Clonidine pretreatment enhances the sensitivity of the β-noradrenergic receptor coupled adenylate cyclase system in astrocytes

A portion of alpha sub(2)-noradrenergic receptor in brain appears to be located on non-noradrenergic cells. Evidence presented in this communication suggests that alpha sub(2)-noradrenergic receptors may play an important role in regulating the function of the beta -noradrenergic receptor system. The results suggest that clonidine can affect the activity of the beta -noradrenergic receptor coupled adenylate cyclase system in two ways. When added together with isoproterenol, clonidine inhibits the isoproterenol-induced accumulation of cyclic AMP. In addition, treatment with clonidine alone increases the responsiveness of the beta -noradrenergic receptor coupled adenylate cyclase system to subsequent isoproterenol exposure.