Nicotinic acetylcholine receptor (nAChR) antagonist blockade of pretreatment effect on cocaine self-administration. Adolescent rats were pretreated intravenously with the selective nAChR antagonists, DHβE (3β-1,6-didehydro-14,17-dihydro-3-methoxy-16(15H)-oxaerythrinan-15-one hydrobromide) (2 mg/kg) or MLA (1α,4(S),6β,14α,16β-20-Ethyl-1,6,14,16-tetramethoxy-4-[[[2-(3-methyl-2,5-dioxo-1-pyrrolidinyl)benzoyl]oxy]methyl]aconitane-7,8-diol citrate salt) (1 mg/kg), or vehicle before daily nicotine pretreatment. Nicotine pretreatment enhanced responding for cocaine compared with saline-treated rats, **p<0.005. Pretreatment with either DHβE or MLA blocked the nicotine-enhanced self-administration behavior, ##p<0.003, but had no effect on saline treatment. n=8–10 per group.