[Effect of cholecystokinin on prolactin release and its action mechanism in the rats].

The effect of cholecystokinin octapeptide (CCK-8) on the release of prolactin (PRL) in male rats were studied in vivo and in vitro. CCK-8 at the concentrations (microgram) of 0.05 and 0.5 was injected into the third cerebral ventricle (3rd, V. I) of conscious rats, outfitted with chronic 3rd. V. and jugular cannulae, a significant increase in resting secretion and restraint stress-induced release of PRL were observed. The effects of CCK-8 at the concentration of 0.05 microgram were stronger than those of 0.5 microgram. To determine if CCK-8 would exert any direct action on anterior pituitary, CCK-8 of 0.05, 0.5, 1.00 microgram were added to the medium of dispersed anterior pituitary cell, and caused dose-dependent increase of PRL secretion. To study a mechanism of intracellular signal transduction in the action of CCK-8, the levels of cAMP and [Ca2+] in the medium were measured. Intracellular Ca2+ concentration of disperse anterior pituitary cell was significantly elevated by CCK-8 (2 x 10(-4) mol/L), but CCK-8 (10(-8)-10(-6) mol/L) did not change intracellular cAMP content. The results indicate that CCK-8 stimulate prolactin release at both sites of hypothalamic and anterior pituitary and the mechanism of stimulating effects of CCK-8 might be mediated by [Ca2+] but not cAMP.