EFFECT OF AGE AND ESTRADIOL ON FINE MOTOR SKILLS IN FEMALE RHESUS MONKEYS





A. Lacreuse*, J.G. Herndon

Division of Neuroscience, Yerkes Regional Primate Research Center, Emory University, Atlanta, GA 30322



Aging is characterized by a progressive deterioration of motor functions related to dysfunctions of the nigrostriatal system. Because estrogens have been reported to protect dopaminergic neurons and to improve the motor deficits associated with Parkinson’s Disease, we hypothesized that they would partially reverse age-related decline of motor function in normal aging. We tested this hypothesis in a rhesus monkey model of human menopause. We examined the effects of estrogen treatment and withdrawal on fine motor performance in five aged (21-24 years old) and five young (6-9 years old) ovariectomized female rhesus monkeys. The motor tests required the monkeys to use each hand in order to retrieve a lifesaver candy from three metal rods bent in shapes of different complexity (straight, double S and question mark). Monkeys were tested twice a week for eight consecutive weeks, while treated with placebo and ethinyl estradiol (EE2) in alternating 14-days blocks. Each behavioral test was videotaped and subsequently reviewed to score motor performance. Two main dependent variables were analyzed: the duration and the success of each trial. Although the monkeys were allowed as many as 5 attempts to retrieve the candy on a particular shape, we limited the analysis to the first of these, as successive attempts to retrieve the candy may have reflected motivational levels rather than motor ability. We found that both groups of monkeys improved rapidly with practice both in speed and accuracy of retrieval. The young monkeys were faster than the older monkeys, but were not more successful in retrieving the candy at the first attempt. The left hand was faster than the right hand for both the aged and young females. We failed to detect any effect of EE2 treatment on speed or accuracy in either group These results confirm the slowing of fine motor performance with aging in female rhesus monkeys. They also indicate that estradiol, at least as administered in this study, does not benefit fine manual performance. Future studies should investigate whether longer duration of estrogen treatment is necessary to improve hand function. Supported by NIH grants AG 18998, MH 59243 and RR 00165.




Key words: aging/ estrogen/ manual performance/ ovariectomy/ menopause







Problems or questions regarding this site should be directed to webmaster@americanaging.org