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Journal of Experimental Biology 150,111-122 (1990)
Published by Company of Biologists 1990

Electrophysiological Properties of Crayfish Retinal Photoreceptors

ARTURO PICONES 1 and HUGO ARÉCHIGA 1

1 Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN México, DF

Electrical properties of crayfish retinular photoreceptors were studied in the dark-adapted state and during responses to light. In fully dark-adapted photoreceptors, the resting potential was -49.8±3.3mV and input resistance was 31.3±5.4M{Omega} (mean±S.E.). The current—voltage relationship showed rectification near the resting potential, with decreased resistance within the depolarizing range. A value of 29.8±5.0k{Omega}cm2 was calculated for specific resistance, and 3.0±0.4µFcm-2 for specific capacitance. Electrotonic analysis showed that the photoreceptor was isopotential.

During the light response, membrane conductance increased depending on the stimulus intensity. This relationship was steeper for the conductance change during the initial transient of the receptor potential than during the plateau. A depolarizing afterpotential usually ensued at the end of the light response, concurrent with a residual increased conductance. The time course of the conductance increase during the receptor potential showed two kinetic components, suggesting that at least two distinct membrane processes were involved in its generation.

Key words: crayfish photoreceptors, light responses, membrane constants

Accepted on November 28, 1989






© The Company of Biologists Ltd 1990