Plasma levels and estimated dopamine D2 receptor occupancy of long-acting injectable risperidone during maintenance treatment of schizophrenia: a 3-year follow-up study

INTRODUCTION

Dopamine D₂ receptor occupancy levels needed for the maintenance treatment of schizophrenia remain to be elucidated. We examined 3-year clinical outcomes of patients with schizophrenia who received long-acting injectable risperidone (LAI risperidone) at baseline and investigated their dopamine D₂ receptor occupancy levels, estimated from plasma drug concentrations.

METHODS

A chart review of 52 outpatients with schizophrenia who participated in the original cross-sectional study was conducted to examine their 3-year clinical outcomes between April and September 2015. Patients who continued outpatient treatment with LAI risperidone without any usage of concomitant chlorpromazine equivalent antipsychotic dosage at >200 mg/day for the 3-year period were asked to participate in the follow-up assessments that included the Brief Psychiatric Rating Scale (BPRS) and estimated dopamine D₂ receptor occupancy levels at trough, using plasma concentrations of risperidone plus 9-hydroxyrisperidone. Data were compared with the same patients collected 3 years earlier.

RESULTS

Among the original 52 participants, 14 participants (27 %) continued outpatient treatment with LAI risperidone. Ten participants (19 %) provided plasma samples; mean ± SD measured trough concentration of risperidone plus 9-hydroxyrisperidone significantly increased from 22.9 ± 15.6 to 31.8 ± 17.5 ng/mL (P = 0.02). Estimated dopamine D₂ receptor occupancy numerically increased from 63.0 ± 10.9 to 69.0 ± 11.0 % (P = 0.12). A significant worsening was observed in the BPRS total score among these patients (mean ± SD, 34.3 ± 12.7 to 46.5 ± 16.9, P = 0.003).

CONCLUSION

Paradoxically, the increased plasma concentration was found to be associated with a significant worsening of the clinical outcome. More investigations are indicated to shed further light on optimal levels of D₂ blockade in the maintenance treatment of schizophrenia.

Long-term stability of measuring D(2) receptors in schizophrenia patients treated with antipsychotics

BACKGROUND

While antipsychotic-free schizophrenia patients showed a high degree of within-subject variability in dopamine D(2) receptor density over 6-24 months, no study has examined the long-term stability of D(2) receptor measures in medicated patients.

METHODS

Four schizophrenia patients receiving a stable dose of risperidone underwent [(11)C]raclopride positron emission tomography scans on two occasions 5-14 months apart.

RESULTS

Plasma risperidone levels were found to be consistent between scans, and consistencies of nondisplaceable D(2) binding potential and D(2) occupancy were good.

CONCLUSIONS

The finding supports the validity of quantification of D(2) receptor binding in longitudinal PET studies of medicated patients with schizophrenia.

Possible interaction between MAOA and DRD2 genes associated with antisocial alcoholism among Han Chinese men in Taiwan

