Development of the rat pineal alpha 1-adrenoceptor.

Pineal alpha 1-adrenoceptors in rats from 19 days of gestation until 11 months of age were studied using [125I]iodo-2-[beta-(4-hydroxyphenyl)ethylaminomethyl]tetralone ( [125I]HEAT). The number of specific [125I]HEAT binding sites increased markedly between 18 days of gestation (101.7 +/- 13.1 fmol/mg protein) and 10 days of age (336.2 +/- 34.3 fmol/mg protein). A significant decline occurred after 1 month of age. A saturation study showed similar changes in receptor density with age (Bmax; 20 days of gestation, 130.5 fmol/mg protein; 35 days old, 288.1 fmol/mg protein) but no difference in Kd (58.4 pM at both -1 and +35 days). The developmental appearance of the pineal alpha 1-adrenoceptor and the decline in its density with age are remarkably similar to changes reported for pineal beta-adrenoceptors.