Blockade of Ovulation in Rabbits by Hypothalamic Implants of Norethindrone

Effect of Progesterone on Induced Ovulation in Immature Rats

“…Both inhibitory (Zeilmaker & Moll, 1967) and stimulatory effects (Sawyer & Kawakami, 1961;Kanematsu & Sawyer, 1965;Barraclough, Yrarrazaval & Hatton, 1964) …”

The site of action of ‘chlormadinone acetate’ (6‐chloro‐Δ6‐dehydro‐17α‐acetoxyprogesterone) in blocking ovulation in the mated rabbit

“…This evidence indicates that the block to ovulation which follows mating is located in the nervous system at a level above the median eminence of the hypothalamus. It may be at some other hypothalamic site (such as the posterior tuber cinereum, as indicated by the work ofKanematsu & Sawyer, 1965), or more peripherally on the afferent limb of the reflex arc excited by coitus. It is unlikely that chlormadinone acetate exerts its effect by an action on the peripheral sensory inputs to the central nervous system (including the sensory input from the pelvis) since there is evidence that these are individually dispensable to mating-induced ovulation.…”

“…afterreaction' for the duration of the ovulation blockade. Further, Kanematsu & Sawyer (1965) showed that local norethindrone implants placed in the posterior tuberal region of the hypothalamus blocked copulation-induced ovulation in the rabbit, although similar implants in other regions of the hypothalamus, or the pituitary, did not. The available evidence indicates therefore that the ovulation-blocking steroids exert their action on the central nervous system or pituitary gland.…”

Neural control of cyclic reproductive functions in the mammal

“…According to results of experiments with norethindrone (McCann and Kanematsu and Sawyer, 1965) and chlormadinone (Dörner and Docke, 1967) implants, synthetic gestagens may also inhibit sexual function in the female at the ME. The implantation of minute amounts of reserpine caused pseudopregnancy, disturbance of the vaginal cycle and formation of deciduoma.…”