In vivo kinetics of blood cholinesterase inhibition by 9-amino-1, 2, 3, 4-tetrahydroacridine, its 7-methoxy derivative and physostigmine in rats.

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.