Effects of selective dopamine receptor and nicotinic acetylcholine receptor antagonists on nicotine-induced changes in neurotensin-like immunoreactivity (NTLI) content in the ventral tegmental area. Animals were given 5 administrations of (±) nicotine (N; 0.8 mg/kg/injection, i.p., 2-h intervals) or saline (S; control), alone or 15 min after administration of SCH 23390 (SCH; dopamine D1 receptor antagonist; 0.5 mg/kg/injection, i.p.), eticlopride (ETI; dopamine D2 receptor antagonist; 0.5 mg/kg/injection, i.p.), or mecamylamine (MEC; nicotinic acetylcholine receptor antagonist; 3.0 mg/kg/injection, s.c.). Animals were killed 18 h following the last treatment. Values represent the means ± S.E.M. expressed as percentages of control (n= 8 control and 9 drug-treated animals per group). The control value ± S.E.M. for NTLI concentrations (pg/mg protein) was 403 ± 65. *P < 0.05 vs. saline control; †P < 0.05 vs. corresponding nicotine group.