Cyclic 3'5'-adenosine monophosphate in the hypothalamo-neurohypophysial system of normal, NaCl-treated and lactating rats.

The presence and production of cyclic 3', 5'-adenosine monophosphate (cAMP) were investigated in the hypothalamus and neural lobe of the rat. Theophylline (concentrations from 10(-3) to 8 X 10(-3) M) increased the in vitro content of cAMP in the isolated neural lobe and in hypothalamic tissue samples containing supraoptic (SO) or paraventricular (PV) nuclei. Acetylcholine (ACH; 10(-2) and 10(-4) M) or carbachol (10(-4) M) did not increase cAMP content in the isolated neural lobe. Small increases were apparent (p less than 0.05, t-test for paired samples) in the hypothalamus. The amounts of cAMP were significantly higher in isolated neural lobes but not in hypothalami of NaCl-treated or lactating as compared to control rats. Presence of cAMP in the neural lobe and activation of adenylate cyclase under stimulated hormone release conditions indicate a possible involvement of cAMP in the process of neurohypophysial hormone secretion.