The dopamine-serotonin relationship in clozapine response

The effects of clozapine on the dopamine and serotonin systems may underlie its atypical pharmacologic and clinical profile. To examine this hypothesis, we measured dopamine and serotonin plasma and cerebrospinal (CSF) metabolites and the relationship of these values to treatment response in 19 neuroleptic refractory and intolerant schizophrenic patients. Only a small change in the CSF and plasma homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5HIAA) levels was found. However, the pretreatment CSF HVA/5HIAA ratio and, to a lesser extent, the CSF HVA level predicted treatment response. These results suggest that the modest relationship between HVA and 5-HIAA and treatment response supports the involvement of both neurotransmitters in the pathophysiology of schizophrenia.     

Determinations of 5-hydroxyindoleacetic acid and homovanillic acid in human CSF with monitoring of probenecid levels in CSF and plasma

The accumulation of 5-HIAA and HVA in cerebrospinal fluid (CSF) was studied in eight healthy volunteers after oral administration of probenecid. Simulation indicated that a dose of 4.5 g probenecid should be used to achieve probenecid plasma concentrations between 200 and 400 g/ml. Almost complete inhibition of the active transport of the acidic metabolites was assumed to be obtained at these concentrations. Probenecid 4.5 g was administered in two doses (2.5 g and 2 g), separated by 4 h. Plasma samples were drawn at varying intervals over a period of 46 h and lumbar puncture (LP) was performed at either 14 h or 20 h after the first administration of probenecid. The concentration of probenecid, 5-HIAA and HVA in CSF was estimated and the probenecid-induced accumulation of 5-HIAA and HVA was compared with their baseline values. There were no statistically significant differences (P>0.05) in the accumulation of the monoamine metabolites between the two LP (14 h and 20 h), neither were there any differences in CSF concentrations of probenecid at the time of LP. There were only small differences in probenecid plasma concentrations, although statistically significant. Due to maximum blockade of the active transport system no correlation was observed between the CSF concentration of probenecid and the induced accumulation of 5-HIAA and HVA, respectively. The range of probenecid-induced accumulation for 5-HIAA and HVA in these volunteers was 156–429% and 183–600%, respectively. The suggested monitoring of probenecid plasma levels is proposed as a suitable model to investigate central neuronal activity of dopamine and serotonin in the central nervous system.     

Neurochemical changes in pigeon cerebrospinal fluid during chronic administration of buspirone or 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)

Cerebrospinal fluid (CSF), collected repeatedly from White Carneau pigeons chronically implanted with guide cannulae located in the lateral ventricles, was analyzed for metabolites of serotonin, dopamine and norepinephrine after acute and chronic administration of buspirone or 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). Following the acute administration of 3.0 mg/kg buspirone, levels of 5-hydroxyindoleacetic acid (5-HIAA) decreased, while increases occurred in the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC). Decreases in 5-HIAA persisted throughout the chronic dosing regimen (36 days), while dopamine metabolites returned to control levels within 8 days. When chronic buspirone was discontinued, levels of 5-HIAA were restored to predrug control levels, while levels of HVA, DOPAC and 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) decreased. All metabolites returned to predrug control levels within one week following buspirone discontinuation except for MHPG, which remained depressed. When the acute effects of buspirone were reexamined, levels of 5-HIAA were again significantly decreased, while HVA and DOPAC levels, as well as those of MHPG, increased significantly. Acute administration of the 5-HT1A receptor ligand 8-OH-DPAT (3.0 mg/kg) resulted in large decreases in 5-HIAA levels that persisted throughout the period of chronic administration. Neither acute nor daily administration of 8-OH-DPAT changed levels of HVA, DOPAC or MHPG. Large increases in 5-HIAA occurred when chronic 8-OH-DPAT was discontinued but declined within one week to control levels. Following a two-week drug-free period, 8-OH-DPAT again caused a significant reduction in 5-HIAA levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dopamine and serotonin metabolites in rat cerebroventricular fluid following withdrawal of haloperidol or electroshock treatment

