Abstract:The time course of resensitization of the down‐regulated β‐adrenoceptor system of rat myometrium was studied. The isoprenaline‐induced decrease of myometrial cAMP reversed rather rapidly and after 4 and 8 days no significant change of the cAMP level was demonstrated, however, the cAMP level was higher than in the control myometrium after 12 days. The elevated phosphodiesterase activity dereased to 80% of control activity after 4 days, but returned to control activity after 8 days. The decreased number of β‐adrenoceptors increased gradually after discontinueing the treatment and reached the number of the controls after 12 days. Our results suggest that the resensitization of the β‐adrenoceptor‐cAMP‐system is rather complex, the normalization of the cAMP content and the phosphodiesterase activity is more rapid than the normalization of the β‐adrenoceptor number which is a rather slow process i