7-Nitroindazole blocks nicotine-induced conditioned place preference but not LiCl-induced conditioned place aversion.

We have shown previously that the neuronal nitric oxide synthase (nNOS) is involved in the rewarding effect of cocaine as determined by the conditioned place preference (CPP) paradigm. In the present study we investigated the effect of the nNOS inhibitor 7-nitroindazole (7-NI) on nicotine-induced CPP and LiCl-induced conditioned place aversion (CPA) in Swiss Webster mice. Mice treated with nicotine (0.5 mg/kg) or saline every other day for 8 days (four drug and four saline sessions) developed CPP that was completely blocked by pretreatment with 7-NI (25 mg/kg). Mice treated with LiCl (150 mg/kg) developed marked aversion to the LiCl-paired compartment. LiCl-induced CPA was not affected by the pretreatment with 7-NI. These findings suggest that nitric oxide (NO) plays a role in the acquisition of reward but not of aversion and that the blockade of nicotine-induced CPP is probably not due to impairment of learning and memory.