Influence of moclobemide on cognitive functions of nine depressed patients: pilot trial with neurophysiological and neuropsychological indices

Resting State Quantitative Electroencephalogram Power Spectra in Patients with Depressive Disorder as Compared to Normal Controls: An Observational Study

INTRODUCTION

A significant number of quantitative electroencephalogram (qEEG) studies indicate that increased spectral activities distinguish patients with depressive disorder from control subjects. But they did not yield consistent findings in the delta, theta, alpha, or beta bands.

METHODS

A total of 30 drug-naïve or drug-free subjects with a depressive episode or recurrent depressive disorder were compared with 30 age, sex, education, and handedness-matched healthy controls using qEEG power spectra in six frequency bands (delta, theta, alpha, beta, slow beta, and fast beta) and total activities separately. Spectral analysis was performed on a section of 180 s of qEEG digitized at the rate of 512 samples/s/channel, and absolute powers were log-transformed before statistical analysis.

RESULTS

Statistically significant differences between the patients and normal controls were found in the delta and the total bands, while Structured Interview Guide for the Hamilton Depression Rating Scale ( SIGH-D) score predicted the fast beta spectral power at the left temporal region. In the entire region of the brain, in the theta band, lesser absolute spectral power was found in patients than normal controls, whereas in the fast beta band, it was greater. In other bands, greater powers of spectral activities were found in patients than normal controls consistently in the parietal and occipital regions.

CONCLUSION

Various findings of qEEG absolute power spectra could demonstrate a difference between the patients with depressive disorder and the normal controls independently and efficiently. However, all the differences collectively showed stronger evidence. The findings may steer future studies to differentiate the patients with depressive disorder from controls.

Intermediate phenotypes and biomarkers of treatment outcome in major depressive disorder

Major depressive disorder (MDD) is a pleomorphic illness originating from gene x environment interactions. Patients with differing symptom phenotypes receive the same diagnosis and similar treatment recommendations without regard to genomics, brain structure or function, or other physiologic or psychosocial factors. Using this present approach, only one third of patients enter remission with the first medication prescribed, and patients may take longer than 1 year to enter remission with repeated trials. Research to improve treatment effectiveness recently has focused on identification of intermediate phenotypes (IPs) that could parse the heterogeneous population of patients with MDD into subgroups with more homogeneous responses to treatment. Such IPs could be used to develop biomarkers that could be applied clinically to match patients with the treatment that would be most likely to lead to remission. Putative biomarkers include genetic polymorphisms, RNA and protein expression (transcriptome and proteome), neurotransmitter levels (metabolome), additional measures of signaling cascades, oscillatory synchrony, neuronal circuits and neural pathways (connectome), along with other possible physiologic measures. All of these measures represent components of a continuum that extends from proximity to the genome to proximity to the clinical phenotype of depression, and there are many levels along this continuum at which useful IPs may be defined. Because of the highly integrative nature of brain systems and the complex neurobiology of depression, the most useful biomarkers are likely to be those with intermediate proximity both to the genome and the clinical phenotype of MDD. Translation of findings across the spectrum from genotype to phenotype promises to better characterize the complex disruptions in signaling and neuroplasticity that accompany MDD, and ultimately to lead to greater understanding of the causes of depressive illness.

The use of the EEG in measuring therapeutic drug action: focus on depression and antidepressants

A major issue in proof of concept studies and early clinical trials of novel therapeutic agents is that the active drugs can often have a relatively small additional effect compared with placebo. This is especially the case in psychiatry when we usually have no direct method of measuring the pathology underlying the disorder being studied but, rather, have to rely on the subjective assessment of psychiatric symptoms. The use of the electroencephalogram (EEG) offers two potential major means of addressing this problem. First it is able to provide direct data relating to neural activity that may be abnormal in certain disorders. As such there are opportunities for utilizing the EEG in a variety of ways as an objective outcome measure. Second there is growing evidence that in certain circumstances the EEG can be used to predict which patients are likely to respond to treatment, thus potentially increasing the power of studies by decreasing non-response rates and increasing mean changes in outcome measure. Both of these uses of the EEG are illustrated in reference to the study of mood disorders and in particular depression and its treatment with antidepressants.

