Conditioning of nicotine effects on motility and behaviour in rats

Nicotine produces behavioural signs which are, in part, characteristic of dopaminergic activation. In the present study, it was investigated, to which degree these signs can be conditioned. The drug produced dose-dependent (0.15-0.60 mg/kg s.c.) increases in locomotor activity, hyperkinesia and stereotyped sniffing. The effects produced by 0.6 mg/kg nicotine were significantly inhibited by mecamylamine (1 mg/kg i.p.), but only in part by haloperidol (0.2 mg/kg i.p.). In a subsequent series, the administration of nicotine (0.6 mg/kg s.c.) was repeatedly associated with well-defined environmental (conditioned) stimuli: a wire cage associated with an auditory and an olfactory stimulus. Another group was pseudoconditioned, a third group remained drug-naive. When the animals were given saline in presence of the conditioned stimuli 24 h after the last conditioning session, locomotor activity, hyperkinesia and stereotyped sniffing were significantly higher in conditioned than in pseudoconditioned and drug-native rats. Similarly, when the rats were injected with nicotine (0.6 mg/kg s.c.) in presence of the conditioned stimuli 24 h after the last conditioning session, locomotor activity and stereotyped sniffing were most pronounced in the conditioned animals. These results demonstrated that behavioural effects of nicotine can be conditioned. Phenomena of this kind might contribute to the addictive behaviour to nicotine.