Changes in the cannabinoids receptors in rats following treatment with antidepressants

Impact of MAOA Gene Polymorphism on the Efficacy of Antidepressant Treatment and Craving Severity for Betel Quid Use Disorder

Betel quid (BQ) use disorder (BUD) is prevalent in many Asian countries, impacting approximately 600 million people. We conducted a randomized clinical trial to analyze the impact of MAOA genetic variations on the severity of BQ craving. This was measured using DSM-5 criteria and the Yale-Brown Obsessive-Compulsive Scale modified for betel quid use (Y-BOCS-BQ). Participants were grouped according to the severity of BUD and MAOA gene single-nucleotide polymorphism (SNP) rs5953210 genotypes. The Y-BOCS-BQ scores were assessed at baseline (week 0) and during follow-up at weeks 2, 4, 6, and 8. The AA genotype group showed significantly greater reductions in Y-BOCS-BQ at weeks 2 (p = 0.0194), 4 (p = 0.0078), 6 (p = 0.0277), and 8 (p = 0.0376) compared to the GG genotype group. Additionally, within the antidepressant group, the AA genotype showed significant reductions in the Y-BOCS-BQ scores at weeks 2 (p = 0.0313), 4 (p = 0.0134), 6 (p = 0.0061), and 8 (p = 0.0241) compared to the GG genotype. The statistical analysis revealed a significant interaction between the treatment and placebo groups based on MAOA genotypes, with the AA genotype in the treatment group exhibiting a more pronounced decrease in Y-BOCS-BQ score (p interaction <0.05) at week 6. Our study highlights the importance of considering genetic factors when developing personalized treatment plans for BUD.

How depression and antidepressant drugs affect endocannabinoid system?-review of clinical and preclinical studies

As major depressive disorder is becoming a more and more common issue in modern society, it is crucial to discover new possible grip points for its diagnosis and antidepressive therapy. One of them is endocannabinoid system, which has been proposed as a manager of emotional homeostasis, and thus, endocannabinoid alterations have been found in animals undergoing various preclinical models of depression procedures as well as in humans suffering from depressive-like disorders. In this review article, studies regarding those alterations have been summed up and analyzed. Another important issue raised by the researchers is the impact of currently used antidepressive drugs on endocannabinoid system so that it would be possible to predict reversibility of endocannabinoid alterations following stress exposure and, in the future, to be able to design individually personalized therapies. Preclinical studies investigating this topic have been analyzed and described in this article. Unfortunately, too few clinical studies in this field exist, what indicates an urgent need for collecting such data, so that it would be possible to compare them with preclinical outcomes and draw reliable conclusions.

Further proof on the role of accumbal nNOS in cocaine-seeking behavior in rats

BACKGROUND

Cocaine use disorder (CUD) remains a severe health problem with no effective pharmacological therapy. One of the potential pharmacological strategies for CUD pharmacotherapy includes manipulations of the brain glutamatergic (Glu) system which is particularly involved in drug withdrawal and relapse. Previous research indicated a pivotal role of ionotropic N-methyl-D-aspartate (NMDA) receptors or metabotropic receptors' type 5 (mGlu5) receptors in controlling the reinstatement of cocaine. Stimulation of the above molecules results in the activation of the downstream signaling targets such as neuronal nitric oxide synthase (nNOS) and the release of nitric oxide.

METHODS

In this paper, we investigated the molecular changes in nNOS in the prefrontal cortex and nucleus accumbens following 3 and 10 days of cocaine abstinence as well as the effectiveness of nNOS blockade with the selective enzyme inhibitor N-ω-propyl-L-arginine hydrochloride (L-NPA) on cocaine seeking in male rats. The effect of L-NPA on locomotor activity in drug-naïve animals was investigated.

RESULTS

Ten-day (but not 3-day) cocaine abstinence from cocaine self-administration increased nNOS gene and protein expression in the nucleus accumbens, but not in the prefrontal cortex. L-NPA (0.5-5 mg/kg) administered peripherally did not change locomotor activity but attenuated the reinstatement induced with cocaine priming or the drug-associated conditioned cue.

