| Abstract: | Incubation of slices of rat cerebral cortex with the beta adrenergic receptor agonist (-)-isoproterenol led to a 30 to 50% decrease in the number of binding sites for [125I]iodohydroxybenzylpindolol and to a 60 to 80% decrease in isoproterenol-stimulated cyclic AMP accumulation. The density of beta adrenergic receptors was also decreased following incubation with (-)-norepinephrine but not with (+)-isoproterenol or dopamine and the decrease in receptor density was blocked by co-incubation with the beta adrenergic receptor antagonist sotalol. The half-time for loss of receptors was approximately 3 min and recovery was observed during a 1 hr reincubation of tissue slices or following exposure to guanine nucleotides. A decrease in beta adrenergic receptor density was also observed following chronic treatment with desmethylimipramine which blocks norepinephrine reuptake and thus potentiates the effects of neurally released norepinephrine at adrenergic receptors. The loss of receptors induced in vitro could be reversed by reincubation or by exposure to guanine nucleotides. In contrast, the loss of receptors induced in vivo was not affected by these procedures. |
