td>Sigma</td>
 <td>M8410</td>
 </tr>
 <tr>
 <td>Tricaine powder</td>
 <td>Sigma</td>
 <td>A5040</td>
 </tr>
 <tr>
 <td>Capillary Tubes</td>
 <td>FHC Inc.</td>
 <td>30-30-1</td>
 </tr>
 </tbody>
</table>

manual drainage of the zebrafish embryonic brain ventricles

Cerebrospinal fluid (CSF) is a protein rich fluid contained within the brain ventricles. It is present during early vertebrate embryonic development and persists throughout life. Adult CSF is thought to cushion the brain, remove waste, and carry secreted molecules1,2. In the adult and older embryo, the majority of CSF is made by the choroid plexus, a series of highly vascularized secretory regions located adjacent to the brain ventricles3-5. In zebrafish, the choroid plexus is fully formed at 144 hours post fertilization (hpf)6. Prior to this, in both zebrafish and other vertebrate embryos including mouse, a significant amount of embryonic CSF (eCSF) is present . These data and studies in chick suggest that the neuroepithelium is secretory early in development and may be the major source of eCSF prior to choroid plexus development7.
eCSF contains about three times more protein than adult CSF, suggesting that it may have an important role during development8,9. Studies in chick and mouse demonstrate that secreted factors in the eCSF, fluid pressure, or a combination of these, are important for neurogenesis, gene expression, cell proliferation, and cell survival in the neuroepithelium10-20. Proteomic analyses of human, rat, mouse, and chick eCSF have identified many proteins that may be necessary for CSF function. These include extracellular matrix components, apolipoproteins, osmotic pressure regulating proteins, and proteins involved in cell death and proliferation21-24. However, the complex functions of the eCSF are largely unknown.
We have developed a method for removing eCSF from zebrafish brain ventricles, thus allowing for identification of eCSF components and for analysis of the eCSF requirement during development. Although more eCSF can be collected from other vertebrate systems with larger embryos, eCSF can be collected from the earliest stages of zebrafish development, and under genetic or environmental conditions that lead to abnormal brain ventricle volume or morphology. Removal and collection of eCSF allows for mass spectrometric analysis, investigation of eCSF function, and reintroduction of select factors into the ventricles to assay their function. Thus the accessibility of the early zebrafish embryo allows for detailed analysis of eCSF function during development.

An example of a drained brain ventricle is shown in Figure 1B-C. Brain ventricles are collapsed as they lack eCSF (Figure 1B vs. C). As seen in dorsal images (Figure 1B-C, and Figure 2A-D) the hindbrain neuroepithelium does retain its characteristic morphology and seems to be open despite lack of eCSF likely due to robust hinge-points. However, lateral views (Figure 2A'-D') demonstrate that the hindbrain ventricle has been drained, consi...

Watch this Scientific Journal Video about Manual Drainage of the Zebrafish Embryonic Brain Ventricles at JoVE.com

Manual Drainage of the Zebrafish Embryonic Brain Ventricles

We present a method to collect cerebrospinal fluid (CSF) and to create a system which lacks CSF within the embryonic zebrafish brain ventricular system. This allows for further examination of CSF composition and its requirement during embryonic brain development.

Cerebrospinal fluid  (CSF) is a protein rich fluid contained within the brain ventricles. It is  present during early vertebrate embryonic development and ...

manual-drainage-of-the-zebrafish-embryonic-brain-ventricles

Research

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Neuroscience

9.9K Views.  Massachusetts Institute of Technology. We present a method to collect cerebrospinal fluid (CSF) and to create a system which lacks CSF within the embryonic zebrafish brain ventricular system. This allows for further examination of CSF composition and its requirement during embryonic brain development.

