Selective D2 receptor PET in manganese-exposed workers.

OBJECTIVE: To investigate the associations between manganese (Mn) exposure, D2 dopamine receptors (D2Rs), and parkinsonism using [11C](N-methyl)benperidol (NMB) PET. METHODS: We used NMB PET to evaluate 50 workers with a range of Mn exposure: 22 Mn-exposed welders, 15 Mn-exposed workers, and 13 nonexposed workers. Cumulative Mn exposure was estimated from work histories, and movement disorder specialists examined all workers. We calculated NMB D2R nondisplaceable binding potential (BPND) for the striatum, globus pallidus, thalamus, and substantia nigra (SN). Multivariate analysis of covariance with post hoc descriptive discriminate analysis identified regional differences by exposure group. We used linear regression to examine the association among Mn exposure, Unified Parkinson's Disease Rating Scale motor subsection 3 (UPDRS3) score, and regional D2R BPND. RESULTS: D2R BPND in the SN had the greatest discriminant power among exposure groups (p < 0.01). Age-adjusted SN D2R BPND was 0.073 (95% confidence interval [CI] 0.022-0.124) greater in Mn-exposed welders and 0.068 (95% CI 0.013-0.124) greater in Mn-exposed workers compared to nonexposed workers. After adjustment for age, SN D2R BPND was 0.0021 (95% CI 0.0005-0.0042) higher for each year of Mn exposure. Each 0.10 increase in SN D2R BPND was associated with a 2.65 (95% CI 0.56-4.75) increase in UPDRS3 score. CONCLUSIONS AND RELEVANCE: Nigral D2R BPND increased with Mn exposure and clinical parkinsonism, indicating dose-dependent dopaminergic dysfunction of the SN in Mn neurotoxicity.

Influence of intravenous administration of the antipsychotic drug benperidol on the QT interval.

A group effect is generally assumed regarding the prolongation of the QT interval through butyrophenone antipsychotics like haloperidol. Consequently intravenous administration of benperidol is seen critically notwithstanding sparse evidence; thus benperidol and haloperidol were compared regarding their cardiac risk of prolonging the QT interval when administered intravenously for acute sedation of psychotic patients. The QT interval was measured by a 12-lead ECG. For the correction of QT values Bazett's formula was used. The resulting QTc intervals of the benperidol and the haloperidol group were compared using Mann-Whitney U-test. Our data provide statistical evidence for benperidol being less prone to cause QTc prolongation than haloperidol (p = 0.049). The results of our study indicate a more favourable risk profile of benperidol compared to haloperidol regarding QTc prolongation when administered intravenously.

Prediction of striatal D2 receptor binding by DRD2/ANKK1 TaqIA allele status.

In humans, the A1 (T) allele of the dopamine (DA) D2 receptor/ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1) TaqIA (rs1800497) single nucleotide polymorphism has been associated with reduced striatal DA D2/D3 receptor (D2/D3R) availability. However, radioligands used to estimate D2/D3R are displaceable by endogenous DA and are nonselective for D2R, leaving the relationship between TaqIA genotype and D2R specific binding uncertain. Using the positron emission tomography (PET) radioligand, (N-[(11) C]methyl)benperidol ([(11) C]NMB), which is highly selective for D2R over D3R and is not displaceable by endogenous DA, the current study examined whether DRD2/ANKK1 TaqIA genotype predicts D2R specific binding in two independent samples. Sample 1 (n = 39) was composed of obese and nonobese adults; sample 2 (n = 18) was composed of healthy controls, unmedicated individuals with schizophrenia, and siblings of individuals with schizophrenia. Across both samples, A1 allele carriers (A1+) had 5 to 12% less striatal D2R specific binding relative to individuals homozygous for the A2 allele (A1-), regardless of body mass index or diagnostic group. This reduction is comparable to previous PET studies of D2/D3R availability (10-14%). The pooled effect size for the difference in total striatal D2R binding between A1+ and A1- was large (0.84). In summary, in line with studies using displaceable D2/D3R radioligands, our results indicate that DRD2/ANKK1 TaqIA allele status predicts striatal D2R specific binding as measured by D2R-selective [(11) C]NMB. These findings support the hypothesis that DRD2/ANKK1 TaqIA allele status may modify D2R, perhaps conferring risk for certain disease states.

