Glutamate modulates the firing rate in oculomotor nucleus motoneurons as a function of the recruitment threshold current.

The Journal of Physiology
Julio Torres-TorreloB Torres

Abstract

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 fre...Continue Reading

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Citations

Apr 15, 2017·Acta Neuropathologica·Jik NijssenEva Hedlund
Jul 19, 2019·Frontiers in Neuroscience·Audrey M G RagagninJulie D Atkin
Jun 29, 2021·Brain Structure & Function·Ümit Suat MayadaliAnja Kerstin Ellen Horn
Sep 16, 2021·Annual Review of Vision Science·Anja K E Horn, Hans Straka

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