Substance P modulation of dopamine in the nucleus accumbens.

Rats were implanted with bilateral injection cannulae in the nucleus accumbens. While microinjection of substance P (1.0-10.0 micrograms/side) did not alter locomotor or rearing behavior, it did potentiate the motor stimulant effects of intra-accumbens injection with dopamine. Further, substance P injection into the nucleus accumbens significantly elevated the levels of dopamine metabolites in that nucleus. Both the behavioral and neurochemical dose-response curves were biphasic, with 3.0 micrograms of substance P producing a maximal response. These data suggest an interaction between substance P and dopamine in the nucleus accumbens.