CONCLUSIONS

Our findings support accumbal nNOS as an important molecular player for cocaine seeking while its inhibitors could be considered as anti-cocaine pharmacological tools in male rats.

Association between Single Nucleotide Polymorphisms in Monoamine Oxidase and the Severity of Addiction to Betel Quid

Betel quid (BQ) is the fourth most popular psychoactive substance in the world, and BQ use disorder (BUD) is prevalent in Asian countries. Although the mechanisms underlying BUD remain unclear, studies have reported influences from monoamine oxidase inhibitor. We enrolled 50 patients with BUD and assessed their BQ consumption habits, emotional conditions, and the clinical severity of addiction-assessed using the Diagnostic and Statistical Manual of Mental Disorders [Fifth Edition] (DSM-5) criteria, Substance Use Severity Rating Scale, and Yale-Brown Obsessive Compulsive Disorder Rating Scale for BQ. Patients were categorized into the severe group when showing six or more symptoms defined by DSM-5. A genome-wide association study was conducted for single nucleotide polymorphisms in BRCA1, COL9A1, NOTCH1, HSPA13, FAT1, and MAOA by using patients' blood samples. More severe BUD symptoms were associated with younger age of using BQ and poor oral hygiene and with severe craving for and more anxiety toward BQ use. The MAOA rs5953210 polymorphism was significantly associated with severe BUD (odds ratio, 6.43; 95% confidence interval, 5.12-7.74; p < 0.01) and might contribute to BQ-associated cancer risk. Further studies are required to investigate the addictive properties of BQ and the development of novel diagnostic tools and pharmacotherapeutic alternatives to BUD treatment.

Cognitive dysfunction and impaired neuroplasticity following repeated exposure to the synthetic cannabinoid JWH-018 in male mice

BACKGROUND AND PURPOSE

Psychotic disorders have been reported in long-term users of synthetic cannabinoids. This study aims at investigating the long-lasting effects of repeated JWH-018 exposure.

EXPERIMENTAL APPROACH

Male CD-1 mice were injected with vehicle, JWH-018 (6 mg·kg-1 ), the CB1 -antagonist NESS-0327 (1 mg·kg-1 ) or co-administration of NESS-0327 and JWH-018, every day for 7 days. After 15 or 16 days washout, we investigated the effects of JWH-018 on motor function, memory, social dominance and prepulse inhibition (PPI). We also evaluated glutamate levels in dialysates from dorsal striatum, striatal dopamine content and striatal/hippocampal neuroplasticity focusing on the NMDA receptor complex and the neurotrophin BDNF. These measurements were accompanied by in vitro electrophysiological evaluations in hippocampal preparations. Finally, we investigated the density of CB1 receptors and levels of the endocannabinoid anandamide (AEA) and 2-arachidonoylglycerol (2-AG) and their main synthetic and degrading enzymes in the striatum and hippocampus.

KEY RESULTS

The repeated treatment with JWH-018 induced psychomotor agitation while reducing social dominance, recognition memory and PPI in mice. JWH-018 disrupted hippocampal LTP and decreased BDNF expression, reduced the synaptic levels of NMDA receptor subunits and decreased the expression of PSD95. Repeated exposure to JWH-018, reduced hippocampal CB1 receptor density and induced a long-term alteration in AEA and 2-AG levels and their degrading enzymes, FAAH and MAGL, in the striatum.

CONCLUSION AND IMPLICATIONS

Our findings suggest that repeated administration of a high dose of JWH-018 leads to the manifestation of psychotic-like symptoms accompanied by alterations in neuroplasticity and change in the endocannabinoid system.

