Cerebrospinal fluid 5-hydroxyindoleacetic acid as an index of central serotonergic processes

Quantification of monoamine biomarkers in cerebrospinal fluid: comparison of a UHPLC-MS/MS method to a UHPLC coupled to fluorescence detection method

Inborn errors of monoamine neurotransmitter metabolism are rare genetic diseases classified as catecholamine and serotonin metabolism disorders or neurotransmitter transportopathies. To diagnose these orphan diseases, monoamine metabolites have been identified and validated as cerebrospinal fluid (CSF) biomarkers: 5-hydroxy-tryptophane, 5-hydroxy-indol-acetic acid, 3-ortho-methyl-DOPA, homovanillic acid, and 3-methoxy-4-hydroxyphenylglycol. The present work presents a UHPLC-MS/MS method developed for the quantification of these metabolites in CSF and compares it to a previously described UHPLC-FD method. MS/MS detection was performed in positive electrospray ionization and multiple reaction monitoring (MRM) mode. The UHPLC-MS/MS and UHPLC-FD methods were validated in terms of accuracy, linearity, precision, and matrix effect. The lower limits of quantification (LLOQ) were ranging between 0.5 nM and 10 nM and between 1 and 5 nM for the UHPLC-MS/MS method and the UHPLC-FD one, respectively. We verified the applicability of both methods by analyzing 30 CSF samples. The measured concentrations were comparable to the reference values described in the literature. The two methods allowed to distinguish pathological samples from healthy ones for clinical diagnosis. UHPLC-MS/MS and UHPLC-FD methods exhibit very close LLOQs. As UHPLC-MS/MS method is more selective, it allows faster analysis with 6 minutes per run versus 10 minutes for the UHPLC-FD method.

Vulnerability to depressive behavior induced by overexpression of striatal Shati/Nat8l via the serotonergic neuronal pathway in mice

The number of patients with depressive disorders is increasing. However, the mechanism of depression onsets has not been completely revealed. We previously identified Shati/Nat8l, an N-acetyltransferase, in the brain using an animal model of psychosis. In this study, we revealed the involvement of Shati/Nat8l in the vulnerability to major depression. Shati/Nat8l mRNA was increased only in the striatum of mice, which were exposed to chronic social defeat stress. Shati/Nat8l-overexpressed mice showed impairment in social interaction and sucrose preference after the subthreshold social defeat (microdefeat) stress. These depression-like behaviors were restored by fluvoxamine and LY341495 injection prior to these tests. Furthermore, the intracerebral administration of only fluvoxamine, but not of LY341495, to the dorsal striatum and direct infusion of LY341495 to the dorsal raphe also rescued. Taken together, Shati/Nat8l in the striatum has an important role in the vulnerability to depression onsets by regulating the origin of serotonergic neuronal system via GABAergic projection neuron in the dorsal raphe from the dorsal striatum.

Serotonin as a drug receptor for Li+: a computational study

Although Li+ is widely used to treat bipolar disorder, its antidepressant pharmacological mechanism of action remains unelucidated. Herein, based on molecular modelling studies, we present the novel hypothesis that one possible receptor for Li+ is serotonin (5-hydroxytryptamine, 5-HT), a small molecule neurotransmitter rather than a large macromolecular protein. The resulting Li+/5-HT drug–receptor complex subsequently interacts with “upstream” macromolecular receptors such as the 5-HT1A receptor differently than 5-HT alone, producing an enhanced antidepressant effect. The notion that a neurotransmitter could itself be a receptor for a therapeutic is an interesting receptor cascade concept. Using molecular mechanics and semi-empirical and ab initio levels of theory, the potential interactions between Li+ and 5-HT and between Li+ and 5-HIAA (5-hydroxyindoleacetic acid, a 5-HT metabolite) were examined. Molecular dynamics simulations were then used to examine how Li+ affects the binding of 5-HT to its target 5-HT1A antidepressant receptor. The results of these calculations suggest that Li+ can interact with 5-HT and in such a way that it modifies the ligand–protein interactions.

