Initial studies of embryonic transplants of human hippocampus and cerebral cortex derived from schizophrenic women

Human fetal brain tissue was obtained from first-trimester elective abortions of two women who also had schizophrenia. Portions of the embryonic hippocampus or cerebral cortex were transplanted into the anterior eye chamber of immunologically compromised athymic nude rats. In this environment, embryonic brain tissue derived from normal women generally continues organotypic growth and development for many months. Although initial survival after transplantation was normal, the tissue derived from schizophrenic women manifested less robust growth. However, cells in the transplants showed typical neuronal differentiation, with development of different neuronal types, such as pyramidal cells, granule cells, and gamma-aminobutyric acid (GABA)-containing interneurons. Rhythmic electrical activity was also observed, indicative of some local synaptic organization. The presence of messenger RNA (mRNA) for brain-derived neuronotrophic factor (BDNF) was observed using in situ hybridization. The reason for the decreased rate of growth of these transplants remains unknown and the significance of the finding cannot be assessed from only two fetuses. However, these preliminary findings suggest that fetal transplants may be a useful model system for the detection of developmental pathogenic processes in the expression and transmission of schizophrenia.

Positron emission tomographic analysis of central D1 and D2 dopamine receptor occupancy in patients treated with classical neuroleptics and clozapine. Relation to extrapyramidal side effects

Positron emission tomography and selective radioligands were used to determine D1 and D2 dopamine receptor occupancy induced by neuroleptics in the basal ganglia of drug-treated schizophrenic patients. In 22 patients treated with conventional dosages of classical neuroleptics, the D2 occupancy was 70% to 89%. Patients with acute extrapyramidal syndromes had a higher D2 occupancy than those without side effects. This finding indicates that neuroleptic-induced extrapyramidal syndromes are related to the degree of central D2 occupancy induced in the basal ganglia. In five patients treated with clozapine, the prototype atypical antipsychotic drug, a lower D2 occupancy of 38% to 63% was found. This finding demonstrates that clozapine is also "atypical" with respect to the central D2 occupancy in patients. During treatment with clozapine, there is a low frequency of extrapyramidal syndromes, which accordingly may reflect the comparatively low D2 occupancy induced by clinical doses of clozapine. Classical neuroleptics, like haloperidol or sulpiride, did not cause any evident D1 occupancy, but the thioxanthene flupentixol induced a 36% to 44% occupancy. In four patients treated with clozapine, the D1 occupancy was 38% to 52%. The D1 occupancy induced by clozapine and flupentixol may contribute to the antipsychotic effect of these drugs.

Regional glucose metabolism in schizophrenic patients before and during neuroleptic treatment

Determination of regional glucose metabolism has been considered to be a tool to elucidate the mechanisms of action of neuroleptics. D2-dopamine antagonists seem to increase glucose consumption in dopamine innervated areas. Studies in humans do not give results in complete accordance with animal findings. In patients neuroleptic compounds and dopamine agonists probably increase and decrease striatal metabolism respectively. Changes in metabolism, especially in the right hemisphere may be coupled with improvement of the patients. Future research must be based on protocols specially designed for the study of drug effects.

Glucose metabolism in psychiatric disorders: how can we facilitate comparisons among studies?

Positron emission tomography (PET) offers a possibility to study brain function and its relationship to psychiatric disorders. Clinical studies have demonstrated that several psychiatric diseases are coupled with changes in brain glucose metabolism. Schizophrenia seems to involve a lower metabolism in wide areas of the brain--both cortical and subcortical structures. Depression probably involves dysfunction of the metabolism in dorsolateral prefrontal cortex. Obsessive compulsive disorder, panic disorder, anorexia nervosa and the experience of anxiety may involve increased metabolic rates. The results from the different studies do not allow quantitative comparisons or detailed analyses because of large differences in experimental and clinical methodology. The term Good Clinical PET Practice (GCPP) is suggested to encourage standardization in clinical investigations. GCPP includes standardization of both experimental factors (lumped constant, arterialization, purity of tracer, regions of interest, relative rates) and clinical factors (state of the subject, wakefulness, anxiety, gender, course of the disease) in PET performance.

