Nicotine increases behavioral variability on radial arm maze extinction. A preliminary study

Abstract

Behavioral variability (BV) is proposed as a general adaptation process to environmental changes related to adjustments for the search of reinforcement sources. During extinction procedures, BV is reflected by increases of the number, topography, or sequences of behaviors. Inhibitory drugs have been found to decrease BV during radial arm-maze extinction procedures. The present research explores the effect of an excitatory drug, nicotine, on BV. Chronic and acute administration of 0.04 mg/kg of nicotine were evaluated for Radial Arm-Maze acquisition and extinction procedures. Both chronic and acute nicotine during extinction diminished behavioral indicators of accuracy and performance. In addition, chronic nicotine administration, but not acute, improved the pattern of acquisition in the task. Nicotine effects during extinction are interpreted in terms of BV-related dimensions and enhancement for the search of potential novel reinforcement sources after the loss of learned reinforcement places. Interestingly, the present nicotine effects on BV, opposite to previous reports using inhibitory drugs, suggest the hypothesis that excitatory and inhibitory drugs might differentially affect general BV neurochemical mechanisms for Radial Arm- Maze extinction.