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Neuroscience

Genotoxic evaluations in Wistar rats of the hallucinogenic plant extract ayahuasca

January 1, 2016 / Ayahuasca, Neuroscience, Papers, Publications / By / , , , ,

Abstract

Ayahuasca, a psychoactive infusion, is a sacrament used by indigenous and non-indigenous communities in Brazil and other countries. This beverage has vaunted healing properties; however, its use in a therapeutic context still lacks preclinical data to certify its safety and effectiveness. This study evaluated the genotoxic, mutagenic and cytotoxic potential of ayahuasca in Wistar rats after a single oral dose. Rats of both sexes were randomly distributed into five experimental groups (n=10): negative control that received filtered water, positive control that received doxorubicin and treated groups that received ayahuasca at 1, 5 and 15 times the usual dose taken in human religious rituals. The rats were euthanized 30 hours after dosage. Genotoxicity was evaluated by flow cytometry, comet assay and micronucleus test. Renal, hepatic and pancreatic functions were evaluated by serum analysis. Ayahuasca showed low genotoxicity, with an increased frequency of micronuclei only at the highest exposure level, and a non-observed-adverse-effect-level established at 5X the dose, or 1.5 mg/kg bw N,N-dimethyltryptamine a major component of the infusion. No cytotoxic effects were observed in the tested conditions. Furthermore, hepatic, renal and pancreatic functions remained without significant changes for all treated groups.

Pic-Taylor, A., Junior, W. M., Souza-Filho, J., Grisolia, C. K., & Caldas, E. D. (2016). Genotoxic evaluations in Wistar rats of the hallucinogenic plant extract ayahuasca. International Journal of Phytomedicine, 8(2). http://dx.doi.org/10.5138/ijpm.v8i2.1828
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Influence of caffeine on 3,4-methylenedioxymethamphetamine-induced dopaminergic neuron degeneration and neuroinflammation is age-dependent

January 1, 2016 / MDMA, Neuroscience, Papers, Publications / By / , , , , , ,

Abstract

Previous studies have demonstrated that caffeine administration to adult mice potentiates glial activation induced by 3,4-methylenedioxymethamphetamine (MDMA). As neuroinflammatory response seems to correlate with neurodegeneration, and the young brain is particularly vulnerable to neurotoxicity, we evaluated dopamine neuron degeneration and glial activation in the caudate-putamen (CPu) and substantia nigra pars compacta (SNc) of adolescent and adult mice. Mice were treated with MDMA (4 × 20 mg/kg), alone or with caffeine (10 mg/kg). Interleukin (IL)-1β, tumor necrosis factor (TNF)-α, neuronal nitric oxide synthase (nNOS) were evaluated in CPu, whereas tyrosine hydroxylase (TH), glial fibrillary acidic protein, and CD11b were evaluated in CPu and SNc by immunohistochemistry. MDMA decreased TH in SNc of both adolescent and adult mice, whereas TH-positive fibers in CPu were only decreased in adults. In CPu of adolescent mice, caffeine potentiated MDMA-induced glial fibrillary acidic protein without altering CD11b, whereas in SNc caffeine did not influence MDMA-induced glial activation. nNOS, IL-1β, and TNF-α were increased by MDMA in CPu of adults, whereas in adolescents, levels were only elevated after combined MDMA plus caffeine. Caffeine alone modified only nNOS. Results suggest that the use of MDMA in association with caffeine during adolescence may exacerbate the neurotoxicity and neuroinflammation elicited by MDMA. Previous studies have demonstrated that caffeine potentiated glial activation induced by 3,4-methylenedioxymethamphetamine (MDMA) in adult mice. In this study, caffeine was shown to potentiate MDMA-induced dopamine neuron degeneration in substantia nigra pars compacta, astrogliosis, and TNF-α levels in caudate-putamen of adolescent mice. Results suggest that combined use of MDMA plus caffeine during adolescence may worsen the neurotoxicity and neuroinflammation elicited by MDMA.

Frau, L., Costa, G., Porceddu, P. F., Khairnar, A., Castelli, M. P., Ennas, M. G., … & Morelli, M. (2016). Influence of caffeine on 3, 4‐methylenedioxymethamphetamine‐induced dopaminergic neuron degeneration and neuroinflammation is age‐dependent. Journal of neurochemistry, 136(1), 148-162. http://dx.doi.org/10.1111/jnc.13377

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Effects of Long-Term Ayahuasca Administration on Memory and Anxiety in Rats