Both monoamine oxidase A (MAOA) and dopamine D(2) receptor (DRD2) genes have been considered as candidate genes for antisocial personality disorder with alcoholism (Antisocial ALC) [Parsian, A., 1999. Sequence analysis of exon 8 of MAO-A gene in alcoholics with antisocial personality and normal controls. Genomics. 45, 290-295.; Samochowiec, J., Lesch, K.P., Rottmann, M., Smolka, M., Syagailo, Y.V., Okladnova, O., Rommelspacher, H., Winterer, G., Schmidt, L.G., Sander, T., 1999. Association of a regulatory polymorphism in the promoter region of the monoamine oxidase A gene with antisocial alcoholism. Psychiatry. Res. 86, 67-72.; Schmidt, L.vG., Sander, T., Kuhn, S., Smolka, M., Rommelspacher, H., Samochowiec, J., Lesch, K.P., 2000. Different allele distribution of a regulatory MAO-A gene promotor polymorphism in antisocial and anxious-depressive alcoholics. J. Neural .Transm. 107, 681-689.]. However, the association between alcoholism and MAOA or DRD2 gene has not been universally accepted [Lee, J.F., Lu, R.B., Ko, H.C., Chang, F.M., Yin, S.J., Pakstis, A.J., Kidd, K.K., 1999. No association between DRD(2) locus and alcoholism after controlling the ADH and ALDH genotypes in Chinese Han population. Alcohol. Clin. Exp. Res. 23, 592-599.; Lu, R.B., Lin, W.W., Lee, J.F., Ko, H.C., Shih, J.C., 2003. Neither antisocial personality disorder nor antisocial alcoholism association with MAOA gene among Han Chinese males in Taiwan. Alcohol. Clin. Exp. Res. 27, 889-893.]. Since dopamine is metabolized to 3,4-dihydroxyphenyl-acetaldehyde (DOPAL) via monoamine oxidase (MAO) [Westerink, B.H., de Vries, J.B., 1985. On the origin of dopamine and its metabolite in predominantly noradrenergic innervated brain areas. Brain. Res. 330, 164-166.], the interaction between MAOA and DRD2 genes might be related to Antisocial ALC. The present study aimed to determine whether Antisocial ALC might be associated with the possible interactions of DRD2 gene with MAOA gene. Of the 231 Han Chinese subjects who were recruited for the study, 73 participants were diagnosed with Antisocial ALC and 158 subjects were diagnosed with antisocial personality disorder without alcoholism (Antisocial Non-ALC). The DRD2 TaqI A and MAOA-uVNTR (variable number of tandem repeat located upstream) polymorphisms were not found to be associated with Antisocial ALC. However, an association between DRD2 TaqI A polymorphisms and Antisocial ALC was shown only after stratification for the MAOA-uVNTR 4-repeat polymorphism. Additionally, after multiple logistic regressions, we found that, under stratification of MAOA-uVNTR 4-repeat polymorphism and in comparison with the DRD2 A1/A1 genotype as a reference group, the DRD2 A1/A2 genotype has a possible protective effect against alcoholism in individuals with antisocial personality disorder (ASPD). We concluded that the possible interactions between MAOA-uVNTR polymorphism and DRD2 TaqI A polymorphism might be related to Antisocial ALC among Han Chinese men in Taiwan.

An affected pedigree member analysis of linkage between the dopamine D2 receptor gene TaqI polymorphism and obesity and hypertension

BACKGROUND

Dopamine modulates a variety of physiological functions including natriuresis and satiety. We have previously reported that the TaqI polymorphism of the dopamine D2 receptor (DD2R) gene is associated with both blood pressure and obesity indices in a normoglycaemic Hong Kong Chinese population. In this study, we present evidence confirming the linkage between this gene polymorphism, obesity and hypertension.

METHODS

Two hundred and seventy-four siblings from 96 normoglycaemic hypertensive families were recruited, including 133 who were hypertensive. Central obesity was defined as a waist-to-hip ratio of > or = 0.9 and > or = 0.85 in males and females, respectively, and was identified in 99 of the siblings. The DD2R gene TaqI polymorphism was identified with a polymerase chain reaction based restriction fragment length polymorphism protocol. The affected pedigree member (APM) linkage analysis (sib-pair program, version 0.99.9, by D.L. Duffy) was used to assess for linkage between this gene polymorphism, obesity and hypertension in 73 families with siblings discordant for hypertension.

RESULTS

The A1 allele frequencies were similar in the 133 hypertensive, and 141 normotensive siblings, including the 99 centrally obese siblings at 0.431, 0.421 and 0.418, respectively. APM linkage analysis suggested that the DD2R gene TaqI polymorphism had evidence of linkage with blood pressure (T = -1.86, P = 0.013), as well as with obesity (T = -1.58, P = 0.007).

CONCLUSION

Our data in normoglycaemic Hong Kong Chinese supports that the DD2R gene TaqI polymorphism is a marker associated with the pathogenesis of obesity and hypertension.

Dopamine receptor D3 mRNA expression in human lymphocytes is negatively correlated with the personality trait of persistence

It has been proposed that neurotransmitter receptor expression in peripheral immune cells reflects expression of these receptors in the brain. To test this "peripheral marker hypothesis", we compared mRNA expression of the dopamine receptors D3 (DRD3) and D4 (DRD4) in peripheral blood lymphocytes (PBL) to personality traits assessed with the Temperament and Character Inventory (TCI) in 50 healthy and unmedicated Caucasian individuals. A shared variance of at least 17% (p=0.016) between DRD3 mRNA expression in PBL and the personality trait of persistence was found. As personality traits have been generally assumed polygenic with a single gene accounting for rarely more than 1-2% of observed variance in a trait, this result lends further support to the peripheral marker hypothesis for DRD3 mRNA expression in PBL. It may also suggest a significant role for the DRD3 in the neurobiology of persistence and point to an interesting link between personality and functioning of the immune system.

