Name: isolation and cannulation of cerebral parenchymal arterioles
Uploaded: 2016-05-23T14:00:00
Description: Watch this Scientific Journal Video about Isolation and Cannulation of Cerebral Parenchymal Arterioles at JoVE.com

Funded by NHLBI R01HL091905 (SE), the United Leukodystrophy Foundation CADASIL research grant (FD) and AHA 15POST247200 (PWP). The authors would like to thank Samantha P. Ahchay for providing the image on Figure 1, and Dr. Gerry Herrera, Ph.D., for providing critical comments on the manuscript.

1. Cannula and Chamber Preparation
<ol>
	<li>Insert clean borosilicate glass capillaries (outer diameter: 1.2 mm; internal diameter: 0.69 mm; 10 mm in length) into the grooves of a pipette puller with a platinum filament (diameter: 100 &#181;m).</li>
	<li>Using appropriate settings, pull the capillary to generate a cannula with a long and thin tip (Figure 2) using a micropipette puller. The settings used are: Heat - 700, Pull - 100, Velocity - 50, Time - 10.</li>
	<li>Insert cannula into the holder of ...

<ol>
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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurovascular+signaling+in+the+brain+and+the+pathological+consequences+of+hypertension.">Neurovascular signaling in the brain and the pathological consequences of hypertension.</a> Am J Physiol Heart Circ Physiol. 306, H1-H14 (2014).</li><li>Iadecola, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurovascular+regulation+in+the+normal+brain+and+in+Alzheimer's+disease.">Neurovascular regulation in the normal brain and in Alzheimer's disease.</a> Nat Rev Neurosci. 5, 347-360 (2004).</li><li>Dabertrand, F., 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=Prostaglandin+E2,+a+postulated+astrocyte-derived+neurovascular+coupling+agent,+constricts+rather+than+dilates+parenchymal+arterioles.">Prostaglandin E2, a postulated astrocyte-derived neurovascular coupling agent, constricts rather than dilates parenchymal arterioles.</a> J Cereb Blood Flow Metab. 33, 479-482 (2013).</li><li>Nishimura, N., Schaffer, C. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+heterogeneity+of+endothelial+P2+purinoceptors+in+the+cerebrovascular+tree+of+the+rat.">Functional heterogeneity of endothelial P2 purinoceptors in the cerebrovascular tree of the rat.</a> Am J Physiol. 277, H893-H900 (1999).</li><li>Nagase, K., Iida, H., Dohi, S. <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+ketamine+on+isoflurane-+and+sevoflurane-induced+cerebral+vasodilation+in+rabbits.">Effects of ketamine on isoflurane- and sevoflurane-induced cerebral vasodilation in rabbits.</a> J Neurosurg Anesthesiol. 15, 98-103 (2003).</li><li>Fisher, C. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+hypertension+on+the+cerebral+circulation.">The effects of hypertension on the cerebral circulation.</a> Am J Physiol Heart Circ Physiol. 304, H1598-H1614 (2013).</li><li>Filosa, J. A., Bonev, A. D., Nelson, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+dynamics+in+cortical+astrocytes+and+arterioles+during+neurovascular+coupling.">Calcium dynamics in cortical astrocytes and arterioles during neurovascular coupling.</a> Circ Res. 95, e73-e81 (2004).</li><li>Dacey, R. G., Duling, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+of+rat+intracerebral+arterioles:+methods,+morphology,+and+reactivity.">A study of rat intracerebral arterioles: methods, morphology, and reactivity.</a> Am J Physiol. 243, H598-H606 (1982).</li><li>Coyne, E. F., Ngai, A. C., Meno, J. R., Winn, H. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+isolation+and+characterization+of+intracerebral+arterioles+in+the+C57/BL6+wild-type+mouse.">Methods for isolation and characterization of intracerebral arterioles in the C57/BL6 wild-type mouse.</a> J Neurosci Methods. 120, 145-153 (2002).</li><li>Cipolla, M. J., Smith, J., Kohlmeyer, M. M., Godfrey, J. 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Cerebral parenchymal arterioles are high resistance arterioles with few anastomoses and branches that perfuse distinct neuronal populations. These specialized blood vessels are central players in cerebrovascular autoregulation and neurovascular coupling through astrocyte-mediated vasodilation 1. The importance of these specialized blood vessels in cerebral vascular disease has been known for approximately 50 years, when the pioneering work of Dr. Miller Fisher described structural alterations in parenchymal ar...

