Abstract
We examined the effects of preoptic knife cuts on estrogen-induced facilitation of locomotor activity in ovariectomized rats to study the possible involvement of the preoptic area in the facilitation of activity. Animals housed in a cage with a running wheel received ovariectomy and one of the following brain surgeries : anterior cut (AC), posterior cut (PC), or dorsal cut (DC) of the preoptic area. Running activity was significantly suppressed following the ovariectomy. The activity of animals with DC was significantly lower than that of the ovariectomized controls. One week after the surgery, they were treated with estradiol-17β using silastic capsules. Recovery of activity in the running wheel was found in animals with AC and in the controls, but the activity was still lower in both PC and DC animals. Open field tests were also carried out on 3 consecutive days starting on the 5th day following the treatment of estrogen. Only DC animals showed significantly lower activity in the open field tests than control animals. These results indicate that facilitation of wheel-running and open field activities by estrogen may be related to different neural mechanisms in the rat forebrain, and the preoptic area may be actively involed in estrogen-induced facilitation of wheel-running but not of open field activity.