Video: Manual Drainage of the Zebrafish Embryonic Brain Ventricles

An Assay for Permeability of the Zebrafish Embryonic Neuroepithelium

The brain ventricular system is conserved among vertebrates and is composed of a series of interconnected cavities called brain ventricles, which form during the earliest stages of brain development and are maintained throughout the animal's life. The brain ventricular system is found in vertebrates, and the ventricles develop after neural tube formation, when the central lumen fills with cerebrospinal fluid (CSF) 1,2. CSF is a protein rich fluid that is essential for normal brain development and function3-6.
In zebrafish, brain ventricle inflation begins at approximately 18 hr post fertilization (hpf), after the neural tube is closed. Multiple processes are associated with brain ventricle formation, including formation of a neuroepithelium, tight junction formation that regulates permeability and CSF production. We showed that the Na,K-ATPase is required for brain ventricle inflation, impacting all these processes 7,8, while claudin 5a is necessary for tight junction formation 9. Additionally, we showed that "relaxation" of the embryonic neuroepithelium, via inhibition of myosin, is associated with brain ventricle inflation.
To investigate the regulation of permeability during zebrafish brain ventricle inflation, we developed a ventricular dye retention assay. This method uses brain ventricle injection in a living zebrafish embryo, a technique previously developed in our lab10, to fluorescently label the cerebrospinal fluid. Embryos are then imaged over time as the fluorescent dye moves through the brain ventricles and neuroepithelium. The distance the dye front moves away from the basal (non-luminal) side of the neuroepithelium over time is quantified and is a measure of neuroepithelial permeability (Figure 1). We observe that dyes 70 kDa and smaller will move through the neuroepithelium and can be detected outside the embryonic zebrafish brain at 24 hpf (Figure 2).
This dye retention assay can be used to analyze neuroepithelial permeability in a variety of different genetic backgrounds, at different times during development, and after environmental perturbations. It may also be useful in examining pathological accumulation of CSF. Overall, this technique allows investigators to analyze the role and regulation of permeability during development and disease.

We describe a live whole animal quantitative measurement for permeability of the embryonic zebrafish brain. The technique analyzes the ability to retain cerebrospinal fluid and molecules of different molecular weights within the neural tube lumen and quantifies their movement out of the ventricles. This method is useful for determining differences in epithelial permeability and maturation during development and disease.

The brain ventricular system is conserved among vertebrates and is composed of a series of interconnected cavities called brain ventricles, which form ...

Micromanipulation of Gene Expression in the Adult Zebrafish Brain Using Cerebroventricular Microinjection of Morpholino Oligonucleotides

Manipulation of gene expression in tissues is required to perform functional studies. In this paper, we demonstrate the cerebroventricular microinjection (CVMI) technique as a means to modulate gene expression in the adult zebrafish brain. By using CVMI, substances can be administered into the cerebroventricular fluid and be thoroughly distributed along the rostrocaudal axis of the brain. We particularly focus on the use of antisense morpholino oligonucleotides, which are potent tools for knocking down gene expression in vivo. In our method, when applied, morpholino molecules are taken up by the cells lining the ventricular surface. These cells include the radial glial cells, which act as neurogenic progenitors. Therefore, knocking down gene expression in the radial glial cells is of utmost importance to analyze the widespread neurogenesis response in zebrafish, and also would provide insight into how vertebrates could sustain adult neurogenesis response. Such an understanding would also help the efforts for clinical applications in human neurodegenerative disorders and central nervous system regeneration. Thus, we present the cerebroventricular microinjection method as a quick and efficient way to alter gene expression and neurogenesis response in the adult zebrafish forebrain. We also provide troubleshooting tips and other useful information on how to carry out the CVMI procedure.

In this article, we demonstrate a method for manipulation of gene expression in the ventricular cells of the adult zebrafish telencephalon using antisense morpholino oligonucleotides. We present this method as an efficient and quick protocol that can be used for functional studies in the adult vertebrate brain.

Manipulation of gene expression in tissues is  required to perform functional studies. In this paper, we demonstrate the  cerebroventricular ...

