Endocrine Abstracts

Novel object discrimination is a widely used ethologically relevant working memory task. However, there is little information regarding gender differences in performance of this test. The aim of this study was to compare the performance of male and female rats in this task following increasing intertrial intervals.

Subjects were 24 female and 24 male adult hooded-Lister rats (250±10 g) group housed under standard laboratory conditions. Testing consisted of a 3 minute acquisition phase where naive rats explored two identical novel objects followed by a 3 minute, 1, 2 or 4 hour inter-trial interval, when rats were returned to the home cage. Finally in the retention trial, rats explored a familiar and a novel object for 3 minutes. Object exploration is defined by rats licking, sniffing, or touching the object with forepaws whilst sniffing. The discrimination index (DI) for the novel object was calculated and data analysed using a paired t-test.

Following a 3 minute inter-trial interval both sexes spent significantly more time exploring the novel object. Increasing the intertrial interval to 1 hour resulted in a significant (p<0.05) difference between male and female discrimination where females had a higher DI; the increase in DI observed in females was not statistically significant at 2 or 4 hours, Table 1.

Table 1 Discrimination index for male and female hooded-Lister rats at increasing inter-trial intervals; *p<0.05 compared with males.

The results of this study suggest that female rats have enhanced working memory. This effect may be attributable to circulating hormones, possibly oestrogen, which has been shown to influence cognitive function.