Printed ¡nU.S.A. Repeated Inhibition of Cholinesterase by Chlorpyrifos in Rats: Behavioral, Neurochemical and Pharmacological Indices of

Accepted for publication March 17,1994 Previous work from this laboratory showed that daily s.c. in jections of the organophosphate diisopropylfluorophosphate caused prolonged inhibition of Cholinesterase (ChE) activity in whole blood and brain and downregulation of muscarinic recep tors in the central nervous system; these changes were accom panied by progressive, persistent deterioration of working mem ory and motor function. Further, a single s.c. injection of the organophosphate insecticide Chlorpyrifos (O,O',-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothionate, CPF), caused neurochem-ical changes of the same magnitude and duration, but transient impairment of working memory and motor slowing. In the present study, weekly injections of CPF (0, 15, 30 or 60 mg/kg s.c.) inhibited ChE activity in whole blood of rats by 60 % to 90 % afte