The Chronic Pharmacological Antagonism of the CB1 Receptor is not Involved in the Behavioral Effects of Antidepressants Administered in Mice Submitted to Chronic Unpredictable Stress

Several pieces of evidence suggest that the monoaminergic theory of depression cannot fully explain all behavioral and neuroplastic changes observed after antidepressant chronic treatment. Other molecular targets, such as the endocannabinoid system, have been associated with the chronic effects of these drugs. In the present study, we hypothesized that the behavioral and neuroplastic effects observed after repeated treatment with the antidepressants (AD) Escitalopram (ESC) or venlafaxine (VFX) in chronically stressed mice depend on CB1 receptor activation. Male mice submitted to the chronic unpredictable stress (CUS) paradigm for 21 days were treated with Esc (10mg/kg) or VFX (20mg/kg) once a day in the presence or not of AM251 (0,3mg/kg), a CB₁ receptor antagonist/inverse agonist. At the end of the CUS paradigm, we conducted behavior tests to evaluate depressive- and anxiety-like behaviors. Our results demonstrated that chronic blockade of the CB₁ receptor does not attenuate the antidepressant- or the anxiolytic-like effects of ESC nor VFX. ESC increased the expression of CB₁ in the hippocampus, but AM251 did not change the pro-proliferative effects of ESC in the dentate gyrus or the increased expression of synaptophysin induced by this AD in the hippocampus. Our results suggest that CB₁ receptors are not involved in behavioral and hippocampal neuroplastic effects observed after repeated antidepressant treatment in mice submitted to CUS.

Evaluation of the 5-HT2C receptor drugs RO 60-0175, WAY 161503 and mirtazepine in a preclinical model of comorbidity of depression and cocaine addiction

BACKGROUND

Epidemiological data indicate a high rate of comorbidity of depression and cocaine use disorder (CUD). The role of serotonin 2C (5-HT_2C) receptors in the mechanisms responsible for the coexistence of depression and CUD was not investigated.

METHODS

We combined bilateral olfactory bulbectomy (OBX), an animal model of depression, with intravenous cocaine self-administration and extinction/reinstatement in male rats to investigate two 5-HT_2C receptor agonists (Ro 60-0175 (RO) and WAY 161503 (WAY)) and the 5-HT_2C-receptor preferring antagonist mirtazapine (MIR; an antidepressant), with the goal of determining whether these drugs alter cocaine-induced reinforcement and seeking behaviors. Additionally, neurochemical analyses were performed following cocaine self-administration and its abstinence period in the brain structures in OBX rats and SHAM-operated controls.

RESULTS

Acute administration of RO reduced, while WAY non-significantly attenuated cocaine reinforcement in both rat phenotypes. Moreover, RO or WAY protected against cocaine-seeking behavior after acute or after repeated drug administration during extinction training in OBX and SHAM rats. By contrast, acutely administered MIR did not alter cocaine reinforcement in both rat phenotypes, while it's acute (but not repeated) pretreatment reduced cocaine-seeking in OBX and SHAM rats. In neurochemical analyses, cocaine reinforcement increased 5-HT_2C receptor levels in the ventral hippocampus; a preexisting depression-like phenotype enhanced this effect. The 10-daily cocaine abstinence reduced 5-HT_2C receptor expression in the dorsolateral striatum, while the coexistence of depression and CUD enhanced local receptor expression.

CONCLUSION

The results support a key role of 5-HT_2C receptors for treating CUD and comorbid depression and CUD. They may be backs the further research of pharmacological strategies with drug targeting receptors.

Antidepressant-like effect of rosmarinic acid during LPS-induced neuroinflammatory model: The potential role of cannabinoid receptors/PPAR-γ signaling pathway

