Axon initial segment geometry in relation to motoneuron excitability

The axon initial segment (AIS) responsible for action potential initiation is a dynamic structure that varies and changes together with neuronal excitability. Like other neuron types, alpha motoneurons in the mammalian spinal cord express heterogeneity and plasticity in AIS geometry, including lengt...

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Autores principales:	Travis M. Rotterman, Darío I. Carrasco, Stephen N. Housley, Paul Nardelli, Randall K. Powers, Timothy C. Cope
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/52ac7e1961b54c428d2e73854a2b8728
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spelling	oai:doaj.org-article:52ac7e1961b54c428d2e73854a2b87282021-11-25T06:19:26ZAxon initial segment geometry in relation to motoneuron excitability1932-6203https://doaj.org/article/52ac7e1961b54c428d2e73854a2b87282021-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC8604372/?tool=EBIhttps://doaj.org/toc/1932-6203The axon initial segment (AIS) responsible for action potential initiation is a dynamic structure that varies and changes together with neuronal excitability. Like other neuron types, alpha motoneurons in the mammalian spinal cord express heterogeneity and plasticity in AIS geometry, including length (AISl) and distance from soma (AISd). The present study aimed to establish the relationship of AIS geometry with a measure of intrinsic excitability, rheobase current, that varies by 20-fold or more among normal motoneurons. We began by determining whether AIS length or distance differed for motoneurons in motor pools that exhibit different activity profiles. Motoneurons sampled from the medial gastrocnemius (MG) motor pool exhibited values for average AISd that were significantly greater than that for motoneurons from the soleus (SOL) motor pool, which is more readily recruited in low-level activities. Next, we tested whether AISd covaried with intrinsic excitability of individual motoneurons. In anesthetized rats, we measured rheobase current intracellularly from MG motoneurons in vivo before labeling them for immunohistochemical study of AIS structure. For 16 motoneurons sampled from the MG motor pool, this combinatory approach revealed that AISd, but not AISl, was significantly related to rheobase, as AIS tended to be located further from the soma on motoneurons that were less excitable. Although a causal relation with excitability seems unlikely, AISd falls among a constellation of properties related to the recruitability of motor units and their parent motoneurons.Travis M. RottermanDarío I. CarrascoStephen N. HousleyPaul NardelliRandall K. PowersTimothy C. CopePublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 16, Iss 11 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Travis M. Rotterman Darío I. Carrasco Stephen N. Housley Paul Nardelli Randall K. Powers Timothy C. Cope Axon initial segment geometry in relation to motoneuron excitability
description	The axon initial segment (AIS) responsible for action potential initiation is a dynamic structure that varies and changes together with neuronal excitability. Like other neuron types, alpha motoneurons in the mammalian spinal cord express heterogeneity and plasticity in AIS geometry, including length (AISl) and distance from soma (AISd). The present study aimed to establish the relationship of AIS geometry with a measure of intrinsic excitability, rheobase current, that varies by 20-fold or more among normal motoneurons. We began by determining whether AIS length or distance differed for motoneurons in motor pools that exhibit different activity profiles. Motoneurons sampled from the medial gastrocnemius (MG) motor pool exhibited values for average AISd that were significantly greater than that for motoneurons from the soleus (SOL) motor pool, which is more readily recruited in low-level activities. Next, we tested whether AISd covaried with intrinsic excitability of individual motoneurons. In anesthetized rats, we measured rheobase current intracellularly from MG motoneurons in vivo before labeling them for immunohistochemical study of AIS structure. For 16 motoneurons sampled from the MG motor pool, this combinatory approach revealed that AISd, but not AISl, was significantly related to rheobase, as AIS tended to be located further from the soma on motoneurons that were less excitable. Although a causal relation with excitability seems unlikely, AISd falls among a constellation of properties related to the recruitability of motor units and their parent motoneurons.
format	article
author	Travis M. Rotterman Darío I. Carrasco Stephen N. Housley Paul Nardelli Randall K. Powers Timothy C. Cope
author_facet	Travis M. Rotterman Darío I. Carrasco Stephen N. Housley Paul Nardelli Randall K. Powers Timothy C. Cope
author_sort	Travis M. Rotterman
title	Axon initial segment geometry in relation to motoneuron excitability
title_short	Axon initial segment geometry in relation to motoneuron excitability
title_full	Axon initial segment geometry in relation to motoneuron excitability
title_fullStr	Axon initial segment geometry in relation to motoneuron excitability
title_full_unstemmed	Axon initial segment geometry in relation to motoneuron excitability
title_sort	axon initial segment geometry in relation to motoneuron excitability
publisher	Public Library of Science (PLoS)
publishDate	2021
url	https://doaj.org/article/52ac7e1961b54c428d2e73854a2b8728
work_keys_str_mv	AT travismrotterman axoninitialsegmentgeometryinrelationtomotoneuronexcitability AT darioicarrasco axoninitialsegmentgeometryinrelationtomotoneuronexcitability AT stephennhousley axoninitialsegmentgeometryinrelationtomotoneuronexcitability AT paulnardelli axoninitialsegmentgeometryinrelationtomotoneuronexcitability AT randallkpowers axoninitialsegmentgeometryinrelationtomotoneuronexcitability AT timothyccope axoninitialsegmentgeometryinrelationtomotoneuronexcitability
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Axon initial segment geometry in relation to motoneuron excitability

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