December 30, 2015 / Ayahuasca, Neuroscience, Papers, Publications / By / , , ,

Abstract

Ayahuasca is a hallucinogenic beverage that combines the action of the 5-HT2A/2C agonist N,N-dimethyltryptamine (DMT) from Psychotria viridis with the monoamine oxidase inhibitors (MAOIs) induced by beta-carbonyls from Banisteriopsis caapi. Previous investigations have highlighted the involvement of ayahuasca with the activation of brain regions known to be involved with episodic memory, contextual associations and emotional processing after ayahuasca ingestion. Moreover long term users show better performance in neuropsychological tests when tested in off-drug condition. This study evaluated the effects of long-term administration of ayahuasca on Morris water maze (MWM), fear conditioning and elevated plus maze (EPM) performance in rats. Behavior tests started 48h after the end of treatment. Freeze-dried ayahuasca doses of 120, 240 and 480 mg/kg were used, with water as the control. Long-term administration consisted of a daily oral dose for 30 days by gavage. The behavioral data indicated that long-term ayahuasca administration did not affect the performance of animals in MWM and EPM tasks. However the dose of 120 mg/kg increased the contextual conditioned fear response for both background and foreground fear conditioning. The tone conditioned response was not affected after long-term administration. In addition, the increase in the contextual fear response was maintained during the repeated sessions several weeks after training. Taken together, these data showed that long-term ayahuasca administration in rats can interfere with the contextual association of emotional events, which is in agreement with the fact that the beverage activates brain areas related to these processes.

Favaro, V. M., Yonamine, M., Soares, J. C. K., & Oliveira, M. G. M. (2015). Effects of Long-Term Ayahuasca Administration on Memory and Anxiety in Rats. PloS one, 10(12), e0145840. http://dx.doi.org/10.1371/journal.pone.0145840
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Neuroimaging in moderate MDMA use: A systematic review

December 30, 2015 / MDMA, Neuroscience, Papers, Publications / By / , , , , , ,

Abstract

MDMA (“ecstasy”) is widely used as a recreational drug, although there has been some debate about its neurotoxic effects in humans. However, most studies have investigated subjects with heavy use patterns, and the effects of transient MDMA use are unclear. In this review, we therefore focus on subjects with moderate use patterns, in order to assess the evidence for harmful effects. We searched for studies applying neuroimaging techniques in man. Studies were included if they provided at least one group with an average of <50 lifetime episodes of ecstasy use or an average lifetime consumption of <100 ecstasy tablets. All studies published before July 2015 were included. Of the 250 studies identified in the database search, 19 were included.

There is no convincing evidence that moderate MDMA use is associated with structural or functional brain alterations in neuroimaging measures. The lack of significant results was associated with high methodological heterogeneity in terms of dosages and co-consumption of other drugs, low quality of studies and small sample sizes.

Mueller, F., Lenz, C., Steiner, M., Dolder, P. C., Walter, M., Lang, U. E., … & Borgwardt, S. (2016). Neuroimaging in moderate MDMA use: A systematic review. Neuroscience & Biobehavioral Reviews, 62, 21-34. http://dx.doi.org/10.1016/j.neubiorev.2015.12.010
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Cytochrome P450 inhibition potential of new psychoactive substances of the tryptamine class

November 17, 2015 / DMT, Neuroscience, Papers, Publications / By / , , , ,

Abstract

New psychoactive substances (NPS) are not tested for their cytochrome P450 (CYP) inhibition potential before consumption. Therefore, this potential was explored for tryptamine-derived NPS (TDNPS) including alpha-methyl tryptamines (AMTs), dimethyl tryptamines (DMTs), diallyl tryptamines (DALTs), and diisopropyl tryptamines (DiPTs) using test substrates preferred by the Food and Drug Administration in a cocktail assay. All tested TDNPS with the exception of DMT inhibited CYP2D6 activity with IC50 values below 100 μM. DALTs inhibited CYP2D6 activity similar to paroxetine and quinidine and CYP1A2 activity comparable to fluvoxamine. 5-Methoxy-N,N-diallyltryptamine reduced in vivo the caffeine metabolism in rats consistent with in vitro results. Five of the AMTs also inhibited CYP1A2 activity comparable to amiodarone. AMT and 6-F-AMT inhibited CYP2A6 activity in the range of the test inhibitor tranylcypromine. CYP2B6 activity was inhibited by 19 tryptamines, but weakly compared to efavirenz. CYP2C8 activity was inhibited by five of the tested TDNPS and three showed values comparable to trimethoprim and gemfibrozil. Six tryptamines inhibited CYP2C9 and seven CYP2C19 activities comparable to fluconazole and chloramphenicol, respectively. Nineteen compounds showed inhibition of CYP2E1 and 18 of CYP3A activity, respectively. These results showed that the CYP inhibition by TDNPS might be clinically relevant, but clinical studies are needed to explore this further.

