OPEN Foundation

Menu
Search
Close this search box.

Neuroscience

Ketamine and rapid-acting antidepressants: a new era in the battle against depression and suicide

May 24, 2018 / Depressive Disorders, Ketamine, Neuroscience, Papers, Psychology, Publications / By /

Abstract

Therapeutic medications for the treatment of depression have serious limitations, particularly delayed onset and low rates of efficacy. However, the discovery that a single subanesthetic dose of ketamine, a glutamate NMDA receptor channel blocker, can produce a rapid (within hours) antidepressant response that is sustained (about 1 week), even in patients considered treatment-resistant, has invigorated the field. In addition to these remarkable actions, ketamine has proven effective for the treatment of suicidal ideation. Efforts are under way to develop ketamine-like drugs with fewer side effects as well as agents that act at other sites within the glutamate neurotransmitter system. This includes ketamine metabolites and stereoisomers, drugs that act as NMDA allosteric modulators or that block mGluR2/3 autoreceptors. In addition, targets that enhance glutamate neurotransmission or synaptic function (or both), which are essential for the rapid and sustained antidepressant actions of ketamine in rodent models, are being investigated; examples are the muscarinic cholinergic antagonist scopolamine and activators of mechanistic target of rapamycin complex 1 (mTORC1) signaling, which is required for the actions of ketamine. The discovery of ketamine and its unique mechanisms heralds a new era with tremendous promise for the development of novel, rapid, and efficacious antidepressant medications.
Duman, R. S. (2018). Ketamine and rapid-acting antidepressants: a new era in the battle against depression and suicide. F1000Research, 7. 10.12688/f1000research.14344.1
Link to full text

Classics in Neuroimaging: The Serotonergic 2A Receptor System-from Discovery to Modern Molecular Imaging

May 15, 2018 / LSD, Neuroscience, Papers, Publications / By / , , , , ,

Abstract

Already in 1953, Woolley and Shaw speculated that serotonin could be involved in a range of central nervous system (CNS) disorders. Lysergic acid diethylamide (LSD) displayed an important role in this respect. It was used not only to antagonize biological effects of serotonin and to study the system itself, but also to identify serotonergic subtype receptors. The 5-HT2A receptor was discovered in the 1970s and identified as the responsible receptor mediating psychedelic effects of LSD. The development of positron emission tomography (PET) allowed to study this receptor system in vivo. Parameters such as abundance of 5-HT2A neuroreceptors or receptor occupancy can be determined using PET. As such, the development of 5-HT2A receptor tracers started immediately after the introduction of PET in the mid-1970s. In this Viewpoint, we provide a historical overview from the discovery of serotonin to the identification of the 5-HT2A receptor subtype and the subsequent development of 5-HT2A receptor subtype specific PET tracers over the last four decades. We emphasize the interplay between pharmacology, medicinal chemistry, radiochemistry, and nuclear medicine that is important while developing a PET tracer. Moreover, we highlight selected examples applying 5-HT2A receptor PET tracers within neurological diseases and drug occupancy studies.
T. L’Estrade, E., Hansen, H. D., Erlandsson, M., Ohlsson, T. G., Knudsen, G. M., & Herth, M. M. (2018). Classics in Neuroimaging: The Serotonergic 2A Receptor System—from Discovery to Modern Molecular Imaging. 10.1021/acschemneuro.8b00176
Link to full text

Biocatalytic production of psilocybin and derivatives in tryptophan synthase-enhanced reactions

May 11, 2018 / Mushrooms / Psilocybin, Neuroscience, Papers, Pharmacology & Chemistry, Publications / By / , , ,

Abstract

Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) is the main alkaloid of the fungal genus Psilocybe, the so-called “magic mushrooms.” The pharmaceutical interest in this psychotropic natural product as a future medication to treat depression and anxiety is strongly re-emerging. Here, we present an enhanced enzymatic route of psilocybin production by adding TrpB, the tryptophan synthase of the mushroom Psilocybe cubensis, to the reaction. We capitalized on its substrate flexibility and show psilocybin formation from 4-hydroxyindole and l-serine, which are less cost-intensive substrates, compared to the previous method. Furthermore, we show enzymatic production of 7-phosphoryloxytryptamine (isonorbaeocystin), a non-natural congener of the Psilocybe alkaloid norbaeocystin (4-phosphoryloxytryptamine), and of serotonin (5-hydroxytryptamine) by means of the same in vitro approach.

