Interaction of OC and β-Adrenoceptor Blocking Agents in the Conscious Rat

Abstract

In the recent article by Gomes and co-workers (3), it was reported that the hypotensive effect of the α-adrenergic receptor blocking agents, phentolamine and phenoxybenzamine, administered intravenously to conscious rats, was totally or partly reversed by subsequent administration of β-adrenergic receptor blocking agents. Conversely, pretreatment with β-blocking agents was found to block the hypotensive response to α-blocking agents. It was concluded that acute injection of phentolamine or phenoxybenzamine, by blocking α-receptors, caused a reflex increase in adrenaline output, which then further decreased the blood pressure and increased the heart rate by β-receptor stimulation.