This work was supported by the Hebei Province Introducing Foreign Intelligence Project in 2023. We thank Lisa Kreiner, PhD, from Liwen Bianji, (Edanz) (www.liwenbianji.cn), for editing the English text of a draft of this manuscript.

The experimental procedure received approval from the Institutional Animal Care and Use Committee at Yantai University (Approval Number: YTDX20230410) and adhered to the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals. Male Sprague-Dawley rats weighing between 300-350 g were utilized for this study. A comprehensive list of the animals, reagents, and equipment used is provided in the Table of Materials.
1. Animal preparation
<ol>
	<li>House the animals in an environment maintaining a 12 h light/dark cycle, controlled temperature, and humidity. Ensure they have unrestricted access to food and water.</li>
</ol>
2. Anesthesia
<ol>
	<li>Anesthetize the rats via intraperitoneal injection with a mixture containing ketamine (80 mg/kg) and xylazine (20 mg/kg). 
	NOTE: Tilt the head and body of rats downward. The injection site is in the animal&#8217;s lower right quadrant of the abdomen. Pull back on the plunger before injecting. The average injection volume is 0.4 mL.</li>
	<li>Confirm the induction of anesthesia by assessing the withdrawal reflex of the hind paw and the blinking reflex. If adequate depth of anesthesia is not achieved, supplement with isoflurane during the surgical procedure.</li>
</ol>
3. Ischemic modeling procedure
<ol>
	<li>Sterilize the surgical tools using an autoclave. Disinfect the operating tables and related equipment with 70% ethanol.</li>
	<li>Prepare the surgical site by shaving the fur around the anticipated incision site. Disinfect the skin at the surgical site three times with betadine and 70% ethanol.</li>
	<li>Make a midline incision on the ventral side, approximately 1.5 cm long, and open the superficial fascia.</li>
	<li>Perform sharp and blunt dissection to expose the external carotid artery (ECA), internal carotid artery (ICA), and common carotid artery (CCA) as per the previously described method7.</li>
	<li>Place three 4-0 silk sutures around the CCA and another silk suture through the ECA near the ICA bifurcation. Tie a releasable slip knot on the proximal CCA. Tighten the suture on the distal CCA using a hemostat to block blood flow. Loosely tie another slip knot around the CCA during suturing to ensure the vessel is not occluded. 
	NOTE: Ensure that the slip knot is not overly tight, only sufficient to block blood flow, as it will need to be released during vascular suturing.</li>
	<li>Make a 0.5 mm incision between the proximal silk suture and the middle suture on the CCA using scissors. 
	NOTE: Ensure that the incision allows the filament (silicon-coated tip) to enter the CCA.</li>
	<li>Introduce a 3 cm length of 4-0 filament (silicon-coated tip) into the CCA. Tighten the silk sutures around the CCA to secure the intraluminal filament and prevent bleeding; then, remove the suture from the distal CCA.</li>
	<li>Continue to insert the filament into the lumen of the MCA, controlling the sutures around the ECA to ensure the filament does not enter the ECA. The insertion length is typically 18 mm to 20 mm.</li>
	<li>Start a timer and record the time when occlusion begins. Suture the neck incision with 3-0 silk sutures and carefully place the animal in a recovery cage. Administer 0.5 mL of normal saline intraperitoneally.</li>
</ol>
4. Microsurgical suturing of the CCA
<ol>
	<li>Re-anesthetize the rat 1.5 h post-ischemia. Disinfect the incision site three times with 70% ethanol and reopen the incision.</li>
	<li>Gently withdraw the occluding filament until the white tip is clearly visible near the CCA incision. Place a micro clamp horizontally close to the secured intraluminal suture knot near the CCA bifurcation. 
	NOTE: Avoid clamping the white filament tip to prevent silicone detachment and subsequent thrombosis.</li>
	<li>Release the secured intraluminal suture knot and completely remove the filament.</li>
	<li>Place another micro clamp near the heart-end side of the proximal CCA knot. Subsequently, remove the suture knot around the proximal CCA. 
	NOTE: Proper placement of clamps is crucial for elevating fixed vessels in later steps to facilitate microvascular suturing. Place clamps horizontally on surrounding muscles to prevent slippage.</li>
	<li>Rinse the incision site with normal saline and dry the area with a sterile cotton ball to remove the blood and achieve a clear surgical field.</li>
	<li>Under a microscope (4x magnification), suture the CCA incision using 11-0 microsurgical sutures in an interrupted pattern, typically requiring two stitches depending on the incision size.</li>
	<li>After suturing, remove the micro clamps from both ends of the CCA to restore blood flow.</li>
	<li>Apply pressure with a sterile cotton ball to the CCA suture site for 30 s. Observe the CCA for 2 min to ensure no bleeding occurs. Suture the rat&#39;s neck incision and place the animal in a 35 &#176;C care box for anesthesia recovery before returning it to the cage. 
	NOTE: Administer intraperitoneally with meloxicam at a dose of 2 mg/kg for post-operative analgesia.</li>
</ol>
5. Staining with 2,3,5-triphenyltetrazolium chloride (TTC)
<ol>
	<li>Three days after the ischemia-reperfusion,&#160;euthanize the animals under deep anesthesia with 4% isoflurane and cervical dislocation.</li>
	<li>Remove the brains and cut them into 2 mm-thick coronal sections using a scalpel blade8.</li>
	<li>Incubate the brain sections with 2% TTC for 20 min at 37 &#176;C.</li>
	<li>Rinse the brain sections twice with 10% formalin, then fix them with 10% formalin for 30 min at room temperature.</li>
	<li>Capture digital photographs of consecutive slices and quantitatively measure the infarction areas using Image J software.</li>
</ol>
6. Neurological function test
NOTE: Neurological function was assessed using the Garcia test, following a previous report9.
<ol>
	<li>Assess spontaneous activity, symmetry in the movement of all four limbs, forepaw outstretching, climbing, body proprioception, and response to vibrissae touch. Assign scores based on the Garcia test criteria, with a maximum score of 18 points indicating normal neurological function.</li>
</ol>
7. Statistical analysis
<ol>
	<li>Utilize GraphPad Prism to conduct statistical analysis using Student&#39;s t-test. Express the data as the mean &#177; standard deviation. Consider differences between means statistically significant if P &#60; 0.05.</li>
</ol>

