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Neuroscience

Inhibition of serotonin transporters disrupts the enhancement of fear memory extinction by 3,4-methylenedioxymethamphetamine (MDMA)

July 24, 2017 / Anxiety Disorders / PTSD, MDMA, Neuroscience, Papers, Psychology / By / , , , , , ,

Abstract

Rationale

3,4-Methylenedioxymethamphetamine (MDMA) persistently improves symptoms of post-traumatic stress disorder (PTSD) when combined with psychotherapy. Studies in rodents suggest that these effects can be attributed to enhancement of fear memory extinction. Therefore, MDMA may improve the effects of exposure-based therapy for PTSD, particularly in treatment-resistant patients. However, given MDMA’s broad pharmacological profile, further investigation is warranted before moving to a complex clinical population.

Objectives

We aimed to inform clinical research by providing a translational model of MDMA’s effect, and elucidating monoaminergic mechanisms through which MDMA enhances fear extinction.

Methods

We explored the importance of monoamine transporters targeted by MDMA to fear memory extinction, as measured by reductions in conditioned freezing and fear-potentiated startle (FPS) in mice. Mice were treated with selective inhibitors of individual monoamine transporters prior to combined MDMA treatment and fear extinction training.

Results

MDMA enhanced the lasting extinction of FPS. Acute and chronic treatment with a 5-HT transporter (5-HTT) inhibitor blocked MDMA’s effect on fear memory extinction. Acute inhibition of dopamine (DA) and norepinephrine (NE) transporters had no effect. 5-HT release alone did not enhance extinction. Blockade of MDMA’s effect by 5-HTT inhibition also downregulated 5-HT2A-mediated behavior, and 5-HT2A antagonism disrupted MDMA’s effect on extinction.

Conclusions

We validate enhancement of fear memory extinction by MDMA in a translational behavioral model, and reveal the importance of 5-HTT and 5-HT2A receptors to this effect. These observations support future clinical research of MDMA as an adjunct to exposure therapy, and provide important pharmacological considerations for clinical use in a population frequently treated with 5-HTT inhibitors.

Young, M. B., Norrholm, S. D., Khoury, L. M., Jovanovic, T., Rauch, S. A., Reiff, C. M., … & Howell, L. L. (2017). Inhibition of serotonin transporters disrupts the enhancement of fear memory extinction by 3, 4-methylenedioxymethamphetamine (MDMA). Psychopharmacology, 234(19), 2883-2895. 10.1007/s00213-017-4684-8
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Posttraumatic Stress Disorder: An Integrated Overview of the Neurobiological Rationale for Pharmacology

July 18, 2017 / Anxiety Disorders / PTSD, Neuroscience, Papers, Psychology / By / , , , ,

Abstract

Thirty years of research on the biology of posttraumatic stress disorder now provides a foundation for hypotheses related to the mechanisms underlying the pharmacotherapy of this disorder. Only two medications, sertraline and paroxetine, are approved by the U.S. Food and Drug Administration for the treatment of PTSD. Although these medications are somewhat effective, other treatment mechanisms must be explored to address the unmet need for effective treatment. This article provides a concise summary of advances in our understanding of the neurobiology of PTSD and novel approaches to pharmacotherapy.
Kelmendi, B., Adams, T. G., Southwick, S., Abdallah, C. G., & Krystal, J. H. (2017). Posttraumatic stress disorder: An integrated overview of the neurobiological rationale for pharmacology. Clinical Psychology: Science and Practice. 10.1111/cpsp.12202
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Monoamine receptor interaction profiles of 4-thio-substituted phenethylamines (2C-T drugs)

