Concentration-effect relationships of plasma caffeine on EEG delta power and cardiac autonomic activity during human sleep

Acute caffeine intake affects brain and cardiovascular physiology, yet the concentration-effect relationships on the electroencephalogram and cardiac autonomic activity during sleep are poorly understood. To tackle this question, we simultaneously quantified the plasma caffeine concentration with ultra-high-performance liquid chromatography, as well as the electroencephalogram, heart rate and high-frequency (0.15-0.4 Hz) spectral power in heart rate variability, representing parasympathetic activity, with standard polysomnography during undisturbed human sleep. Twenty-one healthy young men in randomized, double-blind, crossover fashion, ingested 160 mg caffeine or placebo in a delayed, pulsatile-release caffeine formula at their habitual bedtime, and initiated a 4-hr sleep opportunity 4.5 hr later. The mean caffeine levels during sleep exhibited high individual variability between 0.2 and 18.4 μmol L$^{-1}$ . Across the first two non-rapid-eye-movement (NREM)-rapid-eye-movement sleep cycles, electroencephalogram delta (0.75-2.5 Hz) activity and heart rate were reliably modulated by waking and sleep states. Caffeine dose-dependently reduced delta activity and heart rate, and increased high-frequency heart rate variability in NREM sleep when compared with placebo. The average reduction in heart rate equalled 3.24 ± 0.77 beats per minute. Non-linear statistical models suggest that caffeine levels above ~7.4 μmol L$^{-1}$ decreased electroencephalogram delta activity, whereas concentrations above ~4.3 μmol L$^{-1}$ and ~ 4.9 μmol L$^{-1}$ , respectively, reduced heart rate and increased high-frequency heart rate variability. These findings provide quantitative concentration-effect relationships of caffeine, electroencephalogram delta power and cardiac autonomic activity, and suggest increased parasympathetic activity during sleep after intake of caffeine

Molecular and Functional Imaging Studies of Psychedelic Drug Action in Animals and Humans

Hallucinogens are a loosely defined group of compounds including LSD, N,N-dimethyltryptamines, mescaline, psilocybin/psilocin, and 2,5-dimethoxy-4-methamphetamine (DOM), which can evoke intense visual and emotional experiences. We are witnessing a renaissance of research interest in hallucinogens, driven by increasing awareness of their psychotherapeutic potential. As such, we now present a narrative review of the literature on hallucinogen binding in vitro and ex vivo, and the various molecular imaging studies with positron emission tomography (PET) or single photon emission computer tomography (SPECT). In general, molecular imaging can depict the uptake and binding distribution of labelled hallucinogenic compounds or their congeners in the brain, as was shown in an early PET study with N1-([11C]-methyl)-2-bromo-LSD ([11C]-MBL); displacement with the non-radioactive competitor ketanserin confirmed that the majority of [11C]-MBL specific binding was to serotonin 5-HT2A receptors. However, interactions at serotonin 5HT1A and other classes of receptors and pleotropic effects on second messenger pathways may contribute to the particular experiential phenomenologies of LSD and other hallucinogenic compounds. Other salient aspects of hallucinogen action include permeability to the blood–brain barrier, the rates of metabolism and elimination, and the formation of active metabolites. Despite the maturation of radiochemistry and molecular imaging in recent years, there has been only a handful of PET or SPECT studies of radiolabeled hallucinogens, most recently using the 5-HT2A/2C agonist N-(2[11CH3O]-methoxybenzyl)-2,5-dimethoxy- 4-bromophenethylamine ([11C]Cimbi-36). In addition to PET studies of target engagement at neuroreceptors and transporters, there is a small number of studies on the effects of hallucinogenic compounds on cerebral perfusion ([15O]-water) or metabolism ([18F]-fluorodeoxyglucose/FDG). There remains considerable scope for basic imaging research on the sites of interaction of hallucinogens and their cerebrometabolic effects; we expect that hybrid imaging with PET in conjunction with functional magnetic resonance imaging (fMRI) should provide especially useful for the next phase of this research

Urinary concentrations of GHB and its novel amino acid and carnitine conjugates following controlled GHB administration to humans