Middle Cerebral Artery Occlusion in Rats with Preserved Vascular Anatomy

<ol>
	<li>Tu, W. J., 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=China+stroke+surveillance+report+2021.">China stroke surveillance report 2021.</a> Mil Med Res. 10 (1), 33 (2023).</li><li>Wu, 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=Targeting+oxidative+stress+and+inflammation+to+prevent+ischemia-reperfusion+injury.">Targeting oxidative stress and inflammation to prevent ischemia-reperfusion injury.</a> Front in Mol Neurosci. 13, 28 (2020).</li><li>Ringelstein, E. 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=Type+and+extent+of+hemispheric+brain+infarctions+and+clinical+outcome+in+early+and+delayed+middle+cerebral+artery+recanalization.">Type and extent of hemispheric brain infarctions and clinical outcome in early and delayed middle cerebral artery recanalization.</a> Neurology. 42 (2), 289-298 (1992).</li><li>Koizumi, J., Yoshida, Y., Nakazawa, T., Ooneda, G. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+studies+of+ischemic+brain+edema:+A+new+experimental+model+of+cerebral+embolism+in+rats+in+which+recirculation+can+be+introduced+in+the+ischemic+area.">Experimental studies of ischemic brain edema: A new experimental model of cerebral embolism in rats in which recirculation can be introduced in the ischemic area.</a> Jap J Stroke. 8, 1-8 (1986).</li><li>Longa, E. Z., Weinstein, P. R., Carlson, S., Cummins, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reversible+middle+cerebral+artery+occlusion+without+craniectomy+in+rats.">Reversible middle cerebral artery occlusion without craniectomy in rats.</a> Stroke. 20 (1), 84-91 (1989).</li><li>Trueman, R. 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=A+critical+re-examination+of+the+intraluminal+filament+MCAO+model:+Impact+of+external+carotid+artery+transection.">A critical re-examination of the intraluminal filament MCAO model: Impact of external carotid artery transection.</a> Transl Stroke Res. 2 (4), 651-661 (2011).</li><li>Ansari, S., Azari, H., McConnell, D. J., Afzal, A., Mocco, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraluminal+middle+cerebral+artery+occlusion+(MCAO)+model+for+ischemic+stroke+with+laser+Doppler+flowmetry+guidance+in+mice.">Intraluminal middle cerebral artery occlusion (MCAO) model for ischemic stroke with laser Doppler flowmetry guidance in mice.</a> J Vis Exp. (51), e2879 (2011).</li><li>Yu, 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=Icaritin+inhibits+neuroinflammation+in+a+rat+cerebral+ischemia+model+by+regulating+microglial+polarization+through+the+GPER-ERK-NF-&#954;B+signaling+pathway.">Icaritin inhibits neuroinflammation in a rat cerebral ischemia model by regulating microglial polarization through the GPER-ERK-NF-&#954;B signaling pathway.</a> Mol Med. 28 (1), 142 (2022).</li><li>Garcia, J. H., Wagner, S., Liu, K. F., Hu, X. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurological+Deficit+and+extent+of+neuronal+necrosis+attributable+to+middle+cerebral+artery+occlusion+in+rats.">Neurological Deficit and extent of neuronal necrosis attributable to middle cerebral artery occlusion in rats.</a> Stroke. 26 (4), 627-634 (1995).</li><li>Bracko, O., 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=3-Nitropropionic+acid-induced+ischemia+tolerance+in+the+rat+brain+is+mediated+by+reduced+metabolic+activity+and+cerebral+blood+flow.">3-Nitropropionic acid-induced ischemia tolerance in the rat brain is mediated by reduced metabolic activity and cerebral blood flow.</a> J Cereb Blood Flow Metab. 34 (9), 1522-1530 (2014).</li><li>Goldmacher, G. V., 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=Tracking+transplanted+bone+marrow+stem+cells+and+their+effects+in+the+rat+MCAO+stroke+model.">Tracking transplanted bone marrow stem cells and their effects in the rat MCAO stroke model.</a> PLoS One. 8 (3), e60049 (2013).</li><li>Lee, H. J., 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+therapeutic+potential+of+human+umbilical+cord+blood-derived+mesenchymal+stem+cells+in+Alzheimer's+disease.">The therapeutic potential of human umbilical cord blood-derived mesenchymal stem cells in Alzheimer's disease.</a> Neurosci Lett. 481 (1), 30-35 (2010).</li><li>Connolly, E. S., Winfree, C. J., Solomon, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Procedural+and+strain-related+variables+significantly+affect+outcome+in+a+murine+model+of+focal+cerebral+ischemia.">Procedural and strain-related variables significantly affect outcome in a murine model of focal cerebral ischemia.</a> Neurosurgery. 38 (3), 523-531 (1996).</li><li>Barone, F. C., Knudsen, D. J., Nelson, A. H., Feuerstein, G. Z., Willette, R. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+strain+differences+in+susceptibility+to+cerebral+ischemia+are+related+to+cerebral+vascular+anatomy.">Mouse strain differences in susceptibility to cerebral ischemia are related to cerebral vascular anatomy.</a> J Cereb Blood Flow Metab. 13 (4), 683-692 (1993).</li><li>Dittmar, M., Spruss, T., Schuierer, G., Horn, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=External+carotid+artery+territory+ischemia+impairs+outcome+in+the+endovascular+filament+model+of+middle+cerebral+artery+occlusion+in+rats.">External carotid artery territory ischemia impairs outcome in the endovascular filament model of middle cerebral artery occlusion in rats.</a> Stroke. 34 (9), 2252-2257 (2003).</li><li>Virtanen, T., Jolkkonen, J., Sivenius, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=External+carotid+artery+territory+ischemia+impairs+outcome+in+the+endovascular+filament+model+of+middle+cerebral+artery+occlusion+in+rats.">External carotid artery territory ischemia impairs outcome in the endovascular filament model of middle cerebral artery occlusion in rats.</a> Stroke. 34 (9), 2252-2257 (2004).</li></ol>

