Development factors affecting brain acetylcholinesterase inhibition and recovery in DFP-treated rats.

The effect of a single dose of diisopropyl fluorophosphate (DFP; Isoflurophate, 1.1 mg/kg s.c.) administered to rats during pregnancy was evaluated by measuring postpartum maternal and newborn brain-soluble and total acetylcholinesterases (AChE) and their molecular forms at intervals of 1, 2, 3, 4 and 10 days between treatment and sacrifice. Subsequently, the effects of DFP were studied in 18-day-pregnant rats, fetuses and placentae at 90 min and 24 h after treatment. The inhibition of postpartum maternal enzymatic activity did not differ from that previously found in adult males, while inhibition was considerably less pronounced in newborns at all time intervals, with a nearly complete recovery already at 48 h after treatment. An even faster recovery of brain enzyme was observed in 18-day fetuses from DFP-treated mothers (24-hour interval between treatment and sacrifice). In this experiment, a comparable inhibition was observed at 90 min after treatment in the adult and the developing brain, excluding a major influence of disposition factors in the differential recovery phenomena. An experiment on weanling rats yielded intermediate results between those of newborn and those of adult animals. Finally, most data confirmed previous findings that the soluble portion of brain AChE and medium molecular weight enzyme forms may have special significance in the initial phases of recovery.