Levels of the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and of the major serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) were determined in the CSF of rats at various times after repeated electroshock treatment (EST) or chronic administration of haloperidol. The acidic metabolites were analyzed in 25 l CSF using HPLC with an electrochemical detector. A significant decrease in the CSF levels of DOPAC and HVA was found 4 days after the last administration of chronic haloperidol, EST, or both. The decrease in the level of the dopamine metabolites indicated a slower dopamine turnover, which might have resulted from hypersensitivity of presynaptic dopamine receptors after these treatments. Rats treated with haloperidol also showed an increase in 5-HIAA levels, possibly due to enhanced serotonin turnover. The 5-HIAA increase following haloperidol was prevented by a concurrent administration of EST, suggesting attenuation by EST of the haloperidol-induced enhancement of serotonin turnover.     

Neurochemistry of withdrawal emergent symptoms in children

The probenecid procedure was used to study the metabolite accumulations of dopamine (DA) and serotonin (5-HT) in the cerebrospinal fluid (CSF) of 11 children receiving chronic neuroleptic therapy. Specimens were obtained while the children were being given chronically prescribed medication (Condition 1) and again 3–4 weeks later, following the discontinuation of drugs (Condition 2). At that time, five children showed typical dyskinetic withdrawal emergent symptoms (WES) and six were free of symptoms. CSF specimens were also obtained from eight drug-free children, diagnosed as having chronic organic brain disease, who served as a contrast population against which the findings were evaluated. CSF accumulations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) did not differentiate the drug-treated children who showed WES from those who did not manifest these symptoms. A significant decrease in 5-HIAA was found in Condition 2, suggesting that chronic treatment with neuroleptics may effect 5-HT metabolism in children. The contrast population was found to have lower CSF concentrations of probenecid and were consequently of little help in clarifying the nature of the 5-HIAA decrement. A number of serious deficiences were noted regarding the use of the probenecid procedure, and it is felt that the use of spinal taps for studying neuroleptic effects on brain metabolism in children is unlikely to provide important information with regard to either CNS drug actions or toxicity.     

Dystrobrevin-binding protein 1 gene (DTNBP1) variants associated with cerebrospinal fluid homovanillic acid and 5-hydroxyindoleacetic acid concentrations in healthy volunteers

The dystrobrevin binding protein-1 (DTNBP1) gene encodes dysbindin-1, a protein involved in neurodevelopmental and neurochemical processes related mainly to the monoamine dopamine. We investigated possible associations between eleven DTNBP1 polymorphisms and cerebrospinal fluid (CSF) concentrations of the major dopamine metabolite homovanillic acid (HVA), the major serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA), and the major noradrenaline metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) in healthy human subjects (n = 132). Two polymorphisms, rs2619538 and rs760666, were nominally associated with CSF HVA and 5-HIAA concentrations, whereas a third polymorphism, rs909706, showed association only with HVA. After correction for multiple testing only the associations between rs2619538 and HVA and 5-HIAA concentrations remained significant. No significant association was found between any of the investigated DTNBP1 polymorphisms and CSF MHPG concentrations. The results suggest that genetic variation in DTNBP1 gene affects the regulation of dopamine and serotonin turnover in the central nervous system of healthy volunteers.     