The cerebral circulation is uniquely organized to support the metabolic demands of central neurons, cells that have limited energy stores and are consequently highly sensitive to changes in oxygen pressure and supply of necessary nutrients. As particular neuronal subpopulations becomes active when specific tasks are performed, the vasculature promotes a highly localized increase in perfusion to prevent local hypoxia and depletion of nutrients 1. This is a form of functional hyperemia known as neurovascular coupling, and is dependent on the proper operation of the neurovascular unit, composed of active neurons, astrocytes, and cerebral arteries 2. Intracerebral parenchymal arterioles, a group of blood vessels encompassing parenchymal, penetrating and pre-capillary arterioles, are centrally important for this response and it is then critical to study them individually in order to investigate neurovascular coupling 3.
Parenchymal arterioles are small (20 - 70 &#181;m internal diameter) high-resistance blood vessels that perfuse distinct neuronal populations within the brain. Branching out from pial arteries on the surface, parenchymal arterioles penetrate into the brain parenchyma at a nearly 90&#7506; angle to feed the subsurface microcirculation (Figure 1). These arterioles play a critical role in maintaining appropriate perfusion pressure as they are the most distal smooth muscle-containing vessels protecting the capillaries. In contrast to the surface pial circulation, parenchymal arterioles lack collateral branches and anastomoses, and consequently are &#34;bottlenecks&#34; of the cerebral circulation 4. As a result, dysfunction of parenchymal arterioles contributes to the development of cerebrovascular diseases such as vascular cognitive impairment and small ischemic strokes (also known as silent or lacunar strokes). Studies indicate that parenchymal arterioles dysfunction can be induced by essential hypertension 5, chronic stress 6, and is an early event in small vessel disease genetic mouse model 7. Further, experimentally-induced occlusion of single penetrating arterioles in rats is sufficient to cause small ischemic strokes that are cylindrical in shape, similar those observed in older humans 8.
In addition to these anatomical distinctions, mechanisms regulating contractile function differ between pial arteries and parenchymal arterioles. Myogenic vasoconstriction is greater in parenchymal arterioles 9, possibly because of the lack of extrinsic innervation 10, distinct modes of mechanotransduction 11, and differences in intracellular Ca2+ signaling 12,13 in vascular smooth muscle cells. Evidence suggests that endothelium-dependent vasodilator mechanisms also differ between these vascular segments, with parenchymal arteries exhibiting greater reliance on mechanisms involving Ca2+-activated K+ channels and electrotonic communication within the vascular wall compared with diffusible factors such as nitric oxide and prostacyclins 14. Therefore, data gathered in experiments using pial arteries may not necessarily apply to parenchymal arterioles, leaving a gap in our knowledge of local control of cerebral perfusion.
Despite their importance, parenchymal arterioles are vastly under-studied, primarily due to the technical challenges with isolation and mounting for ex vivo study. In this manuscript we describe a methodology to isolate and cannulate cerebral parenchymal arterioles, which can be used for pressure myography, or to isolate tissue for immunolabeling, electrophysiology, molecular biology, and biochemical analysis.

