Journal
NEURON
Volume 71, Issue 1, Pages 166-179Publisher
CELL PRESS
DOI: 10.1016/j.neuron.2011.04.033
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Funding
- Research to Prevent Blindness Career Development award
- Alfred P. Sloan Foundation
- National Institutes of Health [EY14454, EY14454-S1, EY07003]
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Retinal ganglion cells adapt by reducing their sensitivity during periods of high contrast. Contrast adaptation in the firing response depends on both presynaptic and intrinsic mechanisms. Here, we investigated intrinsic mechanisms for contrast adaptation in OFF Alpha ganglion cells in the in vitro guinea pig retina. Using either visual stimulation or current injection, we show that brief depolarization evoked spiking and suppressed firing during subsequent depolarization. The suppression could be explained by Na channel inactivation, as shown in salamander cells. However, brief hyperpolarization in the physiological range (5-10 mV) also suppressed firing during subsequent depolarization. This suppression was selectively sensitive to blockers of delayed-rectifier K channels (K-DR). In somatic membrane patches, we observed tetraethylammonium-sensitive K-DR currents that activated near -25 mV. Recovery from inactivation occurred at potentials hyperpolarized to V-rest. Brief periods of hyperpolarization apparently remove K-DR inactivation and thereby increase the channel pool available to suppress excitability during subsequent depolarization.
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