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Neuroscience

Receptor interaction profiles of novel psychoactive tryptamines compared with classic hallucinogens

May 20, 2016 / Neuroscience, Papers, Publications / By / , , ,

Abstract

The present study investigated interactions between the novel psychoactive tryptamines DiPT, 4-OH-DiPT, 4-OH-MET, 5-MeO-AMT, and 5-MeO-MiPT at monoamine receptors and transporters compared with the classic hallucinogens lysergic acid diethylamide (LSD), psilocin, N,N-dimethyltryptamine (DMT), and mescaline. We investigated binding affinities at human monoamine receptors and determined functional serotonin (5-hydroxytryptamine [5-HT]) 5-HT2A and 5-HT2B receptor activation. Binding at and the inhibition of human monoamine uptake transporters and transporter-mediated monoamine release were also determined. All of the novel tryptamines interacted with 5-HT2A receptors and were partial or full 5-HT2A agonists. Binding affinity to the 5-HT2A receptor was lower for all of the tryptamines, including psilocin and DMT, compared with LSD and correlated with the reported psychoactive doses in humans. Several tryptamines, including psilocin, DMT, DiPT, 4-OH-DiPT, and 4-OH-MET, interacted with the serotonin transporter and partially the norepinephrine transporter, similar to 3,4-methylenedioxymethamphetamine but in contrast to LSD and mescaline. LSD but not the tryptamines interacted with adrenergic and dopaminergic receptors. In conclusion, the receptor interaction profiles of the tryptamines predict hallucinogenic effects that are similar to classic serotonergic hallucinogens but also MDMA-like psychoactive properties.

Rickli, A., Moning, O. D., Hoener, M. C., & Liechti, M. E. (2016). Receptor interaction profiles of novel psychoactive tryptamines compared with classic hallucinogens. European Neuropsychopharmacology. http://dx.doi.org/10.1016/j.euroneuro.2016.05.001

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Psilocybin with psychological support for treatment-resistant depression: An open-label feasibility study

May 17, 2016 / Depressive Disorders, Mushrooms / Psilocybin, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

Background: Psilocybin is a serotonin receptor agonist that occurs naturally in some mushroom species. Recent studies have assessed the therapeutic potential of psilocybin for various conditions, including end-of-life anxiety, obsessive-compulsive disorder, and smoking and alcohol dependence, with promising preliminary results. Here, we aimed to investigate the feasibility, safety, and efficacy of psilocybin in patients with unipolar treatment-resistant depression.

Methods: In this open-label feasibility trial, 12 patients (six men, six women) with moderate-to-severe, unipolar, treatment-resistant major depression received two oral doses of psilocybin (10 mg and 25 mg, 7 days apart) in a supportive setting. There was no control group. Psychological support was provided before, during, and after each session. The primary outcome measure for feasibility was patient-reported intensity of psilocybin’s effects. Patients were monitored for adverse reactions during the dosing sessions and subsequent clinic and remote follow-up. Depressive symptoms were assessed with standard assessments from 1 week to 3 months after treatment, with the 16-item Quick Inventory of Depressive Symptoms (QIDS) serving as the primary efficacy outcome. This trial is registered with ISRCTN, number ISRCTN14426797.

Findings: Psilocybin’s acute psychedelic effects typically became detectable 30–60 min after dosing, peaked 2–3 h after dosing, and subsided to negligible levels at least 6 h after dosing. Mean self-rated intensity (on a 0–1 scale) was 0·51 (SD 0·36) for the low-dose session and 0·75 (SD 0·27) for the high-dose session. Psilocybin was well tolerated by all of the patients, and no serious or unexpected adverse events occurred. The adverse reactions we noted were transient anxiety during drug onset (all patients), transient confusion or thought disorder (nine patients), mild and transient nausea (four patients), and transient headache (four patients). Relative to baseline, depressive symptoms were markedly reduced 1 week (mean QIDS difference −11·8, 95% CI −9·15 to −14·35, p=0·002, Hedges’ g=3·1) and 3 months (−9·2, 95% CI −5·69 to −12·71, p=0·003, Hedges’ g=2) after high-dose treatment. Marked and sustained improvements in anxiety and anhedonia were also noted.

Interpretation: This study provides preliminary support for the safety and efficacy of psilocybin for treatment-resistant depression and motivates further trials, with more rigorous designs, to better examine the therapeutic potential of this approach.

Funding: Medical Research Council.

