Inhibition of pituitary-testicular axis response to gonadotropin releasing hormone by pineal treatment.

Purification by ultrafiltration of the pineal extract with antigonadotropic activity enabled us to obtain two fractions, one above 10,000 daltons molecular weight and one below. Administration of these two fractions to intact or castrated rats showed a dissociation of their activity, namely, the larger fraction proved to be anti-LH and the smaller one anti-FSH, as also demonstrated by the specific biologic tests of these hormones. Pineal pre-treatment of the intact and castrated rats whose pituitary had been stimulated with gonadotropic releasing hormone (GnRH) showed that both fractions lower significantly LH and FSH serum levels in both groups of animals. The pineal treatment inhibited the pituitary response to GnRH both in the intact and castrated animals.