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|Title:||Developmental Changes in Gonadotropin Releasing Hormone Neurons in the Brain of the Female Rabbit (Oryctolagus cuniculus)|
|Authors:||Foster, George Warren|
|Keywords:||Medicine and Health Sciences;Medicine and Health Sciences|
|Abstract:||<p>This thesis examined developmental changes in morphology of the GnRH neuron in the female rabbit brain during sexual maturation. In the adult virgin rabbit approximately 1,000 GnRH cells were counted in half the hypothalamus. Two morphologically distinct populations of GnRH neurons were found. Fusiform cells with relatively smooth contours (smooth) accounted for 34% of the total. Cells with irregular contours (rough) represented 64% of the immunoreactive cells counted. In a subsequent experiment GnRH cell types were quantified in rabbits treated with Tamoxifen (TAM, 10 mg/kg/day), vehicle, and pregnant mare serum (PMS, 50 IU on postnatal days (PND) 25 and 28). Sexual maturity was considered achieved when rabbits attained a body weight of 3.0 kg. The proportion of rough cells increased while the smooth cells decreased with sexual maturation. This change was advanced by PHS treatment and prevented by TAM treatment compared to controls. Sexual maturity was advanced by PMS treatment (92 PND) versus controls (108 PND) and delayed by TAM treatment (128 PND). Mean plasma estradiol was significantly (P= 0.01) elevated in PHS rabbits versus controls between PND 25 and 34 and again at PND 75 (p= 0.05). Since the total number of immunoreactive cells remained constant, it is concluded that smooth cells are transformed to rough cells. In another experiment chronic ovariectomy did not change the total number of GnRH cells counted when compared to sham operated rabbits. However, the developmental shift of smooth cells to rough cells was prevented (p<0.05) in ovariectomized rabbits. These results suggest that the developmental change in GnRH cell morphology is functionally related to puberty onset. Moreover, estradiol seems to induce these changes through indirect mechanisms. It is proposed that estradiol augments the growth neural imputs to GnRH cells.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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