Suckling-induced increase in cyclic AMP exclusively in the central region of the rat adenohypophysis

Investigating the cellular events in the pituitary gland, the intracellular cyclic AMP (cAMP) of the neural lobe (NL), intermediate lobe (IL), the inn er (IZ-AL) and outer zone (OZ-AL) of the anterior lobe (AL) have been measu red during the suckling stimulus. Ten-minutes suckling, parallel to the ele vation of plasma PRL, induced a significant increase of cAMP concentration in the IZ-AL. In contrast, 10- and 30-min suckling resulted in a decrease o f cAMP level in the NL. Changes in cAMP of the OZ-AL and the Lt as well as in the plasma level of alpha-MSH could not be detected. These region-specif ic changes of cAMP in the pituitary gland during suckling stimulus seems to be related to interacting neuroendocrine signals delivered concomitantly f rom the hypothalamus and from the NIL to the IZ-AL. (C) 2000 Elsevier Scien ce B.V. ALI rights reserved.