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

1990; American Medical Association; Volume: 47; Issue: 12 Linguagem: Inglês

10.1001/archpsyc.1990.01810240090014

1538-3636

Philip Seeman,

Neuroscience and Neuropharmacology Research

To the Editor.— In schizophrenia, the brain reveals elevated densities of dopamine D 2 receptors whether or not the patients have received neuroleptic medications. 1-3 In addition, the left putamen in schizophrenia shows D 2 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. 4 It has been puzzling that these unilateral elevations of 2.8 to 3.2 pmol/mL, seen with [ 11 C]raclopride, are less than the bilateral D 2 elevations of 12 and 25 pmol/mL 2,3 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 D 2 is underestimated by radioactive raclopride in the presence of dopamine. Furthermore, when the cerebellum is used as baseline, the apparent value for the total D 2 density is artificially