Evidence for a tonic facilitatory influence of substance P on dopamine release in the nucleus accumbens

Microinjections of a monoclonal antibody substance P (SP) into the nucleus accumbens (NAS) increased the concentrations of dopamine (DA) and its metabolite 3,4-dihydroxyphenyllacetic acid (DOPAC) in the NAS but not neuroanatomically adjacent areas. SP immunoneutralization in the NAS also reduced the locomotor response to systemically administered -amphetamine. Microinjections of control antibody did not significantly alter either DA metabolism or -amphetamine-induced locomotion. These data are consistent with the hypothesis that endogenous SP modulates the release of DA in the NAS.