Strain differences in the acquisition of nicotine-induced conditioned taste aversion

Lewis (LEW) and Fischer (F344) rat strains differ on a variety of physiological and behavioral endpoints, including reactivity to drugs of abuse. Although they differ in drug reactivity, such assessments are generally limited to morphine and cocaine. To determine if these differences generalize to other drugs, the present study examined these strains for their reactivity to the affective properties of nicotine, specifically their sensitivity to nicotine in the conditioned taste aversion preparation. For four or five conditioning cycles given every other day, rats from both strains were allowed access to saccharin and injected with nicotine (0.1, 0.4, 0.8 mg/kg) or vehicle. On intervening days, all rats were given access to water and injected with vehicle. Under this one-bottle training and testing procedure, neither strain displayed aversions at the lowest dose of nicotine (0.1 mg/kg). Aversions were evident for both strains at 0.4 and 0.8 mg/kg, although the F344 rats acquired the aversions at 0.4 mg/kg faster and displayed a significantly greater aversion at 0.8 mg/kg than subjects from the LEW strain. For both strains, aversions were evident at all doses (and in a dose-dependent manner) when subjects were given access to saccharin and water in a two-bottle test. There were, however, no strain differences on this test. Differences between the two strains in their acquisition of nicotine-induced taste aversions were discussed in the context of aversion assessments with other compounds as well as in relation to differences in the self-administration of nicotine in the two strains.