Facilitation of a distributed shuttle-box conditioning with posttraining intracranial self-stimulation in old rats

Old Wistar rats (16-17 months) were trained in a two-way active avoidance task for 5 consecutive days (10 trials/day). Immediately after each training session a lateral hypothalamic intracranial self-stimulation session (ICSS group) or a sham-treatment session (Control group) was given to the animals. Long-term retention was tested 7 days after the last acquisition session. ICSS treatment led to a significant improvement in acquisition. In the long-term retention session the level of avoidance in both groups was similar to that achieved in the last acquisition session, although differences among groups failed to reach statistical significance. These results are compared with those obtained in previous experiments with young adult rats. While ICSS facilitated the process of acquisition in both young and old rats (however, it was much more powerful in young animals), further experiments are needed to elucidate whether this effect is long-lasting in old rats, as occurs in young adult subjects.