MMPI measures of impulsivity and depression correlate with CSF 5-HIAA and HVA in depression but not schizophrenia

Dynamic quantitative monitoring of cerebrospinal fluid monoamine neurotransmitter markers during the modeling process of chronic stress-induced depression in monkeys (Macaca mulatta)

BACKGROUND

Depression is known as the "mental cold" and is also considered a major cause of disability worldwide. It is estimated that over 300 million people worldwide suffer from severe depression, equivalent to 4.4% of the world's population. The monoamine hypothesis of depression predicts the underlying pathophysiological mechanisms of depression, but in-depth research has failed to find convincing evidence.

METHOD

In this study, we will dynamically and strictly quantitatively monitor the concentration changes of monoamine transmitters in the cerebrospinal fluid (CSF) of macaques, based on our previous work. In the experiment, timed and quantitative collection of CSF samples from macaques was performed and the concentration of monoamine transmitters was determined.

RESULT

The results showed that after 2 months of chronic stress, the concentrations of high vanillin acid (HVA) and 3,4-dihydroxy-phenylacetic acid were significantly higher in the maternal separation (MS) group, whereas there was no significant difference in dopamine and 5-hydroxyindoleacetic acid.

CONCLUSION

This study is the first to observe the long-term dynamic relationship between early adversity, chronic stress, adolescent depression, and CSF monoamine concentrations. The research suggests that MS and chronic stress play an undeniable role in the pathogenesis of depression and that concentrations of HVA and dihydroxyphenylacetic acid are likely to serve as early markers of depressive-like symptoms in macaques.

Insight into the relationship between impulsivity and substance abuse from studies using animal models

Drug use disorders are often accompanied by deficits in the capacity to efficiently process reward-related information and to monitor, suppress, or override reward-controlled behavior when goals are in conflict with aversive or immediate outcomes. This emerging deficit in behavioral flexibility and impulse control may be a central component of the progression to addiction, as behavior becomes increasingly driven by drugs and drug-associated cues at the expense of more advantageous activities. Understanding how neural mechanisms implicated in impulse control are affected by addictive drugs may therefore prove a useful strategy in the search for new treatment options. Animal models of impulsivity and addiction could make a significant contribution to this endeavor. Here, some of the more common behavioral paradigms used to measure different aspects of impulsivity across species are outlined, and the importance of the response to reward-paired cues in such paradigms is discussed. Naturally occurring differences in forms of impulsivity have been found to be predictive of future drug self-administration, but drug exposure can also increase impulsive responding. Such data are in keeping with the suggestion that impulsivity may contribute to multiple stages within the spiral of addiction. From a neurobiological perspective, converging evidence from rat, monkey, and human studies suggest that compromised functioning within the orbitofrontal cortex may critically contribute to the cognitive sequelae of drug abuse. Changes in gene transcription and protein expression within this region may provide insight into the mechanism underlying drug-induced cortical hypofunction, reflecting new molecular targets for the treatment of uncontrolled drug-seeking and drug-taking behavior.

Is there a role for the endocannabinoid system in the etiology and treatment of melancholic depression?

With advances in basic and clinical neuroscience, many gaps have appeared in the traditional monoamine theory of depression that have led to reformulation of the hypotheses concerning the neurobiology of depression. The more recent hypotheses suggest that melancholic depression is characterized by central glucocorticoid resistance that results in hypercortisolemia, which in turn leads to down-regulation of neurotrophins and subsequent neurodegeneration. Examining the neurobiology of depression from this perspective suggests that the endocannabinoid system may play a role in the etiology of melancholic depression. Specifically, pharmacological and genetic blockade of the cannabinoid CB1 receptor induces a phenotypic state that is analogous to melancholic depression, including symptoms such as reduced food intake, heightened anxiety, increased arousal and wakefulness, deficits in extinction of aversive memories and supersensitivity to stress. These similarities between melancholic depression and an endocannabinoid deficiency become more interesting in light of recent findings that endocannabinoid activity is down-regulated by chronic stress and possibly increased by some antidepressant regimens. We propose that an endocannabinoid deficiency may underlie some of the symptoms of melancholic depression, and that enhancement of this system may ultimately be a novel form of pharmacotherapy for treatment-resistant depression.