The relevance of 'mixed anxiety and depression' as a diagnostic category in clinical practice

According to ICD-10 criteria, mixed anxiety and depressive disorder (MADD) is characterized by co-occurring, subsyndromal symptoms of anxiety and depression, severe enough to justify a psychiatric diagnosis, but neither of which are clearly predominant. MADD appears to be very common, particularly in primary care, although prevalence estimates vary, often depending on the diagnostic criteria applied. It has been associated with similarly pronounced distress, impairment of daily living skills, and reduced health-related quality of life as fully syndromal depression and anxiety. Although about half of the patients affected remit within a year, non-remitting patients are at a high risk of transition to a fully syndromal psychiatric disorder. The validity and clinical usefulness of MADD as a diagnostic category are under debate. It has not been included in the recently released DSM-5 since the proposed diagnostic criteria turned out to be not sufficiently reliable. Moreover, reviewers have disputed the justification of MADD based on divergent results regarding its prevalence and course, diagnostic stability over time, and nosological inconsistencies between subthreshold and threshold presentations of anxiety and depressive disorders. We review the evidence in favor and against MADD and argue that it should be included into classification systems as a diagnostic category because it may enable patients to gain access to appropriate treatment early. This may help to reduce patients' distress, prevent exacerbation to a more serious psychiatric disorder, and ultimately reduce the societal costs of this very common condition.

Reconciling the role of central serotonin neurons in human and animal behavior

Animal research suggests that central serotonergic neurons are involved in behavioral suppression, particularly anxiety-related inhibition. The hypothesis linking decreased serotonin transmission to reduced anxiety as the mechanism in the anxiolytic activity of benzodiazepines conflicts with most clinical observations. Serotonin antagonists show no marked capacity to alleviate anxiety. On the other hand, clinical signs of reduced serotonergic transmission (low 5-HIAA levels in the cerebrospinal fluid) are frequently associated with aggressiveness, suicide attempts, and increased anxiety. The target article attempts to reconcile such human and animal findings by investigating whether anxiety reduction or increased impulsivity is more Likely to account for animal behavioral changes associated with decreased serotonergic transmission. The effects of manipulating central serotonin in experimental anxiety paradigms in animals (punishment, extinction, novelty) are reviewed and compared with the effects of antianxiety drugs. Anxiety seems neither necessary nor sufficient to induce control by serotonergic neurons on behavior. Further evidence suggests that behavioral effects of anxiolytics thought to be mediated by decreases in anxiety are not caused by the ability of these drugs to reduce serotonin transmission. Blockade of serotonin transmission, especially at the level of the substantia nigra, results in a shift of behavior toward facilitation of responding. This behavioral shift is particularly marked when there is competition between acting and restraining response tendencies and when obstacles prevent the immediate attainment of an anticipated reward. It is proposed that serotonergic neurons are involved not only in behavioral arousal but also in enabling the organism to arrange or tolerate delay before acting. Decreases in serotonin transmission seem to be associated with the increased performance of behaviors that are usually suppressed, though not necessarily because of the alleviation of anxiety, which might contribute to the suppression.

SEROTONERGIC MECHANISMS IN AMYOTROPHIC LATERAL SCLEROSIS

Serotonin (5-HT) has been intimately linked with global regulation of motor behavior, local control of motoneuron excitability, functional recovery of spinal motoneurons as well as neuronal maturation and aging. Selective degeneration of motoneurons is the pathological hallmark of amyotrophic lateral sclerosis (ALS). Motoneurons that are preferentially affected in ALS are also densely innervated by 5-HT neurons (e.g., trigeminal, facial, ambiguus, and hypoglossal brainstem nuclei as well as ventral horn and motor cortex). Conversely, motoneuron groups that appear more resistant to the process of neurodegeneration in ALS (e.g., oculomotor, trochlear, and abducens nuclei) as well as the cerebellum receive only sparse 5-HT input. The glutamate excitotoxicity theory maintains that in ALS degeneration of motoneurons is caused by excessive glutamate neurotransmission, which is neurotoxic. Because of its facilitatory effects on glutaminergic motoneuron excitation, 5-HT may be pivotal to the pathogenesis and therapy of ALS. 5-HT levels as well as the concentrations 5-hydroxyindole acetic acid (5-HIAA), the major metabolite of 5-HT, are reduced in postmortem spinal cord tissue of ALS patients indicating decreased 5-HT release. Furthermore, cerebrospinal fluid levels of tryptophan, a precursor of 5-HT, are decreased in patients with ALS and plasma concentrations of tryptophan are also decreased with the lowest levels found in the most severely affected patients. In ALS progressive degeneration of 5-HT neurons would result in a compensatory increase in glutamate excitation of motoneurons. Additionally, because 5-HT, acting through presynaptic 5-HT1B receptors, inhibits glutamatergic synaptic transmission, lowered 5-HT activity would lead to increased synaptic glutamate release. Furthermore, 5-HT is a precursor of melatonin, which inhibits glutamate release and glutamate-induced neurotoxicity. Thus, progressive degeneration of 5-HT neurons affecting motoneuron activity constitutes the prime mover of the disease and its progression and treatment of ALS needs to be focused primarily on boosting 5-HT functions (e.g., pharmacologically via its precursors, reuptake inhibitors, selective 5-HT1A receptor agonists/5-HT2 receptor antagonists, and electrically through transcranial administration of AC pulsed picotesla electromagnetic fields) to prevent excessive glutamate activity in the motoneurons. In fact, 5HT1A and 5HT2 receptor agonists have been shown to prevent glutamate-induced neurotoxicity in primary cortical cell cultures and the 5-HT precursor 5-hydroxytryptophan (5-HTP) improved locomotor function and survival of transgenic SOD1 G93A mice, an animal model of ALS.

