Locomotor inhibition induced by procaine injections into the nucleus accumbens core, but not the medial ventral striatum: implication for cocaine-induced locomotion.

Abstract

We examined whether injections of the local anesthesia procaine into the nucleus accumbens core disrupts locomotion more readily than those into the medial ventral striatum. Spontaneous locomotion decreased during the first 10 min immediately following injections of procaine into the core. When procaine was co-administered with d-amphetamine into the core, the injections also decreased amphetamine-induced locomotion during the initial 10 min. On the other hand, no detectable effect on spontaneous or amphetamine-induced locomotion was found when procaine was injected into the medial ventral striatum, including the medial shell and medial olfactory tubercle. We replicated our recent finding that cocaine injections into the core induced delayed, modest locomotion, while cocaine injections into the medial ventral striatum induced immediate, vigorous locomotion. Injections of amphetamine into the core induced as equally vigorous locomotion as that of the medial ventral striatum. These results show that the neurons of the core involved in locomotion are more vulnerable to local anesthesia than the neurons of the medial ventral striatum. In other words, cocaine at the doses inducing vigorous locomotion in the medial ventral striatum induces local anesthesia when applied to the core.