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This Article Full Text Full Text (PDF) All Versions of this Article: 557/2/355    most recent jphysiol.2004.064022v1 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 Fedirchuk, B. Articles by Dai, Y. Search for Related Content PubMed PubMed Citation Articles by Fedirchuk, B. Articles by Dai, Y.

Department of Physiology, University of Manitoba, 730 William Avenue, Winnipeg, MB, Canada R3E 3J7

During fictive locomotion in the adult decerebrate cat, motoneurone excitability is increased by a hyperpolarization of the threshold potential at which an action potential is elicited (V_th). This lowering of V_th occurs at the onset of fictive locomotion, is evident for the first action potential elicited and is presumably caused by a neuromodulatory process. The present study tests the hypothesis that the monoamines serotonin (5-HT) and noradrenaline (NA) can hyperpolarize neuronal V_th. The neonatal rat isolated spinal cord preparation and whole-cell recording techniques were used to examine the effects of bath-applied 5-HT and NA on the V_th of spinal ventral horn neurones. In the majority of lumbar ventral horn neurones, 5-HT (13/26) and NA (10/16) induced a hyperpolarization of V_th ranging from –2 to –8 mV. 5-HT and NA had similar effects on V_th for individual neurones. This hyperpolarization of V_th was not due to a reduction of an accommodative process, and could be seen without changes in membrane potential or membrane resistence. These data reveal a previously unknown action of 5-HT and NA, hyperpolarization of V_th of spinal neurones, a process that would facilitate both neuronal recruitment and firing.

(Received 9 March 2004; accepted after revision 13 April 2004; first published online 16 April 2004)
Corresponding author B. Fedirchuk: Department of Physiology, University of Manitoba, 730 William Avenue, Winnipeg, MB, Canada R3E 3J7. Email: brent{at}scrc.umanitoba.ca

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