Effect of sulpiride on monoaminergic mechanisms in psychotic women

Concentrations of the major monoamine metabolites homovanillic acid (HVA) 4-hydroxy-3-methoxyphenylethylene glycol (MOPEG), and 5-hydroxyindoleacetic acid (5-HIAA) were determined in lumbar CSF of psychotic women with a schizophrenic symptomatology before and 4 weeks after treatment with sulpiride (Dogmatil 200 mg×4). The metabolites were determined by a mass fragmentographic method. Prolactin concentrations in CSF and plasma were determined by radioimmunoassay. The clinical effects were evaluated by ratings according to the comprehensive psychopathology rating scale (CPRS) and a scale for side effects. Levels of HVA and prolactin in CSF and plasma were significantly elevated during treatment. No effects on concentrations of MOPEG or 5-HIAA were observed. The biochemical data indicate that clinical doses of sulpiride blocked dopamine receptors in the nigrostriatal pathway as well as in the tuberoinfundibular system. Treatment with sulpiride was associated with marked reductions in psychotic morbidity.A preliminary report of parts of this study was presented at the Symposium on Receptors of Dopamine Antagonists: New Biochemical Approaches, July 6–8, 1978, Beerse, Belgium     

Differential effects of clorgyline on catecholamine and indoleamine metabolites in the cerebrospinal fluid of rhesus monkeys

The effects of acute and chronic administration of clorgyline, an irreversible inhibitor of monoamine oxidase type A (MAO-A), on the deaminated metabolites of norepinephrine, dopamine and serotonin were examined in rhesus monkey cerebrospinal fluid (CSF). Acute clorgyline treatment resulted in highly significant, dose-dependent reductions in 3-methoxy-4-hydroxyphenylglycol (MHPG) of 50% (1 mg/kg) and 68% (2 mg/kg) compared to pretreatment values. Chronic clorgyline administration (0.25 to 0.5 mg/kg X 24 days) resulted in a 67% reduction in CSF MHPG. In contrast, the concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were less affected by acute clorgyline administration, being reduced significantly only after the 2 mg/kg dose, which lowered 5-HIAA 27% and HVA 48%. Chronic clorgyline treatment had no significant effect on the CSF concentrations of HVA and 5-HIAA. These data, which suggest that MAO-A inhibition by clorgyline in vivo is more closely associated with changes in the noradrenergic than the serotonergic or dopaminergic systems in nonhuman primates, are in general agreement with the effects of clorgyline on CSF and urinary biogenic amine metabolites in man. They differ from several in vitro studies which indicate a primary role of MAO-A in the metabolism of serotonin and of MAO-B in norepinephrine degradation in primate brain. The discrepancies may reflect modulating effects of synaptic feedback mechanisms on the actions of clorgyline in vivo or perhaps a failure of CSF metabolites to adequately reflect brain amine metabolism changes. The lack of change in platelet MAO-B activity during clorgyline treatment together with the minimal changes in HVA concentrations indicate that the selective inhibitory effects of clorgyline on MAO-A were maintained during chronic administration of low drug doses.     

The effect of olanzapine treatment on m-chlorophenylpiperazine-induced hormone release in schizophrenia.

In addition to dopamine, serotonin (5-hydroxytryptamine, 5-HT) has been reported to play an important role in schizophrenia. Besides blocking dopamine, atypical antipsychotics also block 5-HT receptors. The clinical efficacy of the atypical antipsychotic clozapine is associated with the 5-HT antagonistic action of the drug and a high serotonergic tone before treatment. The atypical antipsychotic olanzapine has a receptor-binding profile similar to that of clozapine. The present study investigated whether treatment with olanzapine blocks hormone release induced by the 5-HT2c agonist m-chlorophenylpiperazine (m-CPP) and, if so, whether this 5-HT antagonistic effect is related to treatment response. Eighteen male schizophrenic patients participated in this study. All patients were challenged with m-CPP (0.5 mg/kg orally) in a double-blind, randomized, placebo-controlled design after a drug-free period of at least 2 weeks. Adrenocorticotropic hormone (ACTH), cortisol, and prolactin plasma levels were measured every 30 minutes up to 210 minutes after challenge. Patients were treated for 6 weeks with 10 mg olanzapine daily in an open design, after which the challenge tests were repeated. Olanzapine significantly blocked m-CPP-induced ACTH, cortisol, and prolactin release, suggesting that it is a potent 5-HT2c antagonist in vivo. This 5-HT antagonistic effect of olanzapine was not significantly correlated with treatment response. Also, no significant correlation was found between m-CPP-induced hormone release before treatment and clinical response after treatment with olanzapine. These findings suggest that olanzapine is a potent 5-HT2c antagonist in vivo but that this is unrelated to its clinical efficacy in this nonrefractory sample of schizophrenic patients.     