Dinger, J., Woods, C., Brandt, S. D., Meyer, M. R., & Maurer, H. H. (2015). Cytochrome P450 inhibition potential of new psychoactive substances of the tryptamine class. Toxicology Letters. http://dx.doi.org/10.1016/j.toxlet.2015.11.013
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Binge Ethanol and MDMA Combination Exacerbates Toxic Cardiac Effects by Inducing Cellular Stress

October 28, 2015 / MDMA, Neuroscience, Papers, Publications / By / , , , ,

Abstract

Binge drinking is a common pattern of ethanol consumption among young people. Binge drinkers are especially susceptible to brain damage when other substances are co-administered, in particular 3,4 methylendioxymethamphetamine (MDMA). The aim of the present work was to study the mechanisms implicated in the adaptive changes observed after administration of these drugs of abuse. So, we have evaluated the cardiac sympathetic activity and the expression and activation of heat shock protein 27 (HSP27), after voluntary binge ethanol consumption, alone and in combination with MDMA. Both parameters are markers of stressful situations and they could be modified inducing several alterations in different systems. Adolescent mice received MDMA, ethanol or both (ethanol plus MDMA). Drinking in the dark (DID) procedure was used as a model of binge. Noradrenaline (NA) turnover, tyrosine hydroxylase (TH), TH phosphorylated at serine 31 and HSP27 expression and its phosphorylation at serine 82 were evaluated in adolescent mice 48 h, 72 h, and 7 days after treatments in the left ventricle. NA and normetanephrine (NMN) were determined by high-performance liquid chromatography (HPLC); TH and HSP27 expression and phosphorylation were measured by quantitative blot immunollabeling using specific antibodies. Ethanol and MDMA co-administration increased NA turnover and TH expression and phosphorylation versus the consumption of each one of these drugs. In parallel with the described modifications in the cardiac sympathetic activity, our results showed that binge ethanol+MDMA exposure is associated with an increase in HSP27 expression and phosphorylation in the left ventricle, supporting the idea that the combination of both drugs exacerbates the cellular stress induced by ethanol or MDMA alone.

Navarro-Zaragoza, J., Ros-Simó, C., Milanés, M. V., Valverde, O., & Laorden, M. L. (2015). Binge ethanol and MDMA combination exacerbates toxic cardiac effects by inducing cellular stress. PloS one, 10(10), e0141502.

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The serotonergic hallucinogen 5-methoxy-N,N-dimethyltryptamine disrupts cortical activity in a regionally-selective manner via 5-HT1A and 5-HT2A receptors.

October 20, 2015 / Neuroscience, Papers, Publications / By / , , , ,

Abstract

5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a natural hallucinogen, acting as a non-selective serotonin 5-HT1A/5-HT2A-R agonist. Psychotomimetic agents such as the non-competitive NMDA-R antagonist phencyclidine and serotonergic hallucinogens (DOI and 5-MeO-DMT) disrupt cortical synchrony in the low frequency range (<4 Hz) in rat prefrontal cortex (PFC), an effect reversed by antipsychotic drugs. Here we extend these observations by examining the effect of 5-MeO-DMT on low frequency cortical oscillations (LFCO, <4 Hz) in PFC, visual (V1), somatosensory (S1) and auditory (Au1) cortices, as well as the dependence of these effects on 5-HT1A-R and 5-HT2A-R, using wild type (WT) and 5-HT2A-R knockout (KO2A) anesthetized mice. 5-MeO-DMT reduced LFCO in the PFC of WT and KO2A mice. The effect in KO2A mice was fully prevented by the 5-HT1A-R antagonist WAY-100635. Systemic and local 5-MeO-DMT reduced 5-HT release in PFC mainly via 5-HT1A-R. Moreover, 5-MeO-DMT reduced LFCO in S1, Au1 and V1 of WT mice and only in V1 of KO2A mice, suggesting the involvement of 5-HT1A-R activation in the 5-MeO-DMT-induced disruption of V1 activity. In addition, antipsychotic drugs reversed 5-MeO-DMT effects in WT mice. The present results suggest that the hallucinogen action of 5-MeO-DMT is mediated by simultaneous alterations of the activity of sensory (S1, Au1, V1) and associative (PFC) cortical areas, also supporting a role of 5-HT1A-R stimulation in V1 and PFC, in addition to the well-known action on 5-HT2A-R. Moreover, the reversal by antipsychotic drugs of 5-MeO-DMT effects adds to previous literature supporting the usefulness of the present model in antipsychotic drug development.