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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">artificial Cerebrospinal Fluid</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
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			<td height="20" style="height:21px;width:216px;">NaCl</td>
			<td style="width:127px;">Fisher Scientific</td>
			<td style="width:119px;">S-640</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">KCl</td>
			<td style="width:127px;">Fisher Scientific</td>
			<td style="width:119px;">P217</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MgCl Anhydrous</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">M-8266</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">NaHCO3</td>
			<td style="width:127px;">Fisher Scientific</td>
			<td style="width:119px;">S233</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">NaH2PO4</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">S9638</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">D-(+)-Glucose</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">G2870</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">CaCl2</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">C4901</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Bovine Serum Albumin</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;">A9647</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Name</td>
			<td style="width:127px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Isolation/ Cannulation</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stereo Microscope</td>
			<td style="width:127px;">Olympus</td>
			<td style="width:119px;">SZX7</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:21px;width:216px;">Super Fine Forceps</td>
			<td style="width:127px;">Fine Science Tools</td>
			<td style="width:119px;">11252-00</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:21px;width:216px;">Vannas Spring Scissors</td>
			<td style="width:127px;">Fine Science Tools</td>
			<td style="width:119px;">15000-00</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Wiretrol 50 &#956;L</td>
			<td style="width:127px;">VWR Scientific</td>
			<td style="width:119px;">5-000-1050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">0.2 &#956;m Sterile Syringe Filter</td>
			<td style="width:127px;">VWR Scientific</td>
			<td style="width:119px;">28145-477</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Micropipette Puller</td>
			<td style="width:127px;">Sutter Instruments</td>
			<td style="width:119px;">P-97</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Borosilicate Glass O.D.: 1.2 mm, I.D.: 0.68 mm</td>
			<td style="width:127px;">Sutter Instruments</td>
			<td style="width:119px;">B120-69-10</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dark Green Nylon Thread</td>
			<td style="width:127px;">Living Systems Instrumentation</td>
			<td style="width:119px;">THR-G</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Linear Alignment Single Vessel Chamber</td>
			<td style="width:127px;">Living Systems Instrumentation</td>
			<td style="width:119px;">CH-1-LIN</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Pressure Servo Controller with Peristaltic Pump</td>
			<td style="width:127px;">Living Systems Instrumentation</td>
			<td style="width:119px;">PS-200</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Video Dimension Analyzer</td>
			<td style="width:127px;">Living Systems Instrumentation</td>
			<td style="width:119px;">VDA-10</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Four Channel Recorder with LabScribe 3 Recording and Analysis Software</td>
			<td style="width:127px;">Living Systems Instrumentation</td>
			<td style="width:119px;">DAQ-IWORX-404</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Heating Unit</td>
			<td style="width:127px;">Warner Instruments</td>
			<td style="width:119px;">64-0102</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Automatic Temperature Controller</td>
			<td style="width:127px;">Warner Instruments</td>
			<td style="width:119px;">TC-324B</td>
			<td></td>
		</tr>
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isolation and cannulation of cerebral parenchymal arterioles

Intracerebral parenchymal arterioles (PAs), which include parenchymal arterioles, penetrating arterioles and pre-capillary arterioles, are high resistance blood vessels branching out from pial arteries and arterioles and diving into the brain parenchyma. Individual PA perfuse a discrete cylindrical territory of the parenchyma and the neurons contained within. These arterioles are a central player in the regulation of cerebral blood flow both globally (cerebrovascular autoregulation) and locally (functional hyperemia). PAs are part of the neurovascular unit, a structure that matches regional blood flow to metabolic activity within the brain and also includes neurons, interneurons, and astrocytes. Perfusion through PAs is directly linked to the activity of neurons in that particular territory and increases in neuronal metabolism lead to an augmentation in local perfusion caused by dilation of the feed PA. Regulation of PAs differs from that of better-characterized pial arteries. Pressure-induced vasoconstriction is greater in PAs and vasodilatory mechanisms vary. In addition, PAs do not receive extrinsic innervation from perivascular nerves &#8212; innervation is intrinsic and indirect in nature through contact with astrocytic endfeet. Thus, data regarding contractile regulation accumulated by studies using pial arteries does not directly translate to understanding PA function. Further, it remains undetermined how pathological states, such as hypertension and diabetes, affect PA structure and reactivity. This knowledge gap is in part a consequence of the technical difficulties pertaining to PA isolation and cannulation. In this manuscript we present a protocol for isolation and cannulation of rodent PAs. Further, we show examples of experiments that can be performed with these arterioles, including agonist-induced constriction and myogenic reactivity. Although the focus of this manuscript is on PA cannulation and pressure myography, isolated PAs can also be used for biochemical, biophysical, molecular, and imaging studies.

