Comprehensive deficits in performance of an attentional task produced by co-administering alcohol and nicotine to rats

Abstract

Background: Nicotine can improve and alcohol can impair attentional performance in rats, but little is known about the effects of mixtures of the two drugs with respect to attention. Aims: The aims were to investigate the effects of alcohol and nicotine alone and when co-administered on performance of a five-choice serial reaction time task, and to examine the impact of task difficulty by varying durations of the limited hold (LH) for availability of the reinforcer. Methods: Male hooded rats were trained to respond (nose-poke) to a 0.5 s light stimulus presented randomly in one of five apertures to obtain food reinforcers. Three groups of rats trained with different LH values were used ( n=10). Results: The first experiment showed that training at different LH values had little effect on performance when the LH value during testing was held constant. Experiment 2 showed that alcohol (0.4–1.6 g/kg, i.p.) had no effect on the percentage of correct responses (accuracy) but it impaired all speed-related indices. In the third experiment, the effects of nicotine (0.1 and 0.2 mg/kg, s.c.) were determined alone and on the dose-response curve for alcohol (0.4–1.2 g/kg, i.p.). Nicotine alone produced small improvements in performance whereas co-administration of nicotine and alcohol produced large decrements at doses of alcohol that themselves only slightly impaired performance. These decrements included impairments of accuracy as well as of anticipatory responding, omission errors, response latencies and reinforcers earned. There were no marked or consistent interactions of drug effects with LH values. Conclusions: Task performance was disrupted to a much greater extent by co-administration of alcohol and nicotine than by alcohol alone; therefore, it seems unlikely that an ability of nicotine to reverse the effects of alcohol can account for associations between the use of the two substances.