Permanent deficits in serotonergic functioning of olfactory bulbectomized rats: an in vivo microdialysis study

BACKGROUND

Bilateral removal of the olfactory bulbs (OBX) in rats results in a complex constellation of behavioral, neurochemical, neuroendocrine, and neuroimmune alterations, many of which are also reported in patients with major depressive disorder (MDD). Drawing on clinical findings, there has been considerable interest in the role of serotonin in the mechanism of action of OBX. However, to date, there has been no report of direct measurement of serotonergic functioning of bulbectomized animals using microdialysis. The present study describes the effects of olfactory bulbectomy on functioning of the serotonergic system.

METHODS

In vivo microdialysis was performed in conscious rats that underwent OBX or sham surgery. Alterations in the functioning of the serotonergic system were assessed by administration of fluvoxamine, fenfluramine, and 3-hydroxybenzylhydrazine (NSD-1015). Animals were also repeatedly tested in an open field.

RESULTS

Bilateral removal of the olfactory bulbs decreased basal extracellular levels by decreasing the releasable pool of serotonin (5-HT) in the basolateral amygdala 2 weeks after surgery and in the dorsal hippocampus 2 weeks and 5 months after surgery. Olfactory bulbectomized animals showed a lower rate of 5-HT synthesis under basal conditions. However, the capacity of the system to synthesize 5-HT was not affected. Olfactory bulbectomized rats were hyperactive in the open field. This hyperactivity remained after successive testing, indicating permanent behavioral changes.

CONCLUSIONS

This microdialysis study shows that OBX has profound and long-lasting effects on serotonergic functioning and on activity levels and is therefore considered an intriguing and promising animal model for affective processes in the brain.

Higher cerebrospinal fluid homovanillic acid levels in depressed patients with comorbid posttraumatic stress disorder

Major depression and posttraumatic stress disorder (PTSD) are often comorbid, resulting in more impairment compared than with either diagnosis alone. Both major depression and PTSD are thought to be associated with monoamine transmitter abnormalities. This study compared clinical features and cerebrospinal fluid (CSF) monoamine metabolites in drug-free depressed subjects with a current major depressive episode (MDE) without comorbid PTSD, subjects with a current MDE and comorbid PTSD, and healthy volunteers. Depressed subjects with comorbid PTSD had higher CSF homovanillic acid (HVA) levels compared with depressed subjects without comorbid PTSD or healthy volunteers. Higher HVA was present after adjustment for sex, lifetime aggression severity and depression scores, alcoholism, tobacco smoking, comorbid cluster B personality disorder, reported childhood abuse, and psychosis. We found no group difference in CSF 5-hydroxyindolacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) levels. Higher dopaminergic activity may contribute to alterations in memory and other cognitive functions, anhedonia, and hypervigilance observed in PTSD.

Lower CSF homovanillic acid levels in depressed patients with a history of alcoholism

Major depression and alcoholism are often comorbid, resulting in more impairment and more suicidal behavior compared with either diagnosis alone. This study compared clinical features and cerebrospinal fluid (CSF) monoamine metabolites in depressed subjects with and without a history of alcoholism and healthy volunteers. We hypothesized that depressed subjects with a history of alcoholism would be more aggressive, impulsive, and suicidal than depressed subjects without a history of alcoholism, and would have lower CSF monoamine metabolite levels. We compared 63 subjects with a current major depressive episode (MDE) and a history of alcoholism, 72 subjects with a current MDE but without a history of alcoholism, and 22 healthy volunteers. Participants with a history of alcoholism were in remission for at least 6 months. All subjects were free from prescribed medications known to affect brain serotonin, dopamine, or norepinephrine systems for a minimum of 14 days. Depressive symptoms, lifetime aggression, impulsivity, Axis II disorders, and suicidal behavior were assessed. CSF was sampled and homovanillic acid (HVA), 5-hydroxyindolacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) were assayed by high-performance lipid chromatography with electrochemical detection. Depressed subjects with a history of alcoholism did not differ from depressed subjects without a history of alcoholism in current severity of depressive symptoms, or in past suicidal behavior. Depressed subjects with a history of alcoholism had lower CSF HVA levels, and higher lifetime aggression and current suicide ideation scale scores and were more likely to be tobacco smokers compared with depressed subjects without a history of alcoholism. Low HVA was present after adjustment for sex, aggression and depression scores, cigarette smoking, antisocial and borderline personality disorders, psychomotor retardation, and delusions. Controls had CSF HVA levels intermediate between the two depressed groups. We found no group difference in CSF 5-HIAA and MHPG levels. In individuals with current MDE, those with a history of comorbid alcoholism had lower CSF HVA levels compared with those without a history of alcoholism. Low CSF HVA suggests that impaired dopaminergic activity is associated with a history of alcoholism in persons with current MDE.

