Abstract
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.
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