Modulation by Monoamines of Somatostatin‐Sensitive Adenylate Cyclase on Neuronal and Glial Cells from the Mouse Brain in Primary Cultures

Abstract

Primary cultures of mouse embryonic neuronal or glial cells from the cerebral cortex, striatum, and mesencephalon were used to identify and determine the cellular localization of somatostatin receptors coupled to an adenylate cyclase. Somatostatin inhibited basal adenylate cyclase activity on neuronal but not on glial crude membranes in the three structures examined. The somatostatin-inhibitory effect on neuronal crude membranes was still observed in the presence of (—)-isoproterenol, 3,4-dihydroxyphenylethylamine (dopamine, DA), or 5-hydroxytryptamine (5-HT, serotonin) used at a concentration (10⁻⁵M) inducing maximal adenylate cyclase activation. In addition, in most cases biogenic amines modified the pattern of the somatostatin-inhibitory effect, triggering either an increase in the peptide apparent affinity for its receptors or an increase in the maximal reduction of adenylate cyclase activity or both. However, 5-HT did not modify the somatostatin-inhibitory response on striatal and cortical neuronal crude membranes. The changes in somatostatin-inhibitory responses were interpreted as a colocalization of the amine and the peptide receptors on subtypes of neuronal cell populations. Finally, somatostatin was shown to inhibit adenylate cyclase activity following its activation by (—)-isoproterenol on glial crude membranes of the striatum and the mesencephalon but not on those of the cerebral cortex.