Cerebral blood flow-metabolism coupling after administration of soman at nontoxic levels

The effect of soman, an irreversible organophosphorus cholinesterase inhibitor, on regional cerebral blood flow and glucose utilization were studied with a double-tracer, autoradiographic technique in rats. Soman was given at a subtoxic dose of 55 micrograms/kg SC and variables were measured 45 min later. No changes in arterial blood pressure or signs of toxicity were present in the animals studied. Soman induced a pronounced increase in cerebral blood flow. This change was not accompanied by an increase in cerebral metabolism, with exception of superior colliculi. Brain regions showing the more pronounced (greater than 200% over control) increases in blood flow were motor, sensory and temporal cortex, area 18a of the occipital cortex, claustrum, inferior colliculus and cerebellum. These findings differ from those previously reported for the carbamate cholinesterase inhibitor, physostigmine, and constitute the first demonstration of cerebrovascular effects for an organophosphorus cholinesterase inhibitor, soman, at nonsymptomatic doses.