Frits-Axel Wiesel

Central D2-dopamine receptor occupancy in relation to antipsychotic drug effects: a double-blind PET study of schizophrenic patients.

The relationship between central D2-dopamine receptor occupancy and antipsychotic drug effects was examined in a double-blind study. Raclopride was the compound used to induce a selective occupancy of the D2-dopamine receptors. In addition, 11C-labeled raclopride was the radioligand used to measure occupancy by positron emission tomography (PET). Seventeen schizophrenic patients were randomly assigned to one of three parallel groups treated for 4 weeks with daily doses of 2, 6, or 12 mg of raclopride. D2-receptor occupancy was determined by PET at steady-state conditions in 13 patients who completed the study. A statistically significant relationship was demonstrated between antipsychotic effect and degree of D2-receptor occupancy (p < 0.05). Patients with extrapyramidal side effects had significantly higher D2-receptor occupancy than those without (p = 0.02). The finding of a relationship between selective occupancy of the D2-dopamine receptors and clinical effects in schizophrenic patients principally provides new support for the dopamine hypothesis of antipsychotic drug action.

D1- and D2-dopamine receptor occupancy during treatment with conventional and atypical neuroleptics

Using positron emission tomography and the selective ligands 11C-SCH23390 and 11C-raclopride, central D1- and D2-dopamine receptor occupancy was determined in schizophrenic patients treated with clinical doses of classical and atypical neuroleptics. Treatment with ten chemically distinct classical neuroleptics resulted in a 65–89% occupancy of D2-dopamine receptors. This finding represents strong support for the hypothesis that the mechanism of action of antipsychotic drugs is indeed related to a substantial degree of D2-dopamine receptor occupancy. In two patients treated with teh atypical neuroleptic clozapine, 300 mg b.i.d. and 150 mg b.i.d., the D2-dopamine receptor occupancy was 65 and 40%, respectively. D1-dopamine receptor occupancy was determined in six antipsychotic drugtreated patients. No D1-dopamine receptor occupancy was found in patients treated with sulpiride and perphenazine, compounds known to be selective D2-dopamine receptor antagonists. The highest D1-dopamine receptor occupancy, 42%, was found in the patient treated with clozapine 150 mg b.i.d. The effects of the atypical neuroleptic clozapine may be related to a combined effect on both D1- and D2-dopamine receptors.

Simultaneous determination of the three major monoamine metabolites in brain tissue and body fluids by a mass fragmentographic method

A mass fragmentographic method for the simultaneous determination of 4-hydroxy-3-methoxyphenylacetic acid (HVA), 4-hydroxy-3-methoxyphenylethylene glycol (MOPEG), and 5-hydroxyindole-3-acetic acid (5-HIAA) was described. Deuterated analogues of the compounds were used as internal standards. The specificity was proved by multiple ion analysis. The experimental error was below 7% when applied to the analysis of human lumbar cerebrospinal fluid, urine, or rat brain tissue. In cerebrospinal fluid the major part of the monoamine metabolites occurred in the free form. In rat brain and human urine considerable amounts of conjugated HVA was found.

Lack of apparent antipsychotic effect of the D1-dopamine recepotr antagonist SCH39166 in acutely ill schizophrenic patients

SCH 39166 is the first selective D1 dopamine receptor antagonist developed for the treatment of schizophrenic patients. To examine potential antipsychotic effect, tolerability and safety, SCH 39166 was given orally to 17 acutely ill drug free schizophrenic patients (DSMIIIR) in an open 4-week study. Doses were escalated from 10 to 100 mg b.i.d. according to a fixed schedule over 17 days and remained at 100 mg b.i.d. for another 11 days. The drug was withdrawn prematurely in ten patients because of deterioration or refusal to take SCH 39166. In the nine patients participating for more than 2 weeks, none had an apparent reduction of BPRS or CGI scores. Side effects were agitation, akathisia and emesis in single patients. After withdrawal of SCH 39166 of the patients improved when treated with classical neuroleptics or clozapine. The result of the study does not support the prediction that selective D1 dopamine receptor antagonism will produce antipsychotic effects in schizophrenia

Regional brain glucose metabolism in drug free schizophrenic patients and clinical correlates

Regional brain glucose metabolism was investigated in healthy volunteers (n= 10) and in drug free schizophrenic patients (n= 20). The metabolism was determined by positron emission tomography (PET) with 11C‐glucose as the tracer. Diagnosis of schizophrenia was made according to RDC and DSM III. Eight patients had their first psychotic episode, four patients had a subchronic course and eight patients had a chronic course with an exacerberation of their illness. Computed tomography (CT) of the brain were made in all the subjects. Regions of interest (n= 35) were drawn on displayed CT images and the marked regions were transferred to the corresponding slice of the PET examination. The PET investigation was made in a dimly lit, quiet room with the eyes of the subject covered. The time course of the 11C‐glucose uptake was measured by a four ring PET scanner (PC‐384‐7B).

