The objectives of the present study were to examine the effects of acute and chronic nicotine on dopamine (DA) release in the ventral tegmental area (VTA) of Long-Evans rats using in vivo microdialysis. Systemic application of acute nicotine (0.1-0.3 mg/kg, s.c.) significantly increased (145% of baseline) DA release in the VTA. Chronic exposure to nicotine (0.3 mg/kg, s.c.) for 5 days followed by a challenge dose of nicotine (0.3 mg/kg, s.c.) also produced significant enhancement (136% of baseline) of DA release in the VTA. The results suggest that both acute and chronic nicotine treatment exert stimulatory effects on somatodendritic DA release in the VTA. The enhancement of DA release to subsequent challenge nicotine may be susceptible to mild desensitization.