July 15, 2017 / Neuroscience, Papers / By / , , ,

Abstract

BACKGROUND:
4-Thio-substituted phenethylamines (2C-T drugs) are potent psychedelics with poorly defined pharmacological properties. Because of their psychedelic effects, 2C-T drugs are sometimes sold as new psychoactive substances (NPSs). The aim of the present study was to characterize the monoamine receptor and transporter interaction profiles of a series of 2C-T drugs.
METHODS:
We determined the binding affinities of 2C-T drugs at monoamine receptors and transporters in human cells that were transfected with the respective receptors or transporters. We also investigated the functional activation of serotonergic 5-hydroxytryptamine 2A (5-HT2A) and 5-HT2B receptors, activation of human trace amine-associated receptor 1 (TAAR1), and inhibition of monoamine uptake transporters.
RESULTS:
2C-T drugs had high affinity for 5-HT2A and 5-HT2C receptors (1-54 nM and 40-350 nM, respectively). With activation potencies of 1-53 nM and 44-370 nM, the drugs were potent 5-HT2A receptor and 5-HT2B receptor, respectively, partial agonists. An exception to this were the benzylthiophenethylamines, which did not potently activate the 5-HT2B receptor (EC50 > 3000 nM). Furthermore, the compounds bound to serotonergic 5-HT1A and adrenergic receptors. The compounds had high affinity for the rat TAAR1 (5-68 nM) and interacted with the mouse but not human TAAR1. The 2C-T drugs did not potently interact with monoamine transporters (Ki > 4000 nM).
CONCLUSION:
The receptor binding profile of 2C-T drugs predicts psychedelic effects that are mediated by potent 5-HT2 receptor interactions.
Luethi, D., Trachsel, D., Hoener, M. C., & Liechti, M. E. (2017). Monoamine receptor interaction profiles of 4-thio-substituted phenethylamines (2C-T drugs). Neuropharmacology. 10.1016/j.neuropharm.2017.07.012
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The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro

July 13, 2017 / Ayahuasca, Depressive Disorders, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

Banisteriopsis caapi is the basic ingredient of ayahuasca, a psychotropic plant tea used in the Amazon for ritual and medicinal purposes, and by interested individuals worldwide. Animal studies and recent clinical research suggests that B. caapi preparations show antidepressant activity, a therapeutic effect that has been linked to hippocampal neurogenesis. Here we report that harmine, tetrahydroharmine and harmaline, the three main alkaloids present in B. caapi, and the harmine metabolite harmol, stimulate adult neurogenesis in vitro. In neurospheres prepared from progenitor cells obtained from the subventricular and the subgranular zones of adult mice brains, all compounds stimulated neural stem cell proliferation, migration, and differentiation into adult neurons. These findings suggest that modulation of brain plasticity could be a major contribution to the antidepressant effects of ayahuasca. They also expand the potential application of B. caapi alkaloids to other brain disorders that may benefit from stimulation of endogenous neural precursor niches.
Morales-García, J. A., de la Fuente Revenga, M., Alonso-Gil, S., Rodríguez-Franco, M. I., Feilding, A., Perez-Castillo, A., & Riba, J. (2017). The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro. Scientific reports, 7, 5309. 10.1038%2Fs41598-017-05407-9
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The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro

July 13, 2017 / Ayahuasca, Depressive Disorders, Neuroscience, Papers, Psychology / By / , , , , , ,

Abstract

Banisteriopsis caapi is the basic ingredient of ayahuasca, a psychotropic plant tea used in the Amazon for ritual and medicinal purposes, and by interested individuals worldwide. Animal studies and recent clinical research suggests that B. caapi preparations show antidepressant activity, a therapeutic effect that has been linked to hippocampal neurogenesis. Here we report that harmine, tetrahydroharmine and harmaline, the three main alkaloids present in B. caapi, and the harmine metabolite harmol, stimulate adult neurogenesis in vitro. In neurospheres prepared from progenitor cells obtained from the subventricular and the subgranular zones of adult mice brains, all compounds stimulated neural stem cell proliferation, migration, and differentiation into adult neurons. These findings suggest that modulation of brain plasticity could be a major contribution to the antidepressant effects of ayahuasca. They also expand the potential application of B. caapi alkaloids to other brain disorders that may benefit from stimulation of endogenous neural precursor niches.
Morales-García, J. A., de la Fuente Revenga, M., Alonso-Gil, S., Rodríguez-Franco, M. I., Feilding, A., Perez-Castillo, A., & Riba, J. (2017). The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro. Scientific Reports, 7. 10.1038%2Fs41598-017-05407-9
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Neuropathic and inflammatory antinociceptive effects and electrocortical changes produced by Salvia divinorum in rats

July 12, 2017 / Neuroscience, Papers, Psychiatry & Medicine, Salvia / Salvinorin A / By / , , , , , ,

Abstract

Ethnopharmacological relevance

Salvia divinorum is a medicinal plant traditionally used in hallucinogenic ethnopharmacological practices and for its analgesic and antinflammatory properties. Its active compounds include diterpenes known as salvinorins which act as potent κ opioid receptor agonists.

