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Axon initial segment geometry in relation to motoneuron excitability.
Rotterman, Travis M; Carrasco, Darío I; Housley, Stephen N; Nardelli, Paul; Powers, Randall K; Cope, Timothy C.
Afiliação
  • Rotterman TM; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States of America.
  • Carrasco DI; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States of America.
  • Housley SN; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States of America.
  • Nardelli P; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States of America.
  • Powers RK; Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States of America.
  • Cope TC; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States of America.
PLoS One ; 16(11): e0259918, 2021.
Article em En | MEDLINE | ID: mdl-34797870
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.
Assuntos

Texto completo: 1 Base de dados: MEDLINE Assunto principal: Segmento Inicial do Axônio / Neurônios Motores Limite: Animals Idioma: En Ano de publicação: 2021 Tipo de documento: Article

Texto completo: 1 Base de dados: MEDLINE Assunto principal: Segmento Inicial do Axônio / Neurônios Motores Limite: Animals Idioma: En Ano de publicação: 2021 Tipo de documento: Article