Effects of voluntary alcohol intake on nicotine-induced behavioural sensitisation in rats

Behavioural sensitisation has been suggested to play a role in the acquisition and maintenance of addictive behaviour. The aim of the present study was to assess nicotine-induced behavioural sensitisation in chronic voluntary alcohol drinking rats. Subjects had free access to alcohol/water or glucose/water solutions since weaning. Rats were pretreated after 2 months of voluntary alcohol drinking. Pretreatment consisted of once-daily intraperitoneal injection of nicotine (0.5 mg/kg) or saline administered for five consecutive days. The nicotine-induced behavioural sensitisation of locomotor activity was tested 3 weeks latter. Horizontal motor activity was monitored for 30 min and expressed as distance travelled (in centimetres). During all the experimental procedure, the animals were maintained under 1-h limited access to alcohol. In glucose-drinking animals, results indicated that nicotine induced locomotor activity sensitization: The locomotor effects of nicotine challenge in the nicotine-pretreated group of rats were significantly enhanced as compared with the saline-pretreated group (Duncan, P<.01). Instead, in the alcohol-drinking animals, no significant differences were observed between the nicotine- and saline-pretreated groups. Thus, chronic alcohol consumption at mild doses prevented the development and/or the long-term expression of the nicotine-induced sensitisation at the doses tested.