Patch Clamp Recordings from Embryonic Zebrafish Mauthner Cells

Mauthner cells (M-cells) are large reticulospinal neurons located in the hindbrain of teleost fish. They are key neurons involved in a characteristic behavior known as the C-start or escape response that occurs when the organism perceives a threat. The M-cell has been extensively studied in adult goldfish where it has been shown to receive a wide range of excitatory, inhibitory and neuromodulatory signals1. We have been examining M-cell activity in embryonic zebrafish in order to study aspects of synaptic development in a vertebrate preparation. In the late 1990s Ali and colleagues developed a preparation for patch clamp recording from M-cells in zebrafish embryos, in which the CNS was largely intact2,3,4. The objective at that time was to record synaptic activity from hindbrain neurons, spinal cord neurons and trunk skeletal muscle while maintaining functional synaptic connections within an intact brain-spinal cord preparation. This preparation is still used in our laboratory today. To examine the mechanisms underlying developmental synaptic plasticity, we record excitatory (AMPA and NMDA-mediated)5,6 and inhibitory (GABA and glycine) synaptic currents from developing M-cells. Importantly, this unique preparation allows us to return to the same cell (M-cell) from preparation to preparation to carefully examine synaptic plasticity and neuro-development in an embryonic organism. The benefits provided by this preparation include 1) intact, functional synaptic connections onto the M-cell, 2) relatively inexpensive preparations, 3) a large supply of readily available embryos 4) the ability to return to the same cell type (i.e. M-cell) in every preparation, so that synaptic development at the level of an individual cell can be examined from fish to fish, and 5) imaging of whole preparations due to the transparent nature of the embryos.

We have developed an intact brain-spinal cord preparation to record and monitor electrical activity via patch clamp recording from the Mauthner neurons and other reticulospinal cells in zebrafish embryos. Thus, we are able to record excitatory and inhibitory synaptic currents, voltage-gated channel activity and action potentials from key neurons in a developing embryo.

Mauthner cells (M-cells) are large  reticulospinal neurons located in the hindbrain of teleost fish. They are key  neurons involved in a characteristic ...

Isolation and Culture of Endothelial Cells from the Embryonic Forebrain

Embryonic brain endothelial cells can serve as an important tool in the study of angiogenesis and neurovascular development and interactions. The two vascular networks of the embryonic forebrain, pial and periventricular, are spatially distinctive and have different origins and growth patterns. Endothelial cells from the pial and periventricular vascular networks have unique gene expression profiles and functions. Here we present a step-by-step protocol for isolation, culture, and verification of pure populations of endothelial cells from the periventricular vascular network (PVECs) of the embryonic forebrain (telencephalon). In this approach, telencephalon devoid of pial membrane obtained from embryonic day 15 mice is minced, digested with collagenase/dispase, and dispersed mechanically into a single cell suspension. PVECs are purified from cell suspension using positive selection with anti-CD-31/PECAM-1 antibody conjugated to MicroBeads using a strong magnetic separation method. Purified cells are cultured on collagen 1&#160;coated culture dishes in endothelial cell culture medium until they become confluent and further subcultured. PVECs obtained with this protocol exhibit cobblestone and spindle shaped phenotypes, as visualized by phase-contrast light microscopy and fluorescence microscopy. Purity of PVEC cultures was established with endothelial cell markers. In our hands, this method reliably and consistently yields pure populations of PVECs. This protocol will benefit studies aimed at gaining mechanistic insights into forebrain angiogenesis, understanding PVEC interactions, and cross-talks with neuronal cell types and holds tremendous potential for therapeutic angiogenesis.

This video demonstrates an easy and reliable strategy for preparation of pure cultures of endothelial cells from the embryonic forebrain within 10-12 days and will be useful for research focused on many aspects of cerebral angiogenesis.

Embryonic brain endothelial cells can serve as an important tool in the study of angiogenesis and neurovascular development and interactions. The two ...

Electrophysiological Recording in the Brain of Intact Adult Zebrafish

Previously, electrophysiological studies in adult zebrafish have been limited to slice preparations or to eye cup preparations and electrorentinogram recordings. This paper describes how an adult zebrafish can be immobilized, intubated, and used for in vivo electrophysiological experiments, allowing recording of neural activity. Immobilization of the adult requires a mechanism to deliver dissolved oxygen to the gills in lieu of buccal and opercular movement. With our technique, animals are immobilized and perfused with habitat water to fulfill this requirement. A craniotomy is performed under tricaine methanesulfonate (MS-222; tricaine) anesthesia to provide access to the brain. The primary electrode is then positioned within the craniotomy window to record extracellular brain activity. Through the use of a multitube perfusion system, a variety of pharmacological compounds can be administered to the adult fish and any alterations in the neural activity can be observed. The methodology not only allows for observations to be made regarding changes in neurological activity, but it also allows for comparisons to be made between larval and adult zebrafish. This gives researchers the ability to identify the alterations in neurological activity due to the introduction of various compounds at different life stages.

