ELECTROPHYSIOLOGY AND PHARMACOLOGY OF DRAGONFLY OCELLAR NERVE IMPULSE ACTIVITY.
Item
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Title
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ELECTROPHYSIOLOGY AND PHARMACOLOGY OF DRAGONFLY OCELLAR NERVE IMPULSE ACTIVITY.
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Identifier
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AAI8401907
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identifier
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8401907
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Creator
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RIND, JEFFREY DAVID.
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Contributor
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Richard L. Chappell
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Date
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1983
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, General
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Abstract
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A preparation has evolved which utilizes extracellular recordings of the light inhibited impulse activity from the cornea of the dragonfly ocellus to study the pharmacology of the ocellus. Computer software was developed which collects and analyzes spike frequency data. Ablation studies suggest that the impulse activity recorded in this fashion is originating from the lateral ocellar nerves and not the median ocellar nerve. TTX blocks all impulse activity. Latencies between action potentials suggest that there is only one spiking cell so recorded per lateral ocellar nerve that fires light inhibited spikes. Impulse activity appears to be more sensitive to green light (484 nm) than it is to UV light (360 nm) and unlike the ocellar photoreceptors or L-neurons it does not exhibit a reverse Purkinje shift at higher light intensities.;Intracellular recordings from the lateral ocellar nerve reveal non-spiking cells that have L-neuron like light responses (resting potentials = -30 to -55 mv). The spiking neuron (resting potential = -55 mv) fires light inhibited spikes analagous to those recorded extracellularly. The amplitude of the impulses was 30 mv. Recordings of extracellular impulse activity made simultaneously with an intracellular recording from an L-neuron suggest that the slow potential responses of the L-neuron may be normal for that cell and that it is not a damaged spiking neuron.;Agents that have been reported to effect the L-neuron also effect the corneally recorded impulse activity. 50 uM curare lowered the response threshold of the light response and decreased the interflash spike frequency. 50 uM curare also changed the slope of the intensity-frequency relationship. It has been suggested that these effects are mediated by curare's effect on the presumptive lateral inhibitory interactions between photoreceptors. Increasing doses of curare greater than 100 uM block the light mediated inhibition of impulses and cause an increase in the interflash spike frequency and spontaneous dark adapted impulse rate.;GABA inhibited spontaneous impulse activity in the dark and caused a light dependent increase in spike frequency which is shifted towards light "off" at high intensities. 12 mM cobalt, an inhibitor of synaptic transmission blocked all impulse activity. A model was suggested to explain the data which proposes that spiking activity occurs between two thresholds.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biology