Reduced dopamine D 3 receptor expression in blood lymphocytes of smokers is negatively correlated with daily number of smoked cigarettes: A peripheral correlate of dopaminergic alterations in smokers

The mesolimbic dopaminergic system is known to mediate rewarding effects of nicotine administration, and dysfunctions of this system may underlie failure to stop cigarette smoking. Expression of dopamine receptors in peripheral blood lymphocytes (PBLs) has been indicated as a peripheral correlate of brain status. Dopamine receptor D(3) (DRD3) and D(4) (DRD4) mRNA expression in PBLs was measured by real-time polymerase chain reaction in smokers (n=26) and former smokers (n=14), compared with nonsmoking control subjects (n=35). A significant (p=.032, Bonferroni corrected) 30% reduction of DRD3 mRNA expression in PBLs was found in smokers but not former smokers in comparison with controls. DRD3 mRNA expression in PBLs in smokers but not former smokers was negatively correlated with daily number of cigarettes consumed (Pearson correlation coefficient r=-.54, p=.005). These data suggest a selective inhibiting effect of smoking on DRD3 mRNA expression and, with the known involvement of DRD3 in reward mediation, indicates a vicious-cycle explanation for the motivation for continued smoking.

Childhood inattention and dysphoria and adult obesity associated with the dopamine D4 receptor gene in overeating women with seasonal affective disorder

There is significant evidence that altered dopamine activity plays a role in seasonal affective disorder (SAD). The current study examined three separate genetic hypotheses for SAD related to the 7-repeat allele (7R) of the dopamine-4 receptor gene (DRD4), a variant associated with decreased affinity for dopamine. We examined the possible contribution of 7R to the overall expression of SAD, attention deficit disorder (ADD) comorbidity, and body weight regulation. As part of an ongoing genetic study of increased eating behavior and mood in female subjects, 108 women with winter SAD and carbohydrate craving/weight gain were administered the Wender-Utah Rating Scale to measure childhood ADD symptomatology, and a questionnaire to assess maximal lifetime body mass index (BMI). To test for an association between 7R and the categorical diagnosis of SAD, the transmission disequilibrium test (TDT) was used in a subsample of probands providing familial DNA. Standard parametric tests were used to compare childhood ADD symptoms and maximal lifetime BMI across the two genotypic groups defined by the presence or absence of 7R. The TDT found no initial evidence for an association between 7R and the categorical diagnosis of SAD. However, 7R carriers reported significantly greater inattention and dysphoria in childhood (p=0.01 and 0.001, respectively) and a higher maximal lifetime BMI (p=0.007) than did probands without this allele. Furthermore, excluding probands with extreme obesity (maximal BMI >40), a strong correlation was found linking childhood inattentive symptoms and maximal lifetime BMI (r=0.35, p=0.001). In overeating women with SAD, the 7R allele of DRD4 may be associated with a unique developmental trajectory characterized by attentional deficits and dysphoria in childhood and mild to moderate obesity in adulthood. This developmental course may reflect different manifestations of the same underlying vulnerability related to central dopamine dysfunction. Given the possibility of population stratification when studying genotype/phenotype relationships, future use of genomic controls and replication of our findings in other overeating and/or ADD populations are needed to confirm these initial results.