Family history of alcoholism is associated with lower 5-HT2A receptor binding in the prefrontal cortex

BACKGROUND

5-Hydroxytryptophan (5-HT(2A)) receptor involvement in alcoholism is suggested by less 5-HT(2A) binding in alcohol preferring rats, association of a 5-HT(2A) receptor gene polymorphism with alcohol dependence and reduced alcohol intake with 5-HT(2A) antagonists. We sought to determine postmortem whether 5-HT(2A) receptors are altered in the prefrontal cortex (PFC) of alcoholics.

METHODS

Brain tissue from 25 alcoholics and 19 controls was collected at autopsy. Diagnosis of DSM-IV alcoholism/abuse and other psychiatric disorders and the determination of family history of alcoholism were made by psychological autopsy. Specific binding to 5-HT(2A) ((3)H-ketanserin) receptors in the PFC was measured by quantitative autoradiography.

RESULTS

5-HT(2A) binding decreased with age [Brodmann areas (BA) 9, 46 gyrus; r = -0.381, -0.334, p < 0.05]. No differences in receptor binding between alcoholics and controls were detected in the gyrus or sulcus of any PFC area examined. Cases (controls or alcoholics) with a family history of alcoholism (n = 23) had less 5-HT(2A) binding throughout PFC than subjects without (n = 21) a family history of alcoholism (p < 0.05). 5-HT(2A) receptor binding in alcoholics without a family history of alcoholism (n = 7) did not differ from controls without a family history of alcoholism (n = 14). There was no association between alcoholism or alcohol rating and genotype. There was an association between genotype and the total amount of (3)H-ketanserin binding in BA46 with the TT genotype having more binding (TT>TC approximately CC).

CONCLUSIONS

Lower 5-HT(2A) receptor binding in the PFC of cases with a family history of alcoholism suggests a genetic predisposition to alcoholism. Alcohol abuse by itself did not have a significant effect on PFC 5-HT(2A) binding and as 5-HT(2A) binding in alcoholics is not different from controls and antagonists may be therapeutic, fewer receptors may result in downstream developmental effects on the brain resulting in a predisposition to alcoholism.

CSF monoamine metabolites and lethality of suicide attempts in depressed patients with alcohol dependence

BACKGROUND

Alcohol dependence (alcoholism) and major depressive disorder are frequently comorbid and are risk factors for suicidal behavior. Monoaminergic abnormalities have been implicated in the pathophysiology of depression, alcohol dependence, and suicidal behavior. Lower cerebrospinal fluid (CSF) 5-hydroxyindolacetic acid (5-HIAA) levels are associated with higher lethality of suicide attempts in major depression and predict a higher rate of future suicide. We sought to study the relationship of CSF monoamine metabolites to lethality of suicidal acts in depressed subjects with comorbid alcoholism.

METHODS

We compared 16 high- and 16 low-lethality drug-free depressed suicide attempters with comorbid alcoholism. Subjects were free from any substance use disorder for at least two months. Demographic and clinical parameters, and CSF 5-HIAA, homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) levels were examined.

RESULTS

The two groups did not differ with regard to the demographic characteristics. CSF 5-HIAA levels were lower in high-lethality attempters compared to low-lethality attempters. There were no group difference in CSF HVA or MHPG levels.

