Several papers have indicated the participation of cyclic AMP as a second messenger for the release of neurohypophysial hormones. Since very little is known about the effects of stress and drugs of abuse on this process, we studied the activity of adenylyl cyclase in the neurohypophyses after immobilization stress and chronic amphetamine treatment. Our findings indicate the involvement of cyclic AMP in the regulation of neurohypophysis as well as the increase in total adenylyl cyclase both after application of immobilization stress combined with water immersion and after chronic amphetamine treatment.