The role of glutamatergic modulation in the mechanism of action of ketamine,a prototype rapid-acting antidepressant drug

Over the past decade, ketamine has been one of the most commonly studied potential antidepressants. This is because it produces a spectacularly rapid and persistent therapeutic effect in people suffering from severe treatment-resistant depression (TRD), for which classical drugs are ineffective. Similar efficacy was demonstrated for scopolamine, a drug belonging to a completely different pharmacological group. This interesting coincidence piqued the interest of psychopharmacologists and prompted them to search for a possible common mechanism of these rapid acting antidepressant drugs (RAADs). A thorough explanation of this mechanism is also important because each of these substances induces serious side effects. Knowing the mechanism responsible for the therapeutic efficacy of RAADs could lead to minimizing, or even avoiding certain undesirable effects. This review provides an overview of the mechanism of action of a prototype RAAD, ketamine, in animal models, with a particular focus on the roles of NMDA receptors, AMPA receptors, synaptogenesis, and modulation of glutamate transmission by other modulators of this system, such as mGlu receptor ligands. Recently studied roles for ketamine enantiomers and metabolites in its rapid antidepressant effect are also considered. Finally, the results of multiple clinical trials are reported and discussed in relation to basic research. This review concludes that success in introducing novel therapeutic RAADs will depend on better cooperation and integration of neuroscience research and clinical practice.     

Antidepressants for older people: What can we learn from the current evidence base?

This paper updates our previous review of the evidence base for managing depression in old age while focusing more specifically on the use of antidepressants. Overall, recent systematic reviews and meta-analyses indicate that antidepressants are effective in the acute treatment of depression in old age but that the superiority of active drug over placebo is quite modest. The depression of Alzheimer's disease is probably not treated effectively with antidepressants. The most consistent evidence is for the effectiveness of continued antidepressant treatment in those depressed patients who respond well to acute treatment. There remains a clear need for more research to identify effective treatments for resistant depression though therapeutic nihilism should be avoided if first-line treatment fails.     

Antioxidant and Proliferative Activities of Bupleuri Radix Extract Against Serum Deprivation in SH-SY5Y Cells

Objective

Bupleuri Radix (BR) is a major component of several Oriental herbal medicines used to treat stress and mental illness. There are evidences that antidepressant drugs modulate oxidative damage implicated in the pathophysiology of neuropsychiatric disorder, including depression. The aim of the present study was to investigate antioxidant and proliferative effects of BR against oxidative stress induced by serum deprivation in SH-SY5Y cells.

Methods

We examined the antioxidant effects of BR on a number of measures, including cell viability, formation of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and levels of both Bcl-2 and Bax. We also investigated the effects of BR on cell proliferation using the bromodeoxyuridine (BrdU) assay, and used Western blot analysis to measure changes in expression of the cell cycle phase regulators.

Results

1) Serum deprivation significantly induced the loss of cell viability, the formation of ROS, the reduction of SOD activity, down-regulation of Bcl-2 expression and up-regulation of Bax expression. However, BR extract reversed these effects in dose-dependent manner. 2) Serum deprivation significantly reduced cell proliferation. Western blot analysis revealed that serum deprivation significantly decreased cyclinD1 and phosphorylated retinoblastoma (pRb) expression, and increased p27 expression. On the other hand, BR dose dependently reversed these effects.

Conclusion

This study suggests that aqueous extract of BR may exert potent antioxidant effects and also play an important role in regulating cell cycle progression during neurogenesis. These effects of BR may be a potentially important mechanism of antidepressant underlying the observed antioxidant and proliferative effects.     

