Feeding elicited by dynorphin (1-13) microinjections into the ventral tegmental area in rats.

Both the endogenous opioid peptide, dynorphin (1-13) (DYN), and morphine elicited dose-dependent feeding when microinjected into the ventral tegmental area of food-satiated rats. DYN was 50,000 times more potent than morphine in producing feeding. Whereas the ED50 for morphine was in the nanomole range, the ED50 for DYN was in the femtomole range. Administration of a narcotic antagonist attenuated DYN-elicited feeding. These data suggest a possible role for DYN in the VTA in opioid modulation of feeding behavior.