Carhart-Harris, R. L., Bolstridge, M., Rucker, J., Day, C. M., Erritzoe, D., Kaelen, M., … & Taylor, D. (2016). Psilocybin with psychological support for treatment-resistant depression: an open-label feasibility study. The Lancet Psychiatry. http://dx.doi.org/10.1016/S2215-0366(16)30065-7
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Mood and neuropsychological effects of different doses of ketamine in electroconvulsive therapy for treatment-resistant depression

May 12, 2016 / Depressive Disorders, Ketamine, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

BACKGROUND: Treatment-resistant depression (TRD) is a growing clinical challenge. Electroconvulsive therapy (ECT) is an effective tool for TRD treatment. However, there remains a subset of patients who do not respond to this treatment with common anesthetic agent. Ketamine, a noteworthy anesthetic agent, has emerged as an augmentation to enhance the antidepressant efficacy of ECT. Trials of i.v. ketamine in TRD indicated dose-related mood enhancing efficacy. We aimed to explore anesthetic and subanesthetic concentrations of ketamine in ECT for TRD with respect to their impact on mood and neuropsychological effects.
METHODS: Ninety TRD patients (36 males, 54 females; average age, 30.6 years old) were randomly assigned to receive either ketamine (0.8mg/kg) (n=30), subanesthetic ketamine (0.5mg/kg) plus propofol (0.5mg/kg) (n=30) or propofol (0.8mg/kg) (n=30) as an anesthetic and underwent 8 ECT sessions. The primary outcome measures were the 17-item Hamilton Depression Rating Scale (HDRS-17), cognitive assessments and seizure parameters.
RESULTS: The ketamine group had an earlier improvement in HDRS-17, longer seizure duration, lower electric quantity, a higher remission rate, and a lower degree of executive cognitive impairment compared to the ketamine+propofol and propofol groups. The ketamine+propofol group showed earlier improvement in the HDRS-17, a longer seizure duration and a different seizure energy index when compared to the propofol group.
LIMITATIONS: The postoperative dissociative side effect was not assessed.
CONCLUSIONS: Both anesthetic and subanesthetic concentrations of ketamine have rapid mood enhancing actions in ECT for TRD, while anesthetic concentrations results in larger magnitudes of antidepression and cognitive protection. ECT with ketamine anesthesia might be an optimized therapy for patients with TRD.
Zhong, X., He, H., Zhang, C., Wang, Z., Jiang, M., Li, Q., … & Huang, X. (2016). Mood and neuropsychological effects of different doses of ketamine in electroconvulsive therapy for treatment-resistant depression. Journal of Affective Disorders, 201, 124-130. http://dx.doi.org/10.1016/j.jad.2016.05.011
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Glutamate and GABA Systems in the Pathophysiology of Major Depression and Antidepressant Response to Ketamine

May 12, 2016 / Depressive Disorders, Ketamine, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

In patients with major depressive disorder (MDD) or bipolar disorder (BD), abnormalities in excitatory and/or inhibitory neurotransmission and neuronal plasticity may lead to aberrant functional connectivity patterns within large brain networks. Network dysfunction in association with altered brain levels of glutamate (Glu) and gamma-aminobutyric acid (GABA) have been identified in both animal and human studies of depression. In addition, evidence of an antidepressant response to subanesthetic dose ketamine has led to a collection of studies that have examined neurochemical (e.g. glutamatergic and GABA-ergic) and functional imaging correlates associated with such an effect. Results from these studies suggest that an antidepressant response in association with ketamine occurs, in part, by reversing these neurochemical/physiological disturbances. Future studies in depression will require a combination of neuroimaging approaches from which more biologically homogeneous subgroups can be identified, particularly with respect to treatment response biomarkers of glutamatergic modulation.

Lener, M. S., Niciu, M. J., Ballard, E. D., Park, M., Park, L. T., Nugent, A., & Zarate, C. A. (2016). Glutamate and GABA Systems in the Pathophysiology of Major Depression and Antidepressant Response to Ketamine. Biological Psychiatry. http://dx.doi.org/10.1016/j.biopsych.2016.05.005
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LSD-induced entropic brain activity predicts subsequent personality change

