Mechanism of the slow depressive potential production in the isolated frog retina.

Abstract

1. The mechanism of the slow depressive potential (SDP) production has been investigated with the isolated frog retina deprived of the pigment epithelium.2. Both the latency and the amplitude of the b-wave were affected by the evolution of the SDP. A decrease in amplitude and an increase in latency were observed during the development of the SDP.3. Reduction of sodium or magnesium in the bathing solution did not affect significantly both the amplitude of the SDP and the b-wave latency.4. Exposing the retina to the calcium-free solution, the amplitude of the SDP was decreased and the b-wave latency was lengthened gradually.5. Lowering the potassium concentration on the receptor side caused an increase, on the contrary, raising the potassium concentration a decrease in amplitude of the SDP. There was a logarithmic relation between the amplitude of the SDP and potassium concentration in the bathing solution. Whereas, raising the potassium concentration on the receptor side led to an increase in the b-wave latency.6. The ratio of E1 and E2 of the SDP remained constant even if various cation concentrations in the bathing solutions were modified.7. The SDP induced by a light stimulus was interpreted as the summed response of the negative response and the positive response.8. Observations from the present study suggested that the SDP is generated most probably by the Muller cell as a depolarization of a cell membrane except that forming the so-called inner limiting membrane.