Date of Award

Summer 1992

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biology

Abstract

This project proposes to investigate the functional significance of the late afterhyperpolarization (AHP) in the identified cell types of the lamprey spinal cord. The late AHP is the result of an outward K+ conductance which peaks 30-70 msec after the action potential and lasts for 60-200 msec. The ionic channel underlying this current is believed to be the sk-ca++_dependent K+ channel (small conductance potassium). The following questions dealing with the late AHP will be addressed: 1) Is the late AHP of lamprey neurons affected by apamin , an 18 amino acid peptide derived from honeybee venom? 2) Does the decreased amplitude of the late AHP, mediated by aparnin, contribute equally to the reshaping of the input-output properties of the various identified neurons of the lamprey spinal cord? 3) What effect does a reduction of the late AHP by aparnin have on swimming activity in the lamprey? 1. Apamin Sensitivity. The late afterhyperpolarization in lamprey is a hyperpolarizing current that is dependent on calcium (Ca++) entry into the cell and is unaffected by changes in chloride concentrations. This suggests that the channel(s) responsible for the late AHP in lamprey is a Ca++_dependent K+ channel. Application of the selective ca++_dependent K+ channel blocker, apamin, will confirm the above work and will determine if the late AHP can be selectively blocked in lamprey neurons. 2 . Differential Sensitivity . The effect of apamin on the known lamprey neuron cell types may vary in intensity. I f apamin has differential effects on the various components of the spinal network responsible for fictive swimming, then the output of the network may be altered in the presence of apamin. 3. Role of the Slow AHP During Locomotion. If the late AHP plays a major role in modulating the frequency of lamprey swimming, then apamin-induced, selective blockade of the late AHP should alter the pattern of ventral root bursts associated with fictive swimming .

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