The ontogenesis of beta-adrenergic receptors and of adenylate cyclase in the developing rat brain.

The development of beta-adrenergic receptors in the developing rat brain was followed for the whole brain, the cortex and the cerebellum. The probe used was 125I-cyanopindolol. Through the use of this probe, the kinetics of appearance of beta-receptors was found to be different from that reported using 125I-hydroxybenzylpindolol as a probe. Also, the number of 125I-cyanopindolol sites is different from the number of 125I-hydroxybenzylpindolol sites. These differences are attributed to the difference in pharmacological specificity of the two ligands. 125I-cyanopindolol binds exclusively to beta-receptors, whereas 125I-hydroxybenzylpindolol binds to both beta-receptors and serotonin receptors. The ontogenesis of GppNHp dependent adenylate cyclase and of Mn2+/forskolin dependent adenylate cyclase indicate that the rate of synthesis of the catalytic component is faster than that of the GTP stimulatory component.