Blei, F., Baldeweg, F., Fricke, J., & Hoffmeister, D. (2018). Biocatalytic Production of Psilocybin and Derivatives in Tryptophan Synthase‐Enhanced Reactions. Chemistry–A European Journal, 24(40), 10028-10031., 10.1002/chem.201801047.
Link to full text

Ibogaine Acute Administration in Rats Promotes Wakefulness, Long-Lasting REM Sleep Suppression, and a Distinctive Motor Profile

April 27, 2018 / Iboga / Ibogaine, Neuroscience, Papers, Publications / By / , , , , , ,

Abstract

Ibogaine is a potent psychedelic alkaloid that has been the focus of intense research because of its intriguing anti-addictive properties. According to anecdotic reports, ibogaine has been originally classified as an oneirogenic psychedelic; i.e., induces a dream-like cognitive activity while awake. However, the effects of ibogaine administration on wakefulness (W) and sleep have not been thoroughly assessed. The main aim of our study was to characterize the acute effects of ibogaine administration on W and sleep. For this purpose, polysomnographic recordings on chronically prepared rats were performed in the light phase during 6 h. Animals were treated with ibogaine (20 and 40 mg/kg) or vehicle, immediately before the beginning of the recordings. Furthermore, in order to evaluate associated motor behaviors during the W period, a different group of animals was tested for 2 h after ibogaine treatment on an open field with video-tracking software. Compared to control, animals treated with ibogaine showed an increase in time spent in W. This effect was accompanied by a decrease in slow wave sleep (SWS) and rapid-eye movements (REM) sleep time. REM sleep latency was significantly increased in animals treated with the higher ibogaine dose. While the effects on W and SWS were observed during the first 2 h of recordings, the decrement in REM sleep time was observed throughout the recording time. Accordingly, ibogaine treatment with the lower dose promoted an increase on locomotion, while tremor and flat body posture were observed only with the higher dose in a time-dependent manner. In contrast, head shake response, a behavior which has been associated in rats with the 5HT2A receptor activation by hallucinogens, was not modified. We conclude that ibogaine promotes a waking state that is accompanied by a robust and long-lasting REM sleep suppression. In addition, it produces a dose-dependent unusual motor profile along with other serotonin-related behaviors. Since ibogaine is metabolized to produce noribogaine, further experiments are needed to elucidate if the metabolite and/or the parent drug produced these effects.
González, J., Prieto, J. P., Rodríguez, P., Cavelli, M., Benedetto, L., Mondino, A., … & Torterolo, P. (2018). Ibogaine Acute Administration in Rats Promotes Wakefulness, Long-Lasting REM Sleep Suppression, and a Distinctive Motor Profile. Frontiers in pharmacology, 9. 10.3389/fphar.2018.00374
Link to full text

Psilocybin modulates functional connectivity of the amygdala during emotional face discrimination

April 25, 2018 / Mushrooms / Psilocybin, Neuroscience, Papers, Psychology, Publications / By / , , , ,

Abstract

Recent studies suggest that the antidepressant effects of the psychedelic 5-HT2A receptor agonist psilocybin are mediated through its modulatory properties on prefrontal and limbic brain regions including the amygdala. To further investigate the effects of psilocybin on emotion processing networks, we studied for the first-time psilocybin’s acute effects on amygdala seed-to-voxel connectivity in an event-related face discrimination task in 18 healthy volunteers who received psilocybin and placebo in a double-blind balanced cross-over design. The amygdala has been implicated as a salience detector especially involved in the immediate response to emotional face content. We used beta-series amygdala seed-to-voxel connectivity during an emotional face discrimination task to elucidate the connectivity pattern of the amygdala over the entire brain.

