Effects of soman, sarin and vx on specific[binding of [3h]qnb in rat cerebral cortex homogenates

The interaction of organophos-phorus anticholinesterases soman, sarin and VX with the muscarinic acetylcholinergic receptor(M-AChR) in CNS was studied by measuring the specific binding of [3H]QNB to the homogenates of rat cerebral cortex. The specific [3H]QNB bound was saturable with increasing concentrations. The non-specific binding, in the presence of 5 UM unlabeled QNB and 5 nM [3H]QNB was not saturable and increased linearly with increasing [3H]QNB. Under our assay condition, the ratio of specific binding/nonspecific binding was 12-15. The specific binding of [3H]QNB decreased regujarjy as the concentrations of soman, sarin and VX increased gradually. The decrease was initiated under low concentration of soman, sarin and VX, which only slightly inhibited the AChE activity. A maximal reduction of about 20% of specific binding of [3H]QNB was observed as compared to controls. These data afforded tentatively a direct evidence for the action of soman, sarin and VX on M-AChR in rat cerebral cortex in vitro. Their dual actions on AChE and M-AChR would be useful for explaining the mechanism of action of organophosphates on CNS.