The transport of tyrosine into the human brain as determined with L-[1-11C]tyrosine and PET

An alteration of dopaminergic transmission in the brain has been proposed for schizophrenia. To explore this, the rate constant for the intransport of L-tyrosine across the blood-brain barrier in healthy controls and in patients with schizophrenia (DSM-III-R) was determined with PET and L-[1-11C] tyrosine as the tracer. Kinetics for tyrosine transport were determined according to a two-compartment model using radioactivity data of arterial blood and brain tissue sampled between 1 and 3.5 min after a bolus injection of L-[1-11C] tyrosine. Radioactivity was measured every second in the blood and in 10-sec intervals in the brain tissue. In the normal controls the brain intransport rate constant for tyrosine was 0.052 ml/g/min with an influx rate of 2.97 nmol/g/min. The patients had a similar intransport rate constant (0.045 ml/g/min) but a lower influx rate of tyrosine 1.95 nmol/g/min (p less than 0.05). The patients' tyrosine concentrations in the blood were lower. For data sampled between 5 and 25 min, the net accumulation rate of tyrosine into the brain was 0.015 ml/g/min in the controls which did not differ to the patients' rate. However, the net utilization of tyrosine was lower in the patients (0.672 nmol/g/min) than in the controls (0.883 nmol/g/min) despite similar tissue concentrations of tyrosine.

Regional brain glucose metabolism: correlations to biochemical measures and anxiety in patients with schizophrenia

Regional brain glucose metabolism in 20 patients with schizophrenia (DSM-III) was investigated by positron emission tomography (PET) with uniformly labeled 11C-glucose as the tracer. Monoamine metabolites were analyzed in cerebrospinal fluid (CSF) and serum, and prolactin was analyzed in serum. Intensity of anxiety was rated directly after the PET study. Ten healthy volunteers served as controls. In the patients, weak positive and negative relationships were found between homovanillic acid in CSF and prolactin in serum, respectively, and regional metabolic rates. In all subjects, positive correlations were found between the level of anxiety and the regional glucose metabolism. In the controls, positive correlations were found between anxiety and the frontal/parietal ratios of the left hemisphere, whereas anxiety scores of the patients correlated negatively to relative metabolic rates of the right medial frontal cortex and the left thalamus. These observations may indicate alterations in the neuronal systems participating in the initiation of anxiety and arousal in schizophrenia.

Neuroendocrine responses to single oral doses of remoxipride and sulpiride in healthy female and male volunteers

Six female and six male healthy volunteers received 100 mg remoxipride, 200 mg sulpiride and placebo as single oral doses in a double blind trial with a randomized crossover design. The main objective was to compare the effect of the two drugs on serum prolactin levels, but effects on other hormones were also investigated. Remoxipride and sulpiride increased the serum levels of prolactin to similar peak levels. This effect was larger in female than in male subjects. Sulpiride increased prolactin levels at much lower plasma concentrations than remoxipride, and sulpiride's effect on prolactin lasted for considerably longer than remoxipride's. No consistent effects on serum levels of LH, FSH, GH, oestradiol, progesterone, testosterone or cortisol could be detected after remoxipride and sulpiride compared to placebo. No drug-related effects on plasma homovanillic acid (HVA) were found.

Positron emission tomographic measurements of cerebral glucose utilization using [1-11C]D-glucose

Regional CMRglc was measured in seven healthy volunteers with positron emission tomography using [1-11C]D-glucose. Regional CBF was measured using [11C]fluoromethane. The arteriovenous differences of unlabeled glucose and oxygen together with 11C metabolites were also measured. In addition to the loss of [11C]CO2, a loss of acidic 11C metabolites was also detected. A three-compartment model was applied to the tracer data in the time interval 0-24 min. After correction for the loss of 11C metabolites, the tracer method gave an average CMRglc of 26.4 +/- 1.9 (SD) mumol/100 g/min, close to the value obtained with the Fick principle. After correction for the loss of [11C]CO2 only, the tracer method gave 23.6 +/- 2.1 mumol/100 g/min, compatible with (1/6) CMRO2, obtained with the Fick principle. These results and the time course of the loss of acidic 11C metabolites are consistent with the presence of nonoxidative metabolism of glucose that causes an early loss of mainly [11C]lactate after a bolus injection of the tracer. This implies that [1-11C]D-glucose measures the rate of glucose oxidation rather than the total CMRglc. The experiments using [1-11C]D-glucose were compared to five analogous experiments using [U-11C]D-glucose together with [15O]H2O as a flow tracer. After correction for the loss of [11C]CO2, the two glucose tracers gave similar global values of CMRglc and other parameters associated with glucose utilization, but with labeling in the carbon-1 position, the loss of [11C]CO2 was substantially delayed and the contrast between gray and white matter was improved.(ABSTRACT TRUNCATED AT 250 WORDS)

