Neurotoxic effects of organic solvents on rapidly growing unmyelinated peripheral nerve axons of rat fetuses

点击翻译按钮获取中文摘要

2,5-Hexanedione(2,5-HD), a common metabolite of n-hexane and methyl n-butyl ketone (MnBK), has high neurotoxic potential. Early degenerative changes in the peripheral nervous system (PNS) are characterized by the development of axonal swellings with accumulated neurofilaments on the proximal side of nodes of Ranvier in distal, nonterminal regions of affected fibers. Changes in axonal transport rates were also reported. Axons of the peripheral nerves of rat fetuses are rapidly growing there length and are not yet myelinated. In this stage we can estimate the direct effects of 2,5-HD on growing axons and also the difference in sensitivity to 2,5-HD on fetal axons compared with the adult axons.Three groups of pregnant rats were studied. Group H : exposed to 2,5-HD 680 mg/kg from day 12 through day 16. Group L : exposed to 2,5-HD 340 mg/kg from day 12 through day 19. Group C : control. First the sciatic and peroneal nerves of the fetuses were studied morphologically and morphometrically. The nerve axons showed characterisitc features. One is a fusion of axons among the group surrounded by arms of a Schwann cell, which was more prominent in group H. Another is an appearance of the second peak at larger diameter in axon caliber distribution. The peroneal nerve axons of group H showed a delay in myelination. There were no differences in reproductive indices among the groups. The behavior of pups delivered from 2,5-HD exposed dams were observed until 7 th postnatal week. The growth rates were suppressed in group H and L through out the observation period. Mean landing foot splay of group H male was wider than those of other two in postnatal day 41 but the significance disappeared in postnatal day 52. No changes in spontaneous motor activities were observed.