This paper describes how an adult zebrafish can be immobilized, intubated, and used for in vivo electrophysiological experiments to allow recordings and manipulation of neural activity in an intact animal.

Previously, electrophysiological studies in adult zebrafish have been limited to slice preparations or to eye cup preparations and electrorentinogram ...

Live Imaging of Mitosis in the Developing Mouse Embryonic Cortex

Although of short duration, mitosis is a complex and dynamic multi-step process fundamental for development of organs including the brain. In the developing cerebral cortex, abnormal mitosis of neural progenitors can cause defects in brain size and function. Hence, there is a critical need for tools to understand the mechanisms of neural progenitor mitosis. Cortical development in rodents is an outstanding model for studying this process. Neural progenitor mitosis is commonly examined in fixed brain sections. This protocol will describe in detail an approach for live imaging of mitosis in ex vivo embryonic brain slices. We will describe the critical steps for this procedure, which include: brain extraction, brain embedding, vibratome sectioning of brain slices, staining and culturing of slices, and time-lapse imaging. We will then demonstrate and describe in detail how to perform post-acquisition analysis of mitosis. We include representative results from this assay using the vital dye Syto11, transgenic mice (histone H2B-EGFP and centrin-EGFP), and in utero electroporation (mCherry-&#945;-tubulin). We will discuss how this procedure can be best optimized and how it can be modified for study of genetic regulation of mitosis. Live imaging of mitosis in brain slices is a flexible approach to assess the impact of age, anatomy, and genetic perturbation in a controlled environment, and to generate a large amount of data with high temporal and spatial resolution. Hence this protocol will complement existing tools for analysis of neural progenitor mitosis.

Neural progenitor mitosis is a critical parameter of neurogenesis. Much of our understanding of neural progenitor mitosis is based on analysis of fixed tissue. Live imaging in embryonic brain slices is a versatile technique to assess mitosis with high temporal and spatial resolution in a controlled environment.

Although of short duration, mitosis is a complex and dynamic multi-step process fundamental for development of organs including the brain. In the ...

Conditional Genetic Transsynaptic Tracing in the Embryonic Mouse Brain

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits during embryonic maturation of the brain however is technically challenging because most transsynaptic tracing methods developed to date depend on stereotaxic tracer injection. To overcome this problem, we developed a binary genetic strategy for conditional genetic transsynaptic tracing in the mouse brain. Towards this end we generated two complementary knock-in mouse strains to selectively express the bidirectional transsynaptic tracer barley lectin (BL) and the retrograde transsynaptic tracer Tetanus Toxin fragment C from the ROSA26 locus after Cre-mediated recombination. Cell-specific tracer production in these mice is genetically encoded and does not depend on mechanical tracer injection. Therefore our experimental approach is suitable to study neural circuit formation in the embryonic murine brain. Furthermore, because tracer transfer across synapses depends on synaptic activity, these mouse strains can be used to analyze the communication between genetically defined neuronal populations during brain development at a single cell resolution. Here we provide a detailed protocol for transsynaptic tracing in mouse embryos using the novel recombinant ROSA26 alleles. We have utilized this experimental technique in order to delineate the neural circuitry underlying maturation of the reproductive axis in the developing female mouse brain.

Capitalizing on a binary genetic strategy we provide a detailed protocol for neural circuit tracing in mice that express complementary transsynaptic tracers after Cre-mediated recombination. Because cell-specific tracer production is genetically encoded, our experimental approach is suitable to study the formation and maturation of neural circuitry during murine embryonic brain development at a single cell resolution.

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits ...