The authors do not have any potential conflicting interests to disclose.

MCAo is a widely used method to create animal models of stroke, effectively replicating the stroke process observed in patients by restoring blood flow after ischemia10,11,12. Our laboratory has developed an ischemic stroke model that enables reperfusion from the CCA without causing damage to the ECA. Following the induction of ischemia, microsurgical repair of the CCA is performed. Although direct measurement of CCA blood flow ...

Stroke, the leading cause of death and long-term neurological dysfunction in adults worldwide, encompass various types, with ischemic stroke accounting for approximately 81.9% of cases, while cerebral hemorrhage and subarachnoid hemorrhage account for 14.9% and 3.1%, respectively1. Ischemic stroke often results from atherosclerosis or occlusion of the middle cerebral artery (MCA), leading to local cerebral blood flow reduction and subsequent brain damage. This reduction in nutrient supply to ischemic cells triggers energy depletion, causing membrane integrity loss, cell swelling, and eventual lysis. Additionally, factors like increased intracellular calcium, excitatory amino acid release, heightened free radical production, and inflammatory cell activation contribute to brain tissue injury post-stroke2.
The treatment goals for ischemic stroke are multifaceted: reduce ongoing neurological damage and lower mortality and long-term disability; prevent complications arising from immobility and neurological dysfunction; and minimize the risk of stroke recurrence. Given the complexity of ischemic stroke pathophysiology, a robust stroke model is essential for the research and development of treatments targeting ischemic stroke.
Currently, middle cerebral artery occlusion (MCAo) is a common animal model of ischemic stroke3. MCAo is typically performed by inserting a silicon-tipped or flame-blunted monofilament through the cervical vessels until it reaches the origin of the middle cerebral artery (MCA). In 1986, Koizumi and colleagues developed a technique involving the insertion of a silicon-tipped monofilament through an incision in the common carotid artery (CCA), allowing it to reach the entrance of the MCA and block its blood flow4. In 1989, Longa's group reported another MCAo method that involved introducing a monofilament through an incision in the external carotid artery (ECA). The monofilament then traverses the bifurcation of the internal carotid artery (ICA) and ECA before reaching the starting point of the MCA5.
The limitations of the two existing methods for inducing MCAo are evident. Koizumi's method necessitates the permanent blockage of the ipsilateral CCA, leading to reduced MCA perfusion since reperfusion solely relies on the circle of Willis4. Conversely, Longa's method involves cutting the ECA, resulting in damage to the ECA system and subsequent impairment of facial muscle function5. This damage can impact food and water intake, as well as cause sensory dysfunction of the face, affecting rehabilitation and the assessment of neurological function post-ischemic stroke6.
The current protocol seeks to address these limitations by developing a new method to induce an ischemic stroke model without damaging the anatomical structure of cerebral vessels. This novel approach utilizes microsurgical techniques to repair the CCA, thus avoiding the drawbacks associated with previous methods.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>10% formalin</td>
			<td>Beijing Labgic Technology Co.,Ltd.</td>
			<td>BL913A</td>
			<td></td>
		</tr>
		<tr>
