Mechanisms of peritumoural and neuroreceptor findings in brain dysfunction: metabolic striatal C6 glioma

The aetiology of the peritumoural brain dysfunction that is rectified by steroids is unknown. To determine potential aspects of its pathophysiological basis we performed metabolic, histochemical and neuroreceptor studies in rodents with striatal C6 glioma. This model is known to cause focal neurobehavioural and electrophysiological dysfunction. The fully quantitative [C-14]-2-deoxyglucose autoradiographic technique of measuring local cerebral metabolism of glucose (LCMRglu) showed raised LCMRglu (22-29%) in the pallidum, substantia nigra and endopeduncular nucleus. Acetylcholinesterase (AChE) histochemistry and a range of ligand binding studies for dopamine type 1 and 2, and serotonergic 5-HT2 receptors were negative in the tumour and normal in peritumoural brain. 5-HT uptake sites and strong peripheral benzodiazepine receptor expression were present in the tumour. There was extensive up-regulation of peripheral benzodiazepine receptor expression in the peritumoural brain. These studies show there is metabolic dysregulation in brain regions functionally connected to, but anatomically distant from the striatum. There is also a peritumoural region of up-regulated receptors that have many, predominantly inhibitory, functions. The relationship of these findings to peritumoural brain dysfunction is discussed. (C) 2001 Harcourt Publishers Ltd.