Gamma-hydroxybutyrate (GHB) remains a challenging clinical/forensic toxicology drug. Its rapid elimination to endogenous levels mainly causes this. Especially in drug-facilitated sexual assaults, sample collection often occurs later than the detection window for GHB. We aimed to investigate new GHB conjugates with amino acids (AA), fatty acids, and its organic acid metabolites for their suitability as ingestion/application markers in urine following controlled GHB administration to humans. We used LC–MS/MS for validated quantification of human urine samples collected within two randomized, double-blinded, placebo-controlled crossover studies (GHB 50 mg/kg, 79 participants) at approximately 4.5, 8, 11, and 28 h after intake. We found significant differences (placebo vs. GHB) for all but two analytes at 4.5 h. Eleven hours post GHB administration, GHB, GHB-AAs, 3,4-dihydroxybutyric acid, and glycolic acid still showed significantly higher concentrations; at 28 h only GHB-glycine. Three different discrimination strategies were evaluated: (a) GHB-glycine cut-off concentration (1 µg/mL), (b) metabolite ratios of GHB-glycine/GHB (2.5), and (c) elevation threshold between two urine samples (> 5). Sensitivities were 0.1, 0.3, or 0.5, respectively. Only GHB-glycine showed prolonged detection over GHB, mainly when compared to a second time- and subject-matched urine sample (strategy c)

Nocturnal sodium oxybate increases the anterior cingulate cortex magnetic resonance glutamate signal upon awakening

Clinical guidelines recommend sodium oxybate (SXB; the sodium salt of γ-hydroxybutyrate) for the treatment of disturbed sleep and excessive daytime sleepiness in narcolepsy, yet the underlying mode of action is elusive. In a randomised controlled trial in 20 healthy volunteers, we aimed at establishing neurochemical changes in the anterior cingulate cortex (ACC) following SXB-enhanced sleep. The ACC is a core neural hub regulating vigilance in humans. At 2:30 a.m., we administered in a double-blind cross-over manner an oral dose of 50 mg/kg SXB or placebo, to enhance electroencephalography-defined sleep intensity in the second half of nocturnal sleep (11:00 p.m. to 7:00 a.m.). Upon scheduled awakening, we assessed subjective sleepiness, tiredness and mood and measured two-dimensional, J-resolved, point-resolved magnetic resonance spectroscopy (PRESS) localisation at 3-Tesla field strength. Following brain scanning, we used validated tools to quantify psychomotor vigilance test (PVT) performance and executive functioning. We analysed the data with independent t tests, false discovery rate (FDR) corrected for multiple comparisons. The morning glutamate signal (at 8:30 a.m.) in the ACC was specifically increased after SXB-enhanced sleep in all participants in whom good-quality spectroscopy data were available (n = 16; pFDR < 0.002). Further, global vigilance (10th-90th inter-percentile range on the PVT) was improved (pFDR < 0.04) and median PVT response time was shorter (pFDR < 0.04) compared to placebo. The data indicate that elevated glutamate in the ACC could provide a neurochemical mechanism underlying SXB's pro-vigilant efficacy in disorders of hypersomnolence

Potential therapeutic effects of an ayahuasca-inspired N,N-DMT and harmine formulation: a controlled trial in healthy subjects

Background: There is growing scientific evidence for the therapeutic benefits of the Amazonian plant-based psychedelic “ayahuasca” for neuropsychiatric disorders such as depression and anxiety. However, there are certain challenges when incorporating botanical ayahuasca into biomedical research and clinical therapy environments. Formulations inspired by ayahuasca, which contain specific and standardized active components, are a potential remedy. Methods: We investigated subjective acute and persisting effects of a novel formulation containing the reversible monoamine oxidase inhibitor harmine (orodispersible tablet containing 100 mg MAO-I) and N,N-dimethyltryptamine (incremental intranasal dosing of up to 100 mg DMT), compared with two other conditions, namely harmine alone and placebo, in a crossover RCT in 31 healthy male subjects. Results: DMT + harmine, but not harmine alone, induced a psychedelic experience assessed with the 5D-ASC rating scale [global score: F(2,60) = 80.21, p &lt; 0.001] and acute experience sampling items over time, characterized by psychological insights [PIQ, F(2,58.5) = 28.514, p &lt; 0.001], emotional breakthroughs [EBI, F(2,60) = 26.509, p &lt; 0.001], and low scores on the challenging experience questionnaire [CEQ, F(2,60) = 12.84, p &lt; 0.001]. Participants attributed personal and spiritual significance to the experience (GSR) with mainly positive persisting effects (PEQ) at 1- and 4-months follow-up. Acute drug effects correlated positively with persisting effects. We found no changes in trait measures of personality, psychological flexibility, or general well-being, and no increases in psychopathology (SCL-90-R) were reported. Discussion and Conclusion: Our results suggest that the experience induced by the standardized DMT + harmine formulation induces a phenomenologically rich psychedelic experience, demonstrates good psychological safety and tolerability, is well tolerated, and induces beneficial psychological processes that could possibly support psychotherapy. Further studies are required to investigate the psychotherapeutic potential in patients

