Development of Spontaneous Activity and Response Properties of Primary Lagenar Neurons in the Chick |
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Authors: | Salvador Galicia Celso Cortes Fabian Galindo Amira Flores |
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Institution: | 1.Instituto de Fisiología,Universidad Autónoma de Puebla,Puebla,Mexico;2.Escuela de Biología,Universidad Autónoma de Puebla,Puebla,Mexico;3.Laboratorio de Neurobiología,Instituto de Fisiología, BUAP,Puebla, Pue,Mexico |
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Abstract: | Here, we report for the first time developmental changes in spontaneous activity and in response properties of single nerve
fibers from the macular chick lagena. Such aspects are important in order to get insight into the functional role of the lagena
which remains undetermined. For this purpose, we used intracellular and extracellular single-unit recording techniques in
an isolated inner ear preparation from the chicken at ages E15 and P1. At E15, afferent fibers displayed a low irregular spontaneous
discharge rate (41 ± 14 spikes/s, CV = 1.17 ± 0.1), which was replaced by regular high frequency spontaneous activity at P1
(CV = 0.48 ± 0.8, 89 ± 27 spikes/s). During the developmental period including E15, the percentage of silent neurons was 60%
while that of P1 was 40%. The synaptic activity was higher at E15 than at P1. The action potential waveform generated at E15
had small amplitude and derivative depolarization, and consequently, a large duration in correlation with respect to action
potential waveform at P1 (respectively: 53 ± 2 vs. 65 ± 3 mV, 60 ± 11 vs. 109 ± 20 mV/ms, 3.6 ± 0.4 vs. 1.1 ± 0.12 ms). In
addition, we recognized two response dynamics to the injection of current steps: phasic, or rapidly adapting neurons and tonic,
or slowly adapting neurons. Our results indicate similar developmental processes for the lagena as described for the vestibular
system in other species, in agreement with the known morphological characteristics of this otholitic end organ. The presence
of more than one subtype of afferent neuron also correlates with previous reports on vestibular afferents with analogous electrophysiological
properties, strongly suggesting the vestibular nature of the lagena. |
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