Responses to exercise in the heat related to measures of hypothalamic serotonergic and dopaminergic function

We have studied 12 recreationally active men to measure their responses to exercise in the heat and relate these to measures of hypothalamic function explored with a buspirone [5-hydroxytryptamine 1A (5-HT(1A)) agonist, dopaminergic D(2) antagonist] neuroendocrine challenge, with and without pretreatment with pindolol (5-HT(1A) antagonist). Pindolol treatment allowed the serotonergic and non-serotonergic components of prolactin release to be distinguished. Subjects exercised at 73 (5)% maximal rate of oxygen uptake (VO(2max)) until volitional fatigue at 35 degrees C (relative humidity, 30%). On another two occasions they underwent a buspirone challenge [0.5 mg (kg body mass)(-1)], once with, and once without, pindolol [0.5 mg (kg body mass)(-1)] pretreatment and the circulating plasma concentrations of prolactin were measured for the next 2.5 h. Rectal temperature increased throughout exercise, whilst mean skin temperature remained constant. There was a wide inter-subject variation in prolactin response to the neuroendocrine challenges. The proportion of the prolactin response to buspirone attributable to a non-serotonergic component (most likely dopaminergic) correlated both with exercise duration (r=0.657, P=0.028), rectal temperature at fatigue (r=0.623, P=0.041) and the rate of temperature rise (r=-0.669, P=0.024). Our results suggest that high activity of the dopaminergic pathways in the hypothalamus is a predictor of exercise tolerance in the heat.

[Lack of association between 141C Ins/Del promoter polymorphism of DRD2 gene and schizophrenia]

Results of family studies show the importance of genetic factors in etiopathogenesis of schizophrenia. Susceptibility to the disease is probably due to an interaction of many genes. This association study was conducted to investigate frequencies of alleles and genotypes in a group of patients with schizophrenia and in healthy controls. We examined DRD2 gene promoter polymorphism--insertion or deletion of the cytosine in the position -141 of 5'-flanking region of this gene. No relationship between the polymorphism under study and schizophrenia has been found.

D(2) dopamine receptor (DRD2) polymorphism is associated with severity of alcohol dependence

The A(1) allele of the D(2) dopamine receptor (DRD2) gene has been associated with alcohol dependence. However, the expression of this allele risk on the severity of drinking behavior in patients with alcohol dependence has not been systematically explored. The present study examines the association between DRD2 A(1)(+) (A(1)/A(1) and A(1)/A(2) genotypes) and A(1)- (A(2)/A(2) genotype) allele status and key drinking parameters in alcohol-dependent patients. A sample of Caucasian adults was recruited from an alcohol detoxification unit. A clinical interview and the Alcohol Dependence Scale (ADS) questionnaire provided data on consumption, dependence, chronology of drinking and prior detoxification. A(1)(+) allele compared to A(1)- allele patients consumed higher quantities of alcohol, commenced problem drinking at an earlier age, experienced a shorter latency between first introduction to alcohol to the onset of problem drinking and had higher ADS scores. Moreover, A(1)(+) allele patients had more detoxification attempts than their A(1)- allele counterparts. In sum, alcohol-dependent patients with the DRD2 A(1) allele compared to patients without this allele are characterized by greater severity of their disorder across a range of problem drinking indices. The implications of these findings are discussed.

Changes in dopamine receptor responsivity during alcohol detoxification may predict relapse

In the search for clinical and biological variables that may predict relapse of alcohol dependent patients after detoxification, we followed up for 1 year male patients that had undergone successful detoxification. The patients had been tested earlier during their usual alcohol consumption and immediately after detoxification for the responsivity of D2 dopamine receptors (as measured by the increases in prolactin plasma levels caused by intramuscular administration of 5 mg of the dopamine receptor blocker haloperidol). Of the 18 patients, eight had not consumed alcohol for more than 6 months, and ten had relapsed within 6 months. Comparison of the clinical and neuroendocrine data for the two subgroups revealed no significant differences in age, amount of alcohol consumed during alcohol abuse, score in the Beck Depression Inventory, score in the Brief Michigan Alcoholism Screening Test, or prolactin responses to haloperidol before detoxification. In patients who relapsed, the duration of alcoholism was marginally shorter (P=0.055). Patients who did not relapse had significantly higher (P=0.003) prolactin responses to haloperidol in the test performed after detoxification as compared with patients who did relapse, and their responses were similar to those of a group of healthy male subjects. The results show that the increase in dopamine receptor responsivity that occurs after detoxification is a favourable factor for non-relapse; it may reflect recovery from down-regulation of the dopaminergic reward system caused by alcohol consumption.

