Uncoupling between cortical glucose metabolism and blood flow after ibotenate lesion of the rat basal forebrain: a PET study.

We evaluated the cerebral metabolic rate of glucose (CMRGlu) and cerebral blood flow (CBF) after unilateral lesioning of the rat basal forebrain cholinergic projection system using ibotenic acid. Using positron emission tomography, we measured CMRGlu and CBF with [18F]-2-fluoro-2-deoxy-D-glucose (FDG) and with H2(15)O, respectively. Three days after surgery, CMRGlu and k3* (the rate constant for the phosphorylation of FDG) were reduced in the frontal cortex on the ibotenic acid-injected side, whereas CBF and K1* (the rate constant for the FDG transport from the plasma to brain) in the same rats remained in the normal range. It is concluded that the decreased cortical CMRGlu after the lesion of the cholinergic system projecting from the basal forebrain is due to the diminished neural activity rather than to decreased CBF.