P and NP rats respond differently to the discriminative stimulus effects of nicotine

Rats selectively bred for ethanol preference, that is, alcohol-preferring (P) and -nonpreferring (NP) rats, were trained to discriminate the interoceptive stimuli produced by IP-administered 1,000 mg/kg ethanol (10% v/v) in a two-lever, food-motivated, operant task. Once criterion performance was attained, dose-response experiments indicated an ED50 value for P rats = 354.1 mg/kg, whereas NP rats generated an ED50 value of 495.1 mg/kg, not significantly different from each other. In contrast to these similar sensitivities to ethanol, administration of doses of nicotine (0.4-1.2 mg/kg, SC) indicated that P rats were significantly more sensitive to the ethanol-like effects of nicotine than were NP rats. The results provide additional evidence for a possible hereditary co-occurrence of alcohol and nicotine sensitivity.