A possible role for the pituitary-adrenal system in the effects of nicotine on avoidance behaviour

Rats were trained on a Sidman lever-pressing avoidance task. Half the animals received 0.4 mg nicotine/kg before each avoidance session. Rats which were successful performers had heavier adrenal glands. Nicotine facillitated avoidance and increased adrenal weight. Successful avoiders also tended to have higher hippocampal 5-HT levels. Hypothalamic 5-HT was elevated in animals which had just received many shocks during the final avoidance session but not in rats which had received a comparable number of unavoidable shocks. No effects of nicotine on noradrenaline or corticosterone were detected nor were these measures related to avoidance performance.