Rosmarinic acid (RA), an ester of caffeic acid and 3, 4-dihydroxyphenyllactic acid, has anti-inflammatory and neuroprotective activities. Herein, this study investigated in silico the drug-likeness and the potential molecular targets to RA. Moreover, it tested the antidepressant-like potential of RA in the lipopolysaccharide (LPS)-induced depression model. RA (MW = 360.31 g/mol) meets the criteria of both Lipinski's rule of five and the Ghose filter. It also attends to relevant pharmacokinetic parameters. Target prediction analysis identified RA's potential targets and biological activities, including the peroxisome proliferator-activated receptor (PPAR) and the cannabinoid receptors CB1 and CB2 . In vivo, RA's acute, repetitive, and therapeutic administration showed antidepressant-like effect since it significantly reduced the immobility time in the tail suspension test and increased grooming time in the splash test. Further, the pretreatment with antagonists of CB1 , CB2 , and PPAR-γ receptors significantly blocked the antidepressant-like effect of RA. Altogether, our findings suggest that cannabinoid receptors/PPAR-γ signaling pathways are involved with the antidepressant-like effect of RA. Moreover, this molecule meets important physicochemical and pharmacokinetic parameters that favor its bioavailability. RA constitutes a promising, innovative, and safe molecule for the pharmacotherapy of major depressive disorder.

Maternal High-Fat Diet Modulates Cnr1 Gene Expression in Male Rat Offspring

In recent years, strong evidence has emerged that exposure to a maternal high-fat diet (HFD) provokes changes in the structure, function, and development of the offspring’s brain and may induce several neurodevelopmental and psychiatric illnesses. The aims of this study were to evaluate the effects of a maternal HFD during pregnancy and lactation on depressive-like behavior and Cnr1 gene expression (encoding the CB1 receptor) in brain structures of rat offspring and to investigate the epigenetic mechanism involved in this gene expression. We found that a maternal HFD during pregnancy and lactation induced a depressive-like phenotype at postnatal days (PNDs) 28 and 63. We found that a maternal HFD decreased the Cnr1 mRNA levels in the prefrontal cortex with the increased levels of miR-212-5p and methylation of CpG islands at the Cnr1 promoter and reduced the level of Cnr1 gene expression in the dorsal striatum with an increased level of miR-154-3p in adolescent male offspring. A contrasting effect of a maternal HFD was observed in the hippocampus, where upregulation of Cnr1 gene expression was accompanied by a decrease of miR-154-3p (at PNDs 28 and 63) and miR-212-5p (at PND 63) expression and methylation of CpG islands at the Cnr1 promoter in male offspring. In summary, we showed that a maternal HFD during pregnancy and lactation triggered several epigenetic mechanisms in the brains of rat offspring, which may be related to long-lasting alterations in the next generation and produce behavioral changes in offspring, including a depressive-like phenotype.

Peripheral endocannabinoid serum level in association with repetitive transcranial magnetic stimulation (rTMS) treatment in patients with major depressive disorder

Repetitive transcranial magnetic stimulation (rTMS) is an effective and well tolerable biological intervention in major depressive disorder (MDD) contributing to rapid symptom improvement. Molecular mechanisms underpinning the therapeutic effects of rTMS have still not been clarified. Recently published animal data implicated relevant associations with changes in endocannabinoid (eCB) brain levels during rTMS treatment, human studies, however, have not been published. In our study we assessed the detailed phenotypic spectrum of MDD and serum 2-arachidnoylglycerol (2-AG) and anandamide (AEA) levels in 18 patients with treatment-resistant depression before, immediately following, and two weeks after completion of a 10-day rTMS treatment. We found significant associations between serum 2-AG level changes from pretreatment to 2 weeks after treatment and symptom reduction. The greater the increase of 2-AG levels, the greater the improvement of depressive (p = 0.031), anxious (p = 0.007) and anhedonia symptoms (p = 0.047). Here we report for the first time a significant association of human circulating eCB and antidepressant effect of rTMS. Our data may indicate that direct stimulation of targeted brain areas can rapidly alleviate depressive complaints via activation of the eCB system.

Cannabinoid CB1 and CB2 receptors differentially regulate TNF-α-induced apoptosis and LPA1-mediated pro-survival signaling in HT22 hippocampal cells

AIMS

The aim of the study was to investigate the interaction between cannabinoid CB₁/CB₂ and lysophosphatidic acid (LPA) receptors in controlling neuronal signaling and fate.

METHODS

HT22 hippocampal cells were treated with different cannabinoid and LPA receptor agonists and antagonists. Western blot and immunofluorescence microscopy were used to study intracellular signaling and the expression of apoptotic markers. Cell viability was determined by a luminescence assay.

