Involvement of rat dopaminergic system of nucleus accumbens in nicotine-induced anxiogenic-like behaviors.

The objective of the present study was to investigate the involvement of dopamine D₁ and D₂ receptors of the nucleus accumbens (NAc) shell in the anxiogenic-like effect of intra-central amygdala (CeA) nicotine administration. Male Wistar rats with cannula implants in the left CeA and the left shell of NAc were submitted to the elevated plus-maze (EPM). Intra-CeA injections of nicotine (1 μg/rat) decreased % open arm time spent (%OAT) but not % open arm entries (%OAE) and locomotor activity, indicating the possibility of an anxiogenic-like response. Intra-NAc injection of D₁ dopamine receptor antagonist, SCH23390 (0.5 μg/rat) but not other doses of the antagonist (0.06, 0.125 and 0.25 μg/rat) increased both %OAT and %OAE, showing an anxiolytic-like effect for the higher dose of the drug. Similar administration route of sulpiride (0.25, 0.5, 0.75 and 1 μg/rat), a selective antagonist at dopamine D₂ receptor, had no significant effect on OAT%, OAE% and locomotor activity. Moreover, intra-CeA injection of nicotine (1 μg) with intra-NAc injection of sub-threshold doses of antagonists increased %OAT and %OAE without significant effect on locomotor activity. These findings may suggest the involvement of dopamine transmission, through D₁ and D₂ receptors of NAc shell, in the anxiogenic-like effect of nicotine in the EPM task.