			<td>11-0 microsurgical sutures</td>
			<td>Ningbo Medical Suture Needle Co., Ltd.</td>
			<td>3/8 1&#215;5</td>
			<td></td>
		</tr>
		<tr>
			<td>2,3,5-triphenyltetrazolium chloride (TTC)</td>
			<td>SIGMA</td>
			<td>T8877</td>
			<td></td>
		</tr>
		<tr>
			<td>3-0 silk suture</td>
			<td>Ningbo Medical Suture Needle Co., Ltd.</td>
			<td>3-0</td>
			<td></td>
		</tr>
		<tr>
			<td>4% isoflurane&#160;&#160;</td>
			<td>Tianjin Ringpu Bio-Technology Co., Ltd.</td>
			<td>20221102</td>
			<td></td>
		</tr>
		<tr>
			<td>6-0 silk suture</td>
			<td>Ningbo Medical Suture Needle Co., Ltd.</td>
			<td>6-0</td>
			<td></td>
		</tr>
		<tr>
			<td>70% ethanol</td>
			<td>Shandong Lierkang Medical Technology Co., Ltd.</td>
			<td>20230408</td>
			<td></td>
		</tr>
		<tr>
			<td>Filament</td>
			<td>Xinong Technologies Co Ltd.</td>
			<td>2838-A5</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine&#160;&#160;</td>
			<td>Jiangsu Hengrui Pharmaceutical Co., Ltd.</td>
			<td>230613BL</td>
			<td></td>
		</tr>
		<tr>
			<td>Male Sprague Dawley rats</td>
			<td>Jinan Pengyue Experimental Animal Breeding Co., Ltd.</td>
			<td>SCXK (Lu) 20190003</td>
			<td></td>
		</tr>
		<tr>
			<td>Microclips</td>
			<td>Shanghai Jinzhong Medical Device Factory</td>
			<td>W40150</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>ZEISS</td>
			<td>S100 OPMI pico</td>
			<td></td>
		</tr>
		<tr>
			<td>Nursing box</td>
			<td>Beijing Fuyi Electrical Appliance Co., Ltd.</td>
			<td>FYL-YS-100L</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>SIGMA</td>
			<td>PHR3263</td>
			<td></td>
		</tr>
	</tbody>
</table>

a rat model of middle cerebral artery occlusion/reperfusion without damaging the anatomical structure of cerebral vessels

Ischemic stroke stands as the primary cause of long-term disability and mortality among adults worldwide. Animal models of ischemic stroke have significantly contributed to our understanding of its pathological mechanisms and the development of potential treatments. Presently, there are two common methods involving filament (endovascular suture) techniques to induce animal models of cerebral ischemia. However, these methods have inherent limitations, such as reduced blood perfusion to the brain, damage to the external carotid artery system, impaired food and/or water intake, and sensory dysfunction of the face. This article introduces a new method for inducing a rat ischemic stroke model without compromising the cerebral vascular anatomy. In this study, the common carotid artery (CCA) of Sprague-Dawley rats was exposed, and an incision was made. A filament was then inserted through the incision into the internal carotid artery to occlude the middle cerebral artery. After 1.5 h of induced ischemia, the occluding filament was fully removed from both the internal carotid artery and the CCA. The incision in the CCA was subsequently sutured using 11-0 microsurgical sutures under a microscope (magnification 4x). Through the utilization of microsurgical techniques to repair the CCA, this study successfully developed a unique method to induce an ischemic stroke model in rats while preserving the anatomical integrity of cerebral blood vessels.

The process of microsuture 
The filament was withdrawn near the incision of the CCA until the white filament tip was visible (Figure 1A). Micro clamps were then placed on the CCA (Figure 1B). Under a microscope at 4x magnification, the incision of the CCA was sutured using microsurgical sutures in an interrupted pattern (Figure 1C). Subsequently, the microclamps were removed from the CCA, restoring the anatomic...

