Comparison of organophosphate-induced delayed neuropathy between branches of the tibial nerve and the biventer cervicis nerve in chickens.
Delayed neuropathy induced by organophosphorus esters has been reported to be more selective for large diameter myelinated fibers, especially in distal portions of long nerves. This concept was re-evaluated in chickens by quantitatively comparing the effects of the organophosphates tri-ortho-tolyl (TOTP) and phenyl saligenin phosphate (PSP) on two separate nerves, the branch of the tibial nerve that supplies the gastrocnemius muscle, and the small cervical nerve that innervates the biventer cervicis muscle. Histograms illustrating the distribution of myelinated fibers within each nerve showed that the biventer nerve is composed of a population of fibers smaller than those within the tibial nerve branch. However, the number of myelinated fibers measured per mm2 of endoneurium was reduced in both nerves 10 and 15 days after organophosphate administration, providing indirect evidence that fiber diameter is not critical in determining susceptibility to organophosphorus-induced delayed neuropathy (OPIDN). More direct evidence was provided by fiber diameter histograms of both biventer nerves and tibial nerve branches taken from hens that received PSP. In comparison to control values, there was a decrease in all fiber sizes in both nerves, indicating that factors other than axonal size are important in determining nerve fiber susceptibility to OPIDN.
Dyer
K R
KR
Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg 24061.
el-Fawal
H A
HA
Ehrich
M F
MF
D000818:Animals; D002645:Chickens; D005260:Female; D009413:Nerve Fibers, Myelinated / Q000187:drug effects* / Q000473:pathology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000473:pathology; D009943:Organophosphorus Compounds / Q000633:toxicity*; D013979:Tibial Nerve / Q000187:drug effects* / Q000473:pathology
D009943:Organophosphorus Compounds