May 6, 2016 / LSD, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

Personality is known to be relatively stable throughout adulthood. Nevertheless, it has been shown that major life events with high personal significance, including experiences engendered by psychedelic drugs, can have an enduring impact on some core facets of personality. In the present, balanced-order, placebo-controlled study, we investigated biological predictors of post-lysergic acid diethylamide (LSD) changes in personality. Nineteen healthy adults underwent resting state functional MRI scans under LSD (75µg, I.V.) and placebo (saline I.V.). The Revised NEO Personality Inventory (NEO-PI-R) was completed at screening and 2 weeks after LSD/placebo. Scanning sessions consisted of three 7.5-min eyes-closed resting-state scans, one of which involved music listening. A standardized preprocessing pipeline was used to extract measures of sample entropy, which characterizes the predictability of an fMRI time-series. Mixed-effects models were used to evaluate drug-induced shifts in brain entropy and their relationship with the observed increases in the personality trait openness at the 2-week follow-up. Overall, LSD had a pronounced global effect on brain entropy, increasing it in both sensory and hierarchically higher networks across multiple time scales. These shifts predicted enduring increases in trait openness. Moreover, the predictive power of the entropy increases was greatest for the music-listening scans and when “ego-dissolution” was reported during the acute experience. These results shed new light on how LSD-induced shifts in brain dynamics and concomitant subjective experience can be predictive of lasting changes in personality.

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Depression: Ketamine steps out of the darkness

May 4, 2016 / Depressive Disorders, Ketamine, Neuroscience, Papers, Psychology, Publications / By /

Abstract

The way in which ketamine exerts its antidepressant effects has been perplexing. Evidence that a metabolite of the drug is responsible, and acts on a different target from ketamine, might be the key to an answer.

Malinow, R. (2016). Depression: Ketamine steps out of the darkness. Nature. http://dx.doi.org/10.1038/nature17897

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Detailed pharmacological evaluation of methoxetamine (MXE), a novel psychoactive ketamine analogue—Behavioural, pharmacokinetic and metabolic studies in the Wistar rat

May 4, 2016 / Neuroscience, Papers, Publications / By / , , , , ,

Abstract

Methoxetamine (MXE) is a novel psychoactive compound (NPS) that emerged in 2010 as a substitute for the dissociative anaesthetic ketamine. MXE has a reputation of carrying a lower risk of harm than ketamine, however a number of deaths have been reported. Currently very little is known about the psychopharmacological effects of this compound or its toxicity; therefore we tested, in Wistar rats, the effects of MXE in a series of behavioural tasks, measured its pharmacokinetics and urinary metabolites.

Locomotor activity and its spatial characteristics (in the open field) and sensorimotor gating (prepulse inhibition; PPI) were evaluated after 5, 10 and 40 mg/kg subcutaneous (sc.) MXE. Pharmacokinetics and brain: serum ratios were evaluated after 10 mg/kg sc. MXE so that peak drug concentration data could be used to complement interpretation of maximal behavioural effects. Finally, quantification of metabolites in rat urine collected over 24 h was performed after single bolus of MXE 40 mg/kg sc.

5 and 10 mg/kg MXE induced significant locomotor stimulation, in addition it increased thigmotaxis and decreased time spent in the centre of the open field (indicative of anxiogenesis). By contrast, 40 mg/kg reduced locomotion and increased time spent in the centre of the arena, suggesting sedation/anaesthesia or stereotypy. The duration of effects was present for at least 60–90 min, although for 5 mg/kg, locomotion diminished after 60 min. MXE decreased baseline acoustic startle response (ASR) and disrupted PPI, irrespective of testing-onset. MXE (all doses) reduced habituation but only at 60 min. Maximal brain levels of MXE were observed 30 min after administration, remained high at 60 min and progressively declined to around zero after six hours. MXE accumulated in the brain; the brain: serum ratio was between 2.06 and 2.93 throughout the whole observation. The most abundant urinary metabolite was O-desmethylmethoxetamine followed by normethoxetamine.

To conclude, MXE acts behaviourally as a typical dissociative anaesthetic with stimulant and anxiogenic effects at lower doses, sedative/anaesthetic effects at higher doses, and as a disruptor of sensorimotor gating. Its duration of action exceeds that of ketamine which is consistent with reports from MXE users. The accumulation of the drug in brain tissue might reflect MXE’s stronger potency compared to ketamine and indicate increased toxicity.

