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Effects of locally applied chemicals on trans retinal potential and horizontal cells in the isolated carp retina part 2 calcium chelator


Pfluegers Archiv European Journal of Physiology 375(1): 61-68
Effects of locally applied chemicals on trans retinal potential and horizontal cells in the isolated carp retina part 2 calcium chelator
Experiments were performed on isolated retinas of the carp (Cyprinus carpio) to investigate the effects of locally applied Ca2+-chelator (EDTA or EGTA [ethyleneglycol-bis-N'-tetraacetic acid]) on the transretinal potential and the membrane potential of horizontal cells. A minute quantity of a Ca2+-free Ringer solution containing Ca2+-chelator was applied locally at different layers by means of pressure-microinjection. The responses were induced by alternating central and annular stimuli of white light. The agent applied locally at the distal layer (receptor surface or outer plexiform layer) in the centrally stimulated area caused rapid changes in the light-induced potentials; that microinjected into the inner plexiform layer did not. The effects of Ca2+-chelator were dose-dependent. The agent at 2.5 mM, applied locally at the distal layer, transiently enlarged the positive response (PIII) to a central stimulus. At 5.0 mM it reduced the PIII and markedly enlarged a negative potential in response to both central and annular stimuli. At the same time, the transretinal DC and horizontal cell resting potentials were shifted in the negative direction by 10-20 mV and 5-10 mV, respectively. S-potential were considerably reduced in amplitude, particularly in response to a central stimulus. The latencies of the transretinal responses and of the S-potentials were compared before and after drug application. The transretinal response and the S-potential recorded from the chelator-treated central area apparently are electrotonic in nature.


Accession: 005312433



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