某医疗机构2007年与2012年抗抑郁药利用对比

目的分析我中心2007年与2012年抗抑郁药应用情况,了解抗抑郁药应用趋势,为临床合理用药提供参考。方法对我中心2007和2012年抑郁症和精神科住院患者人数、精神科药品总销售金额、抗抑郁药的应用品种、销售金额、用药频度等情况进行对比统计和分析。结果我中心2012年与2007年比较,抑郁症住院人数增长率为115.85%,抗抑郁药销售额涨幅为25.39%,选择性5-HT再摄取抑制剂(SSRIs)是目前临床应用最多的新型抗抑郁药,三环类抗抑郁药(TCAs)用量明显下降。结论抑郁症就诊率以及抗抑郁药用量有上升趋势,SSRIs类抗抑郁药在临床治疗中有举足轻重的作用。同时新型5-HT与NE再摄取抑制剂(SNRIs)有良好的应用前景。     

Pharmacokinetics,metabolism and excretion of [14C]-lanicemine (AZD6765), a novel low-trapping N-methyl-d-aspartic acid receptor channel blocker,in healthy subjects

Abstract

1.?(1S)-1-phenyl-2-(pyridin-2-yl)ethanamine (lanicemine; AZD6765) is a low-trapping N-methyl-d-aspartate (NMDA) channel blocker that has been studied as an adjunctive treatment in major depressive disorder. The metabolism and disposition of lanicemine was determined in six healthy male subjects after a single intravenous infusion dose of 150?mg [¹⁴C]-lanicemine.

2.?Blood, urine and feces were collected from all subjects. The ratios of C_max and AUC_(0–∞) of lanicemine to plasma total radioactivity were 84 and 66%, respectively, indicating that lanicemine was the major circulating component with T_1/2 at 16?h. The plasma clearance of lanicemine was 8.3?L/h, revealing that lanicemine is a low-clearance compound. The mean recovery of radioactivity from urine was 93.8% of radioactive dose.

3.?In urine samples, 10 metabolites of lanicemine were identified. Among which, an O-glucuronide conjugate (M1) was the most abundant metabolite (～11% of the dose in excreta). In plasma, the circulatory metabolites were identified as a para-hydroxylated metabolite (M1), an O-glucuronide (M2), an N-carbamoyl glucuronide (M3) and an N-acetylated metabolite (M6). The average amount of each of metabolite was less than 4% of total radioactivity detected in plasma or urine.

4.?In conclusion, lanicemine is a low-clearance compound. The unchanged drug and metabolites are predominantly eliminated via urinary excretion.     

Neuropharmacological in vivo effects and phytochemical profile of the extract from the aerial parts of Heteropterys brachiata (L.) DC. (Malpighiaceae)

Ethnopharmacological relevance

Heteropterys brachiata is a plant species that has been used in traditional Mexican medicine for the treatment of nervous disorders.

Aim of the study

To evaluate the anxiolytic, anticonvulsant, antidepressant and sedative effects produced by the methanolic extract of Heteropterys brachiata (HbMeOH) in ICR mice. Additionally, we determine the acute toxicity profiles of the extract and the presence of its main constituents.

Material and methods

The neuropharmacological effects of the extract were evaluated using a variety of models, such as the elevated plus maze (EPM), the forced swimming test (FST), the pentobarbital potentiation test (PTBt), pentylenetetrazole-induced seizures test (PTZt), and the open field test (OFT). HPLC was employed for obtention of phytochemical profile.

Results

HbMeOH produced a significant antidepressant effect in FST at 500 and 750 mg/kg doses, while doses from 500 to 1500 mg/kg exhibited a clear dose-dependent anxiolytic activity in EPM. A dose of 500 mg/kg showed a significant anticonvulsant activity in PTZt and an absence of sedation effects in PTBt. The main compounds of HbMeOH were chlorogenic acid and chlorogenic acid methyl ester, as well as less abundant terpene-type compounds. Furthermore, the extract was either safe with no deaths in mice treated orally with 2000 mg/kg.

Conclusions

HbMeOH extract which contains mainly hydroxycinnamic acids and triterpene-type compounds, possesses antidepressant, anxiolytic and anticonvulsive properties and can be considered safe or of low toxicity when orally administrated. These findings lend pharmacological justification to the traditional use of Heteropterys brachiata in the treatment of nervous disorders.     

An open-label trial of the glutamate-modulating agent riluzole in combination with lithium for the treatment of bipolar depression.

