Beta-adrenergic binding sites in fetal rat brain.

The ontogeny of beta-adrenergic binding sites was studied in forebrain homogenates from male and female rats. Specific [3H]dihydroalprenolol binding was defined by the difference between binding in the presence and in the absence of 330 nM (+)oxprenolol. Significant binding was detected at prenatal stages. The dissociation constants (KD) of [3H]dihydroalprenolol binding were similar at gestational day (GD) 19 3/4 and postnatal day (PN) 31. Binding was first detected in forebrain at GD 15 3/4. The amount of binding sites increased until PN 31, when adult values were reached. No sex differences could be detected at any of the stages tested (GD 19 3/4-PN 31).