The main
injuries among victims of the terrorist act in the Tokyo subway resulted from sub-lethal inhalation and whole body exposure to
sarin vapor. In order to study the long term effects of such exposure and to simulate these conditions, freely moving rats were exposed to
sarin vapor (27.2±1.7 μg/l) for 10 min. About 50% of the rats showed no overt symptoms and the rest had mild to moderate clinical symptoms that subsided within 4h following exposure. A reduction of weight was noted during the first 3 days with full recovery on the 4th day. Rat's heart was challenged with
epinephrine 1 and 6 months post exposure. A significant reduction in the threshold for
epinephrine-induced
arrhythmia (EPIA) was noted in rats exposed to
sarin. A time dependent increase in the kD and Bmax values of
muscarinic auto receptors (M2) was recorded in the rat's cortex and striatum. No changes were recorded in the rats' brain trans locator
protein (TSPO) levels, concomitant with no observed changes in the animals' performance in A Morris water maze test. A significant increase in open field activity was noted 6 months following exposure to
sarin vapor as well as a significant decrease in
prostaglandin E₂ (PGE₂) production in the brain. It is speculated that down regulation of the M2 auto receptor function, caused hyper reactivity of the
cholinergic system which leads to the changes described above. The continuous reduction in M2 auto-receptor system through an unknown mechanism may be the cause for long lasting decline in
sarin-exposed casualties' health.