Date of Graduation
School of Medicine
Physiology, Pharmacology & Neuroscience
Robert L. Goodman.
In the ewe, anestrus is caused by increased sensitivity to E2 negative feedback that is mediated by A15 dopaminergic neurons that are only responsive to E2 in anestrus. Experiment 1, tested the hypothesis that synaptic input on A15 neurons varies with season by examining synapsin-positive close contacts on A15 cells using immunofluorescence and confocal microscopy. The number of contacts on dendrites, but not somata, increased during anestrus. There were also corresponding changes in dendritic morphology including an increase in dendritic length, surface area, and number of bifurcations. Because thyroid hormones are necessary for the transition to anestrus, we next examined the role of T4 in these changes. An increase in dendrite mean length was found in thyroid-intact and T4-treated thyroidectomized ewes compared to thyroidectomized animals. Thus, seasonal changes in input to and, dendritic morphology of, A15 neurons may play a role in seasonal breeding, with the latter dependent on T4.
Adams, Van Lee, "Seasonal plasticity of A15 dopaminergic neurons in the ewe" (2001). Graduate Theses, Dissertations, and Problem Reports. 1282.