A long-term study of the effects of diazinon on sleep, the electrocorticogram and cognitive behaviour in common marmosets.

The long-term sequelae of exposure to low doses of organophosphate compounds are ill defined, with effects variously reported on a range of indices of central nervous system functions such as sleep, cognitive performance and electroencephalogram (EEG). These indices were examined in common marmosets exposed to a range of doses of the organophosphorous sheep dip, diazinon. Cognitive performance was assessed by means of elements from the Cambridge Neuropsychological Test Automated Battery (CANTAB), and radiotelemetry techniques were employed to monitor the electrocorticogram and sleep patterns. Data were collected for 12 months following intramuscular administration of a single dose of diazinon (10, 90 or 130 mg.kg (-1)) or vehicle. Although high levels of erythrocyte acetylcholinesterase (AChE) inhibition (up to 82%) and short-term changes in sleep patterns were seen, there was no evidence of biologically significant long-term changes in any measures. The effects of multiple exposures, impurities or mixtures of OP compounds remain to be investigated.