Overcoming the clinical challenges of traditional ayahuasca: a first-in-human trial exploring novel routes of administration of N,N-Dimethyltryptamine and harmine

Recently, the Amazonian plant medicine “ayahuasca”—containing the psychedelic compound N,N-dimethyltryptamine (DMT) and numerous β-carboline alkaloids, such as harmine—has been suggested to exhibit beneficial effects in patients with affective and other mental health disorders. Although ayahuasca ingestion is considered safe, its pharmacokinetics/pharmacodynamics and tolerability profile pose some challenges and may limit the clinical applicability in vulnerable patient populations. While overdosing and the admixture of intolerable plant constituents may explain some of the common adverse reactions, the peroral route of administration may represent another relevant source of gastro-intestinal intolerabilities and unpredictable pharmacokinetics across users. To overcome these challenges, the present work aimed at creating ayahuasca-analogue formulations with improved pharmacokinetics and tolerability profiles. To this end, we developed peroral formulas and compared them with parenteral formulas specifically designed to circumvent the gastro-intestinal tract. In more detail, peroral administration of a capsule (containing purified DMT and harmine) was tested against a combined administration of an oromucosal harmine tablet and an intranasal DMT spray at two dose levels in an open-label within-subject study in 10 healthy male subjects. Pharmacokinetic and pharmacodynamic profiles were assessed by means of continuous blood sampling, vital sign monitoring, and psychometric assessments. Common side effects induced by traditional herbal ayahuasca such as nausea, vomiting, and diarrhea were significantly attenuated by our DMT/harmine formulations. While all preparations were well tolerated, the combined buccal/intranasal administration of harmine and DMT yielded substantially improved pharmacokinetic profiles, indicated by significantly reduced variations in systemic exposure. In conclusion, the combined buccal/intranasal administration of harmine and DMT is an innovative approach that may pave the way towards a safe, rapid-acting, and patient-oriented administration of DMT/harmine for the treatment of affective disorders.Clinical Trial Registration:clinicaltrials.gov, identifier NCT0471633

Gamma-hydroxybutyrate increases brain resting-state functional connectivity of the salience network and dorsal nexus in humans

According to the triple network hypothesis the brain is equipped with three core neurocognitive networks: the default mode (DMN), the salience (SN), and the central executive (CEN) network. Moreover, the so called dorsal nexus, has met growing interest as it is a hub region connecting these three networks. Assessment of resting-state functional connectivity (rsFC) of these networks enables the elucidation of drug-induced brain alterations. Gamma-hydroxybutyrate (GHB) is a GHB/GABA-B receptor agonist that induces a paradoxical state of mixed stimulation and sedation at moderate doses, which makes it a valuable tool to investigate neural signatures of subjective drug effects. Employing a placebo-controlled, double-blind, randomized, cross-over design, we assessed the effects of GHB (35 mg/kg p. o.) in 19 healthy male subjects on DMN-, SN-, CEN-, and dorsal nexus-rsFC measured by functional magnet resonance imaging and applying independent component as well as seed-based analyses, while subjective drug effects were investigated using visual analog scales (VAS). Subjectively, GHB increased VAS ratings of a general drug effect, stimulation, and sedation. Intrinsic DMN-, and CEN-rsFC remained largely unchanged under GHB, but the drug increased SN-DMN-rsFC and SN-dorsal nexus-rsFC, while dorsal nexus-rsFC was reciprocally increased to both the SN (right anterior insula) and to the CEN (right middle frontal gyrus). Increased sedation significantly predicted the observed SN-dorsal nexus-rsFC. In conclusion, GHB generates a unique stimulant/sedative subjective state that is paralleled by a complex pattern of increased functional connectivity encompassing all three core neurocognitive networks of the brain, while increased SN-dorsal nexus-rsFC was demonstrated to be a potential signature of the sedative component of the drug effect

A pilot study of cerebral metabolism and serotonin 5-HT2A receptor occupancy in rats treated with the psychedelic tryptamine DMT in conjunction with the MAO inhibitor harmine

