Adrenergic agonists suppress the proliferation of microglia through β2-adrenergic receptor

The effects of several cyclic adenosine monophosphate (cAMP)-elevating agents on the proliferation of cultured rat microglia were investigated by immunocytochemical staining with an antibody against proliferating cell nuclear antigen (PCNA). Epinephrine, isoproterenol, forskolin and 8Br-cAMP suppressed the microglial proliferation. A beta 2-selective agonist terbutaline but not a beta 1-selective agonist dobutamine mimicked the effect of the above cAMP-elevating agents. Furthermore, a non-selective beta-receptor antagonist oxprenolol and a beta 2-selective antagonist acebutalol, but not a beta 1-selective antagonist butoxamine, counteracted the suppressive effects of the beta-agonists on microglial proliferation. These findings suggest that the beta-agonists suppress the proliferation of microglia by elevating intracellular cAMP level through an action on beta 2-adrenergic receptor. (C) 1998 Elsevier Science Ireland Ltd.