Name: ex vivo pressurized hippocampal capillary-parenchymal arteriole preparation for functional study
Uploaded: 2019-12-18T14:00:00
Description: Watch this Scientific Journal Video about Ex Vivo Pressurized Hippocampal Capillary-Parenchymal Arteriole Preparation for Functional Study at JoVE.com

The authors would like to thank Jules Morin for insightful comments on the manuscript. This research was funded by awards from the CADASIL Together We Have Hope non-profit organization, the Center for Women&#39;s Health and Research, and the NHLBI R01HL136636 (FD).

All experiments were approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Colorado, Anschutz Medical Campus and were performed according to the guidelines from the National Institutes of Health.
1. Solutions
<ol>
	<li>Use MOPS-buffered saline for the dissection and to keep samples at 4 &#176;C before their utilization. Do not gas the solution. Prepare MOPS buffered saline with following composition: 135 mM NaCl, 5 mM KCl, 1 mM KH2PO4,...

<ol>
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The pressurized HiCaPA (hippocampal capillary-parenchymal arteriole) preparation described in the present manuscript is an extension of our well-established procedure to isolate, pressurize, and study parenchymal arterioles29. We recently reported that Kir2.1 channels in brain capillary endothelial cells sense increases in [K+]o associated with neural activation, and generate an ascending hyperpolarizing signal that dilates upstream arterioles20. Revea...

The pial circulation on the surface of the brain has been the object of much study, partly because of its experimental accessibility. However, the topology of the cerebral vasculature creates distinct regions. In contrast to the robust pial network rich in anastomoses with substantial capacity for redirecting the blood flow, the intracerebral parenchymal arterioles (PAs) present limited collateral supply, each of them perfusing a discrete volume of nervous tissue1,2. This creates a bottleneck effect on the blood flow which, combined with unique physiological features3,4,5,6,7,8, makes intracerebral arterioles a crucial site for cerebral blood flow (CBF) regulation9,10. Despite the technical challenges inherent to the isolation and cannulation of PAs, the last decade has seen an increased interest in ex vivo functional studies using pressurized vessels11,12,13,14,15,16,17. One of the reasons for this increased interest is the considerable research effort conducted on neurovascular coupling (NVC), the mechanism sustaining the brain functional hyperemia18.
Regionally, CBF can rapidly increase following local neural activation19. The cellular mechanisms and signaling properties controlling NVC are incompletely understood. However, we identified a previously unanticipated role for the brain capillaries during NVC in sensing neural activity and translating it into a hyperpolarizing electrical signal to dilate upstream arterioles20,21,22. Action potentials23,24 and opening of large-conductance Ca2+-activated K+ (BK) channels on the astrocytic endfeet25,26 increase the interstitial potassium ion concentration [K+]o, which results in activation of strong inward rectifier K+ (Kir) channels in the vascular endothelium of capillaries. This channel is activated by external K+ but also by hyperpolarization itself. Spreading through gap junctions, the hyperpolarizing current then regenerates in adjacent capillary endothelial cells up to the arteriole, where it causes myocyte relaxation and CBF increase20,21. The study of this mechanism led us to develop a pressurized capillary-parenchymal arteriole (CaPA) preparation to measure the arteriolar diameter during capillary stimulation with vasoactive agents. The CaPA preparation is composed of a cannulated intracerebral arteriole segment with an intact, downstream capillary ramification. The capillary ends are compressed against the chamber glass bottom by a micropipette, which occludes and stabilizes the entire vascular formation20,21.
We previously made instrumental innovations by imaging CaPA preparations from the mouse cortex20,21 and arterioles from the rat amygdala13 and hippocampus16,17. As the hippocampal vasculature receives more attention due to its susceptibility to pathological conditions, here we provide a step-by-step method for CaPA preparation from the mouse hippocampus (HiCaPA) that can not only be used in functional NVC studies but also in molecular biology, immunochemistry, and electrophysiology.