Aim of the study

Given its effects in acute animal models of pain, as well as its antinflammatory attributes, we decided to investigate the analgesic effects of an SD extract in neuropathic (sciatic loose nerve ligature) and inflammatory (intra plantar carrageenan) pain models in rats. We also determined in this study the electrocorticographic changes to correlate similar hallucinogenic state and behavior as those produced in humans.

Material and methods

Mechanical and thermonociceptive responses, plantar test and von Frey assay, respectively, were measured in adult Wistar rats 30 min, 3 h and 24 h after the intraperitoneal administration of saline or an hydroponic SD extract. We also evaluated carbamazepine and celecoxib, as gold reference drugs, to compare its antinociceptive effects.

Results

Our results showed that administration of SD extract induced antialgesic effects in both neuropathic and inflammatory pain models. All those effects were blocked by nor-binaltorphimine (a Kappa opioid receptor antagonist). Moreover, it was observed an increase of the anterior power spectral density and a decrease in the posterior region as electrocorticographic changes.

Conclusion

The present investigation give evidence that SD is capable to reduce algesic response associated to neuropathic and inflammatory nociception. This study support therapeutic alternatives for a disabling health problem due to the long term pain with high impact on population and personal and social implications.

Simón-Arceo, K., González-Trujano, M. E., Coffeen, U., Fernández-Mas, R., Mercado, F., Almanza, A., … & Pellicer, F. (2017). Neuropathic and inflammatory antinociceptive effects and electrocortical changes produced by Salvia divinorum in rats. Journal of Ethnopharmacology, 206, 115-124. 10.1016/j.jep.2017.05.016
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Two dose investigation of the 5-HT-agonist psilocybin on relative and global cerebral blood flow

July 12, 2017 / Mushrooms / Psilocybin, Neuroscience, Papers / By / , , , , ,

Abstract

Psilocybin, the active compound in psychedelic mushrooms, is an agonist of various serotonin receptors. Seminal psilocybin positron emission tomography (PET) research suggested regional increases in glucose metabolism in frontal cortex (hyperfrontality). However, a recent arterial spin labeling (ASL) study suggests psilocybin may lead to hypo-perfusion in various brain regions. In this placebo-controlled, double-blind study we used pseudo-continuous ASL (pCASL) to measure perfusion changes, with and without adjustment for global brain perfusion, after two doses of oral psilocybin (low dose: 0.160 mg/kg; high dose: 0.215 mg/kg) in two groups of healthy controls (n = 29 in both groups, total N = 58) during rest. We controlled for sex and age and used family-wise error corrected p values in all neuroimaging analyses. Both dose groups reported profound subjective drug effects as measured by the Altered States of Consciousness Rating Scale (5D-ASC) with the high dose inducing significantly larger effects in four out of the 11 scales. After adjusting for global brain perfusion, psilocybin increased relative perfusion in distinct right hemispheric frontal and temporal regions and bilaterally in the anterior insula and decreased perfusion in left hemispheric parietal and temporal cortices and left subcortical regions. Whereas, psilocybin significantly reduced absolute perfusion in frontal, temporal, parietal, and occipital lobes, and bilateral amygdalae, anterior cingulate, insula, striatal regions, and hippocampi. Our analyses demonstrate consistency with both the hyperfrontal hypothesis of psilocybin and the more recent study demonstrating decreased perfusion, depending on analysis method. Importantly, our data illustrate that relative changes in perfusion should be understood and interpreted in relation to absolute signal variations.
Lewis, C. R., Preller, K. H., Kraehenmann, R., Michels, L., Stämpfli, P., & Vollenweider, F. X. (2017). Two dose investigation of the 5-HT-agonist psilocybin on relative and global cerebral blood flow. NeuroImage. 10.1016/j.neuroimage.2017.07.020
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MDMA-Induced Dissociative State not Mediated by the 5-HT2A Receptor