When we compared psilocybin to placebo, an increase in reaction time for all three categories of affective stimuli was found. Psilocybin decreased the connectivity between amygdala and the striatum during angry face discrimination. During happy face discrimination, the connectivity between the amygdala and the frontal pole was decreased. No effect was seen during discrimination of fearful faces. Thus, we show psilocybin’s effect as a modulator of major connectivity hubs of the amygdala. Psilocybin decreases the connectivity between important nodes linked to emotion processing like the frontal pole or the striatum. Future studies are needed to clarify whether connectivity changes predict therapeutic effects in psychiatric patients.

Grimm, O., Kraehenmann, R., Preller, K. H., Seifritz, E., & Vollenweider, F. X. (2018). Psilocybin modulates functional connectivity of the amygdala during emotional face discrimination. European Neuropsychopharmacology. 10.1016/j.euroneuro.2018.03.016
Link to full text

Ketamine Effects on EEG during Therapy of Treatment-Resistant Generalized Anxiety and Social Anxiety

April 24, 2018 / Depressive Disorders, Ketamine, Neuroscience, Papers, Psychology, Publications / By / , , , , ,

Abstract

BACKGROUND:
Ketamine is swiftly effective in a range of neurotic disorders that are resistant to conventional antidepressant and anxiolytic drugs. The neural basis for its therapeutic action is unknown. Here we report the effects of ketamine on the EEG of patients with treatment-resistant generalized anxiety and social anxiety disorders.
METHODS:
Twelve patients with refractory DSM-IV generalized anxiety disorder and/or social anxiety disorder provided EEG during 10 minutes of relaxation before and 2 hours after receiving double-blind drug administration. Three ascending ketamine dose levels (0.25, 0.5, and 1 mg/kg) and midazolam (0.01 mg/kg) were given at 1-week intervals to each patient, with the midazolam counterbalanced in dosing position across patients. Anxiety was assessed pre- and postdose with the Fear Questionnaire and HAM-A.
RESULTS:
Ketamine dose-dependently improved Fear Questionnaire but not HAM-A scores, decreased EEG power most at low (delta) frequency, and increased it most at high (gamma) frequency. Only the decrease in medium-low (theta) frequency at right frontal sites predicted the effect of ketamine on the Fear Questionnaire. Ketamine produced no improvement in Higuchi’s fractal dimension at any dose or systematic changes in frontal alpha asymmetry.
CONCLUSIONS:
Ketamine may achieve its effects on treatment-resistant generalized anxiety disorder and social anxiety disorder through related mechanisms to the common reduction by conventional anxiolytic drugs in right frontal theta. However, in the current study midazolam did not have such an effect, and it remains to be determined whether, unlike conventional anxiolytics, ketamine changes right frontal theta when it is effective in treatment-resistant depression.
Shadli, S. M., Kawe, T., Martin, D., McNaughton, N., Neehoff, S., & Glue, P. (2018). Ketamine Effects on EEG during Therapy of Treatment-Resistant Generalized Anxiety and Social Anxiety. International Journal of Neuropsychopharmacology. 10.1093/ijnp/pyy032
Link to full text

Indolethylamine-N-methyltransferase Polymorphisms: Genetic and Biochemical Approaches for Study of Endogenous N,N,-dimethyltryptamine

April 23, 2018 / DMT, Neuroscience, Papers, Psychiatry & Medicine, Psychology, Psychotic Disorders, Publications / By /