Rationale: The psychedelic effects of the traditional Amazonian botanical decoction known as ayahuasca are often attributed to agonism at brain serotonin 5-HT2A receptors by N,N-dimethyltryptamine (DMT). To reduce first pass metabolism of oral DMT, ayahuasca preparations additionally contain reversible monoamine oxidase A (MAO-A) inhibitors, namely β-carboline alkaloids such as harmine. However, there is lacking biochemical evidence to substantiate this pharmacokinetic potentiation of DMT in brain via systemic MAO-A inhibition.Objectives: We measured the pharmacokinetic profile of harmine and/or DMT in rat brain, and tested for pharmacodynamic effects on brain glucose metabolism and DMT occupancy at brain serotonin 5-HT2A receptors.Methods: We first measured brain concentrations of harmine and DMT after treatment with harmine and/or DMT at low sub-cutaneous doses (1 mg/kg each) or harmine plus DMT at moderate doses (3 mg/kg each). In the same groups of rats, we also measured ex vivo the effects of these treatments on the availability of serotonin 5-HT2A receptors in frontal cortex. Finally, we explored effects of DMT and/or harmine (1 mg/kg each) on brain glucose metabolism with [18F]FDG-PET.Results: Results confirmed that co-administration of harmine inhibited the formation of the DMT metabolite indole-3-acetic acid (3-IAA) in brain, while correspondingly increasing the cerebral availability of DMT. However, we were unable to detect any significant occupancy by DMT at 5-HT2A receptors measured ex vivo, despite brain DMT concentrations as high as 11.3 µM. We did not observe significant effects of low dose DMT and/or harmine on cerebral [18F]FDG-PET uptake.Conclusion: These preliminary results call for further experiments to establish the dose-dependent effects of harmine/DMT on serotonin receptor occupancy and cerebral metabolism

Repurposing gamma-hydroxybutyrate for neuropsychiatric disorders? Examining its effects on sleep neurophysiology, neuro- immune interaction and brain metabolites in healthy men

