Hyper-excitability in low threshold mechanical A fibers is potentially involved in scorpion BmK sting pain.
In the present study, using the single fiber recording technique, we found that BmK I, the main toxic component in scorpion Buthus martensi Karsch (BmK) venom, induced dramatic increase in excitability of rapidly adapting (RA) and type I slowly adapting (SAI) low threshold mechanical A fibers of rat. Five micrograms BmK I (691 nmol, in 10 microl saline) administrated to the receptive fields induced spontaneous activity in 80% of RA and SAI fibers, increased the response to 10 g-10 s stimulation at about 20 times and altered the firing pattern to burst mode with maximal NS (number of spikes in burst) averaging from all fibers studied as many as 59. The increase in the excitability of RA and SAI fibers did not recover completely in 2h. Our finding suggests that the gigantic abnormal activity in low threshold mechanical A fibers is involved in BmK scorpion sting pain, and the experimental model of BmK scorpion sting pain can be used to study A-fiber related central pathway which is important for relief of refractory neuropathic pain likewise.
Liu
Ying
Y
Graduate School of the Chinese Academy of Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. liuying@sibs.ac.cn
Bai
Zhan-Tao
ZT
Feng
Xing-Hua
XH
Li
Wen-Peng
WP
Yang
Hong-Tian
HT
Zhou
Jing-Jing
JJ
Ji
Yong-Hua
YH
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D004594:Electrophysiology; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000187:drug effects*; D009431:Neural Conduction / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012604:Scorpion Venoms / Q000494:pharmacology*; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors
D012604:Scorpion Venoms