Dynorphin, an endogenous stimulator of feeding.

Many investigations have suggested that endogenous opioids are involved in the regulation of food ingestion. Pharmacological studies have clearly demonstrated that kappa opioid receptors play a role in the modulation of feeding. Dynorphin, a peptide which appears to be the endogenous ligand of the kappa receptor, is a potent stimulator of feeding and its levels in the central nervous system are altered under conditions associated with alterations in the feeding drive. The enhancement of feeding produced by dynorphin involves both the opioid and non-opioid portion of the molecule. These studies suggest that dynorphin is an endogenous stimulator of feeding.