An invertebrate G-protein coupled receptor is a chimeric cannabinoid/melanocortin receptor.

Analysis of a G-protein coupled receptor fragment isolated from the leech CNS reveals that it is a chimeric cannabinoid/melanocortin receptor. Two regions of the leech sequence display high levels of amino acid identity with mammalian cannabinoid receptors while a third region is 98% identical to part of the bovine adrenocorticotropic hormone receptor. The leech receptor may therefore resemble the putative ancestor of mammalian cannabinoid and melanocortin receptors.