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

The development of β-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 preceptors 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 β-receptors, whereas ¹²⁵I-hydroxybenzylpindolol binds to both β-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.