Effects of Selective Serotonin Reuptake Inhibitor Use on 3,4-Methylenedioxymethamphetamine-Assisted Therapy for Posttraumatic Stress Disorder: A Review of the Evidence, Neurobiological Plausibility, and Clinical Significance

Efficacy of fluoxetine and (R,S)-ketamine in attenuating conditioned fear behaviors in male mice

Post-traumatic stress disorder (PTSD) is caused by exposure to a traumatic or stressful event. Symptoms related to this disorder include persistent re-experiencing of memories and fear of generalization. Current pharmacological treatments for PTSD are insufficient, with fewer than 30% of patients reporting symptom remission. This study aims to determine the efficacy of acute (R,S)-ketamine and chronic fluoxetine (FLX) in reducing fear memory and fear generalization. In rodents, fear conditioning (FC) is commonly used in the literature to induce behaviors related to symptoms of PTSD, and the open field test (OFT) can assess anxiety and fear generalization behaviors during the exploration of a novel environment. In this study, FC consisted of a white noise cue stimulus and 4 inescapable foot shocks. Treatments began 4 hours after FC. Fear and anxiety behaviors were recorded during re-exposure to the FC stimuli at 24 hours and 2 weeks. The OFT was conducted 1 day before the last FC re-exposure. Results support the combined use of acute ketamine and chronic FLX as a treatment for reducing behaviors indicative of fear memory during re-exposure at 2 weeks, but not behaviors indicative of anxiety and fear generalization in the OFT. FLX alone was most effective in reducing behaviors related to fear generalization. This study contributes to the existing literature on pharmacological treatment for fear and anxiety behaviors relating to fear memory and fear generalization. Continued research is necessary to replicate results, optimize treatment protocols, and investigate the molecular adaptations to trauma and treatment. SIGNIFICANCE STATEMENT: Up to 6% of people in the United States will develop PTSD within their lifetime, and less than half of those individuals will find relief from their symptoms given the current therapeutic options. This study offers preliminary support for the efficacy of ketamine and FLX in reducing PTSD-like behaviors induced by fear-conditioning in mice. Compared with current standard treatments, the results of the current study indicate the potential for a more effective therapeutic option for those with stress-related disorders, such as PTSD.

Role of the gut-brain axis via the subdiaphragmatic vagus nerve in stress resilience of 3,4-methylenedioxymethamphetamine in mice exposed to chronic restrain stress

3,4-Methylenedioxymethamphetamine (MDMA) is the most widely used illicit substance worldwide. Nevertheless, recent observational studies demonstrated that lifetime MDMA use among U.S. adults was associated with a lower risk of depression and suicide thoughts. We recently reported that the gut-brain axis may contribute to MDMA-induced stress resilience in mice. To further explore this, we investigated the effects of subdiaphragmatic vagotomy (SDV) in modulating the stress resilience effects of MDMA in mice subjected to chronic restrain stress (CRS). Pretreatment with MDMA (10 mg/kg/day for 14 days) blocked anhedonia-like behavior and reduced expression of synaptic proteins and brain-derived neurotrophic factor in the prefrontal cortex (PFC) of CRS-exposed mice. Interestingly, SDV blocked the beneficial effects of MDMA on these alterations in CRS-exposed mice. Analysis of gut microbiome revealed alterations in four measures of α-diversity between the sham + MDMA + CRS group and the SDV + MDMA + CRS group. Moreover, specific microbes differed between the vehicle + CRS group and the MDMA + CRS group, and further differences in microbial composition were observed among all four groups. Untargeted metabolomics analysis showed that SDV prevented the increase in plasma levels of three compounds [lactic acid, 1-(2-hydroxyethyl)-2,2,6-tetramethyl-4-piperidinol, 8-acetyl-7-hydroxyvumaline] observed in the sham + MDMA + CRS group. Interestingly, positive correlations were found between the plasma levels of two of these compounds and the abundance of several microbes across all groups. In conclusion, our data suggest that the gut-brain axis via the subdiaphragmatic vagus nerve might contribute to the stress resilience of MDMA.

A Review of MDMA-Assisted Therapy for Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a common chronic and disabling psychiatric disorder that may develop after exposure to a traumatic life event. There are existing evidence-based psychotherapies and pharmacotherapies for PTSD; however, these treatments have significant limitations. 3,4-methylenedioxymethamphetamine (MDMA) was granted "breakthrough therapy" status by the U.S. Food and Drug Administration (FDA) in 2017 for the treatment of PTSD in conjunction with psychotherapy after preliminary Phase II results. This treatment is currently being investigated in Phase III trials with anticipated FDA approval of MDMA-assisted psychotherapy for PTSD in late 2023. This article reviews the evidence base for MDMA-assisted psychotherapy for PTSD, pharmacology and the proposed causal mechanisms of MDMA, risks and limitations of the current evidence, and challenges and future directions for the field.