Figure 5A shows a representative constriction of mouse PAs to 60 mM KCl aCSF to evaluate the integrity of the preparation. PAs should constrict between 15 - 30% in the presence of 60 mM KCl. If the constriction is below 15%, discard the PA and cannulate another one, as it suggests that the arteriole was damaged during the isolation and cannulation process.
Figure 5B illustrates PA constriction t...

Watch this Scientific Journal Video about Isolation and Cannulation of Cerebral Parenchymal Arterioles at JoVE.com

Isolation and Cannulation of Cerebral Parenchymal Arterioles

This manuscript describes a simple and reproducible protocol for isolation of intracerebral arterioles (a group of blood vessels encompassing parenchymal arterioles, penetrating arterioles and pre-capillary arterioles) from mice, to be used in pressure myography, immunofluorescence, biochemistry, and molecular studies.

Intracerebral parenchymal arterioles (PAs), which include parenchymal arterioles, penetrating arterioles and pre-capillary arterioles, are high resistance ...

The overall goal of this procedure is to isolate and mount cerebral arterioles for studies of vascular function and structure using pressure myography. This method can be used to answer key questions in the cerebrovascular field, such as, how did cerebral microvasculature quickly adapts to changes in intraluminal pressure or nutrient demand or during pathological conditions. The main advantage of this technique is that it allows for pressurization of the arteriole in addition of intraluminal pressure, which are important physiological determinants of vascular function.To begin, using a micropipette puller with the appropriate settings, such as those listed here, pull capillaries to generate cannulas. After inserting a cannula into the holder of a myograph chamber and aligning it, under a dissecting microscope, use forceps to carefully break the tip to the desired diameter, such as 10 micrometers as shown here. Fill both cannulas with cerebrospinal fluid or aCSF containing 1.8 millimolar calcium, and use five to 20 milliliters of calcium free aCSF supplemented with 1%BSA and 10 micromolar diltiazem to fill the chamber.Store the chamber at four degrees Celsius until just before the cannulation. After isolating a mouse brain according to the text protocol, under the dissecting scope, locate the circle of Willis and the middle cerebral artery, or MCA, branching from it. Using sharp and aligned Vannas spring scissors, cut a small rectangle around the MCA.The top part of the rectangle should be past a branching point from the circle of Willis. Then, with the Vannas spring scissors, perform an undercut into the depth of the tissue for approximately two to three millimeters. Using insect pins, pin down the most distal end of the brain slice into the dissecting dish, with the MCA facing upwards.Make a shallow incision to cut the pia near the pin, being careful not to cut too deep into the underlying cerebral cortex. Next, with small forceps, carefully grab each side of the pia and start peeling the pia from the cortex. If necessary, hold onto the MCA ensuring that the surrounding pial membrane is not damaged.Close to the circle of Willis, resistance against peeling will increase. Take extra care at this point, because the longer parenchymal arterioles will be in this region. Continue to peel until the pia containing the MCA is free from the cortex.Care and patience should be taken during this step, as the arterioles are very fragile and sudden movements or pulling with too much force will damage them. Once the pia is free, place it carefully on top of the pad on the dissecting dish, with the surface opposite the parenchymal arterioles facing down. With Vannas spring scissors, free the dissected arterioles from the MCA by bluntly cutting the ends of the vessels.After preparing sutures and securing two onto each cannula, use 10%BSA to coat a glass micropipette, and with calcium free aCSF supplemented with 1%BSA, rinse it off. Move 50 microliters of calcium free aCSF supplemented with 1%BSA into the glass micropipette. Then, pull up a parenchymal arteriole, or PA, and transfer to the pressure myography chamber.Push the plunger in one fluid motion to dispense the parenchymal arteriole into the chamber to prevent it from sticking to the internal chamber of the glass micropipette. With two super fine forceps, open the lumen of the PA, taking care to only touch the very end of the vessel. Then, using the forceps to hold the edges of the PA, carefully pull the vessel onto the cannula.Next, loosen the two sutures on the cannula, and after spacing them slightly apart on the vessel, pull them toward the operator while tightening them on the vessel. Make sure that any branches are tied off before closing the opposite end of the PA.These are the most difficult steps. Opening up and sliding the