Central norepinephrine metabolism during alcohol intoxication in addicts and healthy volunteers.

The concentrations of the major norepinephrine metabolite, 3-methoxy-4-hydroxyphenylethylene glycol (MOPEG), in lumbar cerebrospinal fluid of alcoholic patients were markedly elevated during intoxication and successively declined during 1 and 3 weeks of abstinence. During intoxication the MOPEG concentration in cerebrospinal fluid showed a statistically significant correlation with the blood alcohol concentration. In healthy volunteers who received 80 grams of ethanol, the MOPEG concentration in cerebrospinal fluid increased significantly. Healthy subjects sampled during intoxication had significantly higher concentrations of MOPEG in the cerebrospinal fluid than did subjects sampled after the end of intoxication. The results indicate that alcohol administration markedly stimulates norepinephrine metabolism in the central nervous system in human subjects possibly by increasing unit impulse activity of central noradrenergic neurons.

Quantitative analysis of D2 dopamine receptor binding in the living human brain by PET.

D2 dopamine receptors in the putamen of living human subjects were characterized by using the selective, high-affinity D2 dopamine receptor antagonist carbon-11-labeled raclopride and positron emission tomography. Experiments in four healthy men demonstrated saturability of [11C]raclopride binding to an apparently homogeneous population of sites with Hill coefficients close to unity. In the normal putamen, maximum binding ranged from 12 to 17 picomoles per cubic centimeter and dissociation constants from 3.4 to 4.7 nanomolar. Maximum binding for human putamen at autopsy was 15 picomoles per cubic centimeter. Studies of [11C]raclopride binding indicate that clinically effective doses of chemically distinct neuroleptic drugs result in 85 to 90 percent occupancy of D2 dopamine receptors in the putamen of schizophrenic patients.

PET imaging of dopamine receptors in human basal ganglia: relevance to mental illness.

The development of PET and in vivo ligand-binding techniques over the past decade has allowed the analysis of dopamine receptor functions in the basal ganglia of human subjects. Using ligands selective for the different subtypes of dopamine receptors, their gross distribution, total number of binding sites and affinity have been determined in the caudate-putamen of the living human brain. Recent studies in young, drug-naive schizophrenic patients failed to demonstrate a consistent alteration in the densities or affinities of D2 dopamine receptors in the basal ganglia of these subjects, contradicting the view that elevated densities of D2 dopamine receptors are a major pathophysiological mechanism in this disorder. PET measurements of D2 dopamine receptor occupancy in relation to clinical antipsychotic drug treatment demonstrated that all chemically different categories of antipsychotic drugs induced a marked occupancy of D2 dopamine receptors. This effect was dose-dependent and fully reversible. It appeared earlier than the antipsychotic effect and was also present in neuroleptic-resistant patients. Resistance to neuroleptic drugs is in all probability related to heterogeneity of biological factors causing schizophrenia. Some, but not all, antipsychotic drugs also induced a significant D1 dopamine receptor occupancy. This effect was most marked for the unconventional drug clozapine, which showed about the same degree of D1 as D2 dopamine receptor blockade when given in clinical doses.

Aberrant monoamine metabolite levels in CSF and family history of schizophrenia. Their relationships in schizophrenic patients.

In 36 drug-free schizophrenic patients, lumbar CSF was analyzed by mass fragmentography for the major monoaminergic transmitter metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG). High or deviant concentrations of 5-HIAA were significantly related to a family history of schizophrenia. For patients with deviant 5-HIAA levels, the probability for a family history of schizophrenia was eight times higher than in subjects with normal values. High concentrations of HVA also tended to be significantly related to a family history of schizoprenia. The majority of schizophrenic patients, who lacked family history for the disorder, had normal monoamine metabolite concentrations in CSF. The results suggest a coupling between biochemical variables related to central serotonin and dopamine metabolism and forms of schizophrenia that have a familial disposition.

Central D2-dopamine receptor occupancy in schizophrenic patients treated with antipsychotic drugs.

