Date of Award
2010
Degree Type
Thesis
Degree Name
Master of Science
Program
Anatomy and Cell Biology
Supervisor
Dr. Michael Lehman
Abstract
The neural circuitry underlying seasonal reproduction in sheep involves A15 dopamine neurons that undergo annual changes in synaptic inputs and dendritic complexity. Thyroidectomy (TH×) in late breeding season blocks both seasonal plasticity and the transition to anestrous.
To determine if neurotrophins regulate these morphological changes, we first examined the effects of TH× on the mRNA expression of neurotrophins, and their receptors, during the late breeding season. THX ewes had elevated TrkA expression in
the A15, and elevated NGF expression in the arcuate nucleus (ARC). The effects of TH× on seasonal alterations in glutamatergic inputs onto A15 neurons
were also examined. Anestrous ewes had significantly more vGlutl- and vGlut2-positive appositions than breeding season ewes; THX completely blocked this seasonal increase.
These results point to alterations in NGF∕TrkA signaling between the ARC and A15 in mediating thyroid-dependent processes underlying neural plasticity, and seasonal changes in A15 glutamatergic inputs responsible for the annual transition to anestrous.
Recommended Citation
Ladha, Zamin, "Plasticity in the Neuroendocrine Circuitry Responsible for Seasonal Breeding in the Ewe" (2010). Digitized Theses. 4527.
https://ir.lib.uwo.ca/digitizedtheses/4527