arteriole onto the cannula requires practice.When tying up the knot, hold both sides evenly as to not break the tip of the cannula. Then, turn the chamber around and close the opposite end of the PA as a blind-sac by opening the ties on the opposite cannula and passing it onto the arteriole. Slowly close the knot in such a way that the PA will be tied to the side of the cannula.Avoid a longitudinal stretch of the arteriole. Carefully transfer the chamber to the stage of the microscope to be used for recording vessel diameter. Attach the chamber onto the microscope's stage, connecting a temperature probe and inlet and outlets for perfusion to the correct tubes.Pressurize the arteriole to 40 millimeters mercury intraluminal pressure for mouse parenchymal arterioles, or 50 millimeters mercury for rat arterioles. To carry out an agonist induced constriction experiment, after preparing the agonist solution and adding it to the PA chamber according to the text protocol, incubate the vessel in the solution for 10 minutes to allow the luminal diameter to reach a steady state. Then, record the diameter of the arteriole.After washing out the agonist and adding a drug to induce maximum dilation, record the passive diameter of the arteriole. This figure shows a representative constriction of mouse PAs to 60 millimolar potassium chloride in aCSF to evaluate the integrity of the preparation. PA should constrict between 15 to 30 percent in the presence of 60 millimolar potassium chloride.Illustrated here is the PA constriction in response to incubation with increasing concentrations of the Thromboxane A2 analog, U-46619 into the superfusing bath. The data can be presented as a change in diameter or as a percent vasoconstriction to potassium chloride, which normalizes the change in diameter by the maximum constriction to 60 millimolar potassium chloride. In this figure, a representative tracing of the lumen diameter of a PA in a myogenic reactivity experiment is shown.Stepwise increases in intraluminal pressure cause a graded constriction of PAs in the presence of 1.8 millimolar extracellular calcium. Incubation of the same PA with aCSF without calcium and supplemented with 10 micromolar diltiazem plus two millimolar EGTA abolishes myogenic tone generation, and the lumen diameter of the PA increases according to intraluminal pressure, which is the same as the passive lumen diameter of the arteriole. While attempting this technique, it's important to remember to keep your shoulders relaxed as to prevent pain.And once this technique is mastered, it should take no longer than 30 minutes from the isolation up to the cannulation of the arteriole. Following this method, other techniques like imaging of intracellular calcium can be used to answer additional questions, such as the role of intracellular calcium in control of microvascular tone. After its development, this technique has paved the way for researchers in the field of vascular biology to explore the physiological control and pathological changes of the intercerebral vasculature in many organ systems, including humans and rodents.After watching this video, you should have a good understanding of how to isolate and cannulate a cerebral parenchymal arteriole.

isolation-and-cannulation-of-cerebral-parenchymal-arterioles

Research

JoVE Journal

Neuroscience

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.

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

Focal Cerebral Ischemia Model by Endovascular Suture Occlusion of the Middle Cerebral Artery in the Rat

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable clinical state; in the development of animal models of focal ischemia, however, achieving reproducibility of experimentally induced infarct volume is essential. The rat is a widely used animal model for stroke due to its relatively low animal husbandry costs and to the similarity of its cranial circulation to that of humans2,3. In humans, the middle cerebral artery (MCA) is most commonly affected in stroke syndromes and multiple methods of MCA occlusion (MCAO) have been described to mimic this clinical syndrome in animal models. Because recanalization commonly occurs following an acute stroke in the human, reperfusion after a period of occlusion has been included in many of these models. In this video, we demonstrate the transient endovascular suture MCAO model in the spontaneously hypertensive rat (SHR). A filament with a silicon tip coating is placed intraluminally at the MCA origin for 60 minutes, followed by reperfusion. Note that the optimal occlusion period may vary in other rat strains, such as Wistar or Sprague-Dawley. Several behavioral indicators of stroke in the rat are shown. Focal ischemia is confirmed using T2-weighted magnetic resonance images and by staining brain sections with 2,3,5-triphenyltetrazolium chloride (TTC) 24 hours after MCAO.

