Date of Graduation
2000
Document Type
Thesis
Degree Type
MS
Committee Chair
John M. Connors
Abstract
Previous work has shown that thyroid hormones are required if ewes are to enter the nonbreeding season, and that these hormones allow estradiol to exert its negative feedback effects to achieve this condition. Evidence also suggests that glial plasticity may contribute to this effect. To determine the role of thyroid hormones in reproductive cyclicity, ewes were ovariectomized and given estradiol implants. Some animals were then thyroidectomized and some of these ewes received thyroxine supplements intracerebroventricularly. Dual label immunocytochemistry was employed to determine the degree of Fos/TH colocalization and measure any changes in glial ensheathment of A15 cells. Analysis revealed no change in Fos/TH colocalization, although there was a significant decrease in number of TH-IR cells due to estradiol and to thyroid hormones. There was no effect of treatments upon glial ensheathment of A15 neurons. It was concluded that thyroid hormones do not mediate the effects of estradiol via glial plasticity
Recommended Citation
Griffith, Ronald Deloyd Jr., "Thyroid hormones are required during long-day photoperiods for the establishment of estradiol-sensitive afferent input to, and activation of, dopaminergic neurons in the A15 area of the ovine hypothalamus." (2000). Graduate Theses, Dissertations, and Problem Reports. 10488.
https://researchrepository.wvu.edu/etd/10488