PRL-releasing peptide inhibits food intake in male rats via the dorsomedial hypothalamic nucleus and not the paraventricular hypothalamic nucleus

PRL-releasing peptide inhibits food intake after intracerebroventricular injection. PRL-releasing peptide immunoreactivity is found in several hypothalamic nuclei involved in feeding, with highest levels in the paraventricular and dorsomedial hypothalamic nuclei. The aim of this study was to examine the effect of PRL-releasing peptide on food intake after administration into these nuclei. Paraventricular nucleus injection of PRL-releasing peptide did not alter food intake. Dorsomedial hypothalamic nucleus injection of PRL-releasing peptide decreased 1 h food intake [PRL-releasing peptide (1 nmol) 83.4 ± 6.1% saline all; P < 0.05]; and continued until 8 h postinjection [PRL-releasing peptide (1 nmol) 89.2 ± 4.1% saline; P < 0.05]. To investigate the mechanism of this inhibition of food intake, we examined PRL-releasing peptide's effect on neuropeptide release from hypothalamic explants. αMSH release was increased [PRL-releasing peptide (100 nmol), 5.4 ± 1.6 pmol/explant; change vs. basal, P < 0.01], whereas agouti-related protein release was unchanged. The release of cocaineand amphetamine-regulated transcript was inhibited [PRL-releasing peptide (100 nmol), -33.5 ± 12.6 pmol/explant; change vs. basal, P < 0.01]. PRL-releasing peptide dose-dependently increased neurotensin release [PRL-releasing peptide (1 nmol), 3.7 ± 2.6 pmol/explant; change vs. basal, P = NS; PRL-releasing peptide (10 nmol), 7.2 ± 2.7 pmol/explant; change vs. basal, P < 0.01; PRL-releasing peptide (100 nmol), 36.8 ± 5.4 pmol/explant; change vs. basal, P < 0.001]. Our data suggest that the dorsomedial hypothalamic nucleus is important in the inhibitory effect of PRL-releasing peptide on food intake and that PRL-releasing peptide alters the release of several hypothalamic neuropeptides important in the control of food intake.