The off-overshoot responses of photoreceptors and horizontal cells in the light-adapted retinas of the tiger salamander.
Depolarizing overshoot responses at the cessation of a test light step were observed in horizontal cells (HCs) and in a population of photoreceptors (rodCS) in light-adapted retinas of the tiger salamander. An anode break regenerative conductance may contribute to the overshoot responses in rodcS(o-wave). The overshoot responses in HCs consist of two components: a fast alpha-wave whose amplitude and time course follow those of the o-wave; and a slow beta-wave whose amplitude and time course vary with the HC membrane voltage. These results are consistent with the notion that the alpha-wave is a postsynaptic response to the voltage overshoots of the o-waves in rodCS and the beta-wave is mediated by voltage-dependent conductances in the HC membrane. A possible function of the HC overshoot responses is to reset the amplitude of the light-adapted HC responses during repetitive or rapidly changing light stimulation.
Wu
S M
SM
Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030.
D000200:Action Potentials; D000221:Adaptation, Ocular; D000557:Ambystoma / Q000502:physiology*; D000818:Animals; D066298:In Vitro Techniques; D008027:Light; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology*; D012160:Retina / Q000502:physiology*; D013997:Time Factors