Using positron emission tomography and the carbon 11-labeled ligand raclopride, central D2-dopamine receptor occupancy in the putamen was determined in psychiatric patients treated with clinical doses of psychoactive drugs. Receptor occupancy in drug-treated patients was defined as the percent reduction of specific carbon 11-raclopride binding in relation to the expected binding in the absence of drug treatment. Clinical treatment of schizophrenic patients with 11 chemically distinct antipsychotic drugs (including both classic and atypical neuroleptics such as clozapine) resulted in a 65% to 85% occupancy of D2-dopamine receptors. In a depressed patient treated with the tricyclic antidepressant nortriptyline, no occupancy was found. The time course for receptor occupancy and drug levels was followed after withdrawal of sulpiride or haloperidol. D2-dopamine receptor occupancy remained above 65% for many hours despite a substantial reduction of serum drug concentrations. In a sulpiride-treated patient, the dosage was reduced in four steps over a nine-week period and a curvilinear relationship was demonstrated between central D2-dopamine receptor occupancy and serum drug concentrations. The results demonstrate that clinical doses of all the currently used classes of antipsychotic drugs cause a substantial blockade of central D2-dopamine receptors in humans. This effect appears to be selective for the antipsychotics, since it was not induced by the antidepressant nortriptyline.

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.

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.

Identification of four novel polymorphisms in the calcitonin/alpha-CGRP (CALCA) gene and an investigation of their possible associations with Parkinson disease, schizophrenia, and manic depression.

We identified novel polymorphisms in the calcitonin/CGRPalpha (CALCA) gene by direct sequencing of genomic DNA and subsequent genotyping by RFLP (restriction fragment length polymorphism) detection and investigated association with neurological or psychiatric disease. Four novel polymorphic alleles were found: two (g.979G>A and g.4218T>C) represented single nucleotide polymorphisms (SNPs), one consisted of two coupled SNPs in close vicinity to each other (g.1210T>C and g.1214C>G), and one was an intronic 16-bp microdeletion (2919-2934del16). One of the SNPs (g.4218T>C) causes a non-synonymous amino acid change (Leu66Pro) in the third exon, an exon common to both procalcitonin and pro-alpha-CGRP. In a subsequent association study, frequencies of the identified polymorphisms in Parkinson and schizophrenia patients were compared with frequencies in the normal population. No statistically significant association was found in our material. The 16-bp microdeletion polymorphism was present in a family with multiple cases of unipolar or bipolar depressive disorder. Using this polymorphism as marker, cosegregation with the phenotype was observed in the majority of individuals.

CSF creatinine in schizophrenia.

Concentrations of creatinine in cerebrospinal fluid (CSF) from schizophrenic patients and healthy control subjects were determined by a liquid chromatographic method. The concentration of creatinine in CSF from schizophrenic patients was lower (42.8 nmol/ml) than that of the controls (54.4 nmol/ml). The concentration of creatinine was correlated to the levels of homovanillic acid and 5-hydroxyindoleacetic acid. Treatment of the schizophrenic patients with sulpiride (800 mg daily), but not with chlorpromazine, elevated the concentration of creatinine in the CSF.

Smooth pursuit eye movements, clinical symptoms, CSF metabolites, and skin conductance habituation in schizophrenic patients.

Smooth pursuit eye movements (SPEM) for two stimulus velocities (sinusoidal and triangular) were studied by visual inspection in 12 unmedicated RDC-diagnosed schizophrenic patients and in 13 matched controls. SPEM was worse in the patient group and their performance deteriorated with repeated presentations of the task. Patients with previous antipsychotic medication, previous hospitalization, higher age, late onset of manifest psychotic symptoms, and few positive psychotic symptoms had worse SPEM according to the Comprehensive Psychopathological Rating Scale. Subjects with poor SPEM showed slower habituation of skin conductance responses. There were no correlations between SPEM ratings and levels of CSF monoamine metabolites HVA, 5-HIAA, and MHPG.

Relationships in healthy volunteers between secretion of monoamine metabolites in urine, and family history of psychiatric morbidity.

In 66 physically and mentally healthy human subjects the total concentrations of 3-methoxy-4-hydroxyphenylethylene glycol (MOPEG), 5-hydroxyindole acetic acid (5-HIAA), homovanillic acid (HVA), and dihydroxyphenyl acetic acid (DOPAC) in urine collected between midnight and 8 AM were analyzed by mass fragmentography. In the volunteers reporting the occurrence of psychiatric morbidity among relatives an increased variance in their MOPEG levels was found as compared to the volunteers without such a family history. In the male subjects with no family history of psychiatric disease there was a positive correlation between urine and cerebrospinal fluid levels of MOPEG. The urine levels of 5-HIAA, HVA, and DOPAC did not demonstrate any changes that could be related to psychopathology within the family. Changes in urine secretion of MOPEG indicate an altered metabolism of norepinephrine/MOPEG in some subjects with the occurrence of severe psychiatric disease within the family. MOPEG levels in urine may be a predictor of a family vulnerability for psychiatric morbidity in healthy subjects.

