The goal of this study was to examine effects of arginine vasopressin and angiotensin on cerebral microvascular pressure and segmental vascular resistance. We measured pressure (servo-null) in pial arteries that were ~ 200 μm in diameter and cerebral blood flow (microspheres) in anesthetized cats, and we calculated resistance of large and small cerebral vessels. Resistance of large arteries (> 200 μm diam) was ~ 45% of total cerebral vascular resistance under control conditions. Vasopressin (40 mU/kg iv) decreased resistance of large arteries by 22 ± 7%; increased pial artery pressure by 10 ± 2 mmHg when aortic pressure was maintained at control levels, and increased small vessel resistance by 27 ± 11%. This increase in small vessel resistance apparently was an autoregulatory response to the increase in pial pressure. Cerebral blood flow was not changed (38 ± 4 vs. 37 ± 3 ml · min-1 · 100 g-1). Intravenous infusion of angiotensin (2 μg · kg-1 · min-1) increased large artery resistance by 32 ± 6%, decreased pial artery pressure 6 ± 3 mmHg with aortic pressure maintained constant, and decreased cerebral blood flow by 12 ± 1%. Thus circulating vasopressin, at concentrations similar to those observed during hemorrhage, selectively dilates large cerebral arteries and increases microvascular pressure without changes in cerebral blood flow. In contrast to vasopressin, angiotensin selectively increases resistance of large cerebral arteries and decreases cerebral microvascular pressure. Thus vasopressin and angiotensin, at doses that have minimal effects on cerebral blood flow, may play an important role in regulation of cerebral microvascular pressure.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|State||Published - 1988|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)