Effect of galanin on plasma levels of oxytocin and cholecystokinin.

Galanin, oxytocin and cholecystokinin (CCK) are peptides that influence feeding behaviour. Galanin has been found to stimulate food intake and oxytocin and CCK have been suggested to be satiety agents. The present study was performed in order to investigate if galanin influences the secretion of oxytocin and CCK as a possible indication of a functional relationship between these peptides with respect to their influence on feeding behaviour. Galanin (0.1 and 1 micrograms) was administered intracerebroventricularly (i.c.v.) and intraperitoneally (i.p.) to anaesthetized rats and blood samples were collected 20 and 60 min after administration. Plasma levels of oxytocin and CCK were measured with radioimmunoassay. Galanin, 0.1 and 1 microgram, caused a significant decrease in oxytocin levels after 60 min, both when administered i.c.v. and i.p. In contrast, CCK levels increased following i.c.v. and also i.p. galanin. The possible mechanisms by which galanin causes a decrease in oxytocin and an increase in CCK levels are discussed.