Further studies on nicotine-induced conditioned place preference in the rat

Abstract

Rats received subcutaneous (SC) injections of either nicotine (NIC, 0.001 to 2.0 mg/kg) or saline (SAL, 1 ml/kg) immediately prior to conditioning sessions in a conditioned place preference (CPP) paradigm. NIC was paired for 3 conditioning sessions with one environment of a 3 compartment CPP apparatus; SAL was paired with another environment. The animals were then tested for place preference by determining the proportion of time spent in each compartment during a 15 min test session. A dose-response curve was obtained for the place conditioning effect of nicotine as measured by its ability to alter baseline preferences calculated from control rats NIC's place preference, but not place aversion, effect was linearly correlated with respect to dosage within the range of 0.1 to 0.8 mg/kg. NIC, 0.8 mg/kg, induced a place preference when it was administered immediately prior to conditioning sessions, but not when administered 20, 60 or 120 min prior to the sessions. Three repeated conditioning and testing cycles, or the daily administration of NIC for 2 weeks between conditioning and testing cycles had little or no effect on NIC place conditioning. Lobeline (2, 10 and 20 mg/kg) or cotinine (1 to 50 mg/kg) failed to condition a place preference. NIC, 0.1 or 1.2 mg/kg SC, administered to rat pups on postnatal days 5 through 8, did not alter subsequent place preference (induced by 0.8 mg/kg of NIC) measured at approximately 40 and 70 days of age. Periodic measurements of spontaneous motor activity, forelimb grip strength and negative geotaxis were unaltered by the perinatal exposure to nicotine.