Autoregulation of the regional cortical and thalamic cerebral blood flow in cats.

The autoregulation of regional cerebral blood flow (rCBF) in cortex and thalamus upon an increase in systemic arterial blood pressure (ABP) was investigated in 27 cats before and after pretreatment with phentolamine (1 mg/kg, i.v.), propranolol (1 mg/kg, i.v.) or acebutolol (1.2 mg/kg, i.v.). The animals were anaesthetized with ether and chloralose. rCBF was measured by thermistor thermoclearance technique. ABP elevation was produced by angiotensin i.v. infusion. rCBF autoregulation was evaluated using different criteria--limits and indices of autoregulation. The data obtained indicate that thalamic rCBF is more resistant to ABP elevation than cortical rCBF. Phentolamine did not change rCBF autoregulation in cortex and thalamus. Propranolol did not change the cortical but increased the thalamic rCBF resistance to ABP elevation. Acebutolol did not influence rCBF autoregulation in thalamus. The results suggest that different mechanisms are involved in rCBF autoregulation in cortex and thalamus. They can be selectively influenced by pharmacological agents.