Failure of action potential propagation in sensory neurons: mechanisms and loss of afferent filtering in C-type units after painful nerve injury. J Physiol 2013 Feb 15;591(4):1111-31
Date
11/14/2012Pubmed ID
23148321Pubmed Central ID
PMC3591718DOI
10.1113/jphysiol.2012.242750Scopus ID
2-s2.0-84873713110 (requires institutional sign-in at Scopus site) 72 CitationsAbstract
The T-junction of sensory neurons in the dorsal root ganglion (DRG) is a potential impediment to action potential (AP) propagation towards the CNS. Using intracellular recordings from rat DRG neuronal somata during stimulation of the dorsal root, we determined that the maximal rate at which all of 20 APs in a train could successfully transit the T-junction (following frequency) was lowest in C-type units, followed by A-type units with inflected descending limbs of the AP, and highest in A-type units without inflections. In C-type units, following frequency was slower than the rate at which AP trains could be produced in either dorsal root axonal segments or in the soma alone, indicating that the T-junction is a site that acts as a low-pass filter for AP propagation. Following frequency was slower for a train of 20 APs than for two, indicating that a cumulative process leads to propagation failure. Propagation failure was accompanied by diminished somatic membrane input resistance, and was enhanced when Ca(2+)-sensitive K(+) currents were augmented or when Ca(2+)-sensitive Cl(-) currents were blocked. After peripheral nerve injury, following frequencies were increased in axotomized C-type neurons and decreased in axotomized non-inflected A-type neurons. These findings reveal that the T-junction in sensory neurons is a regulator of afferent impulse traffic. Diminished filtering of AP trains at the T-junction of C-type neurons with axotomized peripheral processes could enhance the transmission of activity that is ectopically triggered in a neuroma or the neuronal soma, possibly contributing to pain generation.
Author List
Gemes G, Koopmeiners A, Rigaud M, Lirk P, Sapunar D, Bangaru ML, Vilceanu D, Garrison SR, Ljubkovic M, Mueller SJ, Stucky CL, Hogan QHAuthors
Quinn H. Hogan MD Professor in the Anesthesiology department at Medical College of WisconsinCheryl L. Stucky PhD Professor in the Cell Biology, Neurobiology and Anatomy department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Action PotentialsAnimals
Behavior, Animal
Ganglia, Spinal
Male
Rats
Rats, Sprague-Dawley
Sensory Receptor Cells
Spinal Nerves
