Search

Utilizing an automated, Dashiell-type hexagonal maze, it was demonstrated that RHA rats: 1) were more active, 2) reversed direction more often, 3) entered radial (blind) alleys less often, and 4) displayed shorter latencies than did RLA rats. Direction reversals (U-turns) tended to increase from day to day with the RHA rats, whereas the opposite was true for the RLA rats. Nicotine injections (0.2 mg/kg) increased activity and the number of U-turns, shortened the latencies and lessened the likelihood of entering radial alleys for both strains. The RHA rats were more sensitive to nicotine than were the RLA rats in all of these measurements, which varied, depending upon alley length and structural complexity, among the maze configurations.

The effects of nicotine and amphetamine were found to be dependent on genetic variables. Nicotine produced a stimulant effect on exploratory behavior, while amphetamine produced stereotyped behavior patterns.

Separate groups of two different rat breeding lines, Roman High Avoidance (RHA/Verh.) and Roman Low Avoidance (RLA/Verh.), treated with either saline, nicotine (0.2 mg/kg), or amphetamine (0.4 mg/kg) were compared for exploratory efficiency and for exploratory locomotion by using two different mazes on alternate testing days. The RHA/Verh. rats generally showed more locomotion but less intermaze transfer of exploratory efficency than the RLA/Verh. rats. Nicotine did not alter exploratory efficiency but stimulated locomotor activity in the RHA/Verh. rats, while it did not significantly alter either category of behavior in the RLA/Verh. rats. Amphetamine stimulated locomotor activity in both rat lines but this stimulation was weaker in comparison with that of nicotine. In contrast to nicotine, amphetamine impaired exploratory efficiency in the RHA/Verh. rats. Like nicotine, amphetamine did not significantly affect exploratory efficiency in the RLA/Verh. rats. The results demonstrate that, when the two lines of rats are compared, there is a dissociation of the two categories of behavior and a further differentiation between nicotine and amphetamine effects.