Coexpression of glucagon-like peptide-1 (GLP-1) receptor, vasopressin, andoxytocin mRNAs in neurons of the rat hypothalamic supraoptic and paraventricular nuclei: Effect of GLP-1(7-36)amide on vasopressin and oxytocin release

This study was designed to gain better insight into the relationship betwee n glucagon-like peptide-1 (GLP-1) (7-36) amide and vasopressin (AVP) and ox ytocin (OX). In situ hybridization histochemistry revealed colocalization o f the mRNAs for GLP-1 receptor, AVP, and OX in neurons of the hypothalamic supraoptic and paraventricular nuclei. To determine whether GLP-1(7-36)amid e alters AVP and/or OX release, both in vivo and in vitro experimental stud y designs were used. In vivo, intravenous administration of 1 mu g of GLP-1 (7-36)amide into the jugular vein significantly decreased plasma AVP and OX concentrations. In vitro incubation of the neurohypophysis with either 0.1 or 1 mu g Of GLP-1(7-36)amide did not modify the release of AVP. However, addition of 1 mu g of GLP-1(7-36)amide to the incubation medium increased s lightly the secretion of OX. The coexpression of GLP-1 receptor and AVP mRN As in hypothalamic supraoptic and paraventricular nuclei gives further supp ort to the already reported central effects of GLP-1(7-36)amide on AVP. Our findings also suggest a dual secretory response of AVP and OX to the effec t of GLP-1(7-36)amide, which most likely is related to the amount and/or th e route of peptide administration.