Effect of cutting the optic nerve on K+ currents in endfeet of Muller cells isolated from frog retina.
Membrane currents were recorded from Muller cells isolated from normal retinas and from retinas whose ganglion cell axons had been cut in the optic nerve 30-60 days previously. The surgical procedure did not block the retinal blood supply and did not allow the axons to regenerate. The principal finding was that after severing the optic nerve there was less inward rectification in response to voltage commands. That is, the maintained inward current (I K(IN)) produced in response to a hyperpolarizing voltage command decreased leading to a decrease in the ratio I K(IN)/I K(OUT) In 98 mM [K+]O, this ratio was 2.86 +/- 0.21 (mean +/- SE; n = 24) in controls and 1.13 +/- 0.13 (n = 21) in Muller cells from denervated retinae. Barium, a blocker of the potassium inward rectifier (I (KIR)), eliminated this difference. Moreover, severing the optic nerve also decreased the resting potentials of Muller cells in 2.5 mM [K+]O from -83 +/- 7 mV to -63 +/- 9 mV. The results suggest that the voltage-dependent behavior and selectivity of K+ inward rectifying channels (K (ir)) in the endfeet depends on the integrity of the closely apposed ganglion cells.
Skatchkov
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SN
Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan 00901, USA.
Vyklicky
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L
Clasen
T
T
Orkand
R K
RK
D000818:Animals; D008564:Membrane Potentials / Q000502:physiology; D009409:Nerve Crush; D009457:Neuroglia / Q000502:physiology; D009900:Optic Nerve / Q000502:physiology* / Q000601:surgery; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D011894:Rana pipiens; D012160:Retina / Q000737:chemistry / Q000166:cytology* / Q000502:physiology
D015221:Potassium Channels