Effects of beta-adrenergic agents on the regional cerebral blood flow in cortex and thalamus of the cat.

The effects of the beta-adrenergic agents isoprenaline, terbutaline, l,d-propranolol, acebutolol, as well as d-propranolol, on the regional cerebral blood flow (rCBF) in cortex and thalamus and arterial blood pressure (ABP) were investigated following i.v. administration. The experiments were performed in 64 cats anaesthetized with ether and chloralose. The rCBF was measured using the thermistor thermoclearance technique. Isoprenaline, as well as terbutaline (1, 3, 5 micrograms/kg) decreased the cortical rCBF and the ABP (p less than .05). Both adrenergic agonists increased the thalamic rCBF despite the decrease in ABP (p less than .05). L,d-propranolol (1 mg/kg) abolished the effects of isoprenaline and terbutaline on thalamic rCBF. Acebutolol (0.6 mg/kg) or d-propranolol (0.5 mg/kg) did not alter isoprenaline- and terbutaline-induced effects on rCBF in thalamus. L,d-propranolol decreased the thalamic rCBF, whereas d-propranolol increased the rCBF in thalamus (p less than .05). Acebutolol did not change the thalamic rCBF significantly. The results obtained indicate that beta-adrenergic agents have heterogeneous effects on rCBF in cortex and thalamus. Their effects on thalamic rCBF seem to be accomplished by beta 2-adrenoceptor stimulation.