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		<tr>
			<td>0.22&#181;m Syringe Filters</td>
			<td>CELLTREAT Scientific Products</td>
			<td>229751</td>
			<td></td>
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			<td>S12-0 NYLON</td>
			<td></td>
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			<td>Automatic Temperature Controller</td>
			<td>Warner Instruments</td>
			<td>TC-324B</td>
			<td></td>
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			<td>Borosilicate Glass O.D.: 1.2 mm, I.D.: 0.68 mm</td>
			<td>Sutter Instruments</td>
			<td>B120-69-10</td>
			<td></td>
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			<td>Bovine serum albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A7030</td>
			<td></td>
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			<td>CaCl2 dihydrate</td>
			<td>Sigma-Aldrich</td>
			<td>C3881</td>
			<td></td>
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			<td>D-(+)-Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G5767</td>
			<td></td>
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			<td>Dissection Scope</td>
			<td>Olympus</td>
			<td>SZ11</td>
			<td></td>
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			<td>ECOLINE VC-MS/CA 4-12 &#8212; complete Pump with Drive and MS/CA 4-12 pump-head</td>
			<td>Ismatec</td>
			<td>ISM 1090</td>
			<td></td>
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			<td>EGTA</td>
			<td>Sigma-Aldrich</td>
			<td>E4378</td>
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			<td>Fine Scissors - Sharp</td>
			<td>Fine Science Tools</td>
			<td>14063-09</td>
			<td></td>
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			<td>Inline Water Heater</td>
			<td>Warner Instruments</td>
			<td>SH-27B</td>
			<td></td>
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			<td>Integra&#8482; Miltex&#8482;Tissue Forceps</td>
			<td>Fisher Scientific</td>
			<td>12-460-117</td>
			<td></td>
		</tr>
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			<td>KCl</td>
			<td>Sigma-Aldrich</td>
			<td>P9333</td>
			<td></td>
		</tr>
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			<td>KH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>P5379</td>
			<td></td>
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			<td>Magnesium sulfate heptahydrate</td>
			<td>Sigma-Aldrich</td>
			<td>M1880</td>
			<td></td>
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			<td>MgCl Anhydrous</td>
			<td>Sigma-Aldrich</td>
			<td>M8266</td>
			<td></td>
		</tr>
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			<td>Micromanipulator</td>
			<td>Narishige</td>
			<td>MN-153</td>
			<td></td>
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			<td>ML 133 hydrochloride</td>
			<td>Tocris</td>
			<td>4549</td>
			<td></td>
		</tr>
		<tr>
			<td>MOPS</td>
			<td>Sigma-Aldrich</td>
			<td>M1254</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich</td>
			<td>S9625</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>S9638</td>
			<td></td>
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			<td>NaHCO3</td>
			<td>Sigma-Aldrich</td>
			<td>S8875</td>
			<td></td>
		</tr>
		<tr>
			<td>NS309</td>
			<td>Tocris</td>
			<td>3895</td>
			<td></td>
		</tr>
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			<td>Picospritzer III - Intracellular Microinjection Dispense Systems, 2-channel</td>
			<td>Parker Hannifin</td>
			<td>052-0500-900</td>
			<td></td>
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			<td>Pressure Servo Controller with Peristaltic Pump</td>
			<td>Living Systems Instrumentation</td>
			<td>PS-200</td>
			<td></td>
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			<td>Sodium pyruvate</td>
			<td>Sigma-Aldrich</td>
			<td>P3662</td>
			<td></td>
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			<td>Super Fine Forceps</td>
			<td>Fine Science Tools</td>
			<td>11252-20</td>
			<td></td>
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			<td>Surgical Scissors - Sharp-Blunt</td>
			<td>Fine Science Tools</td>
			<td>14001-13</td>
			<td></td>
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			<td>Vertical Micropipette Puller</td>
			<td>Narishige</td>
			<td>PP-83</td>
			<td></td>
		</tr>
	</tbody>
</table>

ex vivo pressurized hippocampal capillary-parenchymal arteriole preparation for functional study

From subtle behavioral alterations to late-stage dementia, vascular cognitive impairment typically develops following cerebral ischemia. Stroke and cardiac arrest are remarkably sexually dimorphic diseases, and both induce cerebral ischemia. However, progress in understanding the vascular cognitive impairment, and then developing sex-specific treatments, has been partly limited by challenges in investigating the brain microcirculation from mouse models in functional studies. Here, we present an approach to examine the capillary-to-arteriole signaling in an ex vivo hippocampal capillary-parenchymal arteriole (HiCaPA) preparation from mouse brain. We describe how to isolate, cannulate, and pressurize the microcirculation to measure arteriolar diameter in response to capillary stimulation. We show which appropriate functional controls can be used to validate the HiCaPA preparation integrity and display typical results, including testing potassium as a neurovascular coupling agent and the effect of the recently characterized inhibitor of the Kir2 inward rectifying potassium channel family, ML133. Further, we compare the responses in preparations obtained from male and female mice. While these data reflect functional investigations, our approach can also be used in molecular biology, immunochemistry, and electrophysiology studies.

Endothelial small-conductance (SK) and intermediate-conductance (IK) Ca2+-sensitive K+ channels exert a dilatory influence on the diameter of PAs. Bath application of 1 &#181;M NS309, a synthetic IK and SK channel agonist, caused near maximal dilation (Figure 2A,B). However, capillary endothelial cells lack IK and SK channels and did not hyperpolarize in response to NS30920. As a result, stimulati...

Watch this Scientific Journal Video about Ex Vivo Pressurized Hippocampal Capillary-Parenchymal Arteriole Preparation for Functional Study at JoVE.com

Ex Vivo Pressurized Hippocampal Capillary-Parenchymal Arteriole Preparation for Functional Study

The present manuscript details how to isolate hippocampal arterioles and capillaries from the mouse brain and how to pressurize them for pressure myography, immunofluorescence, biochemistry, and molecular studies.

From subtle behavioral alterations to late-stage dementia, vascular cognitive impairment typically develops following cerebral ischemia. Stroke and ...

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