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Monoamines increase the excitability of spinal neurones in the neonatal rat by hyperpolarizing the threshold for action potential production
Author(s) -
Fedirchuk Brent,
Dai Yue
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.064022
Subject(s) - hyperpolarization (physics) , monoamine neurotransmitter , neuroscience , spinal cord , membrane potential , electrophysiology , chemistry , serotonin , resting potential , biology , anatomy , biochemistry , receptor , organic chemistry , nuclear magnetic resonance spectroscopy
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.