Live Imaging of the Ependymal Cilia in the Lateral Ventricles of the Mouse Brain

Multiciliated ependymal cells line the ventricles in the adult brain. Abnormal function or structure of ependymal cilia is associated with various neurological deficits. The current ex vivo live imaging of motile ependymal cilia technique allows for a detailed study of ciliary dynamics following several steps. These steps include: mice euthanasia with carbon dioxide according to protocols of The University of Toledo&#8217;s Institutional Animal Care and Use Committee (IACUC); craniectomy followed by brain removal and sagittal brain dissection with a vibratome or sharp blade to obtain very thin sections through the brain lateral ventricles, where the ependymal cilia can be visualized. Incubation of the brain&#8217;s slices in a customized glass-bottom plate containing Dulbecco&#8217;s Modified Eagle&#8217;s Medium (DMEM)/High-Glucose at 37 &#176;C in the presence of 95%/5% O2/CO2 mixture is essential to keep the tissue alive during the experiment. A video of the cilia beating is then recorded using a high-resolution differential interference contrast microscope. The video is then analyzed frame by frame to calculate the ciliary beating frequency. This allows distinct classification of the ependymal cells into three categories or types based on their ciliary beating frequency and angle. Furthermore, this technique allows the use of high-speed fluorescence imaging analysis to characterize the unique intracellular calcium oscillation properties of ependymal cells as well as the effect of pharmacological agents on the calcium oscillations and the ciliary beating frequency. In addition, this technique is suitable for immunofluorescence imaging for ciliary structure and ciliary protein localization studies. This is particularly important in disease diagnosis and phenotype studies. The main limitation of the technique is attributed to the decrease in live motile cilia movement as the brain tissue starts to die.

Using high-resolution differential interference contrast (DIC) microscopy, an ex vivo observation of the beating of motile ependymal cilia located within the mouse brain ventricles is demonstrated by live-imaging. The technique allows a recording of the unique ciliary beating frequency and beating angle as well as their intracellular calcium oscillation pacing properties.

Multiciliated ependymal cells line the ventricles in the adult brain. Abnormal function or structure of ependymal cilia is associated with various ...

Exposure of the Pig CNS for Histological Analysis: A Manual for Decapitation, Skull Opening, and Brain Removal

Pigs have become increasingly popular in large-animal translational neuroscience research as an economically and ethically feasible substitute to non-human primates. The large brain size of the pig allows the use of conventional clinical brain imagers and the direct use and testing of neurosurgical procedures and equipment from the human clinic. Further macroscopic and histological analysis, however, requires postmortem exposure of the pig central nervous system (CNS) and subsequent brain removal. This is not an easy task, as the pig CNS is encapsulated by a thick, bony skull and spinal column. The goal of this paper and instructional video is to describe how to expose and remove the postmortem pig brain and the pituitary gland in an intact state, suitable for subsequent macroscopic and histological analysis.

The goal of this paper and instructional video is to describe how to expose and remove the postmortem pig brain and pituitary gland in an intact state, suitable for subsequent macroscopic and histological analysis.

Pigs have become increasingly popular in large-animal translational neuroscience research as an economically and ethically feasible substitute to ...

Exploring Deep Space - Uncovering the Anatomy of Periventricular Structures to Reveal the Lateral Ventricles of the Human Brain

Anatomy students are typically provided with two-dimensional (2D) sections and images when studying cerebral ventricular anatomy and students find this challenging. Because the ventricles are negative spaces located deep within the brain, the only way to understand their anatomy is by appreciating their boundaries formed by related structures. Looking at a 2D representation of these spaces, in any of the cardinal planes, will not enable visualisation of all of the structures that form the boundaries of the ventricles. Thus, using 2D sections alone requires students to compute their own mental image of the 3D ventricular spaces. The aim of this study was to develop a reproducible method for dissecting the human brain to create an educational resource to enhance student understanding of the intricate relationships between the ventricles and periventricular structures. To achieve this, we created a video resource that features a step-by-step guide using a fiber dissection method to reveal the lateral and third ventricles together with the closely related limbic system and basal ganglia structures. One of the advantages of this method is that it enables delineation of the white matter tracts that are difficult to distinguish using other dissection techniques. This video is accompanied by a written protocol that provides a systematic description of the process to aid in the reproduction of the brain dissection. This package offers a valuable anatomy teaching resource for educators and students alike. By following these instructions educators can create teaching resources and students can be guided to produce their own brain dissection as a hands-on practical activity. We recommend that this video guide be incorporated into neuroanatomy teaching to enhance student understanding of the morphology and clinical relevance of the ventricles.

This paper demonstrates the effective use of a fiber dissection method to reveal the superficial white matter tracts and periventricular structures of the human brain, in three-dimensional space, to aid student comprehension of ventricular morphology.

Anatomy students are typically provided with two-dimensional (2D) sections and images when studying cerebral ventricular anatomy and students find this ...