A database of [(11)C]WAY-100635 binding to 5-HT(1A) receptors in normal male volunteers: normative data and relationship to methodological, demographic, physiological, and behavioral variables

PET studies of [(11)C]WAY-100635 binding are proving to be a useful tool to evaluate 5-HT(1A) receptor function in vivo in humans. We describe the pattern of [(11)C]WAY-100635 binding in 61 healthy male brains and examine its variability. For all PET scans, binding potential (BP) values for [(11)C]WAY-100635 in different regions were calculated using a simplified reference tissue model, with the cerebellum as reference region. Specifically we describe (1) region of interest and SPM databases of PET [(11)C]WAY-100635 binding, including test-retest variability; (2) the sensitivity of [(11)C]WAY-100635 binding to manipulations of endogenous 5-HT; and (3) correlations between [(11)C]WAY-100635 binding and radiochemical, demographic, physiological, and behavioral variables. The regional distribution of [(11)C]WAY-100635 binding in healthy human brain was similar to that reported in vitro. The test-retest variability was approximately 12% (range 9-16%) and was similar for all methods of regional sampling. The binding of [(11)C]WAY-100635 was insensitive to changes in brain 5-HT induced by tryptophan infusion and depletion. Although BP values varied greatly across subjects (range 2.9-6.8), there were no significant correlations of regional and global BP with common radiochemical, demographic, physiological, and personality variables. Specifically, in contrast with two recent small studies, we found no decline of [(11)C]WAY-100635 binding with age in our large cohort over the age range of 24 to 53 years. Assessment of 5-HT(1A) receptors in vivo using PET and [(11)C]WAY-100635 gives reliable measures of 5-HT(1A) binding. The large between-subject variability observed could not be explained by common methodological, physiological, or behavioral factors and hence the biological basis of this variability remains to be clarified.

Role of serotonergic and noradrenergic systems in the pathophysiology of depression and anxiety disorders

There is abundant evidence for abnormalities of the norepinephrine (NE) and serotonin (5HT) neurotransmitter systems in depression and anxiety disorders. The majority of evidence supports underactivation of serotonergic function and complex dysregulation of noradrenergic function, most consistent with overactivation of this system. Treatment for these disorders requires perturbation of these systems. Reproducible increases in serotonergic function and decreases in noradrenergic function accompany treatment with antidepressants, and these alterations may be necessary for antidepressant efficacy. Dysregulation of these systems clearly mediates many symptoms of depression and anxiety. The underlying causes of these disorders, however, are less likely to be found within the NE and 5HT systems, per se. Rather their dysfunction is likely due to their role in modulating, and being modulated by, other neurobiologic systems that together mediate the symptoms of affective illness. Clarification of noradrenergic and serotonergic modulation of various brain regions may yield a greater understanding of specific symptomatology, as well as the underlying circuitry involved in euthymic and abnormal mood and anxiety states. Disrupted cortical regulation may mediate impaired concentration and memory, together with uncontrollable worry. Hypothalamic abnormalities likely contribute to altered appetite, libido, and autonomic symptoms. Thalamic and brainstem dysregulation contributes to altered sleep and arousal states. Finally, abnormal modulation of cortical-hippocampal-amygdala pathways may contribute to chronically hypersensitive stress and fear responses, possibly mediating features of anxiety, anhedonia, aggression, and affective dyscontrol. The continued appreciation of the neural circuitry mediating affective states and their modulation by neurotransmitter systems should further the understanding of the pathophysiology of affective and anxiety disorders.

