Cyclic 3’5’-Adenosine Monophosphate in the Hypothalamo-Neurohypophysial System of Normal, NaCl-Treated and Lactating Rats

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Abstract
The presence and production of cyclic[c]AMP were investigated in the hypothalamus and neural lobe of the rat. Theophylline (concentrations from 10-3-8 .times. 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 < 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.