Read this Scientific Article Protocol about A Rat Model of Middle Cerebral Artery Occlusion/Reperfusion without Damaging the Anatomical Structure of Cerebral Vessels at JoVE.com

A Rat Model of Middle Cerebral Artery Occlusion/Reperfusion Without Damaging the Anatomical Structure of Cerebral Vessels

The current protocol describes a rat model of middle cerebral artery occlusion/reperfusion that preserves the anatomical structure of cerebral vessels without causing damage.

Ischemic stroke stands as the primary cause of long-term disability and mortality among adults worldwide. Animal models of ischemic stroke have ...

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363 Aufrufe.  The Third Hospital of Hebei Medical University. The current protocol describes a rat model of middle cerebral artery occlusion/reperfusion that preserves the anatomical structure of cerebral vessels without causing damage.

Serie: A Rat Model of Middle Cerebral Artery Occlusion/Reperfusion Without Damaging the Anatomical Structure of Cerebral Vessels

Cerebral Blood Oxygenation Measurement Based on Oxygen-dependent Quenching of Phosphorescence

Monitoring of the spatiotemporal characteristics of cerebral blood and tissue oxygenation is crucial for better understanding of the 
neuro-metabolic-vascular relationship. Development of new pO2 measurement modalities with simultaneous monitoring of pO2 in larger fields of view with higher 
spatial and/or temporal resolution will enable greater insight into the functioning of the normal brain and will also have significant impact on diagnosis 
and treatment of neurovascular diseases such as stroke, Alzheimer's disease, and head injury.
Optical imaging modalities have shown a great potential to provide high spatiotemporal resolution and quantitative imaging of pO2 based on hemoglobin absorption in visible and near infrared range of optical spectrum. However, multispectral measurement of cerebral blood oxygenation relies on photon migration through the highly scattering brain tissue. Estimation and modeling of tissue optical parameters, which may undergo dynamic changes during the experiment, is typically required for accurate estimation of blood oxygenation. On the other hand, estimation of the partial pressure of oxygen (pO2) based on oxygen-dependent quenching of phosphorescence should not be significantly affected by the changes in the optical parameters of the tissue and provides an absolute measure of pO2. Experimental systems that utilize oxygen-sensitive dyes have been demonstrated in in vivo studies of the perfused tissue as well as for monitoring the oxygen content in tissue cultures, showing that phosphorescence quenching is a potent technology capable of accurate oxygen imaging in the physiological pO2 range. 
Here we demonstrate with two different imaging modalities how to perform measurement of pO2 in cortical vasculature based on phosphorescence lifetime imaging. In first demonstration we present wide field of view imaging of pO2 at the cortical surface of a rat. This imaging modality has relatively simple experimental setup based on a CCD camera and a pulsed green laser. An example of monitoring the cortical spreading depression based on phosphorescence lifetime of Oxyphor R3 dye was presented. In second demonstration we present a high resolution two-photon pO2 imaging in cortical micro vasculature of a mouse. The experimental setup includes a custom built 2-photon microscope with femtosecond laser, electro-optic modulator, and photon-counting photo multiplier tube. We present an example of imaging the pO2 heterogeneity in the cortical microvasculature including capillaries, using a novel PtP-C343 dye with enhanced 2-photon excitation cross section.
Click here to view the related article <a href="http://www.jove.com/Details.php?ID=1731">Synthesis and Calibration of Phosphorescent Nanoprobes for Oxygen Imaging in Biological Systems.</a>

We present an experimental procedure for measuring the partial pressure of oxygen (pO2) in cerebral vasculature based on oxygen-dependent quenching of phosphorescence. Animal preparation and imaging procedures were outlined for both large field of view CCD-based imaging of pO2 in rats and 2-photon excitation based imaging of pO2 in mice.

Cerebral Blutoxygenierung Messung auf Sauerstoff-abhängige Quenching der Phosphoreszenz Based

Monitoring of the spatiotemporal characteristics of cerebral blood and tissue oxygenation is crucial for better understanding of the 
...

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Magnetic Resonance Spectroscopy of live Drosophila melanogaster using Magic Angle Spinning

High-Resolution Magic Angle Spinning (HRMAS) proton magnetic resonance spectroscopy (1H-MRS) is a novel non-destructive technique that improves spectral line-widths and allows high-resolution spectra to be obtained from extracts, intact cells, cell cultures, and more importantly intact tissue to investigate relationships between metabolites and cellular processes. In vivo HRMAS 1H-MRS studies have yet to be reported in the live fruit fly Drosophila melanogaster. Drosophila, as a simpler genetic organism, allows the multiple biological functions and various evolutionarily conserved signaling pathways to be examined at the whole organism level and it is a useful model for investigating genetics and physiology. To this end, we developed and implemented an in vivo HRMAS 1H-MRS method to investigate live Drosophila at 14.1 T. Here, we outline an HRMAS 1H-MRS protocol for the molecular characterization of Drosophila with a conventional MR spectrometer equipped with an HRMAS probe. This technique is a novel, in vivo, non-destructive Drosophila metabolite measurement approach, which enables the identification of disease biomarkers and thus may contribute to novel therapeutic development.