Cerebrospinal fluid 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) following probenecid in unipolar depressives treated with amitriptyline

Lumbar cerebrospinal fluid 5-HIAA, HVA, and the ratio 5-HIAA/HVA were measured followed probenecid administration in eleven patints with unipolar depression before and during treatment with amitriptyline (AMI). Control values were obtained from a group of inmate volunteers. Prior to treatment CSF 5HIAA formation in the depressives was not different from controls. During treatment with AMI, CSF 5-HIAA formation decreased. One patient with psychotic symptoms prior to AMI and two patients who developed psychotic reactions on AMI showed relatively low CSF 5HIAA formation prior to antidepressant therapy. Compared to controls CSF HVA values were higher in the depressives prior to AMI therapy.     

Effects of tiapride on homovanillic acid levels in human cerebrospinal fluid drawn at pneumoencephalography

The effect of tiapride on HVA and 5-HIAA levels in the CSF drawn at pneumoencephalography (PEG) was studied. Five consecutive 5 ml fractions of CSF were drawn from control and tiapride-treated subjects. In both groups, a linear increase in HVA concentrations was found between the first and subsequent fractions. On the contrary, no significant difference in 5-HIAA concentrations was found in sequential CSF samples. Tiapride increased the mean HVA concentrations and caused a steeper caudocranial gradient of this metabolite but failed to modify 5-HIAA concentrations. The results suggest that tiapride blocks dopamine (DA) receptors and increases DA synthesis.     

Effects of raclopride treatment on plasma and CSF HVA: relationships with clinical improvement in male schizophrenics

Thirty-two acutely psychotic, male schizophrenic patients received raclopride, at 2, 6, or 12 mg/day, or haloperidol, 15 mg/day for 4 weeks after randomized, double-blind assignment. Twenty-six patients, including 19 who had been assigned one of the three doses of raclopride, completed the study. Raclopride, particularly at 12 mg/day, increased CSF homovanillic acid (HVA) at 4 weeks, and plasma HVA at 2 days, of treatment. The clinical response to raclopride was significantly correlated with plasma raclopride concentrations and baseline plasma HVA concentrations. Although raclopride is a substituted benzamide with atypical properties in animals, these results suggest that the doses of raclopride required for clinical efficacy and elevation of clinical indices of brain dopamine turnover are similar.     

Vasopressin in CSF and plasma in depressed suicide attempters: preliminary results.

Increased plasma arginine vasopressin (AVP) concentrations have been reported in depressed suicide attempters. Plasma AVP is primarily produced by the magnocellular system in response to increased plasma osmolality, and central AVP may be independently regulated. In the present study we investigated cerebrospinal fluid (CSF) and plasma AVP concentrations in depressed patients and controls. Nineteen drug-free depressed psychiatric inpatients (nine suicide attempters) and nine neurological control subjects underwent lumbar puncture and psychiatric evaluation. CSF and plasma concentrations of AVP, serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and cortisol were assayed. In 15 depressed patients (eight suicide attempters), the combined dexamethasone/corticotropin-releasing hormone (Dex/CRH) test was performed to examine the hypothalamic-pituitary-adrenocortical (HPA) system. There were no differences between depressed subjects and controls in all parameters measured. Suicide attempters did not differ from nonattempters. In depressed patients, plasma AVP correlated positively with cortisol. There was no relationship between CSF AVP and monoamine metabolites in CSF.     

