NON-PSYCHOSTIMULANT DRUGS OF ABUSE AND ANXIOGENIC DRUGS ACTIVATE WITHDIFFERENTIAL SELECTIVITY DOPAMINE TRANSMISSION IN THE NUCLEUS-ACCUMBENS AND IN THE MEDIAL PREFRONTAL CORTEX OF THE RAT

In rats vertically implanted with concentric dialysis probes in the me dial prefrontal cortex and in the medial nucleus accumbens, morphine, ethanol and nicotine failed to modify extracellular dopamine in the me dial prefrontal cortex at doses that were fully effective in raising e xtracellular dopamine in the nucleus accumbens. Conversely, the aversi ve/anxiogenic drugs picrotoxin, pentylenetetrazol and FG 7142, adminis tered at subconvulsant doses, increased extracellular dopamine in the medial prefrontal cortex but failed to do so in the nucleus accumbens. Systemic administration of low doses of the 5HT(3) antagonist ICS 205 930, previously reported to prevent the increase of extracellular dopa mine in the nucleus accumbens elicited by morphine, nicotine, ethanol and haloperidol (Carboni et al. 1989) as well as by stress (Imperato e t al. 1990), also prevented the increase of extracellular dopamine eli cited in the prefrontal cortex by anxiogenic drugs. Therefore, mesocor tical and mesolimbic dopamine neurons show clear-cut differences in th e reactivity to drugs of abuse and to aversive drugs but are both modu lated by a facilitatory serotonergic input mediated by 5HT(3) receptor s.