Dopamine-related genes and their relationships to monoamine metabolites in CSF.

Monoamine metabolite (MM) levels in lumbar cerebrospinal fluid (CSF) are extensively used as indirect estimates of monoamine turnover in the brain. In this study we investigated genotypes for DNA polymorphisms in the D2 (DRD2), D3 (DRD3), and D4 (DRD4) dopamine receptor and tyrosine hydroxylase (TH) genes and their relationships to CSF MM in healthy volunteers (n = 66). Concentrations of homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylglycol (MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) were corrected for back length, a confounding variable. Corrected MM levels were not related to age, gender, height, weight heredity, season or atmospheric pressure at sampling. Individuals with specific DRD2 and TH allele and genotype configurations significantly differed in HVA and MHPG concentrations. DRD3 homo- and heterozygotic genotypes had significantly different CSF 5-HIAA levels. DRD4 genotypes were not related to MM concentrations. The results suggest that specific DRD2, DRD3, and TH genotypes participate in the regulation of monoamine turnover in the central nervous system. Accordingly monoamine receptors and synthesizing enzyme genotypes appear to be variance factors influencing MM concentrations in CSF. The relationships found in this study support MM concentrations as markers for monoamine transmission in the human brain.

D1, D2, and 5-HT2 receptor occupancy in relation to clozapine serum concentration: a PET study of schizophrenic patients.

OBJECTIVE: Central D1, D2, and 5-HT2 receptor occupancy in schizophrenic patients treated with clozapine was determined and related to clozapine serum concentrations. METHOD: Seventeen patients treated with clozapine (125-600 mg/day) were examined with positron emission tomography (PET) and one to three of the following selective radioligands: [11C]SCH23390 (N = 11), [11C]raclopride (N = 16), and [11C]N-methylspiperone (N = 5). Clozapine concentration in serum was determined by gas chromatography/mass spectrometry. RESULTS: D2 receptor occupancy (20%-67%) was lower than that previously determined in patients treated with classical neuroleptics (70%-90%). D1 receptor occupancy (36%-59%) was higher than that induced by classical neuroleptics (0%-44%). 5-HT2 receptor occupancy was very high (84%-94%), even at low clozapine doses. Despite a 20-fold range in clozapine serum concentration (105-2121 ng/ml) at the time of PET examination, D2 receptor occupancy was low in all patients and was not described by the curvilinear relationship between serum drug concentration and receptor occupancy that has been demonstrated for classical antipsychotics. CONCLUSIONS: The results confirm in an extended series of patients that clozapine is atypical with regard to degree of D2 receptor occupancy, a finding that may explain the lack of extrapyramidal side effects. The combination of relatively high D1, low D2, and very high 5-HT2 receptor occupancy values is unique to clozapine. Clozapine serum concentrations have not been unequivocally shown to predict clinical effects. In this study, concentration did not predict degree of occupancy in brain. Thus, careful clinical titration cannot be replaced by monitoring of drug concentrations for optimization of clozapine treatment in individual patients.

Lack of evidence for allelic association between personality traits and the dopamine D4 receptor gene polymorphisms.

OBJECTIVE: Personality traits in human subjects have shown considerable heritable components. Recently, two research groups reported associations between dopamine D4 receptor genotypes and the personality trait known as novelty seeking. This study was an attempt to replicate these findings. METHOD: Three different exonic dopamine D4 receptor polymorphisms were genotyped in 126 healthy Swedish subjects. Personality traits of the subjects were assessed with the Karolinska Scales of Personality. RESULTS: Although there was a tendency in the direction hypothesized, no significant association between genotype constellations and personality traits was found. CONCLUSIONS: The previously reported association between dopamine D4 receptor alleles and novelty seeking was not replicated. Possible reasons for this include differences in personality inventories, ethnicity, and type I or type II errors.

Preprotachykinin-A mRNA expression in the human and monkey brain: An in situ hybridization study.