Abstract

N,N-dimethyltryptamine (DMT) is a powerful serotonergic psychedelic whose exogenous administration elicits striking psychedelic effects in humans. Studies have identified DMT and analogous compounds (e.g., 5-hydroxy-DMT, 5-methoxy-DMT) alongside of an enzyme capable of synthesizing DMT endogenously from tryptamine, indolethylamine-N-methyltransferase (INMT), in human and several other mammalian tissues. Subsequently, multiple hypotheses for the physiological role of endogenous DMT have emerged, from proposed immunomodulatory functions to an emphasis on the overlap between the mental states generated by exogenous DMT and naturally occurring altered states of consciousness; e.g., schizophrenia. However, no clear relationship between endogenous DMT and naturally occurring altered states of consciousness has yet been established from in vivo assays of DMT in bodily fluids. The advent of genetic screening has afforded the capability to link alterations in the sequence of specific genes to behavioral and molecular phenotypes via expression of identified single nucleotide polymorphisms (SNPs) in cell and animal models. As SNPs in INMT may impact endogenous DMT synthesis and levels via changes in INMT expression and/or INMT structure and function, these combined genetic and biochemical approaches circumvent the limitations of assaying DMT in bodily fluids and may augment data from prior in vitro and in vivo work. Therefore, all reported SNPs in INMTwere amassed from genetic and biochemical literature and genomic databases to consolidate a blueprint for future studies aimed at elucidating whether DMT plays a physiological role.

Dean, J. G. (2018). Indolethylamine-N-methyltransferase polymorphisms: genetic and biochemical approaches for study of endogenous N, N,-dimethyltryptamine. Frontiers in neuroscience, 12.,  10.3389/fnins.2018.00232
Link to full text

Hypothesis: The Psychedelic Ayahuasca Heals Traumatic Memories via a Sigma 1 Receptor-Mediated Epigenetic-Mnemonic Process

April 5, 2018 / Anxiety Disorders / PTSD, Ayahuasca, DMT, Neuroscience, Papers, Psychology, Publications / By /

Abstract

Ayahuasca ingestion modulates brain activity, neurotransmission, gene expression and epigenetic regulation. N,N-Dimethyltryptamine (DMT, one of the alkaloids in Ayahuasca) activates sigma 1 receptor (SIGMAR1) and others. SIGMAR1 is a multi-faceted stress-responsive receptor which promotes cell survival, neuroprotection, neuroplasticity, and neuroimmunomodulation. Simultaneously, monoamine oxidase inhibitors (MAOIs) also present in Ayahuasca prevent the degradation of DMT. One peculiarity of SIGMAR1 activation and MAOI activity is the reversal of mnemonic deficits in pre-clinical models. Since traumatic memories in post-traumatic stress disorder (PTSD) are often characterised by “repression” and PTSD patients ingesting Ayahuasca report the retrieval of such memories, it cannot be excluded that DMT-mediated SIGMAR1 activation and the concomitant MAOIs effects during Ayahuasca ingestion might mediate such “anti-amnesic” process. Here I hypothesise that Ayahuasca, via hyperactivation of trauma and emotional memory-related centres, and via its concomitant SIGMAR1- and MAOIs- induced anti-amnesic effects, facilitates the retrieval of traumatic memories, in turn making them labile (destabilised). As Ayahuasca alkaloids enhance synaptic plasticity, increase neurogenesis and boost dopaminergic neurotransmission, and those processes are involved in memory reconsolidation and fear extinction, the fear response triggered by the memory can be reprogramed and/or extinguished. Subsequently, the memory is stored with this updated significance. To date, it is unclear if new memories replace, co-exist with or bypass old ones. Although the mechanisms involved in memory are still debated, they seem to require the involvement of cellular and molecular events, such as reorganisation of homo and heteroreceptor complexes at the synapse, synaptic plasticity, and epigenetic re-modulation of gene expression. Since SIGMAR1 mobilises synaptic receptor, boosts synaptic plasticity and modulates epigenetic processes, such effects might be involved in the reported healing of traumatic memories in PTSD patients. If this theory proves to be true, Ayahuasca could come to represent the only standing pharmacological treatment which targets traumatic memories in PTSD. Lastly, since SIGMAR1 activation triggers both epigenetic and immunomodulatory programmes, the mechanism here presented could help understanding and treating other conditions in which the cellular memory is dysregulated, such as cancer, diabetes, autoimmune and neurodegenerative pathologies and substance addiction.
Inserra, A. (2018). Hypothesis: The Psychedelic Ayahuasca Heals Traumatic Memories via a Sigma 1 Receptor-Mediated Epigenetic-Mnemonic Process. Frontiers in pharmacology, 9, 330. 10.3389/fphar.2018.00330
Link to full text

