HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 96/1/109    most recent 01369.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science 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 Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Wang, Y.-C. Articles by Huang, R.-C. Search for Related Content PubMed PubMed Citation Articles by Wang, Y.-C. Articles by Huang, R.-C.

Effects of Sodium Pump Activity on Spontaneous Firing in Neurons of the Rat Suprachiasmatic Nucleus

Department of Physiology and Pharmacology, Chang Gung University School of Medicine, Tao-Yuan, Taiwan

Submitted 27 December 2005; accepted in final form 7 February 2006

Cell-attached and whole cell recording techniques were used to study the effects of electrogenic sodium pump on the excitability of rat suprachiasmatic nucleus (SCN) neurons. Blocking the sodium pump with the cardiac steroid strophanthidin or zero K⁺ increased the spontaneous firing of SCN neurons to different degrees with different recording modes, whereas turning the sodium pump into a nonselective cation channel with the marine toxin palytoxin invariably increased the spontaneous firing to the point of total blockade. Current-clamp recordings indicated that strophanthidin increased the rate of membrane depolarization and reduced the peak afterhyperpolarization potential (AHP), whereas zero K⁺ also increased the rate of depolarization, but enhanced the peak AHP. The dual effect of zero K⁺ was reflected by the biphasic time course of voltage responses to zero K⁺: an inhibitory phase with enhanced peak AHP and slower firing, followed by a delayed excitatory phase with faster rate of membrane depolarization and faster firing. In the presence of strophanthidin to block the sodium pump, zero K⁺ consistently decreased firing by enhancing the peak AHP. Repetitive applications of K⁺-free solution gradually turned the biphasic inhibitory-followed-by-excitatory voltage response into a monophasic inhibitory response in cells recorded with the whole cell (but not the cell-attached) mode, suggesting rundown of sodium pump activity. Taken together, the results suggest that spontaneous firing of SCN neurons is regulated by sodium pump activity as well as the AHP, and that sodium pump activity is modulated by intracellular soluble substances subject to rundown under the whole cell conditions.

This article has been cited by other articles:

				C.-H. Chen, Y.-T. Hsu, C.-C. Chen, and R.-C. Huang Acid-sensing ion channels in neurones of the rat suprachiasmatic nucleus J. Physiol., April 15, 2009; 587(8): 1727 - 1737. [Abstract] [Full Text] [PDF]

				M. V. Podda, M. D'Ascenzo, L. Leone, R. Piacentini, G. B. Azzena, and C. Grassi Functional role of cyclic nucleotide-gated channels in rat medial vestibular nucleus neurons J. Physiol., February 1, 2008; 586(3): 803 - 815. [Abstract] [Full Text] [PDF]