CONCLUSION

Higher lethality of suicidal behavior in depressed patients with alcoholism is related to lower serotonergic activity.

Alteration of 5-HIAA levels in frontal cortex and dorsal raphe nucleus in rats treated with combined administration of tryptophan and ethanol

The present studies sought to investigate the effect of tryptophan alone or coadministration of tryptophan and ethanol on the interaction of central frontal cortex and dorsal raphe nucleus serotonergic functional activities by utilizing in vivo microdialysis. Tryptophan (50 mg/kg, i.p.) led to a significant increase in the levels of 5-HIAA, a metabolite of serotonin (5-HT), in the dorsal raphe nucleus, but not in the frontal cortex. Coadministration of tryptophan and ethanol caused very marked increases in 5-hydroxyindoleacetic acid (5-HIAA) levels in both the frontal cortex and the dorsal raphe nucleus, although ethanol (1.25 g/kg) did not change 5-HIAA levels in both areas. Moreover, the application of WAY100635 (10 muM), 5-HT(1A) antagonist, into the frontal cortex after coadministration caused a marked increase in 5-HIAA levels in the frontal cortex and a decrease in the levels in the dorsal raphe nucleus, although WAY100635 alone had no effect on these levels. This may suggest that WAY100635-induced increase of 5-HIAA levels in the frontal cortex resulted from negative feedback following the blockade of serotonergic 5-HT(1A) autoreceptors, and that this increase in 5-HIAA levels decreased 5-HIAA levels in the dorsal raphe nucleus by preventing the activation of dorsal raphe 5-HT(1A) autoreceptors. WAY100635 into the dorsal raphe nucleus did not significantly change 5-HIAA levels in both areas. This may indicate that the blockade of dorsal raphe 5-HT(1A) autoreceptors by WAY100635 resulted in unchanged 5-HIAA levels in the frontal cortex. Behavioral sign of teeth-chattering was markedly observed following the coadministration and in combination with WAY100635. These results may suggest that the increased 5-HIAA levels in both areas after coadministration are indicative of the interrelation via activation of serotonergic neurons, and that the increased levels are partly responsible for behavioral activation of rats.

5-Hydroxyindolacetic acid and homovanillic acid are not involved in the cerebrospinal fluid after a seizure in patients with Delirium Tremens

Little is known about 5-hydroxyindolacetic acid (5-HIAA) and homovanillic acid (HVA) levels in cerebrospinal fluid of patients with Delirium Tremens revealed at onset by seizures. The aim of the study is to understand the biochemical abnormalities induced by seizures in the cerebrospinal fluid of patients involved by Delirium Tremens. Nine patients 42-62 years of age, who had experienced a Delirium Tremens after alcohol withdrawal, with one or two seizures at onset, were included in this study. The lumbar puncture (and a CT scan) were performed after the last seizure. Nine patients with neither Delirium Tremens nor seizure, needing a lumbar puncture for their medical problem, were matched by sex and by age. For the measures of 5-HIAA and HVA, we systematically took the first cm3. The mean value of 5-HIAA levels were 12.70 ng ml(-1) in the group of nine patients with Delirium Tremens versus 13.45 ng ml(-1) in the control group. The mean value of HVA levels were 19.81 ng ml(-1) in the group of nine patients with Delirium Tremens versus 25.25 ng ml(-1) in the control group. The differences were not statistically significant. During a Delirium Tremens with seizure at onset, there are no statistically significant changes in 5-HIAA and HVA levels in the cerebrospinal fluid. Our work raises the question of the role of Delirium Tremens in the normalization of the levels of neuro-mediators that usually decrease soon after seizures.

Serotonin in mania and in the mechanism of action of mood stabilizers: a review of clinical studies

OBJECTIVES

Serotonin (5-hydroxytryptamine, 5-HT) was implicated in the pathophysiology of manic-depressive illness as early as 1958. Although extensive evidence has accumulated since then to support 5-HT's role in depression, relatively fewer studies examined its role in mania. The purpose of this paper was to review and summarize the current state of knowledge on the role of 5-HT in mania and its treatment.

METHODS

We systemically reviewed clinical studies of 1) 5-HT function in mania and 2) 5-HT in the mechanism of action of mood stabilizers, including lithium and anticonvulsants.

