A peptide hormone selectively binds to MC1R and MC3R over MC4R and MC5R (Kis 0.025 0.063 >100 and >100 UM respectively in insect cells expressing the human receptors) but also binds to opioid receptors in rat brain tissue homogenates (IC50 5.9 UM) inhibits FMRF-amide-induced contractions in isolated M. edulis catch muscle at 10 UM intracisternal administration increases the latency to tail flick in the tail-flick test and inhibits haloperidol-induced catalepsy in mice at 0.3 nmol/animal inhibits LPS-induced nitric oxide (NO) release in mouse forebrain in vivo at 0.01 nmol/animal