Nicotine in an animal model of attention

Studies in smokers have suggested that at least part of the improved psycho motor performance produced by nicotine is the result of an effect on attent ion. Many animal experiments have assessed the effects of nicotine and its antagonists on diverse types of learning and memory but relatively few have looked at it in tasks designed to assess attention. In a five-choice seria l reaction time task (5-CSRTT), rats with restricted access to food were pr esented with an array of five holes; illumination of a randomly selected ho le signalled that a nose-poke into it would be reinforced by food presentat ion. Initially, signal length and the inter-trial interval (ITI) were varie d and the procedure was demonstrated to satisfy some criteria for a vigilan ce task. The effects of nicotine on deficits in performance induced by vary ing signal length and ITI were assessed. Under appropriate conditions, smal l doses of nicotine increased the percentage of correct responses (accuracy ), decreased omission errors and reaction time, and increased anticipatory responses. Subsequently, the effects of varying the ITI were examined more extensively in a slightly modified task. Here, nicotine produced small but robust, highly significant dose-related increases in accuracy, as well as d ecreases in omission errors and reaction times. Nicotine also increased acc uracy when light stimuli were presented in an unpredictable manner. The nic otine antagonist mecamylamine produced a modest deficit in reaction time on ly. It is concluded that appropriate doses of nicotine can produce robust i mprovements in performance of normal rats in an attentional task. The effec t cannot be attributed easily to changes in sensory or motor capability, le arning or memory and may provide the measures needed to investigate the neu ropharmacological and neuroanatomical bases of the elusive attentional effe ct of nicotine. (C) 2000 Elsevier Science B.V. All rights reserved.