Biophysical Society Thematic Meeting - June 28-July 1, 2015

New Biological Frontiers Illuminated by Molecular Sensors and Actuators

Poster Abstracts

14-POS Board 14 Effect of L and T - Type Calcium Channels in Retinal Ganglion Cells Stimulation Padma Priya K, Krishnan Jayaraman , Malathi Raman. Annamalai University, Annamalai Nagar, India. The retina comprises of atleast 50 distinct types of cell that widely differ in shape and size. It covers the visual field and conveys a complete processed visual image. The Visual system, a marvelous anatomical complex neural circuit composes of image-forming pathways with retinal ganglion cells(RGCs) depending on photoreceptors, rods and cones whereas the non-image- forming pathways involves intrinsically photosensitive RGCs to express the photopigment melanopsin. The retina and the brain communicate through action potentials to realize the time- dependent visual image as projected by the optics of eye. The paper attempts to develop an all active Fohlmeister–Coleman–Miller(FCM) model with five nonlinear ion channels for RGC, with an intracellular resistance(Ra), a membrane mechanism in parallel with a membrane capacitance(C) and a gap junction conductance(G) between cells. The process augurs the functions of sodium, calcium, delayed rectifier potassium, inactivating potassium, non inactivating calcium activated potassium, L- and T-type calcium conductances in the model. The simulation shows the repetitive firing of RGCs without application of the Istim due to the depolarization of the RGCs. In ipRGCs, the depolarization of membrane potential results in the activation of VGNCs further depolarizes, leading to activation of L-type VGCCs. The spontaneous electrical activity spreads as rhythmic bursts of action potential between adjacent cells to produce transient elevations in internal calcium concentration. Such RGC stimulation benefitted severe age-related macular degeneration(AMD), retinitis pigmentosa(RP) patients due to the presence of actively functioning ipRGCs though they are blind. By electrically preferentially stimulating the surviving RGCs with a retinal prosthetic, vision could be partially restored.

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