BACKGROUND: Preclinical and clinical evidence indicate that the glutamatergic system might play a role in the pathophysiology of mood disorders. This study was conducted to determine the efficacy and safety of riluzole, a glutamate-modulating agent, in bipolar depression. METHODS: This was an 8-week add-on study of riluzole in combination with lithium in acutely depressed bipolar patients aged 18 years and older. After open treatment with lithium for a minimum period of 4 weeks, subjects who continued to have a Montgomery-Asberg Depression Rating Scale (MADRS) score of >/=20 received riluzole (50-200 mg/day) for 8 weeks. RESULTS: Fourteen bipolar depressed patients entered the study. The linear mixed models for total MADRS score showed a significant treatment effect. No switch into hypomania or mania was observed. Overall, riluzole was well tolerated. CONCLUSIONS: Although preliminary, these results suggest that riluzole might indeed have antidepressant efficacy in subjects with bipolar depression.     

某精神科门诊抗抑郁药物应用状况调查

目的：评价某精神科门诊抗抑郁剂的适应症、使用状况。方法：采用自行设计的调查表对2003年度某月北京回龙观医院安定门门诊部就诊患中使用了各种抗抑郁剂的185例患的年龄、性别、诊断、用药种类等情况进行调查。结果：抗抑郁剂主要用于情感性精神障碍(66．5％)，其次是精神分裂症(17．8％)、神经症(12．4％)，少部份用于脑器类精神障碍(2.2％)、进食障碍(1.1％)。采用频度最高的是SSRIS(58．4％)，其次是其他新型抗抑郁剂(22.2％)、传统抗抑郁剂(19.5％)。结论：临床上抗抑郁剂的应用(适应症)范围逐渐扩大，临床已经从传统抗抑郁剂转为以SSRIS及其它新型抗抑郁剂为主流的药物治疗方案。     

Functional anatomical correlates of antidepressant drug treatment assessed using PET measures of regional glucose metabolism

Neurophysiological studies of major depression performed using PET imaging have shown abnormalities of regional cerebral blood flow (CBF) and glucose metabolism in multiple prefrontal cortical and limbic structures that have been more generally implicated in emotional processing. The current study investigated the effects of antidepressant drug treatment in these regions using PET measures of glucose metabolism. Subjects with primary MDD (n=27) were imaged while unmedicated and depressed, and, of these, 20 were rescanned following chronic antidepressant drug treatment. Regional metabolism was compared between unmedicated depressives and controls and between the pre- and post-treatment conditions in regions-of-interest (ROI) where metabolism or flow had previously been shown to be abnormal in unmedicated depressives. At baseline, the mean metabolism was increased in the left and right lateral orbital cortex/ventrolateral prefrontal cortex (PFC), left amygdala, and posterior cingulate cortex, and decreased in the subgenual ACC and dorsal medial/dorsal anterolateral PFC in the unmedicated depressives relative to controls, consistent with the results of previous studies. Following treatment, metabolism significantly decreased in the left amygdala and left subgenual ACC, and corresponding changes in the orbital and posterior cingulate cortices approached significance. The metabolic reduction in the amygdala and right subgenual ACC appeared largely limited to those subjects who both responded to treatment and remained well at 6 months follow-up, in whom the reduction in amygdala metabolism tightly correlated with the reduction in HDRS scores. The magnitude of the treatment-associated, metabolic change in the amygdala also correlated positively with the change in the stressed plasma cortisol levels measured during scanning. These data converge with those from other PET studies to indicate that primary MDD is associated with abnormal metabolism in limbic and paralimbic structures of the mesiotemporal and prefrontal cortices. Chronic antidepressant drug treatment reduces metabolism in the amygdala and ventral ACC in subjects showing a persistent, positive treatment response. In contrast, the persistence of the abnormal metabolic deficits in the dorsomedial/dorsal anterolateral PFC in MDD during treatment may conceivably relate to the histopathological changes reported in these regions in post mortem studies of MDD.