1987 Volume 9 Issue 5 Pages 456-462
The present study was designed to investigate whether the sympathetic nervous system modulates the cerebellar dysautoregulation during supratentorial ischemia. We used SHRs in which blood flows to the parietal coretex (CBF) and to the cerebellar cortex (CeBF) were measured by H2 clearance method. The rats were divided into alpha-blockade group (Phenoxybenzamine 1.5 mg/kg i.v.) and beta-blockade group (Propranolol 3.0 mg/kg i.v.). Autoregulations of CBF and CeBF were tested during hemorrhagic hypotension (-15% and -30% of the baseline mean arterial pressure) before and during acute cerebral ischemia induced by bilateral carotid ligation.
Phenoxybenzamine did not affect the resting CBF and CeBF, nor did autoregulations of both CBF and CeBF at the preischemic state. At 30 min ischemia, however, CBF was reduced to 5 ml/100 g/min and autoregulation in the cerebrum was severely damaged. On the other hand, CeBF was preserved better than CBF, i.e., CeBF was 93% and 87% of the resting flow by 15% and 30% reduction of blood pressure, respectively. At the preischemic state, autoregulations of CBF and CeBF were not affected by administration of propranolol. At 30 min ischemia, however, autoregulations in both cerebrum and cerebellum were markedly impaired. CeBF decreased to 77% (p<0.01) and 62% of the resting flow (p<0.01) by 15% and 30% reduction of blood pressure, respectively.
Present results indicate that cerebellar dusautoregulation to hemorrhagic hypotension during supratentorial ischemia is at least in part affected by activation of alpha-adrenoceptor of sympathetic nervous system.
