Effects of anterior hypothalamic implantation of gonadal steroids on serum and pituitary gonadotrophins (follicle-stimulating hormone and luteinizing hormone) in the castrated male rat.

Castrated rats were stereotaxically implanted with 1 microng oestradiol benzoate, 5 microng testosterone isobutyrate or, as a control, 10 microng cholesterol, in the hypothalamus. The effects of the steroids on plasma and pituitary gonadotrophins (FSH and LH) were assessed by radioimmunoassay. Our results indicate that, in the male rat, in addition to the arcuate nucleus-median eminence complex, the preoptic suprachiasmatic area is able to control synthesis and secretion of both gonadotrophins, and that it is sensitive to oestradiol and testosterone.