The 29 amino acid-containing galanin isolated from the porcine intestine is known to play a significant role in the regulation of the function of the hypothalamo-neurohypophyseal system. The basal vasopressin concentration was examined, and also those vasopressin levels following osmotic and non-osmotic stimuli after centrally administered galanin. The effects of rat, porcine and human galanin and the human galanin 1-16 fragment on vasopressin release were studied. Finally, the question was investigated of whether the galanin receptor antagonist galantid (M15) was able to prevent the vasopressin level changes induced by galanin. Galanin administered intravenously did not influence the vasopressin excretion. After the intracerebroventricular (i.c.v.) injection of galanin, the vasopressin level decreased and the enhancement of the plasma vasopressin concentration following intraperitoneal 2.5% NaCI solution or histamine administration was significantly moderated. There was no essential difference in the vasopressin release effects of rat, porcine and human galanins. The human galanin 1-16 fragment proved to be active as concerns vasopressin regulation. Galantid administered i.c.v. before the galanin injection prevented all of the vasopressin- responsive effects of galanin. The results indicate that galaninergic control is of great importance in the regulation of vasopressin secretion