Emotional Eating Phenotype is Associated with Central Dopamine D2 Receptor Binding Independent of Body Mass Index.

PET studies have provided mixed evidence regarding central D2/D3 dopamine receptor binding and its relationship with obesity as measured by body mass index (BMI). Other aspects of obesity may be more tightly coupled to the dopaminergic system. We characterized obesity-associated behaviors and determined if these related to central D2 receptor (D2R) specific binding independent of BMI. Twenty-two obese and 17 normal-weight participants completed eating- and reward-related questionnaires and underwent PET scans using the D2R-selective and nondisplaceable radioligand (N-[(11)C]methyl)benperidol. Questionnaires were grouped by domain (eating related to emotion, eating related to reward, non-eating behavior motivated by reward or sensitivity to punishment). Normalized, summed scores for each domain were compared between obese and normal-weight groups and correlated with striatal and midbrain D2R binding. Compared to normal-weight individuals, the obese group self-reported higher rates of eating related to both emotion and reward (p<0.001), greater sensitivity to punishment (p=0.06), and lower non-food reward behavior (p<0.01). Across normal-weight and obese participants, self-reported emotional eating and non-food reward behavior positively correlated with striatal (p<0.05) and midbrain (p<0.05) D2R binding, respectively. In conclusion, an emotional eating phenotype may reflect altered central D2R function better than other commonly used obesity-related measures such as BMI.

A comparison of D2 receptor specific binding in obese and normal-weight individuals using PET with (N-[(11)C]methyl)benperidol.

Previous PET imaging studies have demonstrated mixed findings regarding dopamine D2/D3 receptor availability in obese relative to nonobese humans. Nonspecific D2/D3 radioligands do not allow for separate estimation of D2 receptor (D2R) and D3 receptor (D3R) subtypes of the D2 receptor family, which may play different roles in behavior and are distributed differently throughout the brain. These radioligands are also displaceable by endogenous dopamine, confounding interpretation of differences in receptor availability with differing levels of dopamine release. The present study used PET imaging with the D2R-selective radioligand (N-[(11)C] methyl)benperidol ([(11)C]NMB), which is nondisplaceable by endogenous dopamine, to estimate D2R specific binding (BPND) and its relationship to body mass index (BMI) and age in 15 normal-weight (mean BMI = 22.6 kg/m(2)) and 15 obese (mean BMI = 40.3 kg/m(2)) men and women. Subjects with illnesses or taking medications that interfere with dopamine signaling were excluded. Striatal D2R BPND was calculated using the Logan graphical method with cerebellum as a reference region. D2R BPND estimates were higher in putamen and caudate relative to nucleus accumbens, but did not differ between normal-weight and obese groups. BMI values did not correlate with D2R BPND . Age was negatively correlated with putamen D2R BPND in both groups. These results suggest that altered D2R specific binding is not involved in the pathogenesis of obesity per se and underscore the need for additional studies evaluating the relationship between D3R, dopamine reuptake, or endogenous dopamine release and human obesity.

Characterization of extrastriatal D2 in vivo specific binding of [¹8F](N-methyl)benperidol using PET.

PET imaging studies of the role of the dopamine D2 receptor family in movement and neuropsychiatric disorders are limited by the use of radioligands that have near-equal affinities for D2 and D3 receptor subtypes and are susceptible to competition with endogenous dopamine. By contrast, the radioligand [¹8F]N-methylbenperidol ([¹8F]NMB) has high selectivity and affinity for the D2 receptor subtype (D2R) and is not sensitive to endogenous dopamine. Although [¹8F]NMB has high binding levels in striatum, its utility for measuring D2R in extrastriatal regions is unknown. A composite MR-PET image was constructed across 14 healthy adult participants representing average NMB uptake 60 to 120 min after [¹8F]NMB injection. Regional peak radioactivity was identified using a peak-finding algorithm. FreeSurfer and manual tracing identified a priori regions of interest (ROI) on each individual's MR image and tissue activity curves were extracted from coregistered PET images. [¹8F]NMB binding potentials (BP(ND) s) were calculated using the Logan graphical method with cerebellum as reference region. In eight unique participants, extrastriatal BP(ND) estimates were compared between Logan graphical methods and a three-compartment kinetic tracer model. Radioactivity and BP(ND) levels were highest in striatum, lower in extrastriatal subcortical regions, and lowest in cortical regions relative to cerebellum. Age negatively correlated with striatal BP(ND) s. BP(ND) estimates for extrastriatal ROIs were highly correlated across kinetic and graphical methods. Our findings indicate that PET with [¹8F]NMB measures specific binding in extrastriatal regions, making it a viable radioligand to study extrastriatal D2R levels in healthy and diseased states.