Antipsychotic radioreceptor assay: a modification identifying selective receptor effects

Radioreceptor assays offer the advantage of a single assay that can assess uniform exposure to multiple chemical compounds. The advent of atypical antipsychotic agents has led to new awareness of the multiple receptor subtypes through which antipsychotic agents may exert their effects, and a renewed interest in comparative drug trials of antipsychotics. The objective of this study was to show the development and validation of antipsychotic radioreceptor assays using clonal cell lines stably expressing isolated human receptors. Model assays were developed using the dopamine(2) (D(2)) and D(4) receptors. D(2) and D(4) activities measured by radioreceptor assay in plasma of antipsychotic-treated subjects were highly correlated with high-performance liquid chromatography determinations of antipsychotic concentrations. Similarly, for a variety of typical and atypical antipsychotic agents, the quotients of D(4)/D(2) activity in plasma of antipsychotic-treated subjects were highly correlated with the quotients of D(4)/D(2) affinities of these agents. Valid receptor-selective antipsychotic assays can be established and may have utility for dissecting the in vivo activity of atypical antipsychotics in relation to specific outcomes in clinical trials.

The prolactin response to sulpiride in major depression: the role of the D2 receptor in depression

Multiple lines of investigations have implicated the role of the dopaminergic system in depression. The aim of the study was to characterise the Dopamine D2 receptor sensitivity status in depressed patients versus controls by means of a novel neuro-endocrine challenge test, the prolactin response to sulpiride. In this intervention, ten patients and ten age matched male volunteers were studied. The patients were diagnosed according to DSM-IV criteria, and Montgomery Asberg and Zung scales were done. There was no significant difference in baseline levels of prolactin between the depressed and control groups. Significantly higher prolactin levels after sulpiride challenge were however found in depressed patients than controls at all time points after sulpiride administration. This neuroendocrine challenge paradigm suggests that the prolactin response to sulpiride, a D2 receptor antagonist, is enhanced in depression, which suggests that this receptor might be supersensitive in depression compared to controls. This adds to the data implicating the dopaminergic system in the pathophysiology of depression, and suggests that dopaminergic mechanisms might be a target of therapeutic interest.

Reduced density of dopamine D2-like receptors on peripheral blood lymphocytes in Alzheimer's disease

Clinical and pathological evidence points to an involvement of dopamine in Alzheimer's disease (AD). The present study was designed to assay dopamine D1-like and D2-like receptors on peripheral blood lymphocytes (PBL) in 20 patients with AD and in 25 healthy controls by radioligand binding assay techniques with [3H][R]-(+)-(-)chloro-2,3,4,5 tetrahydro-5-phenyl-1H-3-benzazepin-al-hemimaleate (SCH 23390) and [3H]7-hydroxy-N,N-di-n-propyl-2-aminotetraline (7OH-DPAT) as radioligands. The density of dopamine D1-like receptors and the affinity of [3H]SCH 23390 and [3H]7OH-DPAT binding to PBL were similar in both groups investigated. AD patients revealed a lower density of dopamine D2-like receptors on PBL than controls (P=0. 0016). The pharmacological profile of [3H]SCH 23390 and [3H]7OH-DPAT binding to PBL was consistent with the labeling of dopamine D5 and D3 receptor subtypes, respectively. The reduced density of dopamine D2-like receptors on PBL is consistent with the observation of changes in the expression of D2-like receptors in dopaminergic brain areas in AD. Our findings support the hypothesis of an involvement of dopamine in AD, even in those patients with no evidence of Parkinsonism, behavioral abnormalities or psychosis.

Migraine patients show an increased density of dopamine D3 and D4 receptors on lymphocytes

Recent studies have revealed peculiar functional and genetic features of dopamine receptors in migraine. As peripheral blood lymphocytes (PBL) may represent a tool for peripheral detection of neuroreceptors, we compared the expression of dopamine D3 (DRD3) and D4 (DRD4) receptors on PBL in migraine patients and in healthy controls using radioligand binding assay techniques in the presence of antidopamine D2-like receptor antibodies. The dopamine D2-like receptor agonist [3H]7-OH-DPAT was used as a radioligand. An increased density of both DRD3 (P=0.0006) and DRD4 (P=0.002) on PBL was observed in migraineurs compared with controls. This up-regulation might reflect central and/or peripheral dopamine receptor hypersensitivity due to hypofunction of the dopaminergic system. These findings support the view that dopamine D2-like receptors are involved in the determination of the so-called migraine trait, which may help to elucidate several clinical features of the disease.