Surgical induction of ischemic brain damage in the rat is a widely used model for stroke research. Here we demonstrate the induction of focal cerebral ischemia by occlusion of the middle cerebral artery. Visualization of the resulting infarct by histological staining and magnetic resonance imaging is also shown.

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable ...

Detection of Microregional Hypoxia in Mouse Cerebral Cortex by Two-photon Imaging of Endogenous NADH Fluorescence

The brain's ability to function at high levels of metabolic demand depends on continuous oxygen supply through blood flow and tissue oxygen diffusion. Here we present a visualized experimental and methodological protocol to directly visualize microregional tissue hypoxia and to infer perivascular oxygen gradients in the mouse cortex. It is based on the non-linear relationship between nicotinamide adenine dinucleotide (NADH) endogenous fluorescence intensity and oxygen partial pressure in the tissue, where observed tissue NADH fluorescence abruptly increases at tissue oxygen levels below 10 mmHg1. We use two-photon excitation at 740 nm which allows for concurrent excitation of intrinsic NADH tissue fluorescence and blood plasma contrasted with Texas-Red dextran. The advantages of this method over existing approaches include the following: it takes advantage of an intrinsic tissue signal and can be performed using standard two-photon in vivo imaging equipment; it permits continuous monitoring in the whole field of view with a depth resolution of ~50 &mu;m. We demonstrate that brain tissue areas furthest from cerebral blood vessels correspond to vulnerable watershed areas which are the first to become functionally hypoxic following a decline in vascular oxygen supply. This method allows one to image microregional cortical oxygenation and is therefore useful for examining the role of inadequate or restricted tissue oxygen supply in neurovascular diseases and stroke.

Here we describe a method to directly visualize microregional tissue hypoxia in the mouse cortex in vivo. It is based on concurrent two-photon imaging of nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation. This method is useful for high resolution analysis of tissue oxygen supply.

The brain's ability to function at high levels of metabolic demand depends on continuous oxygen supply through blood flow and tissue oxygen diffusion. ...

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 ...

Isolation of Cerebrospinal Fluid from Rodent Embryos for use with Dissected Cerebral Cortical Explants

The CSF is a complex fluid with a dynamically varying proteome throughout development and in adulthood. During embryonic development, the nascent CSF differentiates from the amniotic fluid upon closure of the anterior neural tube. CSF volume then increases over subsequent days as the neuroepithelial progenitor cells lining the ventricles and the choroid plexus generate CSF. The embryonic CSF contacts the apical, ventricular surface of the neural stem cells of the developing brain and spinal cord. CSF provides crucial fluid pressure for the expansion of the developing brain and distributes important growth promoting factors to neural progenitor cells in a temporally-specific manner. To investigate the function of the CSF, it is important to isolate pure samples of embryonic CSF without contamination from blood or the developing telencephalic tissue. Here, we describe a technique to isolate relatively pure samples of ventricular embryonic CSF that can be used for a wide range of experimental assays including mass spectrometry, protein electrophoresis, and cell and primary explant culture. We demonstrate how to dissect and culture cortical explants on porous polycarbonate membranes in order to grow developing cortical tissue with reduced volumes of media or CSF. With this method, experiments can be performed using CSF from varying ages or conditions to investigate the biological activity of the CSF proteome on target cells.

The ventricular cerebrospinal fluid (CSF) bathes the neuroepithelial and cerebral cortical progenitor cells during early brain development in the embryo. Here we describe the method developed to isolate ventricular CSF from rodent embryos of different ages in order to investigate its biological function. In addition, we demonstrate our cerebral cortical explant dissection and culture technique that allows for explant growth with minimal volumes of culture medium or CSF.

The CSF is a complex fluid with a dynamically varying proteome throughout development and in adulthood. During embryonic development, the nascent CSF ...