Hypothermia associated with antipsychotic drug use: a clinical case series and review of current literature.

Hypothermia as an adverse reaction of antipsychotic drug use represents a potentially life-threatening complication. However, the mechanisms by which antipsychotic drugs alter thermoregulatory processes in the human body are far from being fully understood. Here we present a case series of 5 patients developing severe hypothermia after administration of olanzapine and benperidol. Controlled by a network of neural structures, body temperature is physiologically regulated in far more narrow boundaries than are other vital functions, and its homeostasis is critical for survival. The preoptic region in the ventral hypothalamus is assumed to act as a coordinating center that is endowed with thermosensory units that constantly compare actual body temperature with target values and initiate regulatory and compensatory mechanisms in case of mismatch. Hypothermia risk seems to increase in the first days after initiation of antipsychotic drug therapy or increases in the daily dose. Schizophrenic patients bear a higher risk than nonschizophrenic patients treated with antipsychotic drugs (such as patients with dementia or depression). Antipsychotic drugs with strong 5-HT2 antagonism seem to be more frequently associated with hypothermia. These cases demonstrate the clinical relevance of hypothermia as an adverse reaction to antipsychotic treatment and the importance of careful monitoring of body temperature.

Validation of the reference tissue model for estimation of dopaminergic D2-like receptor binding with [18F](N-methyl)benperidol in humans.

Positron emission tomography measurements of dopaminergic D2-like receptors may provide important insights into disorders such as Parkinson's disease, schizophrenia, dystonia and Tourette's syndrome. The positron emission tomography (PET) radioligand [18F](N-methyl)benperidol ([18F]NMB) has high affinity and selectivity for D2-like receptors and is not displaced by endogenous dopamine. The goal of this study is to evaluate the use of a graphical method utilizing a reference tissue region for [18F]-NMB PET analysis by comparisons to an explicit three-compartment tracer kinetic model and graphical method that use arterial blood measurements. We estimated binding potential (BP) in the caudate and putamen using all three methods in 16 humans and found that the three-compartment tracer kinetic method provided the highest BP estimates while the graphical method using a reference region yielded the lowest estimates (P<.0001 by repeated-measures ANOVA). However, the three methods yielded highly correlated BP estimates for the two regions of interest. We conclude that the graphical method using a reference region still provides a useful estimate of BP comparable to methods using arterial blood sampling, especially since the reference region method is less invasive and computationally more straightforward, thereby simplifying these measurements.

Radiation dosimetry of N-([11C]methyl)benperidol as determined by whole-body PET imaging of primates.

PURPOSE: N-([(11)C]methyl)benperidol ([(11)C]NMB) can be used for positron emission tomography (PET) measurements of D(2)-like dopamine receptor binding in vivo. We report the absorbed radiation dosimetry of i.v.-administered (11)C-NMB, a critical step before applying this radioligand to imaging studies in humans. MATERIALS AND METHODS: Whole-body PET imaging with a CTI/Siemens ECAT 953B scanner was done in a male and a female baboon. After i.v. injection of 444-1221 MBq of (11)C-NMB, sequential images taken from the head to the pelvis were collected for 3 h. Volumes of interest (VOIs) were identified that entirely encompassed small organs (whole brain, striatum, eyes, and myocardium). Large organs (liver, lungs, kidneys, lower large intestine, and urinary bladder) were sampled by drawing representative regions within the organ volume. Time-activity curves for each VOI were extracted from the PET, and organ residence times were calculated by analytical integration of a multi-exponential fit of the time-activity curves. Human radiation doses were estimated using OLINDA/EXM 1.0 and the standard human model. RESULTS: Highest retention was observed in the blood and liver, each with total residence times of 1.5 min. The highest absorbed radiation doses were to the heart (10.5 µGy/MBq) [DOSAGE ERROR CORRECTED] and kidney (9.19 µGy/MBq), [DOSAGE ERROR CORRECTED] making these the critical organs for [(11)C]NMB. A heart absorption of 50 mGy would result from an injected dose of 4,762 MBq [(11)C]NMB. CONCLUSIONS: Thus, this study suggests that up to 4,762 MBq of [(11)C]NMB can be safely administered to human subjects for PET studies. Total body dose and effective dose for [(11)C]NMB are 2.82 µGy/MBq [DOSAGE ERROR CORRECTED] and 3.7 mSv/kBq, respectively.