RESULTS

Review showed that cerebrospinal fluid, postmortem, platelet, neuroendocrine challenge, and tryptophan depletion studies provided some evidence to support the hypothesis that a 5-HT deficit is involved in mania and that enhancement of 5-HT neurotransmission exerts a mood-stabilizing effect.

CONCLUSIONS

There is some evidence from clinical studies for the contribution of 5-HT in mania and in the mechanism of action of mood stabilizers. However, it is very likely that other neurotransmitters also play important roles. Future directions for research include 1) in vivo study of 5-HT receptor subtypes using positron emission tomography, 2) investigation of the interaction between 5-HT and other neurotransmitter systems, and 3) determination of the relationships between diagnostic subtypes of mania and 5-HT function and other neurotransmitter systems.

Serotonin and neuropeptides in affiliative behaviors

The neuropharmacological study of serotonin and behavior has followed two fundamentally different strategies. One approach has used behavior as a dependent variable for assaying drug effects. To characterize serotonergic drugs, most studies have used relatively simple behaviors, such as locomotor activity, startle, exploration, operant responses, and sleep. A second approach has focused on behavior, with drugs used as tools to elucidate the physiological role of serotonin. These studies have increasingly focused on behaviors of ethological importance, including aggression, sexual behavior, and other forms of social interaction. Here we review studies using this approach to focus on one particular kind of social interaction: affiliation.

Monoamine precursors, transmitters and metabolites in cerebrospinal fluid: a prospective study in healthy male subjects

In order to elucidate methodological aspects of CSF investigations, 14 healthy male subjects were lumbar-punctured at the L4-5 level following a standardised procedure. CSF concentrations of precursors, transmitters and transmitter metabolites were used as dependent variables, while age, height, body weight, atmospheric pressure and some other factors served as independent variables. 5-HIAA and HVA (but not HMPG) have pronounced concentration gradients. We also found CSF gradients for the precursors tryptophan and tyrosine, as well as for serotonin, dopamine and the dopamine metabolite DOPAC. Dopamine and atmospheric pressure showed a positive intercorrelation. Age correlated curvilinearly (convex upward) with tryptophan but showed a negatively directed linear correlation with serotonin. Serotonin and 5-HIAA showed no intercorrelation. Our results suggest an age-dependent disposition of tryptophan in the CSF. The absence of a correlation between serotonin and 5-HIAA might be inconsistent with the notion that 5-HIAA is a marker of central serotonin turnover. The comparatively high body weight of our volunteers might explain the lack of a gradient for HMPG.

Gradients of CSF monoamine metabolites: a comparison between male and female volunteers

Lumbar puncture at the L4-5 level was performed on 12 healthy male and 12 healthy female volunteers. Confirming previous results, we found pronounced gradients in cerebrospinal fluid (CSF) 5-HIAA and HVA (5-hydroxyindoleacetic acid and homovanillic acid). We also found a gradient in 4-hydroxy-3-methoxyphenylglycol (HMPG), but only in the male volunteers. We also found that tapping-time was significantly longer in females than in males. One reason for this discrepancy may be that an estimate of the spinal distance was greater in males, which might indicate that a hydrodynamic factor plays a role. On taking tapping-time into consideration, the 5-HIAA and HMPG concentrations were significantly higher in males than in females.

CSF concentration gradients of monoamine metabolites in patients with hydrocephalus

Concentration gradients of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG), were assessed in 762 successive CSF fractions (2 ml lumbar CSF) from 15 patients with the adult hydrocephalus syndrome (AHS) and 11 patients with hydrocephalus of other causes (mixed group). A mean volume of 49.6 (SD 11.8) ml CSF was removed in the AHS group and 56.4 (10.2) ml in the mixed group. The CSF was collected with a specially designed carousel fraction collector and the corresponding CSF dynamics were continuously registered by a constant pressure CSF infusion method. Pronounced gradients in CSF HVA and CSF 5-HIAA were seen in both patient groups in the first 25 ml of CSF removed. The concentration curves levelled off, despite the removal of larger amounts of CSF and stabilised at about twice the initial concentrations. This phenomenon has not been described before. Concentrations of HVA and 5-HIAA in the first CSF fraction correlated strongly with concentrations in fractions up to about 40 ml. A positive correlation between the first fraction of CSF HVA and CSF 5-HIAA concentrations and CSF outflow conductance was found in the AHS group. There was no gradient in MHPG. It is suggested that the rostrocaudal gradients in CSF HVA and 5-HIAA may be explained by a downward flow of CSF along the spinal cord with absorption of metabolites occurring during passage. Mixing of CSF from different CSF compartments, extraventricular production sites of CSF, clearance of metabolites to venous blood or extracellular fluid, and CSF outflow conductance are probably important determinants of the plateau phase in patients with hydrocephalus. It is concluded that lumbar CSF does not exclusively reflect the concentrations of HVA, 5-HIAA, or MHPG in the ventricles. It should be noted that these results obtained in patients with hydrocephalus may not be applicable to other groups of patients or normal subjects.

