The ACTH-releasing activity of synthetic oxytocin has been investigated in male rats, using adrenal ascorbic acid depletion as an indication of ACTH release. In acute experimental conditions synthetic oxytocin caused a highly significant adrenal ascorbic acid depletion in normal animals, as compared both to intact controls and to controls injected with physiological sodium chloride solution. It did not however, produce any adrenal ascorbic acid depletion in animals blocked by means of prednisolone. Administered as daily injections, synthetic oxytocin no longer caused any significant adrenal ascorbic acid depletion after six to nine days of treatment. It has been concluded that the ACTH-releasing activity of synthetic oxytocin is non-specific and thus is not the hypothalamic neurohumoral substance causing ACTH release from the anterior pituitary gland. The nature of this substance has been discussed in the light of previous results and of those obtained in the present investigations.

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The effect of reserpine on the secretion of FSH and LH was studied as well as the role of the peripheral effect of reserpine after hypophysectomy. The results in the unoperated animals suggest that reserpine inhibits the pituitary secretion of both FSH and LH. Both these hormones combined with reserpine had a very different biological effect than was seen without reserpine. HCG (LH-like) and particularly PMS (FSH-like) hormones combined with reserpine caused definite enlargement of the ovaries. In the hypophysectomized groups, the effect of the PMS and HCG hormones administered together with reserpine or without it was the same with regard to the weight of the ovaries, but not with regard to their histological picture. On the basis of these results, reserpine may be said to have a peripheral effect although the nature of its mechanism of action is difficult to state. Reserpine probably affects the ovaries by inhibiting the follicular cycle and, consequently, the formation of new and more mature follicles.

The purpose of the present work was to establish the effect of follicle stimulating hormone (FSH) on the gonads of the male rat after blocking normal genital function with reserpine. Serum gonadotrophic hormone, which resembles FSH in its effect, was given to male rats for 16 days (40 IU every other day). The genital function of some of the animals was blocked with reserpine (0.05 mg per day). The effect of the treatment was as follows: The serum gonadotrophic hormone inhibited weight loss in the testes and histologically demonstrable atrophy in test animals treated with reserpine. This suggests a possible inhibition of hypophyseal FSH secretion by reserpine. The weight of the seminal vesicle was considerably increased in the abovementioned test animals. The following alternative explanations were offered: a) The secretion of androgenic hormones was increased since the size of the seminal vesicle reflects the hormone content of the organism. b) Retention of secretion in the gland was increased by reserpine. c) Synergism of these two factors.

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