Volume 10 Supplement 1
Electrogenic calcium pump contributes to dopamine neuron repolarization
© Oprisan; licensee BioMed Central Ltd. 2009
Published: 13 July 2009
Dopaminergic neurons (DA) in vitro can produce two distinct firing patterns: single spikes, which are called slow oscillatory potentials (SOP), and square underlying bursting activity. Previously , we proposed a conductance-based computational model that explained the mechanisms of both SOP and square wave activity. Based on experimental data, the SOP mechanism was driven by a calcium (Ca) L-type current and an apamin-sensitive small conductance (SK) current. The square waves could be generated by partially blocking the SK current, but to repolarize the cell, a slow potassium current was hypothesized. Experiments on DA suggested that an ether-a-go-go potassium current could play the role of the hypothetical slow potassium current. Experiments also showed that Ca is a major player in both SOP and square wave firing. Calcium removal is an elusive mechanism and we previously considered that Ca pump is nonelectrogenic [1, 2]. However, a nonelectrogenic Ca pump leads to equal rates of Ca influx and efflux at steady state and also equal rates of charge influx and efflux. As a result, once Ca concentration equilibrates, there should be no persistent inward calcium current, which contradicts experimental observations. In this paper, we hypothesize that Ca pump contributes to cell repolarization. Experimental results already published and our numerical simulations based on electrogenic Ca pump support this hypothesis.
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This article is published under license to BioMed Central Ltd.