BRAIN CHOLINESTERASE ACTIVITY OF BOBWHITE ACUTELY EXPOSED TO CHLORPYRIFOS

Northern bobwhite, Colinus virginianus, were orally dosed with the organophosphorus insecticide chlorpyrifos to examine effects on brain cholinesterase (ChE) activity. Two-week-old quail were acutely exposed and euthanized at selected times following gavage-dosing, ranging from 1 to 120 h later. The ChE activity was determined in treated birds and compared to concurrently tested control (corn oil) birds. It was found that a lag time of 2 to 4 h following exposure was necessary to detect significant ChE depression caused by chlorpyrifos. The lowest dose that produced ChE depression in these tests was between approximately 30 and 50 mg chlorpyrifos/kg body weight, with some mortality occurring at the high end of that range. Depression typically persisted for at least 24 h.