Magnetic Resonance Spectroscopy of live Drosophila melanogaster using Magic Angle Spinning

This technique enables the use of high-resolution magic angle spinning proton MR spectroscopy (HRMAS 1H-MRS) for molecular characterization of live Drosophila melanogaster with a conventional 14.1 tesla spectrometer equipped with an HRMAS probe.

Magnetic Resonance Spectroscopy von Live- Drosophila melanogaster Verwendung von Magic Angle Spinning

High-Resolution Magic Angle Spinning (HRMAS) proton magnetic resonance spectroscopy (1H-MRS) is a novel non-destructive technique that improves spectral ...

Single Sensillum Recordings in the Insects Drosophila melanogaster and Anopheles gambiae

The sense of smell is essential for insects to find foods, mates, predators, and oviposition sites3. Insect olfactory sensory neurons (OSNs) are enclosed in sensory hairs called sensilla, which cover the surface of olfactory organs. The surface of each sensillum is covered with tiny pores, through which odorants pass and dissolve in a fluid called sensillum lymph, which bathes the sensory dendrites of the OSNs housed in a given sensillum. The OSN dendrites express odorant receptor (OR) proteins, which in insects function as odor-gated ion channels4, 5. The interaction of odorants with ORs either increases or decreases the basal firing rate of the OSN. This neuronal activity in the form of action potentials embodies the first representation of the quality, intensity, and temporal characteristics of the odorant6, 7.
Given the easy access to these sensory hairs, it is possible to perform extracellular recordings from single OSNs by introducing a recording electrode into the sensillum lymph, while the reference electrode is placed in the lymph of the eye or body of the insect. In Drosophila, sensilla house between one and four OSNs, but each OSN typically displays a characteristic spike amplitude. Spike sorting techniques make it possible to assign spiking responses to individual OSNs. This single sensillum recording (SSR) technique monitors the difference in potential between the sensillum lymph and the reference electrode as electrical spikes that are generated by the receptor activity on OSNs1, 2, 8. Changes in the number of spikes in response to the odorant represent the cellular basis of odor coding in insects. Here, we describe the preparation method currently used in our lab to perform SSR on Drosophila melanogaster and Anopheles gambiae, and show representative traces induced by the odorants in a sensillum-specific manner.

Single Sensillum Recordings in the Insects Drosophila melanogaster and Anopheles gambiae

Electrophysiological responses of olfactory sensory neurons to odorants can be measured in insects using single sensillum recordings. In this video article we will demonstrate how to perform single sensillum recordings in the antennae of the vinegar fly (Drosophila melanogaster) and the maxillary palps of the malaria mosquito (Anopheles gambiae).

Einzel Sensillum Recordings in der Insekten Drosophila melanogaster Und Anopheles gambiae</em

The sense of smell is essential for insects to find foods, mates, predators, and oviposition sites3. Insect olfactory sensory neurons (OSNs) are enclosed ...

A Novel Approach for Documenting Phosphenes Induced by Transcranial Magnetic Stimulation

Stimulation of the human visual cortex produces a transient perception of light, known as a phosphene. Phosphenes are induced by invasive electrical stimulation of the occipital cortex, but also by non-invasive Transcranial Magnetic Stimulation (TMS)1 of the same cortical regions. The intensity at which a phosphene is induced (phosphene threshold) is a well established measure of visual cortical excitability and is used to study cortico-cortical interactions, functional organization 2, susceptibility to pathology 3,4 and visual processing 5-7. Phosphenes are typically defined by three characteristics: they are observed in the visual hemifield contralateral to stimulation; they are induced when the subject s eyes are open or closed, and their spatial location changes with the direction of gaze 2. Various methods have been used to document phosphenes, but a standardized methodology is lacking. We demonstrate a reliable procedure to obtain phosphene threshold values and introduce a novel system for the documentation and analysis of phosphenes. We developed the Laser Tracking and Painting system (LTaP), a low cost, easily built and operated system that records the location and size of perceived phosphenes in real-time. The LTaP system provides a stable and customizable environment for quantification and analysis of phosphenes.

Phosphenes are transient percepts of light that can be induced by applying Transcranial Magnetic Stimulation (TMS) to visually sensitive regions of cortex. We demonstrate a standard protocol for determining the phosphene threshold value and introduce a novel method for quantifying and analyzing perceived phosphenes.

Ein neuer Ansatz zur Dokumentation Phosphenes durch TMS induzierte

Stimulation of the human visual cortex produces a transient perception of light, known as a phosphene. Phosphenes are induced by invasive electrical ...