Endocrine responses after d-fenfluramine and ipsapirone challenge: further support for Cloninger's tridimensional model of personality

The tridemensional model of personality introduced by Cloninger relates aspects of novelty seeking to the dopaminergic, harm avoidance (HA) to the serotonergic, and reward dependence to the noradrenergic neurotransmitter system. Using a neuroendocrine challenge paradigm, this study investigates whether subjects characterized by blunted cortisol (CORT) responses after ipsapirone (IPS) relate to different subfactors of HA from those characterized by blunted prolactin (PRL) responses after treatment with d-fenfluramine (D-FEN). Moreover, subjects blunted in both responses should differ in scale values of subfactors of HA from those with only one or no blunted reactions. In the first part of the experiment, 16 healthy male volunteers were treated with 15 mg D-FEN. The second part of the study (about 1 year later) consists of a challenge with the partial 5-hydroxytryptamine-1a (5-HT(1a)) agonist IPS (10 mg) in the same subjects. The results indicate that blunted PRL responses are accompanied by high values in HA, while the main effect of IPS responsivity did not relate significantly to this dimension. With respect to the subscales of HA, subjects blunted in both responses (PRL-/C-) exhibit significantly higher levels in fatigability and asthenia when compared to all other groups (PRL-/C+, PRL+/C-,PRL+/C+). The data demonstrate that combined challenge tests may shed more light on the biological basis of personality and that HA and most clearly fatigability and asthenia relate to the 5-HT system.

CSF 5-HIAA levels are lower in impulsive as compared to nonimpulsive violent suicide attempters and control subjects

BACKGROUND

We studied CSF 5-HIAA and HVA concentrations in violent suicide attempters and examined their relationship with depression, anxiety, and impulsivity.

METHODS

CSF 5-HIAA and HVA concentrations were determined very shortly after hospital admission and compared to those of a matched control population. Clinical evaluation was performed concomitantly; the level impulsivity was evaluated by the Impulsivity Rating Scale (IRS).

RESULTS

Twenty-three patients and 23 control subjects were included. According to the IRS, 14 patients were classified as impulsive, including all patients suffering from personality disorders, and 9 as nonimpulsive, with a main DSM-IIIR diagnosis of melancholia. CSF 5-HIAA concentrations in the suicide group were significantly lower than in control subjects. This difference was entirely due to the impulsive suicide attempters. There was an inverse correlation between the IRS score and CSF 5-HIAA (r = -.47, p = .02) and only a trend for HVA (r = -.41, p = .078) levels in the suicide group.

CONCLUSIONS

This study of a group of violent suicide attempters distinguished a subgroup of patients diagnosed with personality disorder with high impulsivity scores and a subgroup of patients with the main diagnosis of severe depression. CSF 5-HIAA was significantly lower in impulsive violent attempters than in nonimpulsive violent attempters, therefore desintangling violence from impulsivity and linking this biologic abnormality to impulsivity.

CSF monoamines, age and impulsivity in wild grivet monkeys (Cercopithecus aethiops aethiops)

Brain monoaminergic activity has been associated with behaviors, such as impulsive risk-taking, that tend to peak during adolescence in humans and nonhuman primates. This study was designed to assess natural variation in monoamine neurotransmitter metabolism in relation to age and behavioral impulsivity in grivet monkeys (Cercopithecus aethiops aethiops) living in their native habitat and subject to natural ecological pressures. Cisternal cerebrospinal fluid, collected from 22 animals living in the Awash National Park, Ethiopia, was assayed for the major metabolites of serotonin (5-hydroxyindoleacetic acid, 5-HIAA), dopamine (homovanillic acid, HVA) and norepinephrine (3-methoxy-4-hydroxyphenylglycol, MHPG). Concentrations of HVA declined significantly from one year of age to older adulthood. Further, a significant curvilinear relationship was identified between age and the 5-HIAA/HVA ratio, with the trough coinciding with the period of adolescence. Finally, behavioral impulsivity, as measured by re-entering baited traps a second time after the animal had already been captured and sampled for CSF, was related to lower levels of MHPG. The results suggest that normal variation in central monoaminergic activity may have functional consequences in wild populations.

