Acetylcholinesterase activity and degenerative changes in various segments of the spinal cord of hens induced by ingestion of subchronic levels of leptophos.

Changes in acetylcholinesterase (AChE) levels in the brain and various segments of the spinal cord of birds fed subchronic repeated oral doses of 0-(4-bromo-2,5 dichlorophenyl) 0-methyl phenylphosphonothioate, (leptophos, 15 mg/kg/day) is reported. The effect of leptophos on the histological structure of the spinal cord has also been described. Three birds each of four groups tested were sacrificed 7, 14, 21 and 35 days after treatment. AChE levels in the cervical, thoracic and lumbar cord were depressed from 29%-33% after 7 days to 34%-56% after 14 days of leptophos administration. This was followed by a gradual recovery at 21 days post treatment with a further decrease (23%-48%) at 35 days post treatment. Similar decreases in brain AChE levels were also observed. Spinal cord lesions in the cervical and thoracic segments were restricted to the anterior and lateral columns, while lumbar cord lesions were restricted to the anterior column. It is concluded that routine histopathology correlated with AChE levels in the cervical, thoracic and lumbar sections of the spinal cord may be useful in monitoring the onset of clinical neuropathy in laboratory animals fed prolonged subacute doses of neurotoxicants.