Title page for ETD etd-07122006-205835


Type of Document Dissertation
Author Sen, Madhumita
Author's Email Address msen1@lsu.edu
URN etd-07122006-205835
Title Determinants of Local Calcium Signaling in Retinal Amacrine Cells
Degree Doctor of Philosophy (Ph.D.)
Department Biological Sciences
Advisory Committee
Advisor Name Title
Evanna Gleason Committee Chair
Jim Belanger Committee Member
John Lynn Committee Member
Richard Bruch Committee Member
Steven Barker Dean's Representative
Keywords
  • amacrine cells
  • glutamate receptors
  • electron microscopy
  • calcium imaging
  • retina
Date of Defense 2006-07-07
Availability unrestricted
Abstract
Amacrine cells mediate complex lateral signaling in the inner plexiform layer of the vertebrate retina. Glutamate is the primary excitatory neurotransmitter that shapes the retinal circuitry by activating ionotropic glutamate receptors (iGluRs)and metabotropic glutamate receptors (mGluRs). One step in understanding the signaling in the inner retina is to understand the role and expression patterns of these glutamate receptors. The expression of iGluRs in amacrine cells is well documented in the literature. This study addresses the localization of Group I mGluRs in the retina. Pre-embedding immunocytochemistry combined with electron microscopy was used to study the expression of Group I mGluRs in the chicken retina. Results indicate that Group I mGluRs are expressed in the synaptic sites of the outer plexiform (OPL) and inner plexiform (IPL) layers and specifically at amacrine cell synapses. In order to understand the intricacies of amacrine cell signaling mechanisms it is important to dissect out the signaling mediated by Ca2+ in these cells. In this dissertation, Ca2+ dependent local signaling in amacrine cells, more specifically the Ca2+ transport mechanisms involving mitochondria and ER, are explored. Calcium imaging experiments were performed on cultured chick amacrine cells. The results presented here suggest that there is physiological interplay between mitochondria and ER. In addition to this, it is demonstrated that ryanodine receptors are specifically involved in Ca2+ transport, probably via calcium-induced calcium release (CICR). Blocking the mitochondrial uniporter with FCCP or the mitochondrial Na+/Ca2+ exchanger (mNCX) with CGP 37157 revealed that mitochondria also influence the duration of glutamate-dependent cytosolic Ca2+ elevations. The effects of FCCP and CGP were detectable only in amacrine cell bodies and also in regions of processes next to mitochondria, thus revealing a spatial limit to the effects of mitochondria on cytosolic Ca2+. Together, these results contribute to our understanding of how local signaling is achieved in the vertebrate retina.
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