Changes of acetylcholinesterase activity in three major brain areas and related changes in behaviour following acute treatment with diisopropyl fluorophosphate

Abstract

In a series of experiments, the recovery of acetylcholinesterase activity in three brain regions following its depression by diisopropyl fluorophosphate was examined. Related changes in behaviour were also studied. The maximum depression in acetylcholinesterase activity in the anterior preoptic area occurred at 4hr, about the same time as the maximum depression of deep body temperature was recorded. A significant recovery of acetylcholinesterase activity was observed at 16hr, while temperature regulation returned to normal by 20 hr. Maximum depression of drinking behaviour and acetylcholinesterase activity in the lateral hypothalamus both occurred at approx. 1 hr following the acute diisopropyl fluorophosphate injections and both showed significant but not complete recovery by 24 hr. Single alternation performance had not completely recovered even at the final test session, i.e. 71 hr following the diisopropyi fluorophosphate injection, at which time acetylcholinesterase activity in the caudate nucleus had reached approximately 23% of normal. These findings generally support the hypothesis that recovery of certain behaviours may be dependent upon the renewed synthesis of acetylcholinesterase activity in brain regions which are important in mediating these behaviours.