The mRNA expression for preprotachykinin-A (PPT-A) was studied throughout the human and cynomolgus monkey brain to assess the neuroanatomical expression pattern of the PPT-A gene in primates. In situ hybridization showed that the PPT-A mRNA is expressed highly in specific regions of the postmortem human brain, including the striatum, islands of Calleja, hypothalamus (posterior, premammillary, medial mammillary, and ventromedial nuclei), superior and inferior colliculi, periaqueductal gray, and oculomotor nuclear complex. PPT-A mRNA-expressing neurons also were present in the paranigralis (ventral tegmental area) and were scattered in the bed nucleus stria terminalis throughout the sublenticular substantia innominata region, including the diagonal band of Broca and the nucleus basalis of Meynert. In the hippocampus, high PPT-A mRNA expression was localized predominantly to the polymorphic layer of the dentate gyrus; no labeled cells were present in the granular layer. Positively labeled cells also were found scattered in the CA regions as well as in the amygdaloid complex. Neocortical expression of PPT-A mRNA was localized mainly to the deep laminae (layers V/VI), except for the striate cortex (labeling was seen also in superficial layers). The subiculum, thalamus, globus pallidus, ventral pallidum, substantia nigra pars compacta, red nucleus, pontine nuclei, and cerebellum were characterized by very weak to undetectable expression of PPT-A mRNA. An expression pattern was evident in the monkey forebrain similar to that observed in the human, except for the absence of PPT mRNA-expressing cells in the medial mammillary nucleus despite intense expression in supramammillary, lateral mammillary, and premammillary nuclei. Overall, more similarities than differences are apparent between primate species in the expression pattern of the PPT-A gene. J. Comp. Neurol. 411;56-72, 1999.

High level of pyridoxal 5'-phosphate in the cerebrospinal fluid of adult celiac patients.

Adults with intestinal malabsorption due to celiac disease show reduced central serotonin metabolism, probably induced by a lack of essential dietary factors. Investigating a role proposed for vitamin B6 deficiency, a regular finding in untreated celiacs, the present study yields no support for the hypothesis that direct inhibition at the decarboxylation step by vitamin B6 deficiency accounts for low central serotonin turnover in adult celiacs: 11 untreated patients showing reduced 5-HIAA in the cerebrospinal fluid (71+/- 26.8 pmol/ml) had a significantly higher concentration of the metabolically active B6 vitamer pyridoxal 5'-phosphate in lumbar cerebrospinal fluid (0.06 +/- 0.34 ng/ml) than controls (0.24 +/- 0.07 ng/ml) (p less than 0.01). Cerebrospinal fluid tryptophan, precursor of serotonin, was normal (2035 %/- 649 pmol/ml). Raised pyridoxal 5'-phosphate in the cerebrospinal fluid in untreated celiac disease is an unexpected finding. Possibly it is secondary to the diminished central monamine metabolism in these patients, but further studies are needed bearing in mind that mental depression is a major cause for disability in adult celiac disease.

The current status of PET scanning with respect to schizophrenia.

PET scan studies of regional brain energy metabolism in schizophrenia have hitherto not been consistent in demonstrating any specific perturbation in heterogenous groups of patients. In some studies there was a tendency to reduced metabolic values in several regions in chronic patients. The variance of metabolic rates also tended to be greater in the group of schizophrenic subjects, but rates for most patients overlapped with those of the controls. Studies of regional brain energy metabolism also failed to disclose consistent effects of clinical antipsychotic drug treatment in schizophrenic patients. PET measurements of dopamine receptor functions in the major basal ganglia using different radioligands for D2 dopamine receptors also gave inconsistent results. One group reporting elevated densities of D2 dopamine receptors in the major basal ganglia of drug-naive schizophrenic patients could not be confirmed. PET measurements of dopamine receptor binding demonstrated profound and selective effects of clinical antipsychotic drug treatment on D2 and D1 dopamine receptor occupancy in schizophrenic patients. All chemically different categories of antipsychotic drugs induced a substantial occupancy of D2 dopamine receptors in relation to clinical treatment. This effect has been shown to be dose dependent and fully reversible. It appears much earlier than the antipsychotic effect and it is also present in neuroleptic-resistant patients. Accordingly, neuroleptic resistance is not related to individual pharmacodynamic or pharmacokinetic factors. Drug resistance is in all probability related to heterogeneity of biologic factors causing schizophrenia. Some, but not all, of the antipsychotic drugs also induce a significant D1 dopamine receptor occupancy. This effect was most marked for the unconventional drug clozapine, which showed about the same degree of D1 and D2 dopamine receptor blockade when given in conventional clinical doses. Further refinements of the resolution of PET scan instruments in the years to come and the development and application of new tracers will supply powerful tools for the further search for fundamental alterations of brain function in schizophrenia.

Distribution of D1- and D2-dopamine receptors, and dopamine and its metabolites in the human brain.

