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This Article Full Text Full Text (PDF) All Versions of this Article: 565/3/757    most recent jphysiol.2005.087601v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wang, Z.-M. Articles by Delbono, O. Search for Related Content PubMed PubMed Citation Articles by Wang, Z.-M. Articles by Delbono, O.

¹ Department of Physiology and Pharmacology
² Department of Internal Medicine, Gerontology
³ Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA

In this work we hypothesized that denervation in flexor digitorum brevis (FDB) muscle from ageing mice is more extensive than predicted by standard functional and structural assays used in the past. In addition, we asked whether denervation is a fully or partially developed process. Despite the reported alteration in skeletal muscle innervation, the quantification of the extension and magnitude of denervation in ageing rodents has remained elusive. To address these two questions we utilized a combination of electrophysiological and immunohistochemical assays directed to detecting the expression of tetrodotoxin (TTX)-resistant sodium channels (Na_v1.5) in FDB muscles from young-adult and senescent mice. Sodium current density measured with the macropatch cell-attached technique did not show significant differences between FDB fibres from young and old mice. The TTX dose–response curve, using the whole cell voltage-clamp technique, showed three populations of fibres in senescent mice, one similar to fibres from young mice (TTX sensitive), another one similar to fibres from experimentally denervated muscle (TTX resistant), and a third group intermediate between these two. Partially and fully denervated fibres added up to approximately 50% of the total number of fibres tested, a number that concurs with the percentage of fibres positive for the Na_v1.5 channel by specific immunostaining.

(Received 28 March 2005; accepted after revision 9 May 2005; first published online 12 May 2005)
Corresponding author O. Delbono: Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. Email: odelbono{at}wfubmc.edu

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