CSF monoamine metabolite concentrations vary according to age,rearing, and sex,and are influenced by the stressor of social separation in rhesus monkeys

In humans, CSF monoamine metabolite concentrations have been shown to vary as a complex function of age, sex, psychiatric diagnosis, and stress. To test for such relationships in rhesus monkeys, 28 subjects, reared either in anxiety producing peer-only groups or in mother-infant dyads, were studied at 6, 18 or 50 months of age. Each monkey underwent a series of four 4-day social separations, each followed by 3 days of reunion. Prior to and during the first and fourth separations, CSF was obtained from the cisterna magna and assayed for the serotonin metabolite 5-HIAA, the dopamine metabolite HVA, and the norepinephrine metabolite MHPG. CSF 5-HIAA showed an age-related decline which was greater in the mother-reared subjects. Peer-only-reared males had an increased 5-HIAA concentration relative to females, and higher 5-HIAA levels than mother-reared males. MHPG was also higher in peer-only-reared monkeys than in mother-reared subjects at all ages. In both groups HVA declined across the three ages, and MHPG increased from the 18- to the 50-month measurements. Both MHPG and 5-HIAA concentrations increased during the initial social separation, although only MHPG remained elevated across the repeated separations; HVA, on the other hand declined during social separation. These results are discussed in terms of established anxiety and aggression differences between peer-only and mother-reared monkeys.     

Biochemical effects of zimelidine in man

Summary The novel drug zimelidine 50–300 mg/day was administered to 12 depressed patients. After about 3 weeks plasma levels of the demethyl metabolite, norzimelidine, were almost thrice those of the parent drug. During incubation of slices of rat brain cortex in plasma from the treated patients, the neuronal uptake of serotonin and noradrenaline was 51.7±10.2 and 82.8±9.6%, respectively, of the control values. The uptake inhibition both of serotonin and noradrenaline was correlated with the plasma level of norzimelidine (r=0.62 and 0.63, respectively). The major central metabolites of serotonin (5-HIAA) and noradrenaline (HMPG) in cerebrospinal fluid (CSF) decreased significantly (29 and 11%, respectively) during treatment with zimelidine. Although there was no mean change in the major dopamine metabolite (HVA) in CSF, the level during treatment (as percentage of the pretreatment level) was correlated with the effect on 5-HIAA in CSF. Thus, administration of zimelidine caused a relatively selective inhibition of serotonin uptake, mainly due to norzimelidine. A small but significant inhibition of noradrenaline uptake was also seen, but this effect was less pronounced than during chlorimipramine treatment. There was also an effect on the dopaminergic system, probably secondary to the action on serotonergic neurons.     

Central nervous system monoamine correlates of social dominance in cynomolgus monkeys (Macaca fascicularis).

Social dominance is a fundamental component of both human and nonhuman primate sociality. However, its neurobiological correlates remain incompletely understood. We evaluated the association between dominance status and monoamine metabolite concentrations in cisternal cerebrospinal fluid (CSF) in adult male (n = 25) and female (n = 21) cynomolgus macaques (Macaca fascicularis) housed in unisexual social groups. Concentrations of the metabolites of dopamine (homovanillic acid [HVA]), norepinephrine (3-methoxy-4-hydroxyphenylglycol [MHPG]) and serotonin (5-hydroxyindoleacetic acid [5-HIAA]) were assayed. Dominant monkeys, both males and females, had significantly higher CSF HVA concentrations than did subordinates (p values <.05). Among males, but not females, dominants also had lower CSF 5-HIAA than subordinates (p <.05). The Dominance-HVA association observed here is consistent with recent speculation that social extraversion, a dominance-related personality trait in humans, may also reflect heightened central nervous system dopaminergic activity.     

Treatment enhances ultradian rhythms of CSF monoamine metabolites in patients with major depressive episodes.

