The Effect of Luteinizing Hormone Reducing Agent on Anxiety and Novel Object Recognition Memory in Gonadectomized Rats

Introduction: Mood disorders such as anxiety and depression are common following menopause and andropause. The lack of sex steroid hormones is suggested as the primary cause of these disturbances. The level of luteinizing hormone (LH) would also rise 3-4 times than normal in these people. The potential effects of LH on mood and cognitive symptoms following menopause and andropause are not clear yet. This study aimed to investigate the effect of increased LH on novel object discrimination (NOD) memory and anxiety like behavior in gonadectomized rats. Methods: Four-month-old male and female Wistar rats were randomly assigned into 4 groups (in each sex): Control rats (Cont), gonadectomized without treatment (GnX), gonadectomized treated with triptorelin (a GnRH agonist which decreases LH release) (GnX+Tr), gonadectomized treated with triptorelin plus sex steroid hormone, estradiol in female and testosterone in male rats (GnX+Tr+S/T). After 4 weeks treatment, anxiety score (elevated plus maze) and NOD were measured. Data were analyzed using 1- way ANOVA, and P values less than 0.05 were considered as significant. Results: Gonadectomy increased anxiety like behaviors (decrease of presence time in the open arms) in female rats (P=0.012), but not in male ones (P = 0.662). Additionally, triptorelin alone reduced the increased anxiety score in gonadectomized female rats, compared to group treated with both triptorelin and estradiol. Furthermore, it was shown that gonadectomy and or treatment with triptorelin and sex steroids had no significant effect on the new object recognition memory in both female (P = 0.472) and male rats (P = 0.798). Conclusion: On the whole, this study revealed that increased level of LH following menopause or andropause should be considered as a possible cause for increased anxiety. Also, this study showed that LH reducing agents would reduce anxiety behavior in gonadectomized female rats. The effect of increased LH on cognitive functions such as new object recognition memory was not evident in this study needs further studies and should be interpreted with caution.