Developmental change of beta-adrenergic receptors in rat brain

The developmental change of beta-adrenergic receptors in rat whole brain, except the cerebellum, was studied by binding assays with (--) 3H-dihydroalprenolol. The synaptic membrane fraction, prepared from 2-day-old and 6-week-old rat brains, had binding sites for (--) 3H-dihydroalprenolol, which seemed to represent physiological beta-adrenoceptors. The maximal binding capacity and the dissociation constant for (--) 3H-dihydroalprenolol of the synaptic membrane fraction did not vary with the age of the rats, but the yield of synaptic membrane fraction from the brain of 2-day-old rats was much less. Therefore, the total number of binding sites was less in 2-day-old rats. In addition, there was a significant difference in the inhibitory effects of 1-isoproterenol on binding of (--) 3H-dihydroalprenolol to the synaptic membrane fractions in the 2-day as compared to the tissues from the 6-week-old animals. The developmental changes in the number and nature of beta-adrenoceptors may result in expression of catecholamine-sensitive adenylate cyclase activity.