Ion Gradients and Metabolic Activity in the Generation of Cone and Rod Responses
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Several recent reports have suggested that the photoresponses of vertebrate receptors are explicable as a change in membrane permeability to sodium. In rods, evidence has been presented that the outer limb is depolarised in darkness (Toyoda et al, 1969) owing to a high sodium permeability. When this is reduced by illumination, the membrane hyperpolarises towards the potassium equilibrium potential (Sillman et al, 1969). By contrast we have concluded (Arden and Ernst, 1970) that in cones illumination produces a reduction in membrane permeability to both sodium and potassium which causes the membrane to hyperpolarise towards the chloride equilibrium potential.
KeywordsResponse Amplitude Sodium Glutamate Slow Peak Calcium Free Medium Tris Chloride
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