Regulation of noradrenergic receptor systems in brain that are coupled to adenylate cyclase.

The current status of regulation of norepinephrine (NE) receptor systems in brain that are coupled to adenylate cyclase is briefly reviewed. The availability of NE and the formation of the NE receptor complex is one prerequisite for the regulation of both the sensitivity of the system and the density of its beta-adrenoceptor population. Serotonergic neuronal input is corequired with NE for the down-regulation of the number of beta-adrenoceptors, which in the absence of serotonergic input, show a marked decrease in agonist affinity. Steroid hormones influence either the sensitivity of the NE receptor system (adrenocorticoids) or the biological responsiveness and the density of beta-adrenoceptors (sex steroids) while preliminary data indicate that 3,5,3'-triiodothyronine can convert a "DMI resistant" to a "DMI responsive" receptor system. The complex neurohormonal and endocrine regulation of the biological responsiveness of NE receptor systems, the number of receptors and the efficacy of their coupling to adenylate cyclase appear to represent control mechanisms for the intensity of signal transfer.