KEY FINDINGS

Cannabinoid agonists induced activation of both ERK1/2 and p38 MAP kinases. The effects of the CB₁/CB₂ receptor agonist HU210 were antagonized by the CB₁ antagonist rimonabant, whereas the responses to the CB₂ agonist JWH133 were blocked by the CB₂ antagonist SR144528. HU210 reduced the apoptotic cell death induced by the pro-inflammatory cytokine TNF-α, whereas JWH133 enhanced the cytokine cytotoxicity. Blockade of ERK1/2 and p38 MAPK activation abrogated the HU210 pro-survival and the JWH133 pro-apoptotic effects, respectively. HU210 and the endocannabinoid anandamide, but not JWH133, potentiated ERK1/2 stimulation by LPA and the tricyclic antidepressant amitriptyline acting through the LPA₁ receptor. HU210 enhanced amitriptyline-stimulated CREB phosphorylation and protection against TNF-α-induced apoptosis, whereas JWH133 had no effect. ERK1/2 stimulation by either HU210 or amitriptyline was dependent on fibroblast growth factor receptor (FGF-R) kinase activity and the combination of the two stimulants induced FGF-R phosphorylation. Moreover, the CB₁ receptor was found to co-immunoprecipitate with the LPA₁ receptor.

CONCLUSIONS

In HT22 hippocampal cells CB₁ and CB₂ receptors differentially regulate TNF-α-induced apoptosis and CB₁ receptors positively interact with amitriptyline-stimulated LPA₁ in promoting FGF-R-mediated ERK1/2 signaling and neuroprotection.

Effect of antidepressants for cessation therapy in betel-quid use disorder: a randomised, double-blind, placebo-controlled trial

AIMS

More than one-half of betel-quid (BQ) chewers have betel-quid use disorder (BUD). However, no medication has been approved. We performed a randomised clinical trial to test the efficacy of taking escitalopram and moclobemide antidepressants on betel-quid chewing cessation (BQ-CC) treatment.

METHODS

We enrolled 111 eligible male BUD patients. They were double-blinded, placebo-controlled and randomised into three treatment groups: escitalopram 10 mg/tab daily, moclobemide 150 mg/tab daily and placebo. Patients were followed-up every 2 weeks and the length of the trial was 8 weeks. The primary outcome was BQ-CC, defined as BUD patients who continuously stopped BQ use for ⩾6 weeks. The secondary outcomes were the frequency and amount of BQ intake, and two psychological rating scales. Several clinical adverse effects were measured during the 8-week treatment.

RESULTS

Intention-to-treat analysis shows that after 8 weeks, two (5.4%), 13 (34.2%) and 12 (33.3%) of BUD patients continuously quit BQ chewing for ⩾6 weeks among placebo, escitalopram, moclobemide groups, respectively. The adjusted proportion ratio of BQ-CC was 6.3 (95% CI 1.5-26.1) and 6.8 (95% CI 1.6-28.0) for BUD patients who used escitalopram and moclobemide, respectively, as compared with those who used placebo. BUD patients with escitalopram and moclobemide treatments both exhibited a significantly lower frequency and amount of BQ intake at the 8th week than those with placebo.

CONCLUSIONS

Prescribing a fixed dose of moclobemide and escitalopram to BUD patients over 8 weeks demonstrated treatment benefits to BQ-CC. Given a relatively small sample, this study provides preliminary evidence and requires replication in larger trials.