Correlates of aggressive behaviour in schizophrenia: an overview

OBJECTIVE

This review aims to critically evaluate the reported biological, psychological and social correlates of aggression in schizophrenia and to delineate those correlates which could be of use clinically and those which require further research.

METHOD

The literature from 1974-1996 was searched using Psychlit and supplemented by suggestions from senior members of the authors' Department.

RESULTS

Past history of aggression, psychopathology, extrapyramidal side effects of neuroleptic medications, substance abuse, reduced serotonin function, antisocial and impulsive personality traits, neurological/neuropsychological deficits, electroencephalography, neuroimaging abnormalities and environmental factors were all found to be correlated with aggressive behaviour in schizophrenia. However, there are many methodological limitations of previous studies in this field, often leading to inconsistent and inconclusive findings.

CONCLUSIONS

Some tentative conclusions regarding clinically useful predictors of aggression in schizophrenia can be drawn at this stage. There is a need for methodological limitations of previous studies to be overcome before more firm conclusions can be reached.

Comparative studies of the biological distinction between unipolar and bipolar depressions

Although unipolar depression and bipolar depression are considered distinct entities both by clinicians and researchers, it is not clear whether a pathophysiological distinction, which is the bridge between etiology and treatment, exists between these two conditions. The objective of this paper was to systematically review the studies that examined the biological differences between unipolar and bipolar depression. Using computerized Medline and manual searches, we located and reviewed studies that directly compared patients with unipolar depression with bipolar depressed patients on at least one biological variable. The results showed that patients with bipolar depression had lower levels of urinary NE and its metabolites and lower platelet MAO activity, and higher platelet free and stimulated intracellular calcium levels compared with unipolar depressed patients, but none of the variables examined appeared to differentiate the two groups consistently. We discuss some of the methodological flaws that might have contributed to this, and suggest that further studies should control for such confounding variables.

Aggression and personality: association with amino acids and monoamine metabolites

Associations in 52 normal individuals were examined between plasma and cerebrospinal fluid (CSF) concentrations of tryptophan (Trp) and tyrosine, and concentrations of monoamine metabolites in the CSF, and scores on an aggression questionnaire, the Kinsey Institute Reaction List II, and the Eysenck Personality Questionnaire. There was a significantly positive correlation between CSF 5-hydroxyindoleacetic acid (5-HIAA) levels and extroverted aggression scores, and a significantly negative correlation between CSF 5-HIAA levels and introverted aggression scores. Males showed higher plasma Trp concentrations than females, and significantly positive correlations between plasma Trp concentrations and scores on extroverted aggression and the Eysenck E scale. Males, furthermore, showed a significantly negative correlation between CSF Trp levels and scores on the Eysenck P scale, and a significantly positive correlation between concentrations of 3-methoxy-4-hydroxy-phenylglycol in CSF and scores on moral aggression. These results suggest that central serotonin influences aggression in normal individuals through effects on personality.

Cerebrospinal fluid monoamine metabolites in boys with attention-deficit hyperactivity disorder

Cerebrospinal fluid (CSF), plasma, and urinary monoamine metabolites were determined for 29 boys, aged 6-12, with attention-deficit hyperactivity disorder (ADHD). Levels of CSF 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG), the metabolites of serotonin, dopamine, and norepinephrine, respectively, correlated significantly with behavioral measures of aggression and impulsivity/hyperactivity. However, these correlations were in the unexpected direction; for example, CSF 5-HIAA correlated positively with the Brown-Goodwin Lifetime History of Aggression Scale. HVA in CSF was positively correlated with several measures of hyperactivity. The replicability of these findings, as well as possible socioenvironmental effects, and the predictive value of CSF monoamines in prepubertal hyperactivity are the subjects of ongoing study.