Diisopropyl phosphorofluoridate (DFP) disrupts circadian activity patterns

A single dose (1.75 mg/kg SC) of diisopropyl phosphorofluoridate (DFP) was given to rats living continuously in modified activity cages in which wheel running, lever pressing and feeding were monitored twenty four hours per day. The first twenty four hours following DFP injection was characterized by a marked reduction in all monitored activities. Within a few days, food intake and lever pressing had recovered to pre-injection levels, but running remained suppressed throughout the remainder of the experiment. A comparison of the circadian distribution of activities for individual subjects showed phase shifts and a reduction in amplitude of all three monitored activities, persisting well beyond the initial reductions in the daily totals.