An open label trial of raclopride in acute schizophrenia. Confirmation of D2-dopamine receptor occupancy by PET.

Raclopride, a highly selective D2-dopamine receptor antagonist, was administered in doses up to 4 mg b.i.d. to ten schizophrenic patients in an open label non-comparative study lasting 4 weeks. Safety, tolerability, potential antipsychotic effect, prolactin response and drug effect on plasma homovanillic acid were evaluated. Central D2-dopamine receptor occupancy was determined by positron emission tomography (PET). No major deviations were found in biochemical and physiological safety parameters. Raclopride was well tolerated. The mean BPRS score was reduced by 55% at endpoint. In the global evaluation seven patients were “very much” or “much” improved. Extrapyramidal side effects were recorded in four patients and disappeared after dose reduction or single doses of biperiden. An increase in plasma prolactin of short duration was observed in both sexes. A significant decrease of plasma HVA was obtained after 4 weeks of treatment. In two of the patients the central D2-dopamine receptors occupancy was measured using PET. The receptor occupancy was 68 and 72% which is the same as that found in patients treated with conventional neuroleptics.

Simultaneous quantification of homovanillic acid and 5-hydroxyindoleacetic acid in cerebrospinal fluid by mass fragmentography.

Abstract A mass fragmentographic technique for the simultaneous quantification of HVA and 5-HIAA in CSF was described. Deuterium labelled analogues of the acids were used as internal standards. Derivatives of the compounds were prepared by reacting CSF extracts with a mixture of pentafluoropropanol and pentafluoropropionic anhydride. Fragments set into focus were the molecular ion of the HVA derivatives and M + −177 of the 5-HIAA derivatives. The experimental error was below 7% for both acids and the recovery of authentic compounds added to CSF was 93–96%. With an AVA allowing simultaneous recording of four mass numbers, both acids could be determined concomitantly. The technique would be appropriate for analysis of large numbers of samples especially when it is of interest to determine the relation between levels of HVA and 5-HIAA in CSF.

The pharmacokinetics of intravenous and oral sulpiride in healthy human subjects

SummaryThe pharmacokinetics of sulpiride was studied in 6 healthy volunteers after intravenous and oral (tablets) administration of 100 mg. An open two- and in two subjects a three-compartment model was applied following intravenous administration. The average total distribution volume during the terminal slope was 2.72±0.66 l/kg and total systemic clearance was 415±84 ml/min. The serum half-life of the terminal slope following intravenous administration averaged 5.3 h (range 3.7–7.1 h) according to the two-compartment model. In two subjects the half-lives were 11.0 and 13.9 h when the three-compartment model was applied. Determination of urinary excretion rates of unchanged sulpiride indicated a half-life of 7.15 h. Following intravenous administration, 70±9% of the dose was recovered unchanged in urine within 36 h; the mean renal clearance was 310±91 ml/min. Sulpiride was absorbed slowly, with peak concentrations appearing between 3 and 6 h after oral administration. The recovery of unchanged drug in urine following oral administration was 15±5% of the dose, with a mean renal clearance of 223±47 ml/min. The bioavailability determined from combined plasma and urine data was only 27±9%. The low bioavailability was probably due to incomplete absorption.

Cerebroventricular size and cerebrospinal fluid monoamine metabolites in schizophrenic patients and healthy volunteers.

Computed tomography (CT) measures and cerebrospinal fluid (CSF) levels of the monoamine metabolites homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylglycol (MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) were determined in 43 healthy volunteers and in 26 patients with an acute psychosis of the schizophrenic type. There were no differences in the mean CSF levels of monoamine metabolites between the two groups. However, the patients had significantly wider lateral and third ventricles as compared to the volunteers. In the volunteers there were no significant correlations between ventricular sizes and monoamine metabolite levels, whereas in the patients a significant negative correlation was obtained between the size of the lateral ventricles and the levels of HVA and 5-HIAA in the CSF. These results may indicate that the enlargements of the brain ventricles found in a subgroup of schizophrenic patients may be associated with deficiencies in central monoamine transmission mechanisms.

Effect of antipsychotic drugs on homovanillic acid levels in striatum and olfactory turbercle of the rat

Dose-response curves for the elevation of homovanillic acid levels in corpus striatum and olfactory tubercle of rats were determined by mass fragmentography after treatment with antipsychotic drugs. The older of potency in both regions was: haloperidol greater than chlorpromazine greater than thioridazine and clozapine. The relative elevation of the content of homovanillic acid was significantly greater in the striatum than in the olfactory tubercle for all drugs except thioridazine. The antipsychotic effect of the drugs tested may be related to the interference with dopaminergic mechanisms in striatal and/or limbic areas.