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Effect of prazosin on microvascular perfusion during middle cerebral artery ligation in the rat
M Anwar1, E Buchweitz-Milton, H R Weiss
1Department of Physiology and Biophysics and Pediatrics, UMDNJ-Robert Wood Johnson Medical School, Piscataway 08854-5635.
Abstract:
The purpose of this study was to evaluate the effects of prazosin, an alpha 1-adrenoceptor antagonist, on morphometric indexes of the total and perfused cerebral microvascular bed 1 hour after middle cerebral artery (MCA) ligation in pentobarbital-anesthetized rats. We hypothesized that this agent would prevent catecholamine-induced vasoconstriction in the ischemic brain. Cerebral blood flow (CBF) was determined with 14C-iodoantipyrine, and the perfused microvascular bed was visualized using fluorescein isothiocyanate-dextran. MCA occlusion did not alter systemic hemodynamic or blood gas parameters. CBF averaged 29 +/- 15 (mean +/- SD) ml/min/100 g in the MCA-ligated cortex and 49 +/- 18 in the other examined brain regions. Prazosin did not significantly alter these CBF values, averaging 26 +/- 14 and 48 +/- 10, respectively. There were no significant regional differences in total capillaries/mm2 in either group. The percent of the capillaries/mm2 perfused (51 +/- 6%) was similar in the two groups in all examined regions except the ischemic cortex. In the MCA-ligated cortex, 22 +/- 8% of the capillary volume was perfused in comparison with 49 +/- 8% in the prazosin-treated group. Prazosin-treated rats had an increased percentage of their microvasculature perfused despite a similarly reduced CBF. Prazosin appeared to reduce diffusion distances in the ischemic cortex. This might be due to its alpha 1-adrenoceptor blocking activity.
Insights
Prazosin, an alpha 1-adrenoceptor antagonist, increased microvascular perfusion in the ischemic brain after middle cerebral artery ligation. This enhanced perfusion occurred despite unchanged cerebral blood flow, suggesting reduced diffusion distances in the affected brain tissue.
Area of Science:
- Neuroscience
- Cardiovascular Science
- Pharmacology
Background:
- Middle cerebral artery (MCA) ligation in rats is a model for ischemic stroke.
- Alpha 1-adrenoceptors play a role in regulating cerebral vascular tone.
- Catecholamine-induced vasoconstriction can exacerbate ischemic brain injury.
Purpose of the Study:
- To investigate the effect of prazosin, an alpha 1-adrenoceptor antagonist, on the cerebral microvasculature following MCA ligation.
- To determine if prazosin prevents vasoconstriction in the ischemic brain.
- To assess morphometric indexes of the cerebral microvascular bed post-ischemia.
Main Methods:
- Rats underwent MCA ligation under pentobarbital anesthesia.
- Cerebral blood flow (CBF) was measured using 14C-iodoantipyrine.
- Perfused microvasculature was visualized with fluorescein isothiocyanate-dextran.
- Morphometric analysis of total and perfused capillaries was performed.
Main Results:
- MCA ligation reduced CBF in the cortex but did not alter systemic hemodynamics or blood gases.
- Prazosin treatment did not significantly change CBF values in either ischemic or non-ischemic regions.
- In the ischemic cortex, prazosin significantly increased the percentage of perfused capillaries (49% vs. 22%) compared to controls.
- Prazosin treatment increased microvascular perfusion in the ischemic cortex despite similar CBF reductions.
Conclusions:
- Prazosin enhances microvascular perfusion in the ischemic brain following MCA ligation.
- The alpha 1-adrenoceptor antagonist appears to improve the distribution of blood flow within the ischemic microvasculature.
- Prazosin may reduce diffusion distances in the ischemic cortex, potentially by counteracting vasoconstriction.