Document Detail

Glutamate modulates the firing rate in oculomotor nucleus motoneurons as a function of the recruitment threshold current.
MedLine Citation:
PMID:  22570384     Owner:  NLM     Status:  MEDLINE    
Studies in alert preparations have demonstrated that ocular motoneurons exhibit a phasic–tonic firing rate related to eye velocity and position, respectively. The slopes of these relationships are higher in motoneurons with higher recruitment threshold and have been proposed to depend upon synaptic input. To investigate this hypothesis, motoneurons of the rat oculomotor nucleus were recorded in a brain slice preparation in control conditions and during glutamate (5 μm) application to the bath. Glutamate did not affect membrane potential or input resistance, but produced a decrease in rheobase and depolarization voltage as a function of the current needed for generating a maintained repetitive discharge (recruitment threshold current). In addition, glutamate compressed the range of recruitment threshold current (0.1–0.4 nA) as compared to the control (0.15–0.7 nA). Glutamate exposed motoneurons showed an increase in the tonic frequency gain and the peak frequency. Such increments depended on the recruitment threshold current and the last recruited motoneurons almost doubled the tonic frequency gain (35.2 vs. 57.9 spikes s(−1) nA(−1)) and the peak frequency (52.4 vs. 102.6 spikes s(−1)). Finally, glutamate increased the spike frequency adaptation due to a significant increase in the phasic firing component as compared to the tonic one. In conclusion, glutamate modulates tonic and phasic discharge properties as a function of the recruitment threshold current and, presumably, motoneuron size. These findings contribute to understand the link between cellular functions and motoneuron discharge during oculomotor behaviour.
Julio Torres-Torrelo; David Rodríguez-Rosell; Pedro Nunez-Abades; Livia Carrascal; Blas Torres
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-05-08
Journal Detail:
Title:  The Journal of physiology     Volume:  590     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-07-03     Completed Date:  2013-06-07     Revised Date:  2013-07-02    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3113-27     Citation Subset:  IM    
Department of Physiology, University of Seville, Seville, Spain.
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MeSH Terms
Glutamic Acid / pharmacology*
Membrane Potentials / drug effects
Mesencephalon / drug effects,  physiology
Motor Neurons / drug effects*,  physiology
Oculomotor Nerve / cytology*
Rats, Wistar
Reg. No./Substance:
56-86-0/Glutamic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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