Analysis of pharmacology data and the prediction of adverse drug reactions and off-target effects from chemical structure.

Preclinical Safety Pharmacology (PSP) attempts to anticipate adverse drug reactions (ADRs) during early phases of drug discovery by testing compounds in simple, in vitro binding assays (that is, preclinical profiling). The selection of PSP targets is based largely on circumstantial evidence of their contribution to known clinical ADRs, inferred from findings in clinical trials, animal experiments, and molecular studies going back more than forty years. In this work we explore PSP chemical space and its relevance for the prediction of adverse drug reactions. Firstly, in silico (computational) Bayesian models for 70 PSP-related targets were built, which are able to detect 93% of the ligands binding at IC(50) < or = 10 microM at an overall correct classification rate of about 94%. Secondly, employing the World Drug Index (WDI), a model for adverse drug reactions was built directly based on normalized side-effect annotations in the WDI, which does not require any underlying functional knowledge. This is, to our knowledge, the first attempt to predict adverse drug reactions across hundreds of categories from chemical structure alone. On average 90% of the adverse drug reactions observed with known, clinically used compounds were detected, an overall correct classification rate of 92%. Drugs withdrawn from the market (Rapacuronium, Suprofen) were tested in the model and their predicted ADRs align well with known ADRs. The analysis was repeated for acetylsalicylic acid and Benperidol which are still on the market. Importantly, features of the models are interpretable and back-projectable to chemical structure, raising the possibility of rationally engineering out adverse effects. By combining PSP and ADR models new hypotheses linking targets and adverse effects can be proposed and examples for the opioid mu and the muscarinic M2 receptors, as well as for cyclooxygenase-1 are presented. It is hoped that the generation of predictive models for adverse drug reactions is able to help support early SAR to accelerate drug discovery and decrease late stage attrition in drug discovery projects. In addition, models such as the ones presented here can be used for compound profiling in all development stages.

Benperidol for schizophrenia.

BACKGROUND: Benperidol is a relatively old antipsychotic drug that has been marketed since 1966. It has been used in Germany for 30 years, but is also available in Belgium, Greece, Italy, the Netherlands and the UK. Benperidol is a butyrophenone antipsychotic, with the highest neuroleptic potency in terms of D2 receptor blockade. Those taking it are therefore reputed to be at high risk of extrapyramidal side effects, but benperidol's unusual profile may render it valuable to subgroups of people with schizophrenia. OBJECTIVES: To examine the clinical effects and safety of benperidol for those with schizophrenia and schizophrenia-like psychoses. SEARCH STRATEGY: We searched the Cochrane Schizophrenia Group's register (November 2004) for this update. SELECTION CRITERIA: We included all randomised controlled trials that compared benperidol with other treatments for people with schizophrenia, or schizophrenia-like psychoses. DATA COLLECTION AND ANALYSIS: We reliably selected studies, quality rated them and extracted data. We independently extracted data but excluded data if loss to follow up was greater than 50%. For dichotomous data, we estimated relative risks (RR), with the 95% confidence intervals (CI). Where possible, we calculated the number needed to treat/harm statistic (NNT/H) and used intention-to-treat analysis. MAIN RESULTS: The update yielded no further studies for inclusion in the review. We identified only one unpublished poorly randomised controlled trial (N=40, duration 30 days, comparison perphenazine). Although benperidol was inferior to perphenazine (1 RCT, N=40, global state no better or worse RR 8.0 CI 2.1 to 30, NNH 1.4 CI 1 to 2) poor reporting suggests that an overestimate of effect is likely. It was not possible to report other outcomes. AUTHORS' CONCLUSIONS: Currently, there are insufficient data from randomised trials to assess the clinical effects of benperidol. This compound merits further research interest.

In vivo measurement of D2 receptor density and affinity for 18F-(3-N-methyl)benperidol in the rat striatum with a PET system for small laboratory animals.