Out of the box: A psychedelic model to study the creative mind

March 23, 2018 / Anxiety Disorders / PTSD, Depressive Disorders, Mushrooms / Psilocybin, Neuroscience, Papers, Psychiatry & Medicine, Publications / By /

Abstract

Our creativity is challenged daily when facing new situations asking for novel solutions. Creativity, a multicomponent construct includes flexible divergent and rigid convergent thinking. Psychedelic drugs like psilocybin can enhance creativity and affect state of mind (mood, empathy, openness). Of note, flexible thinking is disturbed in psychopathological conditions like anxiety disorders and depression and preliminary findings have shown psychedelics to be efficacious in the treatment of those conditions. The question how psychedelics induce this state of enhanced flexible thinking remains to be answered and investigating the neurobiology underlying this phenomenon will not only help in understanding why psychedelics are of use in the therapeutic setting but also in other settings where flexible thinking is challenged. A model including neuronal networks, neurotransmitters and personal factors playing a role in this process will be proposed which can be put to the test by means of placebo-controlled pharmaco-imaging studies in healthy volunteers.

Kuypers, K. P. C. (2018). Out of the box: A psychedelic model to study the creative mind. Medical hypotheses, 115, 13-16.,  10.1016/j.mehy.2018.03.010

Link to full text

Salvinorin A preserves cerebral pial artery autoregulation after forebrain ischemia via the PI3K/AKT/cGMP pathway

March 15, 2018 / Neuroscience, Papers, Publications, Salvia / Salvinorin A / By / , , , ,

Abstract

This study aimed to investigate the protective effect of salvinorin A on the cerebral pial artery after forebrain ischemia and explore related mechanisms. Thirty Sprague-Dawley rats received forebrain ischemia for 10 min. The dilation responses of the cerebral pial artery to hypercapnia and hypotension were assessed in rats before and 1 h after ischemia. The ischemia reperfusion (IR) control group received DMSO (1 µL/kg) immediately after ischemia. Two different doses of salvinorin A (10 and 20 µg/kg) were administered following the onset of reperfusion. The 5th, 6th, and 7th groups received salvinorin A (20 µg/kg) and LY294002 (10 µM), L-NAME (10 μM), or norbinaltorphimine (norBIN, 1 μM) after ischemia. The levels of cGMP in the cerebrospinal fluid (CSF) were also measured. The phosphorylation of AKT (p-AKT) was measured in the cerebral cortex by western blot at 24 h post-ischemia. Cell necrosis and apoptosis were examined by hematoxylin-eosin staining (HE) and TUNEL staining, respectively. The motor function of the rats was evaluated at 1, 2, and 5 days post-ischemia. The dilation responses of the cerebral pial artery were significantly impaired after ischemia and were preserved by salvinorin A treatment. In addition, salvinorin A significantly increased the levels of cGMP and p-AKT, suppressed cell necrosis and apoptosis of the cerebral cortex and improved the motor function of the rats. These effects were abolished by LY294002, L-NAME, and norBIN. Salvinorin A preserved cerebral pial artery autoregulation in response to hypercapnia and hypotension via the PI3K/AKT/cGMP pathway.
Dong, H. P., Zhou, W., Ma, X. X., He, Z. Z., & Wang, Z. H. (2018). Salvinorin A preserves cerebral pial artery autoregulation after forebrain ischemia via the PI3K/AKT/cGMP pathway. Brazilian Journal of Medical and Biological Research, 51(5). 10.1590/1414-431X20176714
Link to full text

interested in becoming a trained psychedelic-assisted therapist?

Management of Psychedelic-Related Complications - Online Event - Nov 20th

REGISTER NOW