Neuropsychiatric disorders represent a major health care challenge of the 21st century. Despite the high prevalence of these disorders, most of the currently available psychopharmacological therapies show suboptimal efficacy. Thus, there is an urgent need for novel, effective and sustainable psychiatric treatments. Unfortunately, major pharmaceutical companies have abandoned neuropsychiatric research due to the high risk of failure associated with the particular complexity of psychopharmacological drug development. Thus, drug repurposing has gained substantial interest in research areas of high failure risk, such as psychiatry. Drug repurposing means to discover new therapeutic aspects of an existing or abandoned drug, with the goal of expanding the drug’s therapeutic indications. A promising repurposing candidate, which is under current investigation for the treatment of several neuropsychiatric disorders, is gamma-hydroxybutyrate (GHB), also known as liquid ecstasy, k.o. drops or date-rape drug. GHB is an endogenous GABAB/GHB receptor agonist that occurs naturally in the mammalian brain. Due to its stimulating, euphorogenic and prosexual effects it is abused recreationally. Beyond that, GHB is approved for the treatment of alcohol withdrawal syndrome and narcolepsy with cataplexy. The latter condition is characterized by severe sleep disturbances, excessive daytime sleepiness and cataplexy. Intriguingly, nocturnal administration of GHB has proven potency to reduce excessive daytime sleepiness and the number of cataplectic episodes in narcolepsy patients. Likewise, GHB has been effective in ameliorating sleep and waking quality in Parkinson’s disease and fibromyalgia. Given the high prevalence of impaired sleep quality in neuropsychiatric diseases, GHB has become a promising candidate to treat sleep disturbances and insomnia-related symptoms in these disorders. Despite GHB’s therapeutic potential, little is known about its underlying mechanisms of action. Thus, in the current thesis, I explored the effects of nocturnal GHB administration on biological functions that are frequently impaired in neuropsychiatric patients, namely: sleep neurophysiology (chapter 2), neuro-immune interactions (chapter 3) and brain metabolism (chapter 4). To this end, GHB (50 mg/kg body weight) and placebo were administered in 20 young male volunteers at 2:30 am, in the middle of a sleep episode, the time when GHB is typically given in narcolepsy. The sleep study followed a randomized, double-blinded, balanced, cross- over design. In chapter 2, a detailed neurophysiological assessment of GHB’s sleep promoting effects was conducted, by analyzing the drug effects on sleep architecture, regional changes in electroencephalographic (EEG) sleep spectra, brain electrical sources, and lagged phase synchronization. GHB prolonged slow wave sleep (stage N3) at the cost of rapid-eye-movement (REM) sleep. Furthermore, it enhanced delta- theta (0.5-8 Hz) activity in non-rapid-eye-movement (NREM) and REM sleep, while reducing activity in the spindle frequency range (13-15 Hz) in sleep stage N2. The increase in delta power predominated in medial prefrontal cortex, parahippocampal and fusiform gyri, and posterior cingulate cortex. Theta power was particularly increased in the prefrontal cortex and both temporal poles. Finally, the brain areas which were significantly affected by GHB, also exhibited increased lagged phase synchronization in the theta range among each other. This detailed neurophysiological analysis revealed distinct similarities between GHB-augmented sleep and physiologically augmented sleep as seen in recovery sleep after prolonged wakefulness. The promotion of the sleep neurophysiological mechanisms by GHB may, thus, provide a rationale for GHB-induced sleep and waking quality in neuropsychiatric disorders beyond narcolepsy. In chapter 3, effects of GHB on neuro-immune interactions were explored. More specifically, tryptophan catabolites (TRYCATs), brain derived neurotrophic factor (BDNF), the cortisol awakening response (CAR) and affective states (Positive and Negative Affect Schedule, PANAS) were measured in the morning, following nocturnal GHB or placebo administration. GHB reduced morning plasma levels of the TRYCATs, indolelactic acid, kynurenine, kynurenic acid, 3- hydroxykynurenine, and quinolinic acid, the 3-hydroxykynurenine to kynurenic acid ratio and the CAR. Serotonin, tryptophan, and BDNF levels, as well as PANAS scores in the morning remained unchanged after nocturnal GHB challenge. These findings indicate, that GHB may protect the brain against the detrimental impact of inflammation and chronic stress on neuronal functioning and mood. This action may explain some of GHB’s therapeutic effects in neuropsychiatric disorders involving neuro-immunological pathologies. In chapter 4, the effects of GHB on post-awakening brain metabolite levels in the anterior cingulate cortex (ACC) were assessed using J- resolved magnetic resonance spectroscopy (JPRESS-MRS). Moreover, psychomotor vigilance, executive functions and subjective sleepiness were assessed. The analyses revealed increased morning glutamate levels in the ACC in all subjects in the GHB condition compared to placebo. Moreover, GHB reduced median reaction times on the psychomotor vigilance task. Executive functions and subjective sleepiness remained unaffected by the drug. It is hypothesized that GHB may reduce glutamate release during its acute phase, causing a presynaptic glutamate accumulation and a subsequent rebound when acute drug effects fade away in the early morning. With that, GHB may exert protecting effects against excitoxicity, by suppressing glutamate release during the night. On the other hand, this acute suppression may restore glutamate storages for the subsequent day, giving account for GHB’s wake-promoting effects. In chapter 5, the acute effects of GHB (20 and 35 mg/kg) on behavioral and neurophysiological correlates of performance and conflict monitoring (PM and CM) were assessed in 15 healthy male volunteers, using the Eriksen-Flanker paradigm in a randomized, double-blind, placebo-controlled, balanced, cross-over study. PM and CM represent two essential cognitive abilities, required to appropriately respond to demanding tasks and can be investigated by means of event-related brain potentials (ERP) and associated neuronal oscillations. Thereby, the error-related negativity (ERN) represents a correlate of PM, whereas the N2 component reflects the process of CM. GHB prolonged reaction times, without affecting error rates or post-error slowing. Moreover, GHB decreased ERN amplitudes and associated neuronal oscillations in the theta/alpha1 range. Similarly, neuronal oscillations associated with the N2 were reduced in the theta/alpha1 range, but conversely the N2 amplitude was increased. Hence, GHB shows a dissociating effect on electrophysiological correlates of PM and CM, which is suggested to be mediated by an acute inhibition of the ACC. In summary, the current thesis suggests that GHB may owe its unique clinical potential to the remarkable ability to enhance physiological sleep functions in a biomimetic manner. This biomimetic sleep enhancement may reduce oxidative stress load by decreasing the concentration of free-radical producing metabolites, such as 3- hydroxykynurenin. Moreover, GHB may protect the brain against excitotoxicity, by suppressing glutamate release during the night and reducing plasma levels of the neurotoxic TRYCAT quinolinic acid. On the other hand, GHB may promote waking-quality by reducing sleep pressure, restock cerebral energy reserves and provide refilled glutamate storages for the next day. Each of these attributes may reflect GHB’s unique capacity to induce a regenerative state of metabolic arrest similar to that found in natural sleep