UCLA

ABSTRACT OF DISSERTATION

Localization and contribution of voltage-gated calcium channels in retinal ganglion cells and their unmyelinated axons

by

Allison Michelle Sargoy

Doctor of Philosophy in Neurobiology

University of California, Los Angeles

Dr. Nicholas C. Brecha, Chair

Retinal ganglion cell (RGC) death has been attributed to aberrant calcium signaling in injury and disease. Calcium has a dual nature in mediating both homeostatic and apoptotic signaling pathways that modulate cell survival and cell death, respectively. The regulation of excessive calcium signaling through the inhibition of voltage-gated calcium channels (VGCCs) provides a potential strategy to reduce the loss of RGCs in injury and disease. My dissertation outlines the identification and contribution of the VGCCs, their modulation through the use of pharmacological blockers and the identification of an injury-resistant subtype of RGCs to provide a platform for future studies to investigate the expression and functional properties of VGCCs that may contribute to the superior ability to withstand injury.

Calcium channel expression studies that utilized immunohistochemical techniques localized the L-, P/Q- and N-type VGCCs to the RGCs and the L-type VGCCs to the RGC axons. Weak immunostaining of the N-type VGCC was detected in the RGC axons. Likewise, calcium imaging studies investigating the functional contributions of the VGCCs provided evidence for the L-, P/Q-, N- and T-type VGCCs to the RGCs and the L-type VGCCs to the RGC axons. Patch clamp analysis further confirmed the presence of T-type VGCCs in RGCs. Lastly, the survival of RGCs and their axons that underwent optic nerve transection was investigated to identify a RGC type that is more resistant to injury than any other RGC type in the retina. Immunohistochemical analysis further confirmed the M1 RGC as the most resistant RGC type in the retina to injury.