DIFFERENTIAL-EFFECTS OF THE 5-HT1B 2C RECEPTOR AGONIST MCPP AND THE 5-HT1A AGONIST FLESINOXAN ON HYPOTHALAMIC NEUROPEPTIDE-Y IN THE RAT - EVIDENCE THAT NPY MAY MEDIATE SEROTONINS EFFECTS ON FOOD-INTAKE/

To determine whether NPY and 5-HT interact, we studied the effects on hypothalamic NPY and NPY mRNA levels of acute (10 mg/kg) and 7-day adm inistration (10 mg/kg/day) of mCPP (a 5-HT1B/2C agonist) and flesinoxa n (a 5-HT1A agonist). After both treatments, mCPP reduced food intake and NPY levels in the PVN (p < 0.01). NPY mRNA levels were only increa sed by comparable food restriction (p < 0.05). Acute flesinoxan inject ion increased food intake and NPY levels in the PVN and ARC (p < 0.01) . This suggests that food intake changes induced by mCPP and flesinoxa n are associated with altered NPYergic activity. Stimulation of differ ent hypothalamic 5-HT1 receptors may alter NPY levels available for re lease in the PVN, possibly by altering transport along the ARC-PVN pro jection. Therefore, inhibition of the ARC-PVN projection may at least partly mediate the hypophagic effects of serotonin.