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The aim of this study was to demonstrate changes in acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities, tyrosine aminotransferase activity (TAT) and plasma corticosterone level, neuroexcitability and behavior following 24 hours and 4 weeks of soman sublethal inhalation exposure at low level. AChE activity in erythrocytes and BuChE activity in plasma was decreased (dependent on the concentration of soman) 24 h and 4 weeks after the exposure. Similar decrease in AChE activity in different brain parts was observed. One of stressogenic parameters (TAT) was changed after 24 h exposure only. 4 weeks after the exposure, these parameters (corticosterone and TAT) were in the range of normal values. Behaviour of experimental animals was changed 24 h after the exposure persisting 4 weeks after the exposure as well as neuroexcitability.

Toxicities of O-ethyl-S-(2-dimethylaminoethyl)-methylphosphonothioate were determined by i. v. (17.0 microgram/kg), i.m. (23.6 microgram/kg), i. p. (54.5 microgram/kg) and p. o. (121.9 microgram/kg) administration to female rats. Following intoxication with this compound (42 microgram/kg) at these routes of administration, acetylcholinesterase activity in the blood was continuously monitored and half-times of inhibition in vivo were determined. It appears from a comparison of inhibitions in vivo and in vitro that only a part of the dose administered is effective to inhibit acetylcholinesterase in the blood vessel.

In vivo inhibition of blood acetylcholinesterase activity by 9-amino-1, 2, 3, 4-tetrahydroacridine, its 7-methoxy derivative and physostigmine was studied in rats. Changes of enzyme activity in the blood were continually registered using an automatic colorimeter Auto Analyzer system. The dependence of % enzyme inhibition upon time in semilogarithmic transformation was characterized by a two phase curve. The first phase reflected the increase in the concentration of inhibitors in the blood during their resorption; this was followed by a slow second phase of inhibition. The inhibitory effect decreased in the order: physostigmine greater than tacrine greater than 7-methoxytacrine. The relationship between the anticholinesterase and antipsychotomimetic action of the examined substances is discussed.

0-isopropylmethyl phosphonofluoridate and 0-ethyl-S-(2-dimethylaminoethyl) methylphosphonothioate were i.m. administered in doses of 2 x LD50 to female rats and the blood acetylcholinesterase was continuously monitored using the automatic colorimeter Auto Analyzer. This activity rapidly decreased after the injection of the two organophosphates studied. If the blood flow in the leg muscles was stopped by compression and reopened by relaxation at different time intervals, acetylcholinesterase activity was either unaffected (detoxication present) or decreased (detoxication absent). It was observed that phosphonofluoridate was detoxified; on the other hand, phosphonothioate was not detoxified in the rat organism.