Imidazoline I(2) receptor density increases with the malignancy of human gliomas

Current glioma grading schemes are limited by subjective histological criteria. Imidazoline I(2) receptors are principally expressed on glial cells. To investigate the feasibility of using the measurement of imidazoline I(2) receptor expression to differentiate glial tumours from other types of brain tumours and for grading the different gliomas. The specific binding of [(3)H]idazoxan to imidazoline I(2) receptors was measured in homogenates from human gliomas of different grades. The density of imidazoline I(2) receptors was significantly greater in the three types of malignant glial tumours than in postmortem control brain or non-glial tumours. The increase in density correlated with the malignancy grade of the gliomas. No significant differences in affinity values were observed. These results suggest that the density of imidazoline I(2) receptors may be a useful radioligand parameter for the differentiation of glial tumours from other types of brain tumours and for grading the different gliomas.