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Elevation of Dopamine D2 Receptors in Schizophrenia is Underestimated by Radioactive Raclopride

Philip Seeman, MD, PhD; Hyman B. Niznik, PhD; Hong-Chang Guan, MD
Arch Gen Psychiatry. 1990;47(12):1170-1172. doi:10.1001/archpsyc.1990.01810240090014.
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To the Editor.—  In schizophrenia, the brain reveals elevated densities of dopamine D2 receptors whether or not the patients have received neuroleptic medications.1-3 In addition, the left putamen in schizophrenia shows D2 to be elevated by 2.8 pmol/mL, significantly different from the right side, but nonsignificantly elevated by 3.2 pmol/mL compared with controls.4It has been puzzling that these unilateral elevations of 2.8 to 3.2 pmol/mL, seen with [11C]raclopride, are less than the bilateral D2 elevations of 12 and 25 pmol/mL2,3 found in never-medicated patients measured with radioactive spiperone compounds. There are many factors that may explain such differences.5 We report herein, using human tissues, that the density of D2 is underestimated by radioactive raclopride in the presence of dopamine. Furthermore, when the cerebellum is used as baseline, the apparent value for the total D2 density is artificially


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