UNLABELLED: A recent investigation showed that intracerebral radioactivity concentrations can reliably be quantified in vivo with a small-animal PET device. The purpose of the current study was to investigate the binding characteristics of the D(2) receptor radioligand (18)F-(3-N-methyl)benperidol ((18)FMB) in rat striatum by determining receptor density (B(max)) and affinity (K(d)) in vivo. For validation, K(d) and B(max) additionally were determined in vitro using storage phosphor autoradiography. METHODS: Striatal radioactivity was measured with PET in 8 Sprague-Dawley rats after injection of (18)FMB in increasing specific activities. Free radioligand concentrations were estimated from cortical radioactivity concentrations and were subtracted from striatal radioactivity concentrations to obtain specific binding. In vitro saturation experiments were performed on 7 further rats according to the isotopic dilution method. Specific binding was determined by both subtraction of (18)FMB binding in the presence of raclopride and subtraction of cortical radioactivity concentrations from total radioligand binding. Saturation binding curves were obtained by plotting specifically bound radioligand concentrations against free radioligand concentrations and were evaluated with regression analysis. RESULTS: PET yielded a K(d) of 6.2 nmol/L and a B(max) of 16 fmol/mg for the striatal D(2) receptor. In vitro, K(d) and B(max) amounted to 4.4 nmol/L and 84.1 fmol/mg (subtraction of (18)FMB binding in the presence of raclopride), respectively, and 7.9 nmol/L and 70.1 fmol/mg (subtraction of cortical radioactivity concentrations), respectively. CONCLUSION: K(d) values measured with PET and autoradiography agreed and corresponded to inhibition constants obtained in previous in vitro studies. B(max) values lay within the same order of magnitude. The results of in vitro saturation binding analyses also agreed, irrespective of the mode of determination of free radioligand concentrations. Thus, B(max) and K(d) may be determined with PET in analogy to the evaluation of in vitro binding data by regression analysis of bound-versus-free ligand concentrations. Our results show that small-animal tomographs are valuable tools for the in vivo characterization of receptor radioligands as an alternative to autoradiography.

Bilateral increase in striatal dopamine D2 receptor density in the 6-hydroxydopamine-lesioned rat: a serial in vivo investigation with small animal PET.

Unilateral destruction of the substantia nigra by local application of 6-hydroxydopamine (6-OHDA) serves as an animal model for Parkinson's disease. In this study, the changes in neostriatal dopamine D(2) receptor density were investigated with a small animal positron emission tomograph (PET) before and after 6-OHDA lesion. PET scans were performed in 14 rats after injection of the D(2) receptor radioligand [(18)F] N-methylbenperidol. After the first scan (day 0), nigrostriatal pathways were lesioned by unilateral injections of 6-OHDA. Further PET scans were performed on days 2 and 14 post-lesion. For both striata, B(max) values were determined from saturation binding curves with non-linear regression analysis. In the striatum ipsilateral to the lesion, B(max) initially amounted to 19.3+/-1. 9 fmol/mg (mean+/-SD) and increased to 19.7+/-2.2 and 29.9+/-5.7 fmol/mg on days 2 and 14 post-lesion, respectively. Contralateral B(max) values increased from 19.2+/-2 fmol/mg prior to the lesion to 21.2+/-2.9 and 28.6+/-5.7 fmol/mg on days 2 and 14, respectively. On day 14, the ipsilateral saturation binding curve differed from the ipsilateral pre-lesion curve (P=0.04; F test). When the contralateral pre-lesion saturation binding curve was compared with the contralateral post-lesion curve on day 14, a P value of 0.08 was obtained. This first serial in vivo imaging study of 6-OHDA-lesioned rats showed a time-dependent increase in striatal D(2) receptor density on both sides, the increase being more pronounced ipsilateral to the lesion. This result implies that compensatory mechanisms in the intact hemisphere contribute to regenerative processes following nigrostriatal dopaminergic denervation. Overall, our findings show the feasibility of repetitive in vivo studies of striatal receptor density with a small animal tomograph. Moreover, the applied in vivo saturation binding technique provides a versatile method for the quantification of time-dependent changes in the concentration of receptor binding sites.

Benperidol for schizophrenia.