Dopamine D3 receptor polymorphism is not associated with the polycystic ovary syndrome

OBJECTIVE

To determine if a polymorphism of the dopamine D3 receptor gene (2 allele), which has been reported previously to be associated with polycystic ovary syndrome (PCOS) in a population of United States Hispanic women, is associated with the disorder in the southeastern United States.

DESIGN

Prospective case-control study.

SETTING

University reproductive endocrinology laboratory and outpatient clinic.

PATIENT(S)

Consecutive patients of non-Hispanic white race diagnosed with PCOS (n = 152) and healthy controls (n = 96).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Patient and control dopamine D3 receptor genotypes, with the 1 allele representing the wild type and the 2 allele denoting a highly prevalent polymorphism.

RESULT(S)

No difference was noted in the distribution of the three dopamine D3 receptor genotypes (i.e., 1:1, 1:2, and 2:2) among PCOS patients as compared with controls. Furthermore, in contrast to a previous report, the 2:2 genotype was not more prevalent among PCOS patients than among controls.

CONCLUSION(S)

Our population of non-Hispanic white women from the southeastern United States did not demonstrate an association between a dopamine D3 receptor polymorphism and PCOS.

No interaction of GABA(A) alpha-1 subunit and dopamine receptor D4 exon 3 genes in symptomatology of major psychoses

Previously, we reported on an association of the dopamine receptor D4 (DRD4) gene with delusional symptomatology of major psychoses. However, despite the strength of the association, it only accounted for 2% of the variance, indicating that contributions from other genes were probable. In the present study, we investigated the original cohort of subjects to evaluate the gene for the gamma-aminobutyric acid type A (GABA(A)) receptor alpha-1 subunit (GABRA1). The possible association of GABRA1 with the psychopathology of major psychoses was tested both alone and in interaction with DRD4. Four hundred and sixty-one inpatients affected by major psychoses were assessed by the operational criteria checklist for psychotic illness (OPCRIT) and were also typed for the DRD4 and GABRA1 variants using PCR techniques. Mania, depression, delusion, and disorganization were the four symptomatologic factors used as phenotype definitions. GABRA1 variants were not associated with these symptomatologic factors, and consideration of possible stratification effects such as sex and psychiatric diagnosis also did not reveal any association. GABRA1 variants did not significantly influence the association of DRD4 with delusional symptoms. No interaction was observed on the other symptom factors. The GABA(A) alpha-1 subunit gene does not, therefore, interact with DRD4 in the symptomatology of major psychoses.

Labeling of dopamine D3 and D4 receptor subtypes in human peripheral blood lymphocytes with [3H]7-OH-DPAT: a combined radioligand binding assay and immunochemical study

Molecular biology studies have demonstrated that human peripheral blood lymphocytes express dopamine D2-like receptors belonging to the D3 and D4 receptor subtypes, whereas the characterization of these receptors using radioligand binding assay techniques provided conflicting results. The preferential dopamine D3 receptor agonist [3H]7-hydroxy-N, N-di-n-propyl-2-aminotetralin ([3H]7-OH-DPAT) was used recently for labeling lymphocyte dopamine D3 receptor. However, the selectivity of this compound for the D3 receptor was questioned. In this study we have investigated human peripheral blood lymphocyte dopamine receptor subtypes labeled by [3H]7-OH-DPAT using a conventional radioligand binding assay technique and antibodies against dopamine D2-like receptor subtypes. [3H]7-OH-DPAT was specifically bound to intact human peripheral blood lymphocytes with a dissociation constant (Kd) value of 0.32 + 0.03 nM and a maximum density of binding sites (Bmax) of 18.2 + 0.8 fmol/2 x 10(6) cells. [3H]7-OH-DPAT binding was unaffected by antibodies against dopamine D2 and D2S receptors. Anti-dopamine D3 and D4 receptor antibodies reduced [3H]7-OH-DPAT binding by about 53% and 32% respectively. Combination of anti D3 and D4 receptor antibodies reduced remarkably [3H]7-OH-DPAT binding. The above results suggest that the dopamine receptor agonist [3H]7-OH-DPAT labels dopamine D3 and D4 receptor subtypes in human peripheral blood lymphocytes. The use of antibodies raised against dopamine receptor subtypes in combination with radioligand binding assay may contribute to define receptor subtypes expressed by human peripheral blood lymphocytes in health and disease.