Unipolar and bipolar depressions show abnormal behavioral manifestations of ultradian (less than 24 h) rhythms, but abnormal rhythms of the central neurotransmitters thought to be important for depression pathophysiology (eg dopamine (DA) and serotonin (5-HT)) have not been shown in this time frame. Since antidepressant treatments normalize disrupted rhythms in depression (eg rapid-eye-movement sleep and hormonal rhythms), we hypothesized that depression-related changes in ultradian oscillations of DA and 5-HT might be revealed during antidepressant treatment. Cerebrospinal fluid (CSF) samples collected q10 min for 24 h in 13 patients experiencing major depressive episodes (MDE) before and after treatment for 5 weeks with sertraline or bupropion were assayed for levels of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA), and their ratio was calculated. Data were analyzed in the frequency domain using Fourier transforms and multivariate permutation testing. Antidepressant treatments were associated with decreased variance for 5-HIAA, increased variance for HVA, and markedly increased variance for the HVA : 5-HIAA ratio (p<0.05, p<0.02, and p<0.003, respectively). With treatment, the correlations between 5-HIAA and HVA weakened (p=0.06). Power spectral density (PSD-the Fourier magnitude squared) of the 5-HIAA signals at periods of 1.75 and 3.7 h (both p<0.05) decreased, while circadian cycling of HVA levels (p<0.05) and of the ratio (p<0.005) increased after treatment. The PSD of the full-length HVA : 5-HIAA ratio series after treatment increased in rapid variability (20-103 min periods, p<0.05). Spectrographic windowing demonstrated a focal span of enhanced HVA : 5-HIAA ratio variability following antidepressant treatment, in an approximately 84-min period through the evening (p<0.05). Periodic neurotransmitter relationships in depressed patients were altered by treatment in this analysis of a small data set. This may represent a baseline abnormality in the regulation of periodic functions involved in the depression pathophysiology, but it could also be due to an unrelated antidepressant effect. Further studies including comparisons with healthy subject data are in progress.     

Alterations of cerebrospinal fluid 5-hydroxyindoleacetic acid,and total blood serotonin content during clozapine treatment

Cerebrospinal fluid 5-hydroxyindoleacetic acid level, and total blood serotonin content was measured in groups of manic and schizophrenic patients before and after 2, 4, 6, 10, 20, and 30 days of clozapine treatment. CSF 5-HIAA values were elevated after 2 and 4 days and returned to baseline levels after 6 days or more. Blood serotonin content, in contrast, increased gradually and remained high even after 30 days. Neither CSF 5-HIAA nor blood 5-HT correlated with age, drug dose, or clinical effectiveness, but some relationship between these and the sedative component of the clozapine action was observed.     

CSF 5-HIAA as a predictor of treatment response in trichotillomania.

Trichotillomania is characterized by chronic hair-pulling resulting in noticeable hair loss. In a preliminary study, cerebrospinal fluid (CSF) measures in 8 medication-free, female, trichotillomania patients were compared to those of matched, normal controls. There was no difference between patients and controls in measures of CSF cortisol, 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG). CSF measures did not correlate with measures of trichotillomania symptomatology. However, degree of response to treatment with serotonin re-uptake inhibitors significantly correlated with baseline CSF 5-HIAA. This suggests that central serotonin turnover is specifically relevant to treatment response to serotonin re-uptake inhibitors in trichotillomania.     

Extrapyramidal reactions and amine metabolites in cerebrospinal fluid during haloperidol and clozapine treatment of schizophrenic patients

8 male schizophrenic patients participated in a double-blind, cross over study of the extrapyramidal side-effects of haloperidol and clozapine (acute dystonia, Parkinsonism and tardive dyskinesia), together with their effect on homo-vanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF). Haloperidol (9 mg/day) caused Parkinsonism, reduced tardive dyskinesias and increased the HVA concentration in the CSF. Clozapine (225 mg/day) had no effect on the neurological phenomena but reduced HVA and 5-HIAA concentrations in the CSF. During the discontinuation phase following the administration of haloperidol, tardive dyskinesia occurred or was aggravated; this did not occur after administration of clozapine. Accordingly, it is suggested that clozapine does not induce dopaminergic hypersensibility and, therefore, will not induce tardive dyskinesias.Part of this work was presented at the 9th C.I.N.P. Congress, Paris, July 7–12, 1974.