Serotonin and alcohol intake, abuse, and dependence: clinical evidence

A large body of literature has emerged concerning the role of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) in the regulation of alcohol intake and the development of alcoholism. Despite the wealth of information, the functional significance of this neurotransmitter remains to be fully elucidated. This paper, part one of a two-part review, summarizes the available clinical research along two lines: the effects of alcohol on serotonergic functioning and the effects of pharmacological manipulation of serotonergic functioning on alcohol intake in normal (nonalcohol dependent) and alcohol-dependent individuals. It is concluded that considerable evidence exists to support the notion that some alcoholic individuals may have lowered central serotonin neurotransmission.

Urapidil permeates the intact blood-brain barrier

OBJECTIVE

To determine the plasma and cerebrospinal fluid (CSF) levels of urapidil after i.v. administration and the effect on CSF serotonin and 5-hydroxyindoleacetic acid (5-HIAA) concentrations.

DESIGN

Open, single-dose study.

SETTING

Post-surgery following neurosurgical removal of the hypophysis (n = 5) or aneurysm clipping (n = 1).

PATIENTS

6 patients, aged 32-71 years, with intact blood-brain barrier (BBB); 1 patient was studied twice.

INTERVENTIONS

Single dose of 25 mg urapidil i.v. as prophylaxis of BP increase during extubation or as treatment of hypertensive episodes.

MEASUREMENTS AND RESULTS

Urapidil, serotonin and 5-HIAA were measured by HPLC in CSF during 8 h after urapidil administration. Urapidil was detected in CSF as soon as 5 min after injection in 3 patients. The concentration ratio of plasma/CSF after the distribution phase was about 5:1. No significant effect on serotonin and 5-HIAA in CSF was seen.

CONCLUSION

After administration of a therapeutic dose, urapidil permeates the BBB and may interact with central 5-HT1A-receptors.

An association between low levels of 5-HIAA and HVA in cerebrospinal fluid and early mortality in a diagnostically mixed psychiatric sample

We followed up a sample of psychiatric patients (diagnoses predominantly schizophrenia and depression) who had participated in in-patient studies of their CSF over the past 15 years. The status of 73 former patients was confirmed, of whom 12 had died. Seven of these patients died at age < or = 40, largely of suicide, homicide, or accidental causes. These seven patients had significantly lower CSF 5-HIAA and HVA than living control patients. There were significant direct correlations between age at death and both CSF 5-HIAA and HVA in the deceased patients. The results offer support for CSF monoamine metabolites relating to early death in a diagnostically diverse sample of psychiatric patients.

Clinical and biochemical aspects of depressive disorders: III. Treatment and controversies

The present document is the final of three parts of a review that focuses on recent data from clinical and animal research concerning the biochemical bases of depressive disorders, diagnosis, and treatment. Various treatments for depression, including psychotherapy, pharmacological, and somatic treatments, will be described in this third part. Also, some of the controversies in the field, as well as a summary of the most salient points of the review, will be discussed. Previous sections of this review dealt with the classification of depressive disorders and research techniques for studying the biochemical mechanisms of these disorders (Part I) and various transmitter/receptor theories of depressive disorder (Part II).

CSF amine metabolites in depression

The amine metabolites, namely homovanillic acid (HVA) and 5-hydroxy indoleacetic acid (5-HIAA) were measured in cerebrospinal fluid (CSF) of depressives (n = 30) and controls (n = 30). Depressed patients had significantly lower HVA levels than controls. No significant differences were noted between the two groups in 5-HIAA levels. However, the differences between the groups for the CSF HVA/5-HIAA ratio were larger than those for the CSF HVA alone (p less than 0.01 versus p less than 0.025, respectively). HVA levels correlated positively with monoamine oxidase activity and adenosine deaminase activity.