Repeated use of 3,4-methylenedioxymethamphetamine is associated with the resilience in mice after chronic social defeat stress: A role of gut-microbiota-brain axis

3,4-Methylenedioxymethamphetamine (MDMA), the most widely used illicit compound worldwide, is the most attractive therapeutic drug for post-traumatic stress disorder (PTSD). Recent observational studies of US adults demonstrated that lifetime MDMA use was associated with lower risk of depression. Here, we examined whether repeated administration of MDMA can affect resilience versus susceptibility in mice exposed to chronic social defeat stress (CSDS). CSDS produced splenomegaly, anhedonia-like phenotype, and higher plasma levels of interleukin-6 (IL-6) in the saline-treated mice. In contrast, CSDS did not cause these changes in the MDMA-treated mice. Analysis of gut microbiome found several microbes altered between saline + CSDS group and MDMA + CSDS group. Untargeted metabolomics analysis showed that plasma levels of N-epsilon-methyl-L-lysine in the saline + CSDS group were significantly higher than those in the control and MDMA + CSDS groups. Interestingly, there were positive correlations between plasma IL-6 levels and the abundance of several microbes (or plasma N-epsilon-methyl-L-lysine) in the three groups. Furthermore, there were also positive correlations between the abundance of several microbes and N-epsilon-methyl-L-lysine in the three groups. In conclusion, these data suggest that repeated administration of MDMA might contribute to stress resilience in mice subjected to CSDS through gut-microbiota-brain axis.

Effects of low-doses of methamphetamine on d-fenfluramine-induced head-twitch response (HTR) in mice during ageing and c-fos expression in the prefrontal cortex

BACKGROUND

The head-twitch response (HTR) in mice is considered a behavioral model for hallucinogens and serotonin 5-HT_2A receptor function, as well as Tourette syndrome in humans. It is mediated by 5-HT_2A receptor agonists such as ( ±)- 2,5-dimethoxy-4-iodoamphetamine (DOI) in the prefrontal cortex (PFC). The 5-HT_2A antagonist EMD 281014, can prevent both DOI-induced HTR during ageing and c-fos expression in different regions of PFC. Moreover, the nonselective monoamine releaser methamphetamine (MA) suppressed DOI-induced HTR through ageing via concomitant activation of inhibitory 5-HT_1A receptors, but enhanced DOI-evoked c-fos expression. d-Fenfluramine is a selective 5-HT releaser and induces HTR in mice, whereas MA does not. Currently, we investigated whether EMD 281014 or MA would alter: (1) d-fenfluramine-induced HTR frequency in 20-, 30- and 60-day old mice, (2) d-fenfluramine-evoked c-fos expression in PFC, and (3) whether blockade of inhibitory serotonergic 5-HT_1A- or adrenergic ɑ₂-receptors would prevent suppressive effect of MA on d-fenfluramine-induced HTR.

RESULTS

EMD 281014 (0.001-0.05 mg/kg) or MA (0.1-5 mg/kg) blocked d-fenfluramine-induced HTR dose-dependently during ageing. The 5-HT_1A antagonist WAY 100635 countered the inhibitory effect of MA on d-fenfluramine-induced HTR in 30-day old mice, whereas the adrenergic ɑ₂ antagonist RS 79948 reversed MA's inhibitory effect in both 20- and 30- day old mice. d-Fenfluramine significantly increased c-fos expressions in PFC regions. MA (1 mg/kg) pretreatment significantly increased d-fenfluramine-evoked c-fos expression in different regions of PFC. EMD 281014 (0.05 mg/kg) failed to prevent d-fenfluramine-induced c-fos expression, but significantly increased it in one PFC region (PrL at - 2.68 mm).

CONCLUSION

EMD 281014 suppressed d-fenfluramine-induced HTR but failed to prevent d-fenfluramine-evoked c-fos expression which suggest involvement of additional serotonergic receptors in the mediation of evoked c-fos. The suppressive effect of MA on d-fenfluramine-evoked HTR is due to well-recognized functional interactions between stimulatory 5-HT_2A- and the inhibitory 5-HT_1A- and ɑ₂-receptors. MA-evoked increases in c-fos expression in PFC regions are due to the activation of diverse monoaminergic receptors through increased synaptic concentrations of 5-HT, NE and/or DA, which may also account for the additive effect of MA on d-fenfluramine-evoked changes in c-fos expression. Our findings suggest potential drug receptor functional interaction during development when used in combination.

