Changes of cholinesterases in the blood and some tissues following administration of tacrin and its two derivatives to rats

Tacrin, its 7-methoxy-(MEOTA) and 7-hydroxy-(HYOTA) derivatives were i.m. administered to rats in a dose of 1.2 × LD 50 and acetylcholinesterase (blood, hippocampus, frontal cortex, basal ganglia, septum and diaphragm) or butyrylcholinesterase (liver) activities were detected. The inhibitory effect of the examined substances in vivo decreased in the following order: tacrin HYOTA > MEOTA. The marked inhibition of the enzymes studied following administration of all three compounds in the frontal cortex could suggest importance of this structure for action of these drugs.