Endocannabinoid System Components as Potential Biomarkers in Psychiatry

The high heterogeneity of psychiatric disorders leads to a lack of diagnostic precision. Therefore, the search of biomarkers is a fundamental aspect in psychiatry to reach a more personalized medicine. The endocannabinoid system (ECS) has gained increasing interest due to its involvement in many different functional processes in the brain, including the regulation of emotions, motivation, and cognition. This article reviews the role of the main components of the ECS as biomarkers in certain psychiatric disorders. Studies carried out in rodents evaluating the effects of pharmacological and genetic manipulation of cannabinoid receptors or endocannabinoids (eCBs) degrading enzymes were included. Likewise, the ECS-related alterations occurring at the molecular level in animal models reproducing some behavioral and/or neuropathological aspects of psychiatric disorders were reviewed. Furthermore, clinical studies evaluating gene or protein alterations in post-mortem brain tissue or in vivo blood, plasma, and cerebrospinal fluid (CSF) samples were analyzed. Also, the results from neuroimaging studies using positron emission tomography (PET) or functional magnetic resonance (fMRI) were included. This review shows the close involvement of cannabinoid receptor 1 (CB1r) in stress regulation and the development of mood disorders [anxiety, depression, bipolar disorder (BD)], in post-traumatic stress disorder (PTSD), as well as in the etiopathogenesis of schizophrenia, attention deficit hyperactivity disorder (ADHD), or eating disorders (i.e. anorexia and bulimia nervosa). On the other hand, recent results reveal the potential therapeutic action of the endocannabinoid tone manipulation by inhibition of eCBs degrading enzymes, as well as by the modulation of cannabinoid receptor 2 (CB2r) activity on anxiolytic, antidepressive, or antipsychotic associated effects. Further clinical research studies are needed; however, current evidence suggests that the components of the ECS may become promising biomarkers in psychiatry to improve, at least in part, the diagnosis and pharmacological treatment of psychiatric disorders.

Cannabis consumption and non-alcoholic fatty liver disease. A three years longitudinal study in first episode non-affective psychosis patients

INTRODUCTION

Increased incidence of obesity and excess weight lead to an increased incidence of non-alcoholic fatty liver disease (NAFLD). Recent evidence indicates a protective effect of cannabis consumption on weight gain and related metabolic alterations in psychosis patients. Overall, patients are at greater risk of presenting fatty diseases, such as NAFLD, partly due to lipid and glycemic metabolic disturbances. However, there are no previous studies on the likely effect of cannabis on liver steatosis. We aimed to explore if cannabis consumption had an effect on hepatic steatosis, in a sample of first-episode (FEP) non-affective psychosis.

MATERIAL AND METHODS

A total of 390 patients were evaluated at baseline and after 3 years of initiating the antipsychotic treatment. Anthropometric measurements and liver, lipid, and glycemic parameters were obtained at both time points. All but 6.7% of patients were drug-naïve at entry, and they self-reported their cannabis use at both time points. Liver steatosis and fibrosis were evaluated through validated clinical scores (Fatty Liver Index [FLI], Fibrosis-4 [FIB-4], and NAFLD).

RESULTS

At 3-year follow-up, cannabis users presented significantly lower FLI scores than non-users (F = 13.874; p < .001). Moreover, cannabis users less frequently met the criteria for liver steatosis than non-users (X² = 7.97, p = .019). Longitudinally, patients maintaining cannabis consumption after 3 years presented the smallest increment in FLI over time, which was significantly smaller than the increment in FLI presented by discontinuers (p = .022) and never-users (p = .016). No differences were seen in fibrosis scores associated with cannabis.

CONCLUSIONS

Cannabis consumption may produce a protective effect against liver steatosis in psychosis, probably through the modulation of antipsychotic-induced weight gain.

Antidepressant-like effects of β-caryophyllene on restraint plus stress-induced depression

Chronic stress is depressogenic by altering neurotrophic and neuroinflammatory environments of the organism. The endocannabinoid system controls cognitive and emotional responses related with stress through the interaction with endocannabinoid receptors. β-Caryophyllene (BCP) is a CB2 agonist that exhibited anti-inflammatory, analgesic effects but minimal psychoactive effects. To test if BCP exhibits antidepressant-like action, animals were chronically restrained with additional stressors for 28 days, and BCP (25, 50, 100 mg/kg) was intraperitoneally injected once a day during the stress inflicting period. Then despair related behaviors and hippocampal expression of neurotrophic, inflammatory and cannabinoid receptor levels were measured. To test the effect of BCP on long-term depression, field potentials were measured during the application of lipopolysaccharide and low frequency stimulation. In the tail suspension test and forced swim test, chronic stress-induced despair behaviors were reduced by BCP. Also BCP improved the stress-related changes in the hippocampal expression of COX-2, BDNF, and CB2 receptor expression. In organotypic hippocampal slices, BCP reduced the lipopolysaccharide-induced intensification of the long-term depression. In conclusion, BCP improved chronic stress related behavioral and biochemical changes. These results suggest that BCP may be effective in treating depression and stress related mental illnesses.

