ADRENALECTOMY ATTENUATES NICOTINE-INDUCED DOPAMINE RELEASE AND LOCOMOTOR-ACTIVITY IN RATS

Adrenalectomy (ADX) in mice can potentiate several physiological and b ehavioural responses to nicotine. The present experiments sought to ex amine this issue in the rat by characterising the influence of ADX upo n the locomotor depressant, activating and dopamine-releasing properti es of nicotine. Nicotine (0.8-1.2 mg/kg SC) 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 attenu ated by ADX. In both SHAM and ADX rats chronically treated with nicoti ne for 5 days (daily injections of 0.4 mg/kg SC), the locomotor depres sant effects of nicotine did not differ from saline-treated controls. Nicotine (0.4 mg/kg SC) 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 SC). However, both ADX groups of rats showed smaller increases in dopamine followin g administration of nicotine. The results suggest that depletion of ci rculating corticosteroids can modulate sensitivity to nicotine in rats . The suppressant effects of ADX on nicotine-induced locomotor activit y may be due to its effects on dopamine release in the nucleus accumbe ns.