Dopamine D3 receptor in peripheral mononuclear cells of essential hypertensives

Dopamine D3 receptor was studied in peripheral mononuclear cells of high-normal, stage 1, stage 2, and stage 3 essential hypertensives using a radioligand binding assay technique with [3H]-7-hydroxy-N,N-di-n-propyl-2-aminotetraline (7-OH-DPAT) as a radioligand. A group of de novo Parkinsonian patients was also examined as a reference group of impaired dopaminergic function. [3H]-7-OH-DPAT was bound specifically to human peripheral mononuclear cells in a manner consistent with the labeling of a dopamine D3 receptor. No changes in free dopamine, norepinephrine, epinephrine and aldosterone levels, renin activity, dissociation constant of [3H]-7-OH-DPAT binding, or the pharmacological profile of [3H]-7-OH-DPAT binding were found between normotensive control subjects and essential hypertensives or Parkinsonians. The density of peripheral mononuclear cell [3H]-7-OH-DPAT binding sites increased in essential hypertensives parallel to blood pressure value augmentation. A higher density of [3H]-7-OH-DPAT binding sites was found in Parkinsonians. In these patients, the density of [3H]-7-OH-DPAT binding sites was similar to that observed in high-normal subjects and in stage 1 essential hypertensives. The increased density of peripheral mononuclear cell dopamine D3 receptor in hypertension as well as in Parkinson's disease may represent an upregulation mechanism consequent to impaired dopaminergic function. In view of the difficulty in identifying markers of peripheral dopamine function, analysis of dopamine D3 receptor in peripheral mononuclear cells may help evaluate whether the dopaminergic system is involved in hypertension.

Improvement of schizophrenic symptoms and changes in plasma HVA concentrations, plasma anti-D2 and anti-5-HT2 receptor activities with clozapine

In order to investigate the biological mechanisms underlying the clinical efficacy of clozapine, 200 mg/day of clozapine was added to the drug regimens of 19 patients with chronic, anti-psychotic-resistant schizophrenia, and the plasma homovanillic acid (HVA), clozapine concentrations, anti-dopamine D2 and anti-serotonin 5-HT2 receptor activities were measured. After 28 days, six patients showed an improvement of more than 20% over baseline Brief Psychiatric Rating Scale (BPRS) scores. Mean plasma HVA concentrations and anti-D2 receptor activities did not change significantly in the entire group or in the six patients showing improvement. However, anti-5-HT2 receptor activities increased significantly in all 19 patients. Changes in BPRS scores did not correlate significantly with changes in plasma HVA or with changes in clozapine concentrations, or with anti-D2 and anti-5-HT2 receptor activities.

Neuroleptic monitoring: relation between antipsychotic efficiency and radioreceptor assay of serum haloperidol

OBJECTIVE

We report preliminary results from use of a radioreceptor assay (RRA) to measure serum haloperidol levels and their relation to clinical response and adverse effects in 19 psychotic patients with positive symptoms treated with haloperidol.

METHODS

Blood samples were taken on Days 7, 14 and 21. Clinical evaluation was based on the PANSS, and UKU scales. The D2 antidopaminergic RRA was used to measure haloperidol serum levels.

RESULTS

Our results show a correlation between psychosis with positive symptoms assessed by positive scores in the PANSS and the serum drug level measured by RRA concentrations. The observed relationship made it possible to establish a therapeutic serum range of haloperidol equivalents 15-30 ng/ml-1. This range contained no "non-responders". Analysis of the correlation between each item on the positive subscale of the PANSS and the RRA concentration suggested that there was no specific symptom of psychosis closely related to RRA concentration during the first 15 days of treatment. In the third week, however, certain specific symptoms were closely connected to the RRA concentration.

CONCLUSION

From these results, it can be concluded that antipsychotic activity can be related to blockade of serum D2 dopamine receptors. In future would be desirable to monitor neuroleptic treatment in this way. The study also showed that the antipsychotic treatment did not correct any specific component of the psychosis during the first stage of the treatment but that it did so at later times.