D2 dopamine receptors in neuroleptic-naive schizophrenic patients. A positron emission tomography study with [11C]raclopride

Several groups have reported increased densities of D2 dopamine receptors in the basal ganglia of schizophrenic brains postmortem. The significance of this finding has been questioned, since an upregulation of receptor number may be a neuronal response to neuroleptic drug treatment. We have used positron emission tomography and [11C]raclopride to examine central D2 dopamine receptor binding in 20 healthy subjects and 18 newly admitted, young, neuroleptic-naive patients with schizophrenia. An in vivo saturation procedure was applied for quantitative determination of D2 dopamine receptor density (Bmax) and affinity (Kd). When the two groups were compared, no significant difference in Bmax or Kd values was found in the putamen or the caudate nucleus. The hypothesis of generally elevated central D2 dopamine receptor densities in schizophrenia was thus not supported by the present findings. In the patients but not in the healthy controls, significantly higher densities were found in the left than in the right putamen but not in the caudate nucleus.

Relationships between clinical effects and monoamine metabolites and amino acids in sulpiride-treated schizophrenic patients

Twenty-four acutely ill schizophrenic patients (DSM-III-R), 18-42 years old, were treated for 6 weeks with sulpiride. Sulpiride was administered in three different daily dosages (400, 800 or 1200 mg) according to a double dummy blind randomized administration schedule. The psychopathology of the patients was rated by the Comprehensive Psychopathological Rating Scale (CPRS) and the Nurse's Observation Scale for Inpatient Evaluation (NOSIE). The monoamine metabolites homovanillic acid (HVA), 5-hydroxy-indoleacetic acid (5-HIAA), 4-hydroxy-3-methoxy-phenylglycol (HMPG) and the amino acids tyrosine, tryptophan, glutamate and glutamine were measured in serum before and once a week during sulpiride treatment. There were no significant correlations between the CPRS or the NOSIE morbidity scores and the biochemical measures before drug treatment. HVA levels were not correlated to rating scores during treatment, but after 6 weeks HVA had decreased significantly in the patients with a good response but not in the patients with a poor response. A negative relationship between 5-HIAA levels and depressive and negative symptoms was found. Non-responders according to the subscale for depression had low 5-HIAA levels throughout the treatment. An increase of tryptophan was correlated to improvement in the early part of treatment. High levels of glutamate or glutamine were found in non-responders before treatment. During treatment an increase of the glutamate level was correlated to improvement. Low levels of glutamine were related to improvement according to global and NOSIE (total) rating scores. Peripheral biochemical measures may be a valuable tool in the study of pathophysiological mechanisms and treatment effects in patients with schizophrenia.

