The Journal of General Physiology
Cell MicroControls
  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents
This Article
Right arrow PDF (Full Text)
Right arrow Alert me when this article is cited
Services
Right arrow Email this article
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new content in the JGP
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Caldwell, J. H.
Right arrow Articles by Betz, W. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Caldwell, J. H.
Right arrow Articles by Betz, W. J.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

The Journal of General Physiology, Vol 83, 157-173, Copyright © 1984 by The Rockefeller University Press

ARTICLES

Properties of an endogenous steady current in rat muscle

JH Caldwell and WJ Betz

A vibrating probe was used to study a steady electric current generated by isolated, whole lumbrical muscles of the rat. Spatial mapping showed that current leaves the muscle in the synaptic region and re-enters in the flanking extrajunctional regions. The point of maximum outward current coincided precisely with the endplate region. As the probe was moved radially away from the endplate region, the current declined monotonically, and the results could be fit with a simple model. As the probe was moved axially away from the endplate region, the current declined and became inward over a distance of approximately 0.5 mm. The physiological mechanism by which the current is generated was also studied. alpha-Bungarotoxin and tetrodotoxin had no significant effect on the current, which suggests that acetylcholine channels and gated sodium channels are not involved in the generation of the current. Ouabain produced a slowly developing, partial inhibition of the current, reducing it by approximately 40% over a period of 30-40 min. Carbachol produced a large inward current at the endplate region. After the carbachol action was terminated with alpha-bungarotoxin, an outward current reappeared, and a transient "overshoot" developed. During the overshoot, which lasted approximately 30-40 min, the outward current was approximately doubled. This overshoot was completely abolished by ouabain. The overshoot is interpreted as reflecting the increased activity of electrogenic sodium pumping in the endplate region, caused by the influx of Na ions during carbachol application. Because of the very different actions of ouabain on the normal current and on the overshoot after carbachol application, we concluded that the normal outward current is not produced by electrogenic sodium pumping in the endplate region.
Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?




  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents