An MC4R antagonist (Ki = 3.16 nM); selective for MC4R over MC1R, MC3R, and MC5R (Kis = 108, 54.4, and 694 nM, respectively); inhibits α-MSH-induced cAMP accumulation induced by in COS-1 cells expressing MC4R in a concentration-dependent manner; increases food intake in free-feeding rats at 1 or 3 nmol/animal, i.c.v; increases the latency to tail withdrawal in the tail-flick test, as well as inhibits morphine withdrawal-induced decreases in the latency to tail withdrawal in the tail-flick test, in rats at 0.008 ng/animal, i.c.v.; reduces immobility time in the forced swim test, as well as increases time in the open area and reduces the number of droppings in an open field test, in rats at 100 µg/animal