Changes in CSF neurotransmitters during the first year of life

Changes in cerebrospinal fluid neurotransmitter metabolites in 25 children younger than 1 year of age were analyzed to assess maturation of the central nervous system and were compared to cerebrospinal fluid from older children and adults. Significant inverse correlations (P less than .05) with aging were observed for tryptophan, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, kynurenine, tyrosine, dopa, dopamine, dihydroxyphenylacetic acid, homovanillic acid, norepinephrine, and 3-methoxy-4-hydroxyphenylglycol concentrations. There were no significant differences observed with respect to age in the cerebrospinal fluid serotonin, 3-hydroxykynurenine, and 3-methoxytyramine concentrations. This study suggests that changes in the major cerebrospinal fluid neurotransmitters occur with increasing age during the neonatal period. Because these findings are preliminary, additional patients require study.

The functional approach of biological research in psychiatry

When neurobiological investigation looks beyond nosological perspectives into the search for correlations between isolated symptoms or specific behaviour patterns (some of which may be normal) and laboratory findings, many controversies seem to become clear. A paradigm of this approach is the Serotonin (5-HT) involvement in a wide range of psychiatric disorders and specific behaviour patterns all of them characterized by a poor control of impulses. Psychopharmacotherapy with substances able to interfere with the metabolism of this neurotransmitter, mostly antidepressants, are able to compensate what appear to be very dissimilar conditions. Therefore, the hypothesis that Serotonin is important for the control of impulses is a key to the interpretation of many findings and to the penetration of the complex field of biological substrate of psycho (patho) logy.

Lithium and serotonin function: implications for the serotonin hypothesis of depression

Lithium enjoys wide clinical use in the treatment of affective disorders, but the mechanism of its action in these conditions is still controversial. Recent studies have shown that lithium can interact with other antidepressant drugs to enhance their efficacy, perhaps by specific effects on serotonin (5-HT) function. A large body of independent evidence suggests that 5-HT function is abnormal in depression. This review documents preclinical evidence of lithium's effects on 5-HT function at the levels of precursor uptake, synthesis, storage, catabolism, release, receptors, and receptor-effector interactions. The weight of this evidence suggests that lithium's primary actions on 5-HT may be presynaptic, with many secondary postsynaptic effects. Studies in humans, using very different methodological approaches, generally suggest that lithium has a net enhancing effect on 5-HT function. These actions of lithium may serve to correct as-yet unspecified abnormalities of 5-HT function involved in the pathogenesis of depression.

Serotonin concentrations and turnover in brains of depressed suicides

5-Hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations and 5-HT turnover (5-HIAA/5-HT) were determined in 6 brain regions from 19 suicide victims in whom a retrospective diagnosis of depression was established, and 19 age- and sex-matched control subjects. Thirteen of the suicides were free of psychoactive drugs at the time of death; 5 were receiving antidepressant drugs. 5-HT, 5-HIAA and 5-HT turnover did not differ significantly between the total, drug-free and antidepressant-treated suicides and controls in frontal and temporal cortex, caudate and hippocampus. 5-HIAA concentration was significantly higher in amygdala of drug-free suicides than controls, whereas 5-HT and 5-HT turnover did not differ. 5-HT concentration was significantly lower in putamen of the total and antidepressant-treated suicides and a similar reduction was also apparent in the drug-free suicides. 5-HT turnover in putamen was significantly higher in the total and drug-free suicides compared to controls. 5-HT and 5-HIAA concentrations in putamen were significantly lower in drug-free suicides who died by non-violent means than in those who died by violent means. Differences between controls and suicides could not be attributed to age, sex or postmortem delay. These results offer no support for the view that 5-HT turnover is reduced in depressed subjects who commit suicide.

Biogenic amines and their metabolites in body fluids of normal, psychiatric and neurological subjects

The biogenic monoamines and their metabolites have been isolated, identified and quantified in human body fluids over the past forty years using a wide variety of chromatographic separation and detection techniques. This review summarizes the results of those studies on normal, psychiatric and neurological subjects. Tables of normal values and the methods used to obtain them should prove to be useful as a reference source for benchmark amine and metabolite concentrations and for successful analytical procedures for their chromatographic separation, detection and quantification. Summaries of the often contradictory results of the application of these methods to psychiatric and neurological problems are presented and may assist in the assessment of the validity of the results of experiments in this field. Finally, the individual, environmental and the methodological factors affecting the concentrations of the amines and their metabolites are discussed.

