An assessment of the antinociceptive and aversive effects of stimulating identified sites in the rat brain.

At many sites in the brain electrical stimulation with low current intensity is both aversive and causes antinociception. In view of the well documented antinociception caused by various types of stress and pain it is possible that in some parts of the brain the antinociception is secondary to the stress of the stimulation. At 114 sites in the rat brain the intensity of stimulation required to evoke an aversive response has been compared with the antinociceptive current intensity. Only stimulation in the dorsal hippocampus and pretectal area caused antinociception without significant aversion. Strong aversion resulted from stimulation of 46% of the sites including the central gray and nucleus raphe magnus. Antinociception was significantly correlated with the aversiveness of the stimulation although in 15% of the stimulation sites strong aversion was seen with no antinociception. It is concluded that there can be little justification in assigning a primary antinociceptive role to a brain area which evokes strong escape reactions when stimulated.