Shigeto Kanematsu

Effects of Intraventricular Infusions of Norepinephrine and Dopamine on LH Release and Ovulation in the Rabbit

The infusion of 50 µ g norepinephrine (NE) into the third ventricle of the brain was found to be highly effective in stimulating the release of an ovulatory surge of LH from the pitu

Effects of Intrahypothalamic Implants of Reserpine on Lactation and Pituitary Prolactin Content in the Rabbit.

Summary Direct implantation of minute amounts of solid reserpine phosphate into the posterior median eminence-basal tuberal area of the hypothalamus initiated milk secretion and depleted the hypophysis of prolactin in the estrogen primed ovariectomized rabbit. Reserpine implantation into the hypophysis had no effect. The results indicate the focus of reserpine influence essential to the release of pituitary prolactin and activation of mammary glands is the posterior median eminence-posterior tuberal region of the hypothalamus.

Nicotine Delays the Ovulatory Surge of Luteinizing Hormone in the Rat

Summary Nicotine tartrate administered to rats on the afternoon of vaginal proestrus delayed the ovulatory surge of luteinizing hormone (LH) output from the pituitary gland. Ovulation was completely blocked by sequential treatment with nicotine and a central nervous depressant, pentobarbital, under conditions in which neither drug alone would prevent LH release. The principal site of nicotines antigonadotropic action, therefore. appears to be the central nervous system. We thank Mrs. Virginia Hoover for expert technical assistance, Dr. Gordon D. Niswender for H-15 antibody, Dr. Leo Reichert, Jr. for LER-1056-C2 LH for iodination, Mrs. Frances Smith for secretarial assistance, and Mr. Bobby McAlister and Mrs. Sylvia Barr for drawing the figure.

Inhibition of the Progesterone-Advanced LH Surge at Proestrus by Nicotine

Summary When proestrous rats were injected with progesterone at 1130, serum LH was highly elevated (643 ± 142 ng/ml) at 1430 in seven rats that ovulated that night in spite of pentobarbital administration at 1430, and somewhat elevated (175 ng/ml) in two similarly treated rats which failed to ovulate. Five saline-treated controls (no progesterone) showed a serum LH level of 34.5 ± 6.1 ng/ml at 1430. When progesterone treatment at 1130 was followed by six half-hourly injections of nicotine tartrate prior to pentobarbital treatment at 1430 none of seven rats ovulated and their serum LH level was 24.5 ± 4.5 ng/ml. Nicotine blocks the advancement of the proestrous ovulatory surge of LH by progesterone. The authors express their appreciation to Mrs. Virginia Hoover for excellent technical assistance, Dr. C. A. Blake for help with RIA technique, Dr. Gordon D. Niswender, for the H-15 antibody, Dr. Leo Reichert, Jr., for the LER-1056-C2 LH for iodination, Mrs. Frances Smith for secretarial assistance, and Mr. Bobby McAlister for drawing of the figure.