Morphine conditioned taste aversion reversed by periaqueductal gray lesions.

The role of the periaqueductal gray (PAG) in morphine conditioned taste aversion (CTA) was studied using male Wistar rats as subjects. Following the presentation of a novel saccharin solution, animals with or without a lesion of the PAG were intraperitoneally injected with either morphine, lithium, ethanol or fenfluramine. As evident by the amount of saccharin solution consumed on a subsequent presentation, a PAG lesion reversed a morphine CTA but not CTAs produced by the other drugs used. The results suggest that the PAG may in part mediate morphine CTA.