Adaptive mechanisms following antidepressant drugs: Focus on serotonin 5-HT2A receptors

BACKGROUND

There is a strong support for the role of serotonin (5-HT) neurotransmission in depression and in the mechanism of action of antidepressants. Among 5-HT receptors, 5-HT2A receptor subtype seems to be an important target implicated in the above disorder.

METHODS

The aim of the study was to investigate the effects of antidepressants, such as imipramine (15 mg/kg), escitalopram (10 mg/kg) and tianeptine (10 mg/kg) as well as drugs with antidepressant activity, including N-acetylcysteine (100 mg/kg) and URB597 (a fatty acid amide hydrolase inhibitor, 0.3 mg/kg) on the 5-HT2A receptor labeling pattern in selected rat brain regions. Following acute or chronic (14 days) drug administration, rat brains were analyzed by using autoradiography with the 5-HT2A receptor antagonist [3H]ketanserin.

RESULTS

Single dose or chronic administration of imipramine decreased the radioligand binding in the claustrum and cortical subregions. The [3H]ketanserin binding either increased or decreased in cortical areas after acute N-acetylcysteine and URB597 administration, respectively. A similar shift towards reduction of the [3H]ketanserin binding was detected in the nucleus accumbens shell following either acute treatment with imipramine, escitalopram, N-acetylcysteine and URB597 or repeated administration of imipramine, tianeptine and URB597.

CONCLUSIONS

In conclusion, the present result indicate different sensitivity of brain 5-HT2A receptors to antidepressant drugs depending on schedule of drug administration and rat brain regions. The decrease of accumbal shell 5-HT2A receptor labeling by antidepressant drugs exhibiting different primary mechanism of action seems to be a common targeting mechanism associated with the outcome of depression treatment.

Repetitive high-frequency transcranial magnetic stimulation reverses depressive-like behaviors and protein expression at hippocampal synapses in chronic unpredictable stress-treated rats by enhancing endocannabinoid signaling

The anti-depressant effect of repetitive transcranial magnetic stimulation (rTMS), a clinically-useful treatment for depression, is associated with changes to the endocannabinoid system (ECS). However, it is currently unknown whether different frequencies of rTMS alter the ECS differently. To test this, rats exposed to chronic unpredictable stress (CUS) were treated with rTMS at two different frequencies (5 (high) or 1 Hz (low), 1.26 Tesla) for 7 consecutive days. Twenty-four hours after the final rTMS treatment, we evaluated depressive-like behaviors and the expression of several synaptic proteins and ECS-related proteins in the hippocampus. In addition, we knocked-down diacylglycerol lipase alpha (DAGLα) and cannabinoid type 1 receptor (CB1R), two important components of the ECS, and measured depressive-like behaviors and synaptic protein expression following rTMS. Furthermore, we measured the expression levels of several components of the ECS system in hippocampal-derived astrocytes and neurons exposed to repetitive magnetic stimulation (rMS) with different parameters (5 or 1 Hz, 0.84 or 1.26 Tesla). Interestingly, we found that only high-frequency rTMS ameliorated depressive-like behaviors and normalized the expression of hippocampal synaptic proteins in CUS-treated rats; this effect was eliminated by knockdown of DAGLα or CB1R. Moreover, we found that rMS at 5 Hz increased the expression of DAGLα and CB1R in hippocampal astrocytes and neurons. Collectively, our results suggest that high-frequency rTMS exerts its anti-depressant effect by up-regulating DAGLα and CB1R.