The effects of dopaminergic drugs in the ventral hippocampus of rats in the nicotine-induced anxiogenic-like response

Nicotine an active alkaloid of tobacco has dopaminergic properties. The drug alters anxiety-like behavior in rodents. Ventral hippocampus (VHC) may be a site for modulation of anxiety-like behaviors. The possible involvement of ventral hippocampal dopaminergic receptor mechanism in the nicotine influence on anxiogenic-like response has been investigated in the present study. The effects of apomorphine, sulpiride and SCH23390 on nicotine response in elevated plus maze in rats have been investigated. Intraperitoneal administration of nicotine (0.6 mg/kg) decreased percentage of open arm time (%OAT) but not percentage of open arm entries (%OAE) and locomotor activity, indicating an anxiogenic-like response. Intra-hippocampal injection (intra-VHC) of apomorphine, a D1/D2 dopamine receptor agonist (0.1 and 0.2 μg/rat) also caused anxiogenic-like effects, but the drug blocked that of nicotine. Intra-VHC administration of the D2 receptor antagonist, sulpiride (1, 2.5 and 5 μg/rat) or the D1 receptor antagonist, SCH23390 (0.01, 0.1 and 1 μg/rat) did not elicit any response. However, pretreatment with sulpiride (1 μg/rat) or SCH23390 (0.1 μg/rat) decreased nicotine's effect. The results may indicate a modulatory effect for the D1 and D2 dopamine receptors of VHC in the anxiogenic-like response induced by nicotine.