Monoamine regulation of adenosine 3',5'-monophosphate in homogeneous neuronal cultures from chick brain hemispheres.

The effect of isoproterenol, norepinephrine, dopamine, and serotonin on the accumulation of adenosine 3',5'-monophosphate (cAMP) was studied in homogeneous neuronal cultures from 8-day chick embryo hemispheres. Among the catecholamines, isoproterenol had a more pronounced effect on the accumulation of cAMP. Norepinephrine and dopamine were considerably less potent and serotonin was ineffective. The response of neuronal cells to isoproterenol was inhibited by propranolol, suggesting that the cAMP increase was mediated by beta-adrenergic receptors. Maximally effective concentration of isoproterenol (10 microM) produced a 2.5-fold increase in cAMP content which is in contrast to the much greater cAMP response elicited by isoproterenol in chick brain tissue. These results suggest that in chick embryo hemispheres the nonneuronal cells are the major sites of the effect of beta-adrenergic agonists. The low responsiveness of the cAMP-generating system found in neuronal cultures is interpreted as reflecting either the number of beta-adrenergic receptors or the regulation of beta-adrenergic receptors and adenylate cyclase at the membrane level.