Ontogeny of two-way avoidance in male and female rats

In Experiment I, 17-, 21-, 36-, 51-, 90-, and 200-day-old male and female rats were given a single session of 100 two-way avoidance (TWA) trials. In the 2nd experiment, males and females of these ages and 15 and 28 days of age that were obtained from a different source, weaned at a later age, and housed differently received TWA training. Results of both studies showed that avoidance of 15-, 17-, and 21-day-old rats is low, but avoidance increases from 21 to 51 days of age. Avoidance of 95- and 200-day-old animals was generally lower than 51-day-old rats. No significant gender differences appeared until 90 days of age; at this age avoidance of males was lower than females. In Experiment III, CS intensity was varied and the US intensity was lower than that used in Experiment I and II. Avoidance of 21- and 90-day-old rats was higher with a more intense CS, but 21-day-olds were still lower than adults. Avoidance of 17-day-old rats was not affected by CS intensity.