Changes in the Serum Concentration Levels of Serotonin, Tryptophan and Cortisol among Stress-Resilient and Stress-Susceptible Individuals after Experiencing Traumatic Stress

BACKGROUND

Stress is a common response to many environmental adversities. However, once dysregulated, this reaction can lead to psychiatric illnesses, such as post-traumatic stress disorder (PTSD). Individuals can develop PTSD after exposure to traumatic events, severely affecting their quality of life. Nevertheless, not all individuals exposed to stress will develop psychiatric disorders, provided they show enhanced stress-resilience mechanisms that enable them to successfully adapt to stressful situations and thus avoid developing a persistent psychopathology.

METHODS

The study involved 93 participants. Of them, 62 comprised a study group and 31 comprised a control group. The aim of the study was to assess serotonin, cortisol and tryptophan concentration levels in subjects with PTSD (stress-susceptible; PTSD-SS) and in healthy individuals (stress-resilient; PTSD-SR), who had experienced a traumatic event but fully recovered after the trauma. The subjects were between 18 and 50 years of age (mean 35.56 ± 8.26 years). The serum concentration levels of serotonin, cortisol and tryptophan were measured with an ELISA kit.

RESULTS

It was found that the serotonin, tryptophan and cortisol concentration levels were consistent with the features of both PTSD-SR and PTSD-SS patients. It was reported that the mean cortisol concentration levels increased more significantly in the PTSD-SS group than in the PTSD-SR group, versus those in the control group. Similarly, the PTSD-SS group was found to show a larger decrease in the mean serotonin concentration levels than the PTSD-SR group, versus those in the control group. No significant changes were found in the tryptophan concentration levels between the study groups, versus those in the control group.

CONCLUSIONS

These findings can be useful when attempting to improve resilience in individuals using neuropharmacological methods. However, it is necessary to conduct more cross-sectional studies that would address different types of negative stress to find out whether they share common pathways.

Methylone, a rapid acting entactogen with robust anxiolytic and antidepressant-like activity

INTRODUCTION

Selective serotonin reuptake inhibitor (SSRI) antidepressants represent first-line pharmacological treatment for a variety of neuropsychiatric illnesses, including major depressive disorder (MDD), anxiety, and post-traumatic stress disorder (PTSD), which show high rates of comorbidity. SSRIs have a delayed onset of action. Most patients do not show significant effects until 4-8 weeks of continuous treatment, have impairing side effects and as many as 40% of patients do not respond. Methylone (3,4-methylenedioxy-N-methylcathinone; MDMC, βk-MDMA, M1) is a rapid-acting entactogen that showed significant benefit in a clinical case series of PTSD patients and was well-tolerated in two Phase 1 studies of healthy volunteers. Based on these early observations in humans, in the current study we tested the hypothesis that methylone has antidepressant-like and anxiolytic effects in preclinical tests.

METHODS

For all studies, 6-8-week-old male Sprague Dawley rats (N = 6-16) were used. We employed the Forced Swim Test (FST), a classic and widely used screen for antidepressants, to explore the effects of methylone and to probe dose-response relationships, durability of effect, and potential interactions with combined SSRI treatment. We compared the effect of methylone with the prototypical SSRI fluoxetine.

RESULTS

Three doses of fluoxetine (10 mg/kg) given within 24 h before FST testing caused a 50% reduction in immobility compared with controls that lasted less than 24 h. In contrast, a single dose of methylone (5-30 mg/kg) administered 30 min prior to testing produced a rapid, robust, and durable antidepressant-like response in the FST, greater in magnitude than fluoxetine. Immobility was reduced by nearly 95% vs. controls and effects persisted for at least 72 h after a single dose (15 mg/kg). Effects on swimming and climbing behavior in the FST, which reflect serotonergic and noradrenergic activity, respectively, were consistent with studies showing that methylone is less serotoninergic than MDMA. Fluoxetine pretreatment did not change methylone's antidepressant-like effect in the FST, suggesting the possibility that the two may be co-administered. In addition, methylone (5-30 mg/kg) exhibited anxiolytic effects measured as increased time spent in the center of an open field.

DISCUSSION

Taken together, and consistent with initial clinical findings, our study suggests that methylone may have potential for treating depression and anxiety.