PRENATAL AND POSTNATAL DEVELOPMENTAL-CHANGES OF ADRENOCEPTOR SUBTYPES IN RAT-BRAIN

Beta-Adrenergic receptor subtypes, beta-1 and beta-2, were studied during pre- and postnatal development in the rat brain. [I-125]Iodocyanopindolol (6-300 pmol/L) binding assays in the presence of 5-hydroxytryptamine (0.6-6-mu-mol/L) were used to measure exclusively beta-adrenergic receptors. In forebrain tissue, saturable and stereoselective binding was detected on gestational day 13. The amount of beta-adrenergic binding increased until postnatal day 23, when adult values were reached. The dissociation constants of [I-125]iodocyanopindolol binding remained the same throughout development, as did the affinity of several beta-adrenergic and non-beta-adrenergic compounds. The proportion of the beta-2-adrenergic receptors was determined using the beta-1-selective antagonist ICI-89406 (7-150 nmol/L) and was found to change from 65% in prenatal forebrain tissue to 28% in adulthood. In cerebellum/medulla pons tissue, however, the proportion of beta-2-receptor binding (80%) remained unchanged during the whole developmental period.