Cerebellar cAMP levels following acute and chronic morphine administration

Abstract

Acute administration of morphine sulfate at 20 mg/kg decreased mouse cerebellar adenosine 3′,5′-cyclic phosphate (cAMP) levels while not affecting cAMP phosphodiesterase (EC 3.1.4.17). The cAMP levels and cAMP phosphodiesterase activities were not affected by chronic treatment. However, cAMP levels increased during abrupt withdrawal both with and without naloxone precipitation, with cAMP phosphodiesterase activities being correspondingly decreased. Propanolol prevented the cAMP increase during abrupt withdrawal.