Changes in regional cerebral blood flow and glucose metabolism associated with symptoms of pyrethroid toxicity.

Regional rates of blood flow (rCBF) and of glucose metabolism (rCMRG) were measured in rats showing symptoms typical of an early stage of the type-2 syndrome of pyrethroid toxicity ie. salivation, chewing, and repetitive head and forelimb movements induced by deltamethrin. rCBF was significantly increased in the fourteen brain regions examined, while rCMRG was increased in thirteen of them. In many of the regions the rate of blood flow became excessive in relation to the rate of glucose utilization. This was notable in areas of cerebral cortex, caudate putamen and hippocampus. Values for blood flow in the cortical regions were remarkably similar to those found in rats showing symptoms typical of the type-1 syndrome of pyrethroid toxicity ie. tremors and heightened startle response induced with cismethrin. Excessive blood flow in cerebral cortex appears to be intrinsic to pyrethroid intoxication and unrelated to specific motor symptoms. By contrast, in cerebellum increases in both rCMRG and rCBF appear to correlate with motor disturbances. Other than in cerebellum, a significant increase in rCBF was of early onset, occurring in animals showing salivation and chewing as the only symptoms after being given deltamethrin. The very high ratio of rCBF/rCMRG found in many brain regions of rats given synthetic pyrethroid compounds is unusual and unexplained.