July 11, 2017 / MDMA, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

Previous research has shown that a single dose of MDMA induce a dissociative state, by elevating feelings of depersonalization and derealization. Typically, it is assumed that action on the 5-HT2A receptor is the mechanism underlying these psychedelic experiences. In addition, other studies have shown associations between dissociative states and biological parameters (heart rate, cortisol), which are elevated by MDMA. In order to investigate the role of the 5-HT2 receptor in the MDMA-induced dissociative state and the association with biological parameters, a placebo-controlled within-subject study was conducted including a single oral dose of MDMA (75 mg), combined with placebo or a single oral dose of the 5-HT2 receptor blocker ketanserin (40 mg). Twenty healthy recreational MDMA users filled out a dissociative states scale (CADSS) 90 min after treatments, which was preceded and followed by assessment of a number of biological parameters (cortisol levels, heart rate, MDMA blood concentrations). Findings showed that MDMA induced a dissociative state but this effect was not counteracted by pre-treatment with ketanserin. Heart rate was the only biological parameter that correlated with the MDMA-induced dissociative state, but an absence of correlation between these measures when participants were pretreated with ketanserin suggests an absence of directional effects of heart rate on dissociative state. It is suggested that the 5-HT2 receptor does not mediate the dissociative effects caused by a single dose of MDMA. Further research is needed to determine the exact neurobiology underlying this effect and whether these effects contribute to the therapeutic potential of MDMA.
Puxty, D. J., Ramaekers, J. G., de la Torre, R., Farré, M., Pizarro, N., Pujadas, M., & Kuypers, K. P. (2017). MDMA-induced dissociative state not mediated by the 5-HT2A receptor. Frontiers in pharmacology, 8, 455. 10.3389/fphar.2017.00455
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Hallucinogens and Serotonin 5-HT2A Receptor-Mediated Signaling Pathways

July 5, 2017 / LSD, Mescaline / Cacti, Mushrooms / Psilocybin, Neuroscience, Papers / By / ,

Abstract

The neuropsychological effects of naturally occurring psychoactive chemicals have been recognized for millennia. Hallucinogens, which include naturally occurring chemicals such as mescaline and psilocybin, as well as synthetic compounds, such as lysergic acid diethylamide (LSD), induce profound alterations of human consciousness, emotion, and cognition. The discovery of the hallucinogenic effects of LSD and the observations that LSD and the endogenous ligand serotonin share chemical and pharmacological profiles led to the suggestion that biogenic amines like serotonin were involved in the psychosis of mental disorders such as schizophrenia. Although they bind other G protein-coupled receptor (GPCR) subtypes, studies indicate that several effects of hallucinogens involve agonist activity at the serotonin 5-HT2Areceptor. In this chapter, we review recent advances in understanding hallucinogen drug action through characterization of structure, neuroanatomical location, and function of the 5-HT2A receptor.
López-Giménez, J. F., & González-Maeso, J. (2017). Hallucinogens and Serotonin 5-HT2A Receptor-Mediated Signaling Pathways. 10.1007/7854_2017_478
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The Effects of Hallucinogens on Gene Expression

July 5, 2017 / LSD, Neuroscience, Papers / By / ,

Abstract

The classic serotonergic hallucinogens, or psychedelics, have the ability to profoundly alter perception and behavior. These can include visual distortions, hallucinations, detachment from reality, and mystical experiences. Some psychedelics, like LSD, are able to produce these effects with remarkably low doses of drug. Others, like psilocybin, have recently been demonstrated to have significant clinical efficacy in the treatment of depression, anxiety, and addiction that persist for at least several months after only a single therapeutic session. How does this occur? Much work has recently been published from imaging studies showing that psychedelics alter brain network connectivity. They facilitate a disintegration of the default mode network, producing a hyperconnectivity between brain regions that allow centers that do not normally communicate with each other to do so. The immediate and acute effects on both behaviors and network connectivity are likely mediated by effector pathways downstream of serotonin 5-HT2A receptor activation. These acute molecular processes also influence gene expression changes, which likely influence synaptic plasticity and facilitate more long-term changes in brain neurochemistry ultimately underlying the therapeutic efficacy of a single administration to achieve long-lasting effects. In this review, we summarize what is currently known about the molecular genetic responses to psychedelics within the brain and discuss how gene expression changes may contribute to altered cellular physiology and behaviors.
Martin, D. A., & Nichols, C. D. (2017). The Effects of Hallucinogens on Gene Expression. 10.1007/7854_2017_479
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