Publication Date
2008
Document Type
Thesis
Committee Members
Robert Fyffe (Advisor), John Pearson (Committee Member), Larry Ream (Committee Member)
Degree Name
Master of Science (MS)
Abstract
The auditory brainstem has been the area of much focus in recent years due to its advantages in circuitry and synaptic connections. The endbulbs and calyces of Held are large, glutamatergic synapses within the AVCN and MNTB, respectively. Because of their large size and accessibility these synapses have offered the ability to study pre- and post-synaptic mechanisms of neurotransmission within the central nervous system. The calyx of Held synapse is the main excitatory input into the MNTB principal cells, containing hundreds of individual synaptic specializations, or release sites. Previous studies have identified physiological and morphological changes at the endbulb of Held synapse but not the calyx of Held synapse. However, changes in inhibitory innervation at the MNTB were observed as a result of altered input. In this study we have utilized the calyx of Held synapse, apposing inhibitory terminals within the MNTB of CBA/J and congenitally deaf mice (dn/dn) to examine the role of altered input on synaptic strength. The dn/dn strain is of particular importance because they exhibit no spontaneous activity within the VIIIth nerve fiber, lending itself as a valuable model in the altered input studies, particularly an absence of afferent input. Serial electron microscopic analysis of the fine structure of the calyx of Held and inhibitory contacts onto the MNTB principal cells were compared between normal and deaf. Strikingly, the calyceal active zones within the adult deaf animals were significantly larger compared with normal hearing animals despite the fact there were no changes in excitatory currents. Examination of the inhibitory terminals confirmed the increase in mIPSC frequency manifested in an increase in inhibitory synapses expressed on the MNTB principal cells.
Page Count
120
Department or Program
Department of Neuroscience, Cell Biology & Physiology
Year Degree Awarded
2008
Copyright
Copyright 2008, some rights reserved. My ETD may be copied and distributed only for non-commercial purposes and may be modified only if the modified version is distributed with these same permissions. All use must give me credit as the original author.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
