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Title: GnRH network : noradrenaline and sex steroids
Author: Haywood, S. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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The first studies in this thesis use in situ hybridisation to investigate if temporal changes occur in cellular GnRH gene expression during the preovulatory phase of the oestrous cycle and further investigation gene expression in other neurotransmitter systems in the GnRH network within the preoptic area and the brainstem. It is evident from these studies that, during the oestrous cycle, transcriptional changes within GnRH, enkphalin, nitric oxide synthase and noradrenaline containing neural populations, in the preoptic area and brainstem respectively, are small, and are perhaps not pertinent to the imminent LH surge. Nevertheless, it is already established that sex steroid dependent changes in GnRH secretion are associated with an increased in noradrenergic activity. The second study, using immunocytochemical techniques, focuses on this relationship and demonstrates, for the first time, the presence of progesterone receptors (PR) in up to 35% of noradrenaline cells in caudal regions of the nucleus tractus solitarii (A2 cell group). Moreover, this study shows that dynamic fluctuations in sex steroid receptors occur during the oestrous cycle, with the highest percentage of A2 neurones expressing PR and oestrogen receptor (ERα) on proestrous morning with a nadir on dioestrous afternoon. Further studies in steroid-primed female rats provide evidence that this is predominantly an oestrogen-inducing effect on PR expression. Finally, using retrograde tracing techniques combined with dual-labelling immunocytochemistry I show that approximately 5-12% of A cells in the brainstem project to the vicinity of the GnRH perikarya located in the rostral preoptic area (rPOA) and that the majority of these projecting A2 neurones express PR.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available