Effects of tunnel maze complexity on caffeinic hyperactivity in the rat.

The study investigated effects of caffeine on spontaneous tunnel locomotion without consummatory reward. The stimulant effects consisted in delayed intrasession habituation, and they differed in magnitude according to dosage and the complexity of the tunnel arrangements. In a simple hexagonal tunnel without choice points, 16 mg/kg BW produced greater stimulation than other doses, and this most efficient dose became less effective if tunnels were arranged according to the radial maze paradigm. No stimulation was obtained if an open field was incorporated into the maze. Caffeine also had no effect on open field behavior, but it tended to improve the efficiency of radial arm maze patrolling, and its significantly depressed exploration of short tunnel arms branching from the radial arms in favor of exploration of the more distant radial tunnel ends.