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This Article Full Text Full Text (PDF) All Versions of this Article: 102/4/2477    most recent 00446.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Moreno, R. L. Articles by Ribera, A. B. PubMed PubMed Citation Articles by Moreno, R. L. Articles by Ribera, A. B.

RESEARCH-ARTICLE

Zebrafish Motor Neuron Subtypes Differ Electrically Prior to Axonal Outgrowth

Department of Physiology and Biophysics, University of Colorado Denver at Anschutz Medical Campus, Aurora, Colorado

Submitted 22 May 2009; accepted in final form 13 August 2009

ABSTRACT

Different muscle targets and transcription factor expression patterns reveal the presence of motor neuron subtypes. However, it is not known whether these subtypes also differ with respect to electrical membrane properties. To address this question, we studied primary motor neurons (PMNs) in the spinal cord of zebrafish embryos. PMN genesis occurs during gastrulation and gives rise to a heterogeneous set of motor neurons that differ with respect to transcription factor expression, muscle targets, and soma location within each spinal cord segment. The unique subtype-specific soma locations and axonal trajectories of two PMNs—MiP (middle) and CaP (caudal)—allowed their identification in situ as early as 17 h postfertilization (hpf), prior to axon genesis. Between 17 and 48 hpf, CaPs and MiPs displayed subtype-specific electrical membrane properties. Voltage-dependent inward and outward currents differed significantly between MiPs and CaPs. Moreover, by 48 hpf, CaPs and MiPs displayed subtype-specific firing behaviors. Our results demonstrate that motor neurons that differ with respect to muscle targets and transcription factor expression acquire subtype-specific electrical membrane properties. Moreover, the differences are evident prior to axon genesis and persist to the latest stage studied, 2 days postfertilization.