PRESENCE OF MU-OPIOID AND KAPPA-OPIOID RECEPTOR MESSENGER-RNAS IN GALANIN BUT NOT IN GNRH NEURONS IN THE FEMALE RAT

USING a combination of radioactive and non-radioactive in situ hybridi zations, the expression of mu and kappa opioid receptor mRNA was inves tigated in neurons in the female rat preoptic nucleus expressing galan in and gonadotropin-releasing hormone (GnRH) mRNA. Numerous cells expr essing both mu or kappa and galanin were found in the intermediate and rostral regions of the preoptic area whereas little co-localization w as observed at the rostral level. The number of kappa/galanin expressi ng cells was greater than that of mu/galanin cells. mu/galanin co-loca lization was observed essentially in the anteroventral preoptic nucleu s expressing kappa/galanin were present anteroventral preoptic nucleus and in the periventricular hypothalamic nucleus. Go-localization of G nRH with mu or K could not be detected in the preoptic area. These obs ervations showed that galaninergic neurons but not GnRH neurons of the preoptic area might be directly regulated by endogenous opioid peptid es.