Non-invasive Parenchymal, Vascular and Metabolic High-frequency Ultrasound and Photoacoustic Rat Deep Brain Imaging

Photoacoustics and high frequency ultrasound stands out as powerful tools for neurobiological applications enabling high-resolution imaging on the central nervous system of small animals. However, transdermal and transcranial neuroimaging is frequently affected by low sensitivity, image aberrations and loss of space resolution, requiring scalp or even skull removal before imaging. To overcome this challenge, a new protocol is presented to gain significant insights in brain hemodynamics by photoacoustic and high-frequency ultrasounds imaging with the animal skin and skull intact. The procedure relies on the passage of ultrasound (US) waves and laser directly through the fissures that are naturally present on the animal cranium. By juxtaposing the imaging transducer device exactly in correspondence to these selected areas where the skull has a reduced thickness or is totally absent, one can acquire high quality deep images and explore internal brain regions that are usually difficult to anatomically or functionally describe without an invasive approach. By applying this experimental procedure, significant data can be collected in both sonic and optoacoustic modalities, enabling to image the parenchymal and the vascular anatomy far below the head surface. Deep brain features such as parenchymal convolutions and fissures separating the lobes were clearly visible. Moreover, the configuration of large and small blood vessels was imaged at several millimeters of depth, and precise information were collected about blood fluxes, vascular stream velocities and the hemoglobin chemical state. This repertoire of data could be crucial in several research contests, ranging from brain vascular disease studies to experimental techniques involving the systemic administration of exogenous chemicals or other objects endowed with imaging contrast enhancement properties. In conclusion, thanks to the presented protocol, the US and PA techniques become an attractive noninvasive performance-competitive means for cortical and internal brain imaging, retaining a significant potential in many neurologic fields.

The present work describes a new protocol to perform non-invasive high-frequency ultrasound and photoacoustic based imaging on rat brain, to efficiently visualize deep subcortical regions and their vascular patterns by directing signals on skull foramina naturally present on animal cranium.

Photoacoustics and high frequency ultrasound stands out as powerful tools for neurobiological applications enabling high-resolution imaging on the central ...

Evaluation of Bioenergetic Function in Cerebral Vascular Endothelial Cells

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types that comprise the BBB; these cells have a very high-energy demand, which requires optimal mitochondrial function. In the case of disease or injury, the mitochondrial function in these cells can be altered, resulting in disease or&#160;the opening of the BBB. In this manuscript, we introduce a method to measure mitochondrial function in CVE cells by using whole, intact cells and a bioanalyzer. A mito-stress assay is used to challenge the cells that have been perturbed, either physically or chemically, and evaluate their bioenergetic function. Additionally, this method also provides a useful way to screen new therapeutics that have direct effects on mitochondrial function. We have optimized the cell density necessary to yield oxygen consumption rates that allow for the calculation of a variety of mitochondrial parameters, including ATP production, maximal respiration, and spare capacity. We also show the sensitivity of the assay by demonstrating that the introduction of the&#160;microRNA, miR-34a, leads to a pronounced and detectable decrease in mitochondrial activity. While the data shown in this paper is optimized for the bEnd.3 cell line, we have also optimized the protocol for primary CVE cells, further suggesting the utility in preclinical and clinical models.

Endothelial cell mitochondria are critical to maintain blood-brain-barrier integrity. We introduce a protocol to measure bioenergetic function in cerebral vascular endothelial cells.

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types ...

Comprehensive Endovascular and Open Surgical Management of Cerebral Arteriovenous Malformations

Arteriovenious malformations (AVMs) are associated with significant morbidity and mortality, and have a rupture risk of ~3% per year. Treatment of AVMs must be tailored specifically to the lesion, with surgical resection being the gold standard for small, accessible lesions. Pre-operative embolization of AVMs can reduce nidal blood flow and remove high-risk AVM features such as intranidal or venous aneurysms, thereby simplifying a challenging neurosurgical procedure. Herein, we describe our approach for the staged endovascular embolization and open resection of AVMs, and highlight the advantages of having a comprehensively trained neurovascular surgeon leading a multi-disciplinary clinical team. This includes planning the craniotomy and resection to immediately follow the final embolization stage, thereby using a single session of anesthesia for aggressive embolization, and rapid resection. Finally, we provide a representative case of a 22-year-old female with an unruptured right frontal AVM diagnosed during a seizure workup, who was successfully treated via staged embolizations followed by open surgical resection.

