Facilitation of shuttle-box avoidance by the platform method: temporal effects.

Two experiments were carried out in order to 1) replicate a previous finding according to which the treatment on large platforms (commonly used as control for the stress induced by smaller paradoxical sleep deprivation platforms) can facilitate the acquisition and long-term retention (LTR) of a distributed shuttle-box avoidance in rats, and 2) further examine the temporal conditions in which that facilitation can be observed. The results showed that an immediate posttraining treatment lasting 6 hours induced a significant improvement of acquisition both when applied in the light (8 a.m.) and in the dark cycle (8 p.m.), while the LTR (10 and 31 days) seemed to be better preserved when the treatment was applied during the dark cycle. A shorter treatment (3 h) had no effect upon shuttle-box avoidance, regardless of whether it was applied in the dark or in the light cycle and whether it was immediate or delayed for 3 h. In summary, under certain temporal conditions, a posttraining immediate treatment on large platforms can facilitate the acquisition and/or the LTR of shuttle-box avoidance. Stress hormones and/or the enhancement of CNS arousal are suggested to be some of the mechanisms operating in this facilitatory effect.