Neuropeptide FF in the VTA blocks the analgesic effects of both intra-VTA morphine and exposure to stress.

It has been shown previously that i.c.v. administration of neuropeptide FF (NPFF) attenuates the analgesic effects of exogeneous and endogeneous opioids. Here, we report that intra-ventral tegmental area (VTA) NPFF pre-treatment blocks the analgesia induced by either intra-VTA morphine or exposure to footshock stress in the formalin test for tonic pain. These findings suggest that NPFF in the VTA may play an adaptive role in regulating the response to stress.