Chronic caffeine exposure in rats blocks a subsequent nicotine-conditionedtaste avoidance in a one-bottle, but not a two-bottle test

Two experiments were conducted in order to investigate nicotine-conditioned taste avoidance (CTA) following chronic preexposure to caffeine. Rats were given daily intraperitoneal injections of caffeine anhydrous (0, 10, or 30 mg/kg) for 10 or 30 days. Training of the nicotine-CTA began after the las t day of caffeine preexposure. On five separate occasions access to a sacch arin solution was followed immediately by an injection of 1.2 mg/kg nicotin e hydrogen tartrate salt or saline. Nicotine-CTA readily developed in salin e-preexposed controls. That is, paired rats drank less saccharin solution t han unpaired rats after repeated saccharin-nicotine pairings. A similar pat tern of nicotine-CTA was found for rats preexposed to 30 mg/kg caffeine for 10 days. Following 10 days of preexposure to 10 mg/kg caffeine, however, C TA did not develop under standard testing conditions. Thirty days of caffei ne preexposure did not affect the development of a nicotine-CTA even though the anorexic effects of caffeine were evident after exposure to 30 mg/kg f or this duration. Thus, caffeine exposure appears to weaken acquisition or expression of the conditioned avoidance properties of nicotine. This effect is sensitive to the dose of caffeine and duration of preexposure. Importan tly, the pattern of nicotine-CTA does not appear to be due to nonspecific e ffects of caffeine. (C) 2001 Elsevier Science Inc. All rights reserved.