Behavioral cross-sensitization between cocaine and enkephalin in the A10 dopamine region.

The motor stimulant effect produced by cocaine and the injection of opioids onto A10 dopamine neurons is thought to be mediated by an increase in dopaminergic transmission in mesolimbic dopamine terminal fields such as the nucleus accumbens. Following daily administration, the behavioral stimulant effect of both cocaine and intra-A10 injection of opioids is augmented. The data in this report demonstrate that rats receiving daily injection of enkephalin analogue into the A10 have an enhanced motor stimulant response to intraperitoneal cocaine, but not to saline. Conversely, rats receiving daily injection of intraperitoneal cocaine have an enhanced motor stimulant response to intra-A10 injection of enkephalin analogue.