Pharmaco-EEG in psychiatry

In spite of its origins deeply rooted in the discipline, pharmaco-EEG applications in psychiatry remain limited to its achievements in the field of psychotropic drugs classification and, in few instances, discovery. In the present paper two attempts to transfer pharmaco-EEG methods to psychiatric clinical routine will be described: 1) monitoring of psychotropic drug toxicity at the central nervous system level, and 2) prediction of clinical response to treatment with psychotropic drugs. Both applications have been the object of several investigations providing promising and sometimes consistent findings which, however, had no impact on clinical practice. For the first topic, the review is limited to antipsychotics, lithium and recreational drugs, as for other psychotropic drugs mostly case studies are available, while for the response prediction it will include antipsychotics, antidepressants, anxiolytics, psychostimulants and nootropics. In spite of several methodological limitations, pharmaco-EEG studies dealing with monitoring of antipsychotic- and lithium-induced EEG abnormalities went close to, but never became, a clinical routine. EEG studies of recreational drugs are flawed by several limitations, and failed, so far, to identify reliable indices of CNS toxicity to be used in clinical settings. Several QEEG studies on early predictors of treatment response to first generation antipsychotics have produced consistent findings, but had no clinical impact. For other psychotropic drug classes few and inconsistent reports have appeared. Pharmaco-EEG had the potential for important clinical applications, but so far none of them entered clinical routine. The ability to upgrade theories and methods and promote large scale studies represent the future challenge.

A combination drug therapy improves cognition and reverses gene expression changes in a mouse model of Huntington's disease

Huntington's disease is a genetic disease caused by a single mutation. It is characterized by progressive movement, emotional and cognitive deficits. R6/2 mice transgenic for exon 1 of the HD gene with 150+ CAG repeats have a progressive neurological phenotype, including deterioration in cognitive function. The mechanism underlying the cognitive deficits in R6/2 mice is unknown, but dysregulated gene expression, reduced neurotransmitter levels and abnormal synaptic function are present before the cognitive decline becomes pronounced. Our goal here was to ameliorate the cognitive phenotype in R6/2 mice using a combination drug therapy (tacrine, moclobemide and creatine) aimed at boosting neurotransmitter levels in the brain. Treatment from 5 weeks of age prevented deterioration in two different cognitive tasks until at least 12 weeks. However, motor deterioration continued unabated. Microarray analysis of global gene expression revealed that many genes significantly up- or down-regulated in untreated R6/2 mice had returned towards normal levels after treatment, though a minority were further dysregulated. Thus dysregulated gene expression was reversed by the combination treatment in the R6/2 mice and probably underlies the observed improvements in cognitive function. Our study shows that cognitive decline caused by a genetic mutation can be slowed by a combination drug treatment, and gives hope that cognitive symptoms in HD can be treated.

Clinical and neurobiological effects of tianeptine and paroxetine in major depression

Selective serotonin reuptake inhibitors (SSRIs) are widely used as effective pharmacological agents to treat depressive disorders. In contrast to the SSRIs, which block the presynaptic serotonin (5-HT) transporter and by this route increase the concentration of serotonin in the synaptic cleft, the antidepressant tianeptine enhances the presynaptic neuronal reuptake of 5-HT and thus decreases serotonergic neurotransmission. Both SSRIs and tianeptine are clinically effective; however, their opposite modes of action challenge the prevailing concepts on the need of enhancement of serotonergic neurotransmission. To better understand the differences between these two opposite pharmacological modes of action, we compared the changes induced by tianeptine and paroxetine on psychopathology, the hypothalamic-pituitary-adrenocortical (HPA) system, and cognitive functions in a double-blind, randomized, controlled trial including 44 depressed inpatients over a period of 42 days. Depressive symptomatology significantly improved in all efficacy measures, with no significant differences between tianeptine and paroxetine. There was a trend toward better response to the SSRI among women. Assessment of the HPA system showed marked hyperactivity before the beginning of treatment, which then normalized in most of the patients, without significant differences between the two antidepressants. Cognitive assessments showed no significant differences between the two drugs investigated. The results of the current study suggest that the initial effect, i.e., enhancement or decrease of 5-HT release, is only indirectly responsible for antidepressant efficacy, and they support the notion that downstream adaptations within and between nerve cells are crucial. The normalization of the HPA system as a common mode of action of different antidepressants seems to be of special interest.

Moclobemide: evolution, pharmacodynamic, and pharmacokinetic properties

The benzamide moclobemide is a reversible inhibitor of monoamine-oxidase-A (RIMA). It has been extensively evaluated in the treatment of a wide spectrum of depressive disorders and less extensively in anxiety disorders. While clinical aspects will be presented in a subsequent review, this article focuses primarily on moclobemide's evolution, pharmacodynamic and pharmacokinetic properties. In particular, the effects on neurotransmission and intracellular signal transduction, the neuroendocrine system, the tyramine pressure response and animal models of depression are surveyed. In addition, other CNS effects are reviewed with special respect to experimental serotonergic syndrome, anxiolytic and antinociceptive activity, sleep, cognition and driving performance, neuroprotection and seizures.