Brain Dopamine Receptors in Schizophrenia: PET Problems-Reply

In Reply—  Seeman argues, somewhat vaguely, that "the analytical method determining the control values can have considerable influence on whether abnormal values may be detected." He refers to the early PET finding by Wong et al¹ that no D₂ dopamine receptor abnormalities were found in drug-naive schizophrenics and to the more recent report where the same group, using a more sophisticated quantitative method, demonstrated a twofold to threefold elevation of D₂ dopamine receptor densities in the caudate nucleus.² Using a different quantitative method and a different ligand, we could not confirm the occurrence of substantially elevated D₂ dopamine receptor densities in the putamen or the caudate nucleus of drug-naive schizophrenics.The PET determinations of receptor characteristics in vivo are based on a number of measured variables influenced by a number of biologic functions. There are several major differences between the PET methodologies used by Wong et al