Abstract
In an earlier report(l), we were able to demonstrate that implants of either testosterone or estradiol in the median eminence (ME) could decrease the weights of the accessory sex organs in the male rat. These same implants frequently evoked adrenal enlargement and the implants of estradiol produced an enlargement of the anterior pituitary gland. Some of these effects could also be obtained by implantation of the steroids in. the anterior pituitary itself or in the mammillary bodies, but implants in other hypothalamic areas were usually ineffective. The conclusion was drawn that these gonadal steroids acted locally in the hypothalamo-hypophyseal region to inhibit gonadotrophin secretion and to stimulate the release of ACTH. It appeared of interest to determine if similar relationships existed in the female, and the present report describes the results of experiments in which implants of estradiol or testosterone were located in various hypothalamic areas or in the pituitary gland of female rats.
Methods. The experimental animals in this study were female, Sherman rats which weighed 220-300 g. The animals were divided into 3 groups. The first was a group of normal controls sacrificed at 4 stages of the cycle. The other 2 groups of rats were implanted in various loci of the hypothalamo-pituitary region with either gonadal steroids or cholesterol to serve as a control on the possible non-specific effects of the implantation procedure and the implants themselves. For each group implanted with testosterone or estradiol-17B, a group of animals from the same colony was implanted on the same day with cholesterol at the same locus.
The implants of testosterone were prepared by tamping small quantities of crystalline hormones or cholesterol into 20 gauge stainless steel tubing. A thin film of saturated solution of sucrose was then applied to the tip of the tube, which on drying provided a protective layer around the crystalline material.
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