Conduction failures in rabbit saphenous nerve unmyelinated fibers.
Recent experimental and theoretical data indicate that the functional capabilities of axons with specialized structures are much more diverse than traditionally thought. However, few observations were concerned with the main axons without arborization. In the present study, electrical stimulation of the saphenous nerve at different frequencies (2, 5, 10, 20 Hz) was used to test the role of activity-dependent effects on the pattern of action potentials that propagate along individual unmyelinated fibers (C fibers) within the trunk of the saphenous nerve in rabbits. Three basic types of C fiber responses to repetitive stimulation were observed: type-1 fibers showed an entrained response without conduction failure; type-2 fibers discharged with intermittent conduction failures; while only sporadic conduction failures happened in type 3. The failure modality in type-2 and type-3 fibers is closely related to the conductive distance as well as the frequency and duration of stimuli which lead to a critical level of conduction velocity slowing. A novel fluctuation in interspike intervals was always observed immediately before the occurrence of the failures, implying that the fluctuation of conduction velocity is correlated with imminent failures. Both the 4-aminopyridine-sensitive potassium current and hyperpolarization-activated cation current were recognized to be involved in the regulation of conduction failure patterns. The results confirmed, at least in part, the existence of conduction failures in the main axon of C fibers, suggesting that axonal operations may also be determinants for adaptation phenomenon and information processing in peripheral nervous system.
Zhu
Zhi-Ru
ZR
Department of Biomedical Engineeringe, Zhejiang University, Hangzhou, China.
Tang
Xiao-Wei
XW
Wang
Wen-Ting
WT
Ren
Wei
W
Xing
Jun-Ling
JL
Zhang
Jun-Ran
JR
Duan
Jian-Hong
JH
Wang
Yu-Ying
YY
Jiao
Xiying
X
Hu
San-Jue
SJ
D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005260:Female; D005267:Femoral Nerve / Q000166:cytology / Q000502:physiology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008297:Male; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology*; D017933:Peripheral Nervous System / Q000166:cytology / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D015761:4-Aminopyridine