BACKGROUND: Benperidol is a relatively old antipsychotic drug, marketed since 1966, used in Germany for 30 years, but also available in Belgium, Greece, Italy, the Netherlands and the UK. Benperidol is a butyrophenone antipsychotic, with the highest neuroleptic potency in terms of D2 receptor blockade. Those taking it are, therefore, reputed to be at high risk of extrapyramidal side effects, but benperidol's unusual profile may render it of value to subgroups of people with schizophrenia. OBJECTIVES: To examine the clinical effects and safety of benperidol for those with schizophrenia and schizophrenia-like psychoses. SEARCH STRATEGY: The reviewers searched the Cochrane Schizophrenia Group's register (January 2001) which includes relevant randomised controlled trials from the bibliographic databases Biological Abstracts, CINAHL, The Cochrane Library, EMBASE, MEDLINE, PsycLIT, LILACS, PSYNDEX, Sociological Abstracts and Sociofile. We also searched the references of all included studies and contacted pharmaceutical companies and authors of included studies in order to identify further trials. SELECTION CRITERIA: Randomised controlled trials that compared benperidol with other treatments for people with schizophrenia and/or schizophrenia-like psychoses. DATA COLLECTION AND ANALYSIS: Citations and, where possible, abstracts were independently inspected by two reviewers and papers were ordered, re-inspected and quality assessed. We independently extracted data but excluded data if loss to follow up was greater than 50%. For homogeneous dichotomous data, we calculated the relative risk (RR), the 95% confidence interval (CI) and, where appropriate, the number needed to treat/harm (NNT/H), on an intention-to-treat basis. MAIN RESULTS: We identified only one unpublished poorly randomised controlled trial (N=40, duration 30 days, comparison perphenazine). Although benperidol was inferior to perphenazine (1 RCT, N=40, global state no better or worse RR 8.0 CI 2.1 to 30, NNH 1.4 CI 1 to 2) poor reporting suggests that an overestimate of effect is likely. It was not possible to report other outcomes. REVIEWER'S CONCLUSIONS: Currently, there are insufficient data from randomised trials to assess the clinical effects of benperidol. This interesting compound merits further research.

Imaging of striatal dopamine D(2) receptors with a PET system for small laboratory animals in comparison with storage phosphor autoradiography: a validation study with (18)F-(N-methyl)benperidol.

UNLABELLED: Several groups have developed high-resolution PET systems and shown the feasibility of in vivo studies on small laboratory animals. In this investigation, one of these systems was validated for the performance of receptor imaging studies. For this, the radiotracer concentrations obtained in the same animals with PET and with autoradiography were quantified, and the correspondence between both methods was assessed by means of correlation analysis. METHODS: Striatal radioactivity was measured in 10 Sprague-Dawley rats after injection of 60 +/- 10 MBq of the dopamine D(2) receptor ligand (18)F-(N-methyl)benperidol in 6 time frames of 6 min each. On completion of the scans, animals were killed, and their brains were removed and sectioned using a cryostat microtome. Coronal slices were subjected to storage phosphor autoradiography with BaFBr:Eu(2+)-coated imaging plates. Striatal radioactivity was quantified in both modalities using region-of-interest analysis and activity standards. RESULTS: After partial-volume correction, the median of striatal radioactivity concentration measured with PET was 0.40 MBq/cm(3) (25th percentile, 0.32; 75th percentile, 0.44). Radioactivity concentrations determined by means of storage phosphor autoradiography amounted to 0.42 MBq/cm(3) (25th percentile, 0.24; 75th percentile, 0.51). Correlation of striatal radioactivity values yielded a Pearson correlation coefficient of 0.818 (P = 0.002). Radioactivity accumulation in Harder's glands led to an overestimation of striatal activity concentrations by approximately 5%. The median of striatal radioactivity concentration after spillover correction decreased slightly to 0.38 MBq/cm(3) (25th percentile, 0.30; 75th percentile, 0.43). Correlation of striatal radioactivity values after spillover correction yielded a Pearson correlation coefficient of 0.824 (P = 0.002). CONCLUSION: The results show a significant positive correlation between radioactivity values obtained with PET and storage phosphor autoradiography used as the gold standard. Because we applied a selective dopamine D(2) receptor radioligand and because radioactivity concentrations could be reliably quantified in the target region, we may infer that in vivo receptor binding studies will be possible in small laboratory animals.

[D2-dopamine receptor upregulation and treatment response under neuroleptic therapy]. / D2-Dopaminrezeptorhochregulation und Behandlungserfolg unter neuroleptischer Therapie. Eine Verlaufsuntersuchung erstbehandelter Patienten mit schizophrenen Psychosen.