Horsley, R. R., Lhotkova, E., Hajkova, K., Jurasek, B., Kuchar, M., & Palenicek, T. (2016). Detailed pharmacological evaluation of methoxetamine (MXE), a novel psychoactive ketamine analogue—Behavioural, pharmacokinetic and metabolic studies in the Wistar rat. Brain Research Bulletin. http://dx.doi.org/10.1016/j.brainresbull.2016.05.002
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NMDAR inhibition-independent antidepressant actions of ketamine metabolites

May 4, 2016 / Depressive Disorders, Ketamine, Neuroscience, Papers, Psychology, Publications / By / , , , , , ,

Abstract

Major depressive disorder affects around 16 per cent of the world population at some point in their lives. Despite the availability of numerous monoaminergic-based antidepressants, most patients require several weeks, if not months, to respond to these treatments, and many patients never attain sustained remission of their symptoms. The non-competitive, glutamatergic NMDAR (N-methyl-d-aspartate receptor) antagonist (R,S)-ketamine exerts rapid and sustained antidepressant effects after a single dose in patients with depression, but its use is associated with undesirable side effects. Here we show that the metabolism of (R,S)-ketamine to (2S,6S;2R,6R)-hydroxynorketamine (HNK) is essential for its antidepressant effects, and that the (2R,6R)-HNK enantiomer exerts behavioural, electroencephalographic, electrophysiological and cellular antidepressant-related actions in mice. These antidepressant actions are independent of NMDAR inhibition but involve early and sustained activation of AMPARs (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors). We also establish that (2R,6R)-HNK lacks ketamine-related side effects. Our data implicate a novel mechanism underlying the antidepressant properties of (R,S)-ketamine and have relevance for the development of next-generation, rapid-acting antidepressants.

Zanos, P., Moaddel, R., Morris, P. J., Georgiou, P., Fischell, J., Elmer, G. I., … & Dossou, K. S. (2016). NMDAR inhibition-independent antidepressant actions of ketamine metabolites. Nature. http://dx.doi.org/10.1038/nature17998
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LSD alters eyes-closed functional connectivity within the early visual cortex in a retinotopic fashion

April 29, 2016 / LSD, Neuroscience, Papers, Publications / By / , , , , , ,

Abstract

The question of how spatially organized activity in the visual cortex behaves during eyes-closed, lysergic acid diethylamide (LSD)-induced “psychedelic imagery” (e.g., visions of geometric patterns and more complex phenomena) has never been empirically addressed, although it has been proposed that under psychedelics, with eyes-closed, the brain may function “as if” there is visual input when there is none. In this work, resting-state functional connectivity (RSFC) data was analyzed from 10 healthy subjects under the influence of LSD and, separately, placebo. It was suspected that eyes-closed psychedelic imagery might involve transient local retinotopic activation, of the sort typically associated with visual stimulation. To test this, it was hypothesized that, under LSD, patches of the visual cortex with congruent retinotopic representations would show greater RSFC than incongruent patches. Using a retinotopic localizer performed during a nondrug baseline condition, nonadjacent patches of V1 and V3 that represent the vertical or the horizontal meridians of the visual field were identified. Subsequently, RSFC between V1 and V3 was measured with respect to these a priori identified patches. Consistent with our prior hypothesis, the difference between RSFC of patches with congruent retinotopic specificity (horizontal-horizontal and vertical-vertical) and those with incongruent specificity (horizontal-vertical and vertical-horizontal) increased significantly under LSD relative to placebo, suggesting that activity within the visual cortex becomes more dependent on its intrinsic retinotopic organization in the drug condition. This result may indicate that under LSD, with eyes-closed, the early visual system behaves as if it were seeing spatially localized visual inputs.

Roseman, L., Sereno, M. I., Leech, R., Kaelen, M., Orban, C., McGonigle, J., … & Carhart‐Harris, R. L. (2016). LSD alters eyes‐closed functional connectivity within the early visual cortex in a retinotopic fashion. Human Brain Mapping. http://dx.doi.org/10.1002/hbm.23224

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Neuropharmacology of N,N-Dimethyltryptamine

April 25, 2016 / DMT, Neuroscience, Papers, Psychology, Publications / By / ,

Abstract

N,N-Dimethyltryptamine (DMT) is an indole alkaloid widely found in plants and animals. It is best known for producing brief and intense psychedelic effects when ingested. Increasing evidence suggests that endogenous DMT plays important roles for a number of processes in the periphery and central nervous system, and may act as a neurotransmitter. This paper reviews the current literature of both the recreational use of DMT and its potential roles as an endogenous neurotransmitter. Pharmacokinetics, mechanisms of action in the periphery and central nervous system, clinical uses and adverse effects are also reviewed. DMT appears to have limited neurotoxicity and other adverse effects except for intense cardiovascular effects when administered intravenously in large doses. Because of its role in nervous system signaling, DMT may be a useful experimental tool in exploring how brain works, and may also be a useful clinical tool for treatment of anxiety and psychosis.

Carbonaro, T. M., & Gatch, M. B. (2016). Neuropharmacology of N, N-Dimethyltryptamine. Brain Research Bulletin. http://dx.doi.org/10.1016/j.brainresbull.2016.04.016

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