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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.