Densities and distribution of D1-dopamine and D2-dopamine receptors were investigated in vitro using [3H]SCH 23390 and [3H]raclopride in receptor binding assays and autoradiography on human post mortem whole hemisphere slices to serve as anatomical correlates to PET studies using [11C]SCH 23390 and [11C]raclopride. In addition, the levels of dopamine and its metabolites were determined by HPLC in various brain regions. Both dopamine receptor subtypes, as well as dopamine, HVA and DOPAC, were primarily found in the basal ganglia. Very high densities of D1-dopamine receptors were found particularly in the medial caudate nucleus, whereas D2-dopamine receptors were evenly distributed throughout the caudate. The densities of D1- and D2-dopamine receptors were similar in the caudate nucleus and the putamen, whereas there were 4 to 7 times higher densities of the D1- than of the D2-dopamine receptors in several limbic and neocortical regions. The receptor distribution in the autoradiographic study was consistent with that demonstrated in the living human brain using [11C]SCH 23390 and [11C]raclopride.

Dopamine-regulated phosphorylation of synaptic vesicle-associated proteins in rat neostriatum and substantia nigra.

Dopamine, acting through dopamine D1 receptors and cyclic AMP-dependent protein kinase, has been found to increase the state of phosphorylation of the synaptic vesicle-associated phosphoproteins synapsin I and protein III in slices of rat neostriatum and substantia nigra. In the neostriatum, the effect of dopamine was mimicked by SKF 38393, a D2 receptor agonist, and was abolished by preincubation of the slices with fluphenazine or SCH 23390, antipsychotic drugs which are potent D1 receptor antagonists, but not by the D2 receptor antagonists l-sulpiride or spiroperidol. The maximal effect of dopamine in the neostriatum represented approximately 30-35% of the maximal effect induced by 8-bromo cyclic AMP, suggesting that a similar fraction of nerve terminals in the neostriatum may express the dopamine D1 receptor. Evidence for a small population of beta-adrenergic receptors regulating nerve terminal protein phosphorylation in the neostriatum, distinct from the D1 dopamine receptors, was also obtained. In the substantia nigra, the effect of dopamine also appeared to be mediated through a D1 dopamine receptor, since it was abolished by fluphenazine and SCH 23390. The maximal effect of dopamine in the substantia nigra represented approximately two-thirds of the effect induced by 8-bromo cyclic AMP, suggesting that a similar fraction of nerve terminals in the substantia nigra may express the dopamine D1 receptor. The ability of dopamine D1 receptor activation to stimulate both synapsin I and protein III phosphorylation and GABA release in both the neostriatum and substantia nigra may be causally linked.

Distribution of messenger RNAs for D1 dopamine receptors and DARPP-32 in striatum and cerebral cortex of the cynomolgus monkey: relationship to D1 dopamine receptors.

Messenger RNAs for the D1 dopamine receptor and dopamine- and cyclic AMP-regulated phosphoprotein of relative mass 32,000 (DARPP-32) were examined by in situ hybridization in the cynomolgus monkey brain. The messenger RNA distribution was compared to the distribution of D1 dopamine receptors using [3H]SCH 23390 autoradiography. In the caudate nucleus and putamen, D1 dopamine receptor messenger RNA-positive cells were unevenly distributed. Clusters of cells with an approximately three-fold higher intensity of labeling, as compared to surrounding regions, were found. Some of these D1 dopamine receptor messenger RNA intensive cell clusters in the caudate nucleus appeared to some extent to be matched to regions of higher intensity of [3H]SCH 23390 binding. The distribution of cells expressing DARPP-32 messenger RNA in the caudate nucleus and putamen was found to be non-clustered. In neocortical regions, cells of different sizes expressing D1 dopamine receptor messenger RNA were present in layers II-VI. D1 dopamine receptor messenger RNA-positive cells were most abundant in layer V. Unexpectedly, no DARPP-32 messenger RNA signal was detected in neocortex. Chronic SCH 23390 administration did not change the relative levels of messenger RNAs for the D1 dopamine receptor and DARPP-32 or [3H]SCH 23390 binding as measured by quantitative image analysis. The clustered distribution of D1 dopamine receptor messenger RNA is in contrast to that of DARPP-32 messenger RNA. This suggests that D1 dopamine receptors may play a more significant role in regulating DARPP-32 function in patch regions as compared to matrix regions. D1 dopamine receptor messenger RNA-expressing cells could also be visualized in several layers of the primate neocortex, implying that dopamine acts through D1 dopamine receptors within functionally different neuronal circuits of the neocortex.