Effects of chronic nicotine administration on the response and adaptation to stress.

The effects of chronic nicotine administration (0.4 mg/kg for 40 days) and its withdrawal on the adrenocortical response to acute and repeated exposure to stress have been examined and related to changes in brain 5-hydroxyindole levels. No significant effects on the response to acute stress were observed. Repeated exposure to the stressful procedure resulted in complete adaptation of the adrenocortical response and the development of a significant (P less than 0.01) positive correlation between the plasma corticosterone and hippocampal 5-HT concentrations. In nicotine-treated rats, complete adaptation did not occur and the plasma corticosterone showed a significant (P less than 0.05) negative correlation with hippocampal 5-HT. Nicotine withdrawal was not associated with any reduction in plasma corticosterone, but did abolish its relationship with hippocampal 5-HT.