Different vulnerability in female's spatial behaviour after unilateral hippocampal inactivation

This study was aimed to determine the effect of unilateral hippocampal inactivation on spatial memory retrieval in male and female Wistar rats. Subjects were chronically implanted with a stainless-steel cannula that enabled unilateral intrahippocampal injections of tetrodotoxin, a sodium channel blocker. Rats were trained during eight consecutive days on the Morris water maze task. On day 1, subjects received a visible platform session. From day 2 to day 7 the hidden platform was located in North quadrant and on day 8 the hidden platform changed to the opposite location. Subjects were randomly distributed into four groups: male saline, male TTX, female saline, female TTX. Saline or TTX was applied 30min before training but only on days 7 and 8. Results showed that males outperform females during the initial training (days 2-6). After TTX injection, both male and female rats were impaired. However, a detailed analysis revealed that the impairment in females was more pronounced, both during the retrieval session (day 7) as well as during reversal (day 8). This data points to a different role of the hippocampus or a different distribution of memories in both sexes.