The LHRH pulse generator in the New Zealand white rabbit
Lin, Winifred Wei
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Permalink
https://hdl.handle.net/2142/21727
Description
Title
The LHRH pulse generator in the New Zealand white rabbit
Author(s)
Lin, Winifred Wei
Issue Date
1990
Doctoral Committee Chair(s)
Ramirez, Victor D.
Department of Study
Molecular and Integrative Physiology
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Language
eng
Abstract
In my dissertation, I have studied the in vivo activity of the LHRH pulse generator in the rabbit, a reflex ovulator, using a push-pull cannulae (PPC) procedure that allows the detection of the release of this neuropeptide from the hypothalamus of freely behaving animals. The present thesis examines the normal activity of the LHRH pulse generator in the male and female rabbit in vivo as well as the influence of the following internal and external cues which regulate the LHRH pulse generator: steroids, sexual stimuli, and seasonal influences.
The information from the present thesis is summarized as follows. First, in both the male and female rabbit, LHRH release was detected in a widespread area in the hypothalamus as a pulsatile signal with a frequency of about 1 pulse/h. Second, pulsatile and not continuous infusion of progesterone (10ng/ml) and 20$\alpha$-hydroxyprogesterone (10 ng/ml) were effective in stimulating the LHRH pulse generator in the female rabbit. In addition, pregnanolone, a 5$\beta$ reduced metabolite of progesterone, was the most potent steroid in stimulating the LHRH neural apparatus of female rabbits. Third, mounting behavior of the male stimulated mean LHRH release from the tuberal region of the hypothalamus in female rabbits. Fourth, in the male rabbit, the LHRH release showed marked increases during the summer solstice period and marked decreases during the winter solstice period. The increase during the summer solstice was testes dependent. Fifth, castration had no dramatic effect on the mean LHRH release and mean amplitude, but testosterone implants were able to cause a marked, but transient, stimulation on the mean LHRH release in the long-term castrate, thereby suggesting that testosterone may be an important regulator of the LHRH pulse generator.
The present thesis provides a better understanding on the various factors which influence the activity of the LHRH pulse generator in the rabbit. In addition, these studies demonstrate how the PPC procedure can be used as an effective and unique tool in the rabbit to understand the activity of a specific neuronal system, such as the LHRH pulse generator.
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