A DOPAMINE MU(1) OPIOID LINK IN THE RAT VENTRAL TEGMENTUM SHARED BY PALATABLE FOOD (FONZIES) AND NON-PSYCHOSTIMULANT DRUGS OF ABUSE

The role of mu(1) opioid receptors in the stimulation of dopamine tran smission in the rat nucleus accumbens by an unusual palatable food (Fo nzies) and non-psychostimulant drugs of abuse was investigated by the use of naloxonazine, a pseudo-irreversible antagonist of mu(1) opioid receptors. Feeding of Fonzies stimulated dopamine release in the media l prefrontal cortex and in the shell, but not in the core of the nucle us accumbens. Pretreatment with naloxonazine given systemically (15 mg /kg i.p. 20 h before) completely prevented the stimulation of dopamine release in the shell of the nucleus accumbens by Fonzies without affe cting that in the prefrontal cortex. Systemic pretreatment with naloxo nazine reduced or, depending on the dose, abolished, the stimulation o f dopamine release in the nucleus accumbens shell by morphine, nicotin e and ethanol, but did not affect that by haloperidol. Naloxonazine al so prevented the stimulatory effects of Fonzies, nicotine and morphine on nucleus accumbens dopamine transmission when infused bilaterally i n the ventral tegmental area. The results indicate that yl opioid rece ptors in the ventral tegmentum play a major role in the stimulant effe cts of food and drugs of abuse on mesolimbic dopamine transmission.