Riga, M. S., Bortolozzi, A., Campa, L., Artigas, F., & Celada, P. (2015). The serotonergic hallucinogen 5-Methoxy-N, N-dimethyltryptamine disrupts cortical activity in a regionally-selective manner via 5-HT 1A and 5-HT 2A receptors. Neuropharmacology. http://dx.doi.org/10.1016/j.neuropharm.2015.10.016
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The Ups and Downs of 3,4-Methylenedioxymethamphetamine: Linking Subjective Effects to Spontaneous Brain Function

October 15, 2015 / MDMA, Neuroscience, Papers, Psychology, Publications / By / , ,

Abstract

Psychoactive drugs, especially drugs with so-called psychedelic properties, exert profound effects on sensory perception, cognition, and emotion by modulating target neurotransmitter systems. The compound 3,4-methylenedioxymethamphetamine (MDMA) exerts stimulant and psychedelic effects through its actions on dopamine, norepinephrine, and serotonin (5-hydroxytryptamine, [5-HT]) transporters, by inhibiting their reuptake and stimulating their release. In addition to producing euphoria and positive mood, MDMA appears to produce unique “prosocial” or “empathogenic” feelings.

de Wit, H., Gorka, S. M., & Phan, K. L. (2015). The Ups and Downs of 3, 4-Methylenedioxymethamphetamine: Linking Subjective Effects to Spontaneous Brain Function. Biological psychiatry, 78(8), 519-521. http://dx.doi.org/10.1016/j.biopsych.2015.08.015
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The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labeling and Blood Oxygen Level-Dependent Resting State Functional Connectivity

October 15, 2015 / MDMA, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

BACKGROUND:

The compound 3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine releaser that produces an acute euphoria in most individuals.

METHODS:

In a double-blind, placebo-controlled, balanced-order study, MDMA was orally administered to 25 physically and mentally healthy individuals. Arterial spin labeling and seed-based resting state functional connectivity (RSFC) were used to produce spatial maps displaying changes in cerebral blood flow (CBF) and RSFC after MDMA administration. Participants underwent two arterial spin labeling and two blood oxygen level-dependent scans in a 90-minute scan session; MDMA and placebo study days were separated by 1 week.

RESULTS:

Marked increases in positive mood were produced by MDMA. Decreased CBF only was observed after MDMA, and this was localized to the right medial temporal lobe (MTL), thalamus, inferior visual cortex, and the somatosensory cortex. Decreased CBF in the right amygdala and hippocampus correlated with ratings of the intensity of global subjective effects of MDMA. The RSFC results complemented the CBF results, with decreases in RSFC between midline cortical regions, the medial prefrontal cortex, and MTL regions, and increases between the amygdala and hippocampus. There were trend-level correlations between these effects and ratings of intense and positive subjective effects.

CONCLUSIONS:

The MTLs appear to be specifically implicated in the mechanism of action of MDMA, but further work is required to elucidate how the drug’s characteristic subjective effects arise from its modulation of spontaneous brain activity.

Carhart-Harris, R. L., Murphy, K., Leech, R., Erritzoe, D., Wall, M. B., Ferguson, B., … & Tanner, M. (2014). The Effects of Acutely Administered 3, 4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labeling and Blood Oxygen Level–Dependent Resting State Functional Connectivity. Biological psychiatry. http://dx.doi.org/10.1016/j.biopsych.2013.12.015

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Sex differences and serotonergic mechanisms in the behavioural effects of psilocin

October 12, 2015 / Mushrooms / Psilocybin, Neuroscience, Papers, Publications / By / , , , , ,

Abstract

Psilocybin has recently attracted a great deal of attention as a clinical research and therapeutic tool. The aim of this paper is to bridge two major knowledge gaps regarding its behavioural pharmacology – sex differences and the underlying receptor mechanisms. We used psilocin (0.25, 1 and 4 mg/kg), an active metabolite of psilocybin, in two behavioural paradigms – the open-field test and prepulse inhibition (PPI) of the acoustic startle reaction. Sex differences were evaluated with respect to the phase of the female cycle. The contribution of serotonin receptors in the behavioural action was tested in male rats with selective serotonin receptor antagonists: 5-HT1A receptor antagonist (WAY100635 1 mg/kg), 5-HT2A receptor antagonist (MDL100907 0.5 mg/kg), 5-HT2B receptor antagonist (SB215505 1 mg/kg) and 5-HT2C receptor antagonist (SB242084 1 mg/kg). Psilocin induced dose-dependent inhibition of locomotion and suppression of normal behaviour in rats (behavioural serotonin syndrome, impaired PPI). The effects were more pronounced in male rats than in females. The inhibition of locomotion was normalized by 5-HT1A and 5-HT2B/C antagonists; however, PPI was not affected significantly by these antagonists. Our findings highlight an important issue of sex-specific reactions to psilocin and that apart from 5-HT2A-mediated effects 5-HT1A and 5-HT2C/B receptors also play an important role. These findings have implications for recent clinical trials.

Tylš, F., Páleníček, T., Kadeřábek, L., Lipski, M., Kubešová, A., & Horáček, J. (2015). Sex differences and serotonergic mechanisms in the behavioural effects of psilocin. Behavioural pharmacology. https://dx.doi.org/10.1097/FBP.0000000000000198

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