PARTIAL PROTECTION BY DEXAMETHASONE AGAINST MIPAFOX-INDUCED DELAYED NEUROTOXICITY IN HENS

The protective effect of dexamethasone against mipafox-induced delayed neurotoxicity in hens was investigated. Birds treated with Mipafox (1 0.0 mg kg(-1), s.c.) daily for 10 days developed severe ataxia. There was inhibition of neurotoxic esterase (NTE) in the brain, spinal cord and platelets, and inhibition of platelet acetylcholinesterase (AChE). Axonal degeneration in the spinal cord was observed 14 days after the start of exposure. A lower dose of dexamethasone (0.5 mg kg(-1), i.m. ) daily for 10 days reduced the behavioural, biochemical and histopath ological changes, whereas higher dose (5.0 mg kg(-1), i.m.) daily for 10 days aggravated the changes induced by mipafox in hens. Dexamethaso ne alone at the lower dose did not cause behavioural and histopatholog ical changes except increased NTE and decreased AChE activities. Howev er, the higher dose alone caused weakness and loss of body weight, dec reased NTE and AChE activities and with certain histopathological chan ges. The study suggests that dexamethasone may partially protect the h ens against mipafox-induced delayed neurotoxicity.