Administration of LHRH analog can improve working memory in aged female rats.

We had previously found that an age-related deficit in working memory appeared in middle-aged females, possibly related to their ageing reproductive system. This experiment investigates the effect of administering an analog of luteinizing hormone-releasing hormone (LHRH), D-Trp6-LHRH, to 22-mo-old female rats submitted to successive trainings in a water-reinforced matching to sample task since the age of three months. Animals were injected SC with a long-lasting microcapsule formulation (800 micrograms/kg continuously releasing 5 micrograms D-Trp6-LHRH per day for at least 28 days). The action of the analog on ovary weight and estradiol and progesterone levels was also studied. Administration of D-Trp6-LHRH counteracted the deleterious effect of age on performance and inhibited ovary function. However, hormone plasma levels were not modified. These results suggest that the hypothalamo-ovarian axis might be implicated in memory deficits of middle-aged females.