Relaxant effect of forskolin in rabbit detrusor smooth muscle: role of cyclic AMP.

Forskolin caused a concentration dependent relaxation of rabbit detrusor muscle strips. The relaxant effect of forskolin was potentiated by the cyclic AMP sensitive phosphodiesterase inhibitor, Ro20-1274. Pretreatment with the beta-adrenergic antagonist, propranolol, did not inhibit the relaxation of rabbit detrusor induced by forskolin, whereas the relaxation response to forskolin was inhibited in part by the adenylate cyclase inhibitor, SQ22536. Forskolin also increased cyclic AMP levels significantly in rabbit detrusor muscle. These data suggest that detrusor muscle relaxation by forskolin may be mediated by cyclic AMP and that forskolin may activate adenylate cyclase without stimulating beta-adrenergic receptors in detrusor muscle.