Surgery is the gold standard for accessible arteriovenious malformations (AVMs), and pre-operative embolization can simplify this procedure. We describe our approach for staged endovascular embolization and open resection of AVMs, and provide a representative clinical example highlighting the advantages of a comprehensively trained neurovascular surgeon leading a multi-disciplinary clinical team.

Arteriovenious malformations (AVMs) are associated with significant morbidity and mortality, and have a rupture risk of ~3% per year. Treatment of AVMs ...

A Rat Model of Mild Intrauterine Hypoperfusion with Microcoil Stenosis

Intrauterine hypoperfusion/ischemia is one of the major causes of intrauterine/fetal growth restriction, preterm birth, and low birth weight. Most studies of this phenomenon have been performed in either models with severe intrauterine ischemia or models with gradient degree of intrauterine hypoperfusion. No study has been performed in a model on uniform mild intrauterine hypoperfusion (MIUH). Two models have been used for studies of MIUH: a model based on suture ligation of either side of the arterial arcade formed with the uterine and ovarian arteries, and a transient model based on clipping the bilateral ovarian arteries and aorta having patency. Those two rodent models of MIUH have some limitations, e.g., not all fetuses are subjected to MIUH, depending on their position in the uterine horn. In our MIUH model, all fetuses are subjected to a comparable level of intrauterine hypoperfusion. MIUH was achieved by mild stenosis of all four arteries feeding the uterus, i.e., the bilateral uterine and ovarian arteries.
Arterial stenosis was induced by metal microcoils wrapped around the feeding arteries. Producing arterial stenosis with microcoils allowed us to control, optimize, and reproduce decreased blood flow with very little inter-animal variability and a low mortality rate, thus enabling accurate evaluation. When microcoils with an inner diameter of 0.24 mm were used, the blood flow in both the placenta and fetus was mildly decreased (approximately 30% from the pre-stenosis level in the placenta). The offspring of our MIUH model clearly demonstrates long-lasting alterations in neurological, neuroanatomical and behavioral test results.

Mild intrauterine hypoperfusion was produced by artery stenosis with metal microcoils wrapped around the uterine and ovarian arteries in rats at embryonic day 17. This procedure produced prenatal hypoperfusion and intrauterine growth restriction.

Intrauterine hypoperfusion/ischemia is one of the major causes of intrauterine/fetal growth restriction, preterm birth, and low birth weight. Most studies ...

Isolation of Cerebral Capillaries from Fresh Human Brain Tissue

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic strategies that hold the promise to enhance brain drug delivery, improve brain protection, and treat brain disorders. However, studying the human blood-brain barrier function is challenging. Thus, there is a critical need for appropriate models. In this regard, brain capillaries isolated from human brain tissue represent a unique tool to study barrier function as close to the human in vivo situation as possible. Here, we describe an optimized protocol to isolate capillaries from human brain tissue at a high yield and with consistent quality and purity. Capillaries are isolated from fresh human brain tissue using mechanical homogenization, density-gradient centrifugation, and filtration. After the isolation, the human brain capillaries can be used for various applications including leakage assays, live cell imaging, and immune-based assays to study protein expression and function, enzyme activity, or intracellular signaling. Isolated human brain capillaries are a unique model to elucidate the regulation of the human blood-brain barrier function. This model can provide insights into central nervous system (CNS) pathogenesis, which will help the development of therapeutic strategies for treating CNS disorders.

Isolated brain capillaries from human brain tissue can be used as a preclinical model to study barrier function under physiological and pathophysiological conditions. Here, we present an optimized protocol to isolate brain capillaries from fresh human brain tissue.

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic ...