Adrenalectomy attenuates nicotine-induced dopamine release and locomotor activity in rats

Adrenalectomy (ADX) in mice can potentiate several physiological and behavioural responses to nicotine. The present experiments sought to examine this issue in this rat by characterising the influence of ADX upon the locomotor depressant, activating and dopamine-releasing properties of nicotine. Nicotine (0.8-1.2 mg/kg s.c.) dose-dependently depressed locomotor activity, an effect that was potentiated by ADX, while the locomotor activating effects of a smaller dose (0.4 mg/kg) were attenuated by ADX. In both SHAM and ADX rats chronically treated with nicotine for 5 days (daily injections of 0.4 mg/kg s.c.), the locomotor depressant effects of nicotine did not differ from saline-treated controls. Nicotine (0.4 mg/kg s.c.) increased extracellular levels of dopamine in the nucleus accumbens. This response was unaffected in rats pretreated with nicotine for 5 days (daily injections of 0.4 mg/kg s.c.). However, both ADX groups of rats showed smaller increases in dopamine following administration of nicotine. The results suggest that depletion of circulating corticosteroids can modulate sensitivity to nicotine in rats. The suppressant effects of ADX on nicotine-induced locomotor activity may be due to its effects on dopamine release in the nucleus accumbens.