Low-stress Route Learning Using the Lashley III Maze in Mice

Many behavior tests designed to assess learning and memory in rodents, particularly mice, rely on visual cues, food and/or water deprivation, or other aversive stimuli to motivate task acquisition. As animals age, sensory modalities deteriorate. For example, many strains of mice develop hearing deficits or cataracts. Changes in the sensory systems required to guide mice during task acquisition present potential confounds in interpreting learning changes in aging animals. Moreover, the use of aversive stimuli to motivate animals to learn tasks is potentially confounding when comparing mice with differential sensitivities to stress. To minimize these types of confounding effects, we have implemented a modified version of the Lashley III maze. This maze relies on route learning, whereby mice learn to navigate a maze via repeated exposure under low stress conditions, e.g. dark phase, no food/water deprivation, until they navigate a path from the start location to a pseudo-home cage with 0 or 1 error(s) on two consecutive trials. We classify this as a low-stress behavior test because it does not rely on aversive stimuli to encourage exploration of the maze and learning of the task. The apparatus consists of a modular start box, a 4-arm maze body, and a goal box. At the end of the goal box is a pseudo-home cage that contains bedding similar to that found in the animal&#x2019;s home cage and is specific to each animal for the duration of maze testing. It has been demonstrated previously that this pseudo-home cage provides sufficient reward to motivate mice to learn to navigate the maze1. Here, we present the visualization of the Lashley III maze procedure in the context of evaluating age-related differences in learning and memory in mice along with a comparison of learning behavior in two different background strains of mice. We hope that other investigators interested in evaluating the effects of aging or stress vulnerability in mice will consider this maze an attractive alternative to behavioral tests that involve more stressful learning tasks and/or visual cues.

The Lashley III maze is a route-learning task that does not rely on aversive stimuli or visual cues. It is thus a highly attractive option for evaluating learning and memory, especially in aging mice or otherwise where stress is a consideration.

Low-Stress-Route Learning Mit dem Lashley III Maze in Mäuse

Many behavior tests designed to assess learning and memory in rodents, particularly mice, rely on visual cues, food and/or water deprivation, or other ...

A Simple Composite Phenotype Scoring System for Evaluating Mouse Models of Cerebellar Ataxia

We describe a protocol for the rapid and sensitive quantification of disease severity in mouse models of cerebella ataxia. It is derived from previously published phenotype assessments in several disease models, including spinocerebellar ataxias, Huntington s disease and spinobulbar muscular atrophy. Measures include hind limb clasping, ledge test, gait and kyphosis. Each measure is recorded on a scale of 0-3, with a combined total of 0-12 for all four measures. The results effectively discriminate between affected and non-affected individuals, while also quantifying the temporal progression of neurodegenerative disease phenotypes. Measures may be analyzed individually or combined into a composite phenotype score for greater statistical power. The ideal combination of the four described measures will depend upon the disorder in question. We present an example of the protocol used to assess disease severity in a transgenic mouse model of spinocerebellar ataxia type 7 (SCA7).
Albert R. La Spada and Gwenn A. Garden contributed to this manuscript equally.

We describe a protocol for the rapid and sensitive quantification of disease severity in mouse models of cerebellar ataxia. Measures include hind limb clasping, ledge test, gait and kyphosis. This protocol effectively discriminates between affected and non-affected individuals, and detects the progression of affected individuals over time.

Eine einfache Composite-Phänotyp Scoring System für die Beurteilung von Mausmodellen zerebelläre Ataxie

We describe a protocol for the rapid and sensitive quantification of disease severity in mouse models of cerebella ataxia. It is derived from previously ...

Multielectrode Array Recordings of the Vomeronasal Epithelium

Understanding neural circuits requires methods to record from many neurons simultaneously. For in vitro studies, one currently available technology is planar multielectrode array (MEA) recording. Here we document the use of MEAs to study the mouse vomeronasal organ (VNO), which plays an essential role in the detection of pheromones and social cues via a diverse population of sensory neurons expressing hundreds of types of receptors. Combining MEA recording with a robotic liquid handler to deliver chemical stimuli, the sensory responses of a large and diverse population of neurons can be recorded. The preparation allows us to remove the intact neuroepithelium of the VNO from the mouse and stimulate with a battery of chemicals or potential ligands while monitoring the electrical activity of the neurons for several hours. Therefore, this technique serves as a useful method for assessing ligand activity as well as exploring the properties of receptor neurons. We present the techniques needed to prepare the vomeronasal epithelium, MEA recording, and chemical stimulation.

Multielectrode array (MEA) recordings provide a method for studying the electrical activity of large populations of neurons. Here, we present the details of a MEA preparation to record from the mouse vomeronasal epithelium while simultaneously stimulating the tissue.

Multielektroden Array Recordings der Vomeronasal Epithel

Understanding neural circuits requires methods to record from many neurons simultaneously. For in vitro studies, one currently available technology is ...

