Histologic peripheral nerve changes in rats induced by deltamethrin

Synthetic pyrethroid insecticides have been used in the last two decades la rgely because of their high activity as an insecticide and tom mammalian to xicity. Some studies have demonstrated that these products, especially comp ounds with an a-cyano group, are toxic to the mammalian central nervous sys tem (CNS) in acute intoxications. However, morphological studies are scarce . In the present work the histopathologic changes of the sciatic and tibial nerves of rats submitted to acute intoxication with the cyanopyrethroid de ltamethrin were studied. For 3 consecutive days male Wistar rats received b y oral gavage deltamethrin at a dose of 45 mg/kg body mt. On the 4th day fr agments of sciatic and tibial nerves were studied by transmission electron microscopy (TEM) and teasing of individual nerve fibers. In addition, anoth er group of rats mere allowed to recover until the 10th day. Teasing of ner ves of animals sacrificed on the 4th day revealed myelin ovoids, which are indicative of axonal damage. TER I demonstrated rare degenerated axons comp letely filled with organelles, in particular mitochondria, and with electro n-dense lamellar bodies that resemble myelin figures. In addition, great cy toplasmic vacuolization caused by proliferation and dilation of the rough a nd smooth endoplasmic reticulum and Golgi apparatus mas observed in some Sc hwann cells. No lesion was found 7 days after discontinuation of the treatm ent (group 2). Since these histologic changes are transitory and scarce, th e question arises: Are they related to the changes in NA(+), K+-ATPase acti vity or Na+ channels caused by pyrethroid compounds? (C) 2000 Academic Pres s.