The circadian rhythm and photosensitivity of small impulses of the Bulla eye |
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Authors: | Michael E Geusz Terry L Page |
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Institution: | (1) Department of Biology, Vanderbilt University, 37235 Nashville, TN, USA |
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Abstract: | Summary The eye of the mollusk Bulla gouldiana contains a pacemaker that generates a circadian rhythm in compound action potentials (CAPs) in the optic nerve. In this paper, we present evidence of a second circadian rhythm in the optic nerve of the eye maintained in darkness at 15 °C. This is a rhythm in the frequency of small (10–40 V) neural impulses that occurs about 12 h out-of-phase with the rhythm in CAPs. Typically, the small-spike frequency is at a minimum within an hour of the peak in CAP frequency and is maximal during the subjective night. Like the CAP rhythm, the phase of the small-spike rhythm is determined by the prior light/dark cycle. A rebound in small-spike activity following the end of a light pulse and the presence of photoinhibited impulses in surgically reduced eyes suggests that the cells that generate the small-spikes may be photoreceptors that are inhibited by light. In addition, by using isolated nervous system preparations, we have found that smallspikes occur in the two optic nerves in a one-for-one relationship immediately following a light-to-dark transition. This inter-eye communication may be involved in the coupling of the ocular pacemakers.Abbreviations
ASW
artificial sea water
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BRN
basal retinal neuron
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CAP
compound action potential |
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Keywords: | Circadian pacemaker Opisthobranch mollusk Photoreceptor Inhibition Light response |
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