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic nerve. In vivo recordings of ganglion cell spike trains in several animal models have revealed much of what is known about how the early visual system processes and encodes visual information. However, such recordings have been rare in one of the most common animal models, the rat, possibly owing to difficulty in detecting spikes fired by small diameter axons. The many retinal disease models involving rats motivate a need for characterizing the functional properties of ganglion cells without disturbing the eye, as with intraocular or in vitro recordings. Here, we demonstrate a method for recording ganglion cell spike trains from the optic chiasm of the anesthetized rat. We first show how to fabricate tungsten-in-glass electrodes that can pick up electrical activity from single ganglion cell axons in rat. The electrodes outperform all commercial ones that we have tried. We then illustrate our custom-designed stereotaxic system for in vivo visual neurophysiology experiments and our procedures for animal preparation and reliable and stable electrode placement in the optic chiasm.

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Retinal ganglion cells transmit visual information from the eye to the brain with sequences of action potentials. Here, we demonstrate how to record the action potentials of single ganglion cells in vivo from anesthetized rats.

Single-Einheit In-vivo- Aufnahmen aus dem Chiasma der Rat

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic ...

SDS-PAGE/Immunoblot Detection of A&beta; Multimers in Human Cortical Tissue Homogenates using Antigen-Epitope Retrieval

The anomalous folding and polymerization of the &beta;-amyloid (A&beta;) peptide is thought to initiate the neurodegenerative cascade in Alzheimer's disease pathogenesis1. A&beta; is predominantly a 40- or 42-amino acid peptide that is prone to self-aggregation into &beta;-sheet-rich amyloid fibrils that are found in the cores of cerebral senile plaques in Alzheimer's disease. Increasing evidence suggests that low molecular weight, soluble A&beta; multimers are more toxic than fibrillar A&beta; amyloid2. The identification and quantification of low- and high-molecular weight multimeric A&beta; species in brain tissue is an essential objective in Alzheimer's disease research, and the methods employed also can be applied to the identification and characterization of toxic multimers in other proteopathies3. Naturally occurring A&beta; multimers can be detected by SDS-polyacrylamide gel electrophoresis followed by immunoblotting with A&beta;-specific antibodies. However, the separation and detection of multimeric A&beta; requires the use of highly concentrated cortical homogenates and antigen retrieval in small pore-size nitrocellulose membranes. Here we describe a technique for the preparation of clarified human cortical homogenates, separation of proteins by SDS-PAGE, and antigen-epitope retrieval/Western blotting with antibody 6E10 to the N-terminal region of the A&beta; peptide. Using this protocol, we consistently detect A&beta; monomers, dimers, trimers, tetramers, and higher molecular weight multimers in cortical tissue from humans with Alzheimer's pathology.

SDS-PAGE/Immunoblot Detection of A&amp;#946; Multimers in Human Cortical Tissue Homogenates using Antigen-Epitope Retrieval

We describe a technique for the preparation of clarified human cortical homogenates, protein separation by SDS-PAGE, antigen retrieval and immunoblotting with an antibody to the A&beta; peptide. Using this protocol, we consistently detect monomeric and multimeric A&beta; in cortical tissue from humans with Alzheimer's pathology.

SDS-PAGE/Immunoblot Detektion von Aß Multimere in Human Kortikale Gewebehomogenaten mit Antigen-Epitope Retrieval

The anomalous folding and polymerization of the &beta;-amyloid (A&beta;) peptide is thought to initiate the neurodegenerative cascade in Alzheimer's ...

The Subventricular Zone En-face: Wholemount Staining and Ependymal Flow

The walls of the lateral ventricles contain the largest germinal region in the adult mammalian brain. The subventricular zone (SVZ) in these walls is an extensively studied model system for understanding the behavior of neural stem cells and the regulation of adult neurogenesis. Traditionally, these studies have relied on classical sectioning techniques for histological analysis. Here we present an alternative approach, the wholemount technique, which provides a comprehensive, en-face view of this germinal region. Compared to sections, wholemounts preserve the complete cytoarchitecture and cellular relationships within the SVZ. This approach has recently revealed that the adult neural stem cells, or type B1 cells, are part of a mixed neuroepithelium with differentiated ependymal cells lining the lateral ventricles. In addition, this approach has been used to study the planar polarization of ependymal cells and the cerebrospinal fluid flow they generate in the ventricle. With recent evidence that adult neural stem cells are a heterogeneous population that is regionally specified, the wholemount approach will likely be an essential tool for understanding the organization and parcellation of this stem cell niche.

The lateral ventricle walls contain the largest germinal region in the adult mammalian brain. Traditionally, studies on neurogenesis in this region have relied on classical sectioning techniques for histological analysis. Here we present an alternative approach, the wholemount technique, which provides a comprehensive, en-face view of this germinal region.

Die Subventrikularzone En-face: Wholemount Färbung und Ependymale Durchfluss

The walls of the lateral ventricles contain the largest germinal region in the adult mammalian brain. The subventricular zone (SVZ) in these walls is an ...