Consequences of transient retinal hypoxia on rod input to horizontal cells in the rat retina.

The effects of hypoxia on horizontal cells were studied by intracellular recording in the superfused rat retina. Hypoxic challenge from the photoreceptor surface resulted in horizontal cell depolarization, associated with a reduction of the light-evoked hyperpolarization (S-potential). This depolarization, though not the reduction in S-potential, was reversed by non-NMDA receptor antagonists, but not by NMDA related antagonists. Horizontal cells were also depolarized during hypoxia when calcium-dependent synaptic transmitter release was blocked by Co2+. Diazoxide, an activator of ATP-sensitive K+ channels (K+ATP), had no effect on normal cells but blocked the depolarization and the reduction in S-potential. We conclude that retinal hypoxia results in increased activation of the non-NMDA receptors of horizontal cells, whilst the activation of K+ATP channels may be protective in retinal hypoxia.