. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. OCTOPUS PHOTORECEPTOR ELECTROPHYSIOLOGY AND INNERVATION 83. 50 mV _n B •5. £ 100 i 80 - 60 - I I U 40 - 20 - T = 10 15 20 25 30 Delay between flashes (s) 35 Figure 7. Adaptation or recovery responses between light flashes to the epistellar body. (A) Upper traces show examples of photoreceptor cell generator potentials recorded extracellularly from the octopus epi- stellar body in response to a series of 200-ms-duration light flashes with increased delay between flashes, but constant intensity (34 /vW/cnr), as indicated
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. OCTOPUS PHOTORECEPTOR ELECTROPHYSIOLOGY AND INNERVATION 83. 50 mV _n B •5. £ 100 i 80 - 60 - I I U 40 - 20 - T = 10 15 20 25 30 Delay between flashes (s) 35 Figure 7. Adaptation or recovery responses between light flashes to the epistellar body. (A) Upper traces show examples of photoreceptor cell generator potentials recorded extracellularly from the octopus epi- stellar body in response to a series of 200-ms-duration light flashes with increased delay between flashes, but constant intensity (34 /vW/cnr), as indicated in the lower trace. (B) Amplitude of the extracellular response with increasing delay between flashes. intensity levels of 'background' illumination. It can be seen that the greater the level of background illumination, then the smaller the extracellular response to the light flash; Figure 8B shows that the relationship is more-or- less exponential. Intracellular recordings from individual photoreceptor cells demonstrated that, in the dark, these had membrane resting potentials of about —49 ± 7 mV (mean ± SD, n = 43); such recordings could be maintained for up to 45 min. Epistellar body photoreceptors responded to a short flash of white light with a depolarization that often re- sulted in the firing of a burst of action potentials (Fig. 9). Although not studied in detail, this response was depen- dent on the wavelength of the light stimulus, for stimuli at wavelengths greater than 650 nm evoked no response (Fig. 9). This also provided confirmation that the response was not artifactual or related to other stimuli, such as the noise of the mechanical shutter. The amplitude of the intracellular receptor potential response varied with the intensity of the light flash (Fig. 10A). A graph of these responses (Fig. 10B), demonstrated that the amplitude of the depolarization was well correlated to the log of the light-flash intensity across the intensity range examined. Similarly
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