Animal and post mortem studies indicate that neuroleptic therapy may induce D2-dopamine receptor upregulation in the basal ganglia. To address this phenomenon in a clinical study, we investigated the D2-dopamine receptor binding in 15 DSM-III-R schizophrenics in the drug-naive state and three days after completion of a standardized neuroleptic therapy (benperidol 12-16 mg/d for 25 days) using single photon emission computed tomography (SPECT). SPECT scans were obtained 2 h after intravenous injection of 185 MBq 123I-IBZM. For analysis, basal ganglia to frontal cortex (BG/FC) ratios were calculated and the patient sample was subgrouped into patients with a favourable versus a poor treatment response. Neuroleptic treatment led to decreased BG/FC ratios in patients with a favourable response, but increased ratios in the poor responders (df = 1, F = 4.1, p = 0.06). Changes of BG/FC ratios were significantly correlated with extrapyramidal side effects, but not with neurological soft signs (NSS). Our findings indicate that neuroleptic therapy induces D2-dopamine receptor upregulation in a subgroup of patients characterized by poor treatment response and pronounced extrapyramidal side effects.

[Effect of activation tasks on acute neuroleptic-induced akathisia]. / Wirkungen von Aktivierungsaufgaben bei akuter neuroleptikainduzierter Akathisie.

In this study, we investigated experimentally the effects of different activation procedures on both motor and psychic symptoms in of 11 in-patients with acute neuroleptic-induced akathisia using the Hillside and Barnes akathisia rating scales and videotape rating technique. Motor activation was achieved by finger tapping. Cognitive activation tasks consisted of sequences of mental calculations which were designed either to be easy to perform or to produce stress due to a given time limit or to more difficult calculation operations, respectively. Motor as well as psychic symptoms of akathisia decreased during both motor and simple cognitive activation without stress. By contrast, stress-producing calculation tasks led to an increase in motor and psychic symptoms immediately following the task performance. These possibly specific effects of activation procedures on symptoms might be useful in differentiating acute neuroleptic-induced akathisia from other neuroleptic-induced and extrapyramidal movement disorders.

[Leukopenia associated with butyrophenones. A successful treatment of psychoses with pulsed administration of neuroleptics]. / Leukopenie unter Butyrophenonen. Erfolgreiche Psychosebehandlung durch Neuroleptika-Intervallverabreichung.

In the monotherapeutic treatment of an acute schizophrenic psychoses with butyrophenones (haloperidol and benperidol) we saw immediate leucopenic reactions when the medication was given every day. In literature the risk of butyrophenone-induced blood dyscrasias seems to be underestimated. Therefore we decided to report this single case evaluation. When benperidol (short elimination--half life period) was given every other day ("interval-therapy") the blood cell count of the leucocytes normalized. Furthermore, the amount of psychopathological abnormalities measured by the Brief Psychiatric Rating Scale decreased under this intermittent treatment.

Gender differences in D2 dopamine receptor binding in drug-naive patients with schizophrenia: an [123I]iodobenzamide single photon emission computed tomography study.

Recent studies have described a left lateralized striatal asymmetry of D2 dopamine receptors in male patients with schizophrenia. To replicate this finding and to explore its potential functional consequences, we investigated the D2 dopamine receptor system in 23 drug-naive patients with schizophrenia using single photon emission computed tomography (SPECT). Patients were examined in the drug-naive state and 72 h after completing a standardized neuroleptic treatment with benperidol (12-16 mg/day) for 25 days. Each SPECT examination comprised two scans: the first scan was taken 2 h after intravenous injection of 185 MBq [123I]iodobenzamide. After completion of the first scan, patients received benperidol (8 mg) intravenously. The second scan was started 20 min later. For analysis, basal ganglia to frontal cortex ratios were calculated. Fifteen of the 23 patients originally recruited completed the study on day 28. When compared to female patients, male patients showed a left lateralized asymmetry of striatal D2 dopamine receptor binding in the drug-naive state with an almost significant (P = 0.07) sex x hemisphere interaction. In the male patients, benperidol challenge led to a reversal of asymmetry patterns. These findings support previous reports of a left lateralized striatal D2 receptor binding in drug-naive male patients with schizophrenia and suggest that this asymmetry may affect the binding of conventional neuroleptics such as benperidol at the D2 dopamine receptor.