Central D1- and D2-receptor occupancy during antipsychotic drug treatment

1. It has been unequivocally shown that antipsychotic compounds reduce dopaminergic transmission. A relationship in vitro between the potency for the antipsychotic effect and the blockade of D2-dopamine receptors has been shown. No such relationships have been demonstrated for any other central receptor population. 2. Positron emission tomography (PET) has made it possible to investigate interactions of psychotropic drugs with central receptors in the living human brain. Using the selective D2 receptor antagonist raclopride labelled with positron emitting isotope 11C, it has been shown that chemically distinct classical neuroleptics in conventional doses occupy a high degree (65-89%) of the D2-receptors in the human brain. The results substantiate the opinion that the antipsychotic effects is mediated by a blockade of D2-dopamine receptors. 3. The degree of binding to D1-receptors using the 11C-labelled D1-antagonist from Schering (SCH 23390) as the ligand was also determined. The D1-receptor occupancy seemed to be dependent on the type of the antipsychotic compound studied. 4. The atypical neuroleptic compound clozapine demonstrated a different binding profile than the classical neuroleptics. Thus, clozapine in conventional doses occupied D2-receptors to a smaller extent (40%, 40%, 65%) than classical neuroleptics. The occupation of D1-receptors was higher (40%, 42%) than that of classical compounds (0-36%). 5. The unique clinical profile of clozapine may be related to its potency on both D1- and D2-receptors. The distribution of D1-receptors varies from that of D2-receptors in the human brain which may be one reason for the importance of blocking both D1- and D2-receptors for a full antipsychotic response.

Clinical melperone treatment blocks D2-dopamine receptors in the human brain as determined by PET

Positron emission tomography and 11-C-labelled raclopride was used to determine central D2-dopamine receptor occupancy in three melperone treated patients. Treatment with melperone in daily doses of 250 and 300 mg for 3 to 6 weeks, resulted in a receptor occupancy above 70%. Thus, clinical doses of melperone as we previously demonstrated for several classical neuroleptics cause a substantial D2-dopamine receptor blockade in the human brain in vivo.

Monoamine metabolites and amino acids in serum from schizophrenic patients before and during sulpiride treatment

Twenty-four acutely ill schizophrenic patients (DSM-III-R), 18-42 years old, were treated for 6 weeks with sulpiride. Sulpiride was administered in three different daily dosages (starting with 400, 800 or 1200 mg) according to a double blind randomized administration schedule. The monoamine metabolites (MAM) homovanillic acid (HVA), 5-hydroxy-indoleacetic acid (5-HIAA), 4-hydroxy-3-methoxy-phenylglycol (HMPG) and the amino acids tyrosine, tryptophan, glutamate and glutamine were measured in serum before treatment and once a week during treatment. There were no significant differences between healthy controls and schizophrenic patients in serum levels of monoamine metabolites and amino acids before treatment. There was no dose-response effect of sulpiride on serum levels of the monoamine metabolites or the amino acids. The results are therefore based on the whole group of patients. During treatment the HMPG levels were reduced at all points in time. The serum level of HVA was significantly reduced after 6 weeks. The 5-HIAA and the amino acid levels were not changed during treatment. There were no significant correlations among the monoamine metabolites before treatment. During treatment, however, significant correlations were found among MAM and amino acids. Since the biochemical findings during the treatment were not related to the dose or the concentration of sulpiride the results may be related to secondary biochemical effects of sulpiride and/or to changes in the clinical state following treatment.

Effects of sulpiride and chlorpromazine on regional cerebral glucose metabolism in schizophrenic patients as determined by positron emission tomography

Positron emission tomography (PET) was used to determine regional brain glucose metabolism in schizophrenic patients (n = 17) before and during neuroleptic treatment. The patients had not been treated with neuroleptics for at least 3 weeks before the first study. All suffered from acute psychotic symptoms and were hospitalized to obtain neuroleptic treatment. After determination of regional brain metabolism without neuroleptic treatment, 11 patients were treated with sulpiride (800 mg/day) and 6 patients were treated with chlorpromazine (400 mg/day) over 5-6 weeks before the second PET investigation. The control group consisted of seven healthy male volunteers, also investigated twice 5 weeks apart. The PET investigation was made with the subject in a resting state. The tracer was uniformly labelled 11C-glucose. The metabolism was determined bilaterally in 15 brain regions cortical, as well as central regions. Metabolic rates differed among the groups. The sulpiride group had lower metabolic rates than the controls and the schizophrenic patients later treated with chlorpromazine. The sulpiride group, in which absolute metabolic rates were determined, were clinically more autistic and chronic than the chlorpromazine group. It was proposed that these facts could explain the lower metabolic rates in the sulpiride group. A significant change in metabolism in relation to drug treatment was only found in one brain region. The selective D2-receptor antagonist sulpiride increased the metabolic rate in the right lentiform nucleus in comparison with the patients treated with chlorpromazine and the controls. Likewise, relative metabolic rates were increased only in the right lentiform nucleus. Negative correlations between intensity of clinical symptoms and metabolism indicated that emotional tone and drive were related to brain metabolism. No correlations were found between drug concentrations and metabolism or clinical symptoms.

