Regional distribution of prostanoids in rat brain: effect of insulin and 2-deoxyglucose

Abstract

Prostaglandin synthesis in the brain has been suggested as a component in the control mechanism of the cerebral circulation. During insulininduced hypoglycemia there is a significant increase in local cerebral blood flow in various brain regions, however, regional loss of autoregulation occurs under these conditions. In the present study the regional distribution of PGE₂, TXB₂ (the stable metabolite of thromboxane) and 6-keto-PGF_1α (the stable metabolite of prostacyclin) was determined in rat brain following decapitation. Three groups of rats were treated with either saline, insulin or 2-deoxyglucose and their brains were rapidly removed one hour later. Samples from the cortex hypothalamus, hippocampus, striatum, nucleus accumbens and cerebellum were assayed by RIA for the content of PGE₂, TXB₂ and 6-keto-PGF_1α The levels of all three compounds in control rats were the lowest in the striatum and cerebellum, while in the cortex and hippocampus their levels were 4–6 times higher. Insulin had selective effect on the post decapitation levels of prostanoids. It increased PGE₂ in the n. accumbens and TXB₂ in the hippocampus, and reduced 6-keto-PGF_1α and TXB₂ in the cortex. 2-DG reduced all PGs in the cortex and 6-keto-PGF_1α in the hypothalamus and hippocampus. The results demonstrate that discrete brain areas have a differential capacity to accumulate PGs following decapitation. This capacity is selectively affected by insulin and 2-DG.