i ELSEVIER Psychiatry Research: Neuroimaging 67 (1996) 159-162 PSYCHIATRY RESEARCH NEUROIMAGING Letter to the editor In schizophrenia, some dopamine Drlike receptors are still elevated In a recent study, Nordstr6m et al. (1995) con- cluded that their findings fail to support the hy- pothesis that schizophrenia is related to increased D2-1ike dopamine receptor density in putamen (Nordstrtm et al., 1995). In that study, positron emission tomography of N-[ItC]methylspiperone ([HC]NMSP) in neuroleptic-naive patients with schizophrenia yielded no significant elevation of receptor Bnm. The authors scanned seven patients (2 females and 5 males) and seven control subjects (7 males) with [i IC]NMSP and found an elevation of NMSP 8max in the putamen of the schizophre- nic patients of 33% (patients: 32 pmol/cm 3, con- trois: 24 pmol/cm3). However, for the male 60 .--.- 5O E o 40 o E 30 ¢z. x 20 ¢¢1 1= co 10 t ~ men I schizophreniform ¢ w0ml)n 0 I , [] Q [] [] I Controls Schizophrenics Fig. 1. Maximum binding (Bm=D of N-methylspiperone in control subjects and schizophrenic patients from study of NordstrOm et al. (1995). Note elevation of Bm.x in male pa- tients with schizophreniform subtype of schizophrenia. patients, the elevation was 45%, and for the three schizophreniform patients, the elevation was 73% (significant at P < 0.05), as shown in Fig. 1. Four schizophrenic patients had a higher Bma ~ than the highest value of the controls. The study invites a more detailed discussion. First, the authors should be acknowledged for having successfully reproduced the method employed by Wong et al. (1986a). An obvious rea- son for the lack of overall significant increase in the study could be the large variance of the Bnm measurement. Contributions to this variance in- clude uncertainty associated with the assays of serum haloperidol (radioimmunoassay and high performance liquid chromatography), the delay of 3 rather than 4 h after haloperidol administration, the method of estimation of the steady-state slope of NMSP accumulation, and the lack of gender matching in the study. Tune et al. (1993) demonstrated that male, but not female, schizo- phrenic subjects had a significant increase of dopamine D2-1ike Bm~ values measured with [nC]NMSP. Also, Wong et al. (1988) found ef- fects of menstrual cycle on [IIC]NMSP binding. On the basis of the observed data for the male subjects alone, 24 subjects would be required in each group to reject, with the power of 80%, the null hypothesis of no difference, using an, coef- ficient of 0.05, assuming the true difference is that seen in the data. Nordstr6m et al. conclude that 'the finding by Wong et al. of a two- to three-fold elevation of central D 2 receptor density in the putamen of neuroleptic-naive schizophrenic patients could not be replicated in the present study despite our use of a PET camera with superior performance'. However, Wong et al. (1986b) measured D2 recep- 0925-4927/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All fights reserved PII S0925-4927(96)02953-8