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 the 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 drug-treated 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.

PET determination of regional cerebral glucose metabolism in alcohol-dependent men and healthy controls using 11C-glucose

Regional brain glucose metabolism was determined in 9 male alcohol-dependent inpatients and 12 male healthy controls. All the patients were socially impaired by the alcohol abuse. All the subjects had abstained from alcohol and drugs for more than four weeks before entering the study. Brain glucose metabolism was determined by positron emission tomography (PET) with 11C-glucose as the tracer. Regions of interest were drawn on displayed computed tomographic (CT) images of the brain. Regions were transferred to corresponding PET slices, allowing the determination of regional glucose metabolism. In the healthy volunteers there was a reduction in glucose metabolism with age. In 11 of the 19 brain regions examined, the alcoholics had a 20% to 30% lower glucose metabolism than the controls. This was true for both cortical and subcortical structures. The distribution of relative regional metabolic rates indicated that parietal cortical areas were most affected. Atrophic changes as shown by CT were not correlated to the reduced metabolism in the alcohol-dependent patients.

Relationships between glutamate and monoamine metabolites in cerebrospinal fluid and serum in healthy volunteers

The concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), 4-hydroxy-3-methoxyphenylglycol (HMPG), and glutamate were determined in cerebrospinal fluid (CSF) and serum in 10 healthy volunteers. The monoamine metabolites were measured by mass fragmentography and the glutamate by high-performance liquid chromatography. The level of glutamate in CSF was low (0.34 +/- 0.14 nmol/ml) in comparison with previously published values. The concentrations of monoamine metabolites in CSF were in close agreement with earlier findings. There were negative correlations between the concentrations of HVA (r = -0.82, p less than 0.01) and 5-HIAA (r = -0.77, p less than 0.01) and glutamate in CSF, but not in serum. The serum levels of HMPG and glutamate were negatively correlated (r = -0.95, p less than 0.001), but not the CSF levels. The HMPG levels in serum and CSF were positively correlated (r = 0.94, p less than 0.001), but not the HVA and the 5-HIAA levels. The serum and CSF levels of glutamate were positively correlated (r = 0.67, p less than 0.05). The results indicate relationships among the metabolism of dopamine, serotonin, and glutamate in the brain and between the metabolism of noradrenaline and glutamate in peripheral tissue.

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.

PET scanning--a new tool in clinical psychopharmacology

Quantitative methods were developed for the determination of dopamine and benzodiazepine receptor characteristics in the living human brain by positron emission tomography (PET). As ligands, the 11C-labelled analogues of the selective antagonists of dopamine receptor subtypes, SCH 23390 and raclopride, and the benzodiazepine antagonist, Ro 15-1788, were used. Tracer amounts of the ligands were injected intravenously into healthy volunteers and schizophrenic patients. The distribution of ligand indicated high densities of D1 as well as D2 dopamine receptors in the basal ganglia. Binding of [11C]-SCH 23390 was also significant in the neocortex where it was shown to represent binding to D1 as well as to 5-HT2 serotonin receptors. High densities of specific benzodiazepine receptor binding were obtained in most neocortical brain areas and in the cerebellum. Using saturation procedures, Bmax and Kd values could be obtained for D2 and benzodiazepine receptors. A comparison of D2 receptor densities in drug-naive schizophrenic patients and healthy volunteers demonstrated similar receptor characteristics in the major basal ganglia in these groups of subjects. Different chemical classes of conventional and unconventional antipsychotic drugs produced a 65%-85% occupancy of D2 receptors when given in clinical doses to schizophrenic patients. High does of diazepam produced a marked occupancy of benzodiazepine receptors during the first hours after oral administration to healthy volunteers. These in vivo methods should be valuable tools for the further analysis of the effects of drug on neuroreceptors in the living brain of neuropsychiatric patients.