Gender Difference in Memory Functions following Long Term Tryptophan Supplementation in Rats

Evidence shows that tryptophan (TRP) and serotonin (5HT) have a role in memory function. It has been shown in various studies that increase in serotonergic neurotransmission is associated with increased memory consolidation whereas low brain 5HT impairs memory performance. In view of a possible role of TRP and 5HT in memory, the present study was designed to investigate the effect of TRP supplementation on male and female rats and to investigate sex related differences in memory processes. Tryptophan at a dose of 100mg/kg was used. Short term memory (STM) and long term memory (LTM) were evaluated using the Morris water maze. TRP treatment for 6 weeks significantly enhanced STM of female rats but it did not have any effect on the STM of male rats. Female rats when compared with male rats exhibited better performance in the Morris water maze and enhanced memory was observed both before and after TRP treatment, however after TRP treatment a greater improvement was observed. Both male and female rats exhibited improvement in LTM following TRP treatment. The present results emphasize on the involvement of sex difference and 5HT in learning and memory processes. A greater increase in 5HT metabolism and turnover seen in female rats correlates with the enhanced memory function observed in females than male rats.