Nicotine enhancement of contextual fear conditioning

Nicotine has been suggested to have cognitive enhancing effects. The presen t study examined the effects of nicotine and the nicotinic antagonist mecam ylamine on contextual fear conditioning in C57BL/6 mice. The fear condition ing task was chosen because the task examines two types of learning: contex tual learning, and conditioned stimulus (CS)-unconditioned stimulus (US) le arning. Multiple doses of nicotine were tested and 0.5 mg/kg nicotine, give n on both training and testing days, improved contextual learning but had n o effect on formation of an auditory CS-US association. No effect was found at lower doses or when nicotine was given on training day only, or testing day only. The nicotinic receptor antagonist mecamylamine (1 and 2 mg/kg) d id not alter contextual fear conditioning but mecamylamine did prevent the nicotine-associated increase in contextual learning. A higher dose of nicot ine (1 mg/kg, training day only) interfered with contextual conditioning wh en the context was paired with both the CS and US, but had no effect on the auditory CS-US association. This effect of 1 mg/kg nicotine on contextual learning disappeared when mice were trained without the CS. The present res ults indicate that nicotine enhancement of contextual fear conditioning is dose-dependent, but the presence of nicotine is required both during traini ng and testing. (C) 1999 Elsevier Science B.V. All rights reserved.