To assess the effects of long-term treatment with nicotine on several behavioral measures (locomotor activity, exploratory efficiency, habituation, short-term and long-term memory) of young (5 months) and old (22 months) rats in a hexagonal tunnel maze, nicotine was added to the drinking water (0, 20 or 50 mg/l) for up to 131 experimental days. With the exception of effects on exploratory efficiency, young and old rats did not differ in their response to the drug. Nicotine decreased body weight throughout the experiment. Nicotine treatment reduced water intake during the first 30 min of the daily 4.5 h access to drinking water. Nicotine increased locomotor activity throughout the experiment. When nicotine treatment was discontinued during a 7-day withdrawal period, locomotor activity immediately dropped to control values. Intertrial habituation was not affected by nicotine. Long-term nicotine treatment had an attenuating effect on exploratory efficiency in young rats; however, the drug did not influence performance in tasks measuring spatial memory. Finally, age increased weight, decreased locomotor activity and impaired exploratory efficiency and short-term memory. Age, however, did not affect the performance of the long-term memory task.

No abstract

The effects of foodreward on rats' behavior in radial and Dashiell tunnel mazes were examined in two experiments. In the first, with animals at ad-lib body weights, food reward reduced speed of movement at the food locations, but did not affect the patterns of movement in either maze. Exploratory efficiency in the Dashiell maze was unaffected by foodreward, and spontaneous patrolling of the radial maze by the nonrewarded animals was comparable to the behavior, reported by others, of rats running for food reward on elevated eight-arm mazes. In the second experiment, with subjects maintained at 80% of ad-lib body weights, there was some evidence for "winstay" learning: food-rewarded rats in the Dashiell maze were relatively more active near the food locations than were the nonrewarded animals, and more rewarded than nonrewarded rats revisited all foodlocations in the radial maze. Nonetheless, exploratory efficiency in the Dashiell maze was unaffected by food reward, as was patrolling efficiency in the radial maze, which was again comparable to that of rats on elevated mazes. The similarity in behavior of rewarded and nonrewarded animals in these mazes implies that the major determinant of their behavior, whether or not food reward is provided, is a spontaneous tendency to avoid places recently visited.

Male rats of two lines of rats psychogenetically selected and bred for extremes in performance in shuttle box avoidance received an acute IP injection of chlordiazepoxide (CDP; 2.5, 5.0, 10.0 mg/kg), imipramine HCl (IMI: 0.33, 1.0, or 3.0 mg/kg), or vehicle. The rats were placed, 35 min after injection, in an enclosed maze with either a simple configuration with an unilluminated central arena or a complex configuration with a brightly illuminated central arena, and spontaneous maze patrolling was evaluated. Total locomotor activity during the 6-min maze test was significantly reduced by 5--10 mg/kg CDP for both RHA/Verh and RLA/Verh lines of rats in both the simple and the complex maze configurations. Treatment with 10 mg/kg CDP reduced the total explored area for both rat lines in both maze configurations. In addition, the maze area explored by RHA/Verh rats was also reduced by 5.0 mg/kg CDP for the simple configuration and by 2.5 and 5.0 mg/kg CDP for the complex configuration. Entry into the unilluminated central field of the simple maze was reduced by 5--10 mg/kg CDP only in RHA/Verh rats. In contrast, 2.5 mg/kg CDP significantly increased entry into the brightly illuminated central arena of the complex maze for the RLA/Verh rats. The doses of IMI used were without effect on the parameters of maze patrolling behavior evaluated, with the single exception that the locomotor activity of RHA/Verh rats tested in the simple maze configuration was decreased by 3.0 mg/kg IMI. The results indicate that, although the effects of CDP were generally similar for total activity and the area explored in the two psychogenetic lines investigated, there was a qualitative difference in its effect on entry into an illuminated arena.

No abstract