Concentration gradient of CSF monoamine metabolites in children and adolescents

Whether the lumbar cerebrospinal fluid (CSF) concentration gradient of monoamine metabolites found in adults is influenced by age or pubertal status was studied in 26 children ranging from 6.5 to 17.3 years of age. Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) were assayed by high-power liquid chromatography (HPLC) with electrochemical detection. Eight patients were prepubertal (Tanner stage I). The slopes in units of picomoles/milliliter/milliliter for regression lines for CSF monoamine metabolite concentrations versus milliliter of CSF collected were 5.07 +/- 0.65, 10.13 +/- 2.0, and 0.67 +/- 0.22 for 5-HIAA, HVA, and MHPG, respectively, for the group as a whole. Significant correlations with age, height, weight, or Tanner stage were not found for the HVA or MHPG concentration gradients. Tanner stage and 5-HIAA slope were significantly correlated. Three of eight prepubertal patients had nonsignificant 5-HIAA gradients. CSF studies in pediatric populations must control for aliquot collected, as the size of the gradient could produce differences sufficient to mimic a "positive" clinical study if the aliquots collected are not the same.

CSF amine metabolites and depression

Cerebrospinal fluid (CSF) amine metabolites were measured in 37 male subjects with major depressive disorder. Scores on the Hamilton Rating Scale for Depression (HRSD) correlated significantly with 5-hydroxyindoleacetic acid (5HIAA) and with homovanillic acid (HVA). In addition, the single suicide item of the HRSD correlated significantly with 5HIAA. Further, 5HIAA and HVA correlated significantly with each other. There was a significant positive correlation between HVA and two HRSD items, the depersonalization/derealization item and the paranoid item. Since lumbar CSF metabolite concentrations may reflect central nervous system activity of parent amines, these data suggest a relationship between depression and decreased dopaminergic and serotonergic activity.

Aminergic studies and cerebrospinal fluid cations in suicide

Cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) measurements have been collected over six years from 275 drug-free, recently hospitalized psychiatric patients, almost exclusively females. In accord with other observations from various countries, patients who had attempted suicide shortly before admission had significantly lower mean CSF 5-HIAA concentration and this was particularly true for those using violent methods. This finding could be replicated in five subsequent samples of patients evaluated separately and using different assay procedures, and proved to be independent of the clinical diagnoses. CSF HVA also showed similar tendencies but it had much larger variance with respect to suicide attempts and therefore fell short of statistical significance. In two patient populations CSF calcium and magnesium measurements have been obtained. CSF calcium did not prove to be related to either suicidal behavior or the diagnosis of major depression; on the other hand, CSF magnesium was found to be significantly lower in the suicide attempters and also correlated with CSF 5-HIAA. Nonsuicidal depressives had comparable CSF calcium and magnesium levels to the controls.

Intranasal vasotocin decreases cerebrospinal fluid 5-HIAA levels in man

A single dose (10 ng/kg) of the nonapeptide arginine vasotocin (AVT) administered intranasally to healthy young men, significantly decreased 5-HIAA levels in the lumbar cerebrospinal fluid (CSF) 8 hr after its administration. So far, this represents the smallest amount of an active substance able to alter CSF 5-HIAA levels in man. It is suggested that the decrease of CSF 5-HIAA levels after AVT administration reflects an AVT-induced reduction of the brain 5-HT turnover.

Relationship between platelet MAO activity and concentrations of 5-HIAA and HVA in cerebrospinal fluid in chronic pain patients

Platelet monoamine oxidase (MAO) activity and concentrations of 5-HIAA and HVA in the cerebrospinal fluid (CSF) were estimated in a series of 54 chronic pain patients. Platelet MAO activity was found to correlate, positively to CSF concentrations of 5-HIAA and HVA, which had been adjusted in order to eliminate the influence of age and body height. However, only the correlation with 5-HIAA reached a significant level. When partial correlations were sought, only the positive correlation between platelet MAO activity and CSF 5-HIAA remained. The results support the notion that platelet MAO ia a biological marker for some trait dependent property of the central serotonergic system.