The role of endogenous opioids in mindfulness and sham mindfulness-meditation for the direct alleviation of evoked chronic low back pain: a randomized clinical trial

Chronic low back pain (cLBP) is the most prevalent chronic pain condition. There are no treatments that haven been found to directly assuage evoked cLBP. To this extent, mindfulness-meditation is a promising pain therapy. Yet, it is unclear if meditation can be utilized to directly attenuate evoked chronic pain through endogenous opioids. A double-blind, randomized, and placebo-controlled clinical trial with a drug crossover design examined if mindfulness-meditation, as compared to sham mindfulness-meditation, attenuated straight leg-raise test evoked chronic pain during intravenous (0.15 mg/kg bolus + 0.15 mg/kg/hour maintenance) naloxone (opioid antagonist) and placebo-saline infusion. Fifty-nine individuals with cLBP (mean age = 46 years; 30 females) completed all study procedures. After the pre-intervention pain testing session, patients were randomized to a four-session (20-min/session) mindfulness (n = 30) or sham mindfulness-meditation (n = 29) intervention. After the interventions, mindfulness and sham mindfulness-meditation were associated with significant reductions in back pain during saline and naloxone infusion when compared to rest (non-meditation) in response to the cLBP-evoking straight leg-raise test. These results indicate that meditation directly reduces evoked chronic pain through non-opioidergic processes. Importantly, after the interventions, the mindfulness group reported significantly lower straight leg-raise induced pain than the sham mindfulness-meditation group during rest (non-meditation) and meditation. Mindfulness and sham mindfulness-meditation training was also associated with significantly lower Brief Pain Inventory severity and interference scores. The pain-relieving effects of mindfulness meditation were more pronounced than a robust sham-mindfulness meditation intervention, suggesting that non-reactive appraisal processes may be uniquely associated with improvements in chronic low-back pain.Trial Registration: ClinicalTrials.gov identifier: NCT04034004.

Cortical Acetylcholine Levels Correlate With Neurophysiologic Complexity During Subanesthetic Ketamine and Nitrous Oxide Exposure in Rats

BACKGROUND

Neurophysiologic complexity has been shown to decrease during states characterized by a depressed level of consciousness, such as sleep or anesthesia. Conversely, neurophysiologic complexity is increased during exposure to serotonergic psychedelics or subanesthetic doses of dissociative anesthetics. However, the neurochemical substrates underlying changes in neurophysiologic complexity are poorly characterized. Cortical acetylcholine appears to relate to cortical activation and changes in states of consciousness, but the relationship between cortical acetylcholine and complexity has not been formally studied. We addressed this gap by analyzing simultaneous changes in cortical acetylcholine (prefrontal and parietal) and neurophysiologic complexity before, during, and after subanesthetic ketamine (10 mg/kg/h) or 50% nitrous oxide.

METHODS

Under isoflurane anesthesia, adult Sprague Dawley rats (n = 24, 12 male and 12 female) were implanted with stainless-steel electrodes across the cortex to record monopolar electroencephalogram (0.5-175 Hz; 30 channels) and guide canulae in prefrontal and parietal cortices for local microdialysis quantification of acetylcholine levels. One subgroup of these rats was instrumented with a chronic catheter in jugular vein for ketamine infusion (n = 12, 6 male and 6 female). The electroencephalographic data were analyzed to determine subanesthetic ketamine or nitrous oxide-induced changes in Lempel-Ziv complexity and directed frontoparietal connectivity. Changes in complexity and connectivity were analyzed for correlation with concurrent changes in prefrontal and parietal acetylcholine.

RESULTS

Subanesthetic ketamine produced sustained increases in normalized Lempel-Ziv complexity (0.5-175 Hz; P < .001) and high gamma frontoparietal connectivity (125-175 Hz; P < .001). This was accompanied by progressive increases in prefrontal (104%; P < .001) and parietal (159%; P < .001) acetylcholine levels that peaked after 50 minutes of infusion. Nitrous oxide induction produced a transient increase in complexity (P < .05) and high gamma connectivity (P < .001), which was accompanied by increases (P < .001) in prefrontal (56%) and parietal (43%) acetylcholine levels. In contrast, the final 50 minutes of nitrous oxide administration were characterized by a decrease in prefrontal (38%; P < .001) and parietal (45%; P < .001) acetylcholine levels, reduced complexity (P < .001), and comparatively weaker frontoparietal high gamma connectivity (P < .001). Cortical acetylcholine and complexity were correlated with both subanesthetic ketamine (prefrontal: cluster-weighted marginal correlation [CW r] [144] = 0.42, P < .001; parietal: CW r[144] = 0.42, P < .001) and nitrous oxide (prefrontal: CW r[156] = 0.46, P < .001; parietal: CW r[156] = 0.56, P < .001) cohorts.

CONCLUSIONS

These data bridge changes in cortical acetylcholine with concurrent changes in neurophysiologic complexity, frontoparietal connectivity, and the level of consciousness.

Inactivation of Prefrontal Cortex Attenuates Behavioral Arousal Induced by Stimulation of Basal Forebrain During Sevoflurane Anesthesia

Cholinergic stimulation of prefrontal cortex (PFC) can reverse anesthesia. Conversely, inactivation of PFC can delay emergence from anesthesia. PFC receives cholinergic projections from basal forebrain, which contains wake-promoting neurons. However, the role of basal forebrain cholinergic neurons in arousal from the anesthetized state requires refinement, and it is currently unknown whether the arousal-promoting effect of basal forebrain is mediated through PFC. To address these gaps in knowledge, we implemented a novel approach to the use of chemogenetic stimulation and tested the role of basal forebrain cholinergic neurons in behavioral arousal during sevoflurane anesthesia. Next, we investigated the effect of tetrodotoxin-mediated inactivation of PFC on behavioral arousal produced by electrical stimulation of basal forebrain during sevoflurane anesthesia.

The Effects of Mindfulness-Based Stress Reduction on Trauma in Victims of Gun Violence: a Pilot Study

Objectives

Gun violence is a significant problem in the United States of America. Gun violence produces lifelong psychological adversity, trauma, and grief. In the face of this epidemic, efficacious therapies that assuage gun violence-based trauma and negative health are lacking.

Methods

The proposed, longitudinal pilot experiment examined the effects of an 8-week mindfulness-based stress reduction (MBSR) program on traumatized individuals as a direct consequence of gun violence. Twenty-four victims of gun violence (median age = 53 years; 21 female) completed measures of the primary outcome: trauma. Secondary outcomes were characterized as grief, depression, sleep quality, life satisfaction, and mindfulness. All assessments were administered before, after 5, and 8 weeks of MBSR training. It was hypothesized that trauma and other comorbidities would improve following MBSR. It was also predicted that outcomes would be significantly stronger from baseline to 5 weeks of MBSR training than from 5 to 8 weeks of training.

Results

Before MBSR, volunteers exhibited high levels of trauma, depression, sleep difficulty, and grief. Participation in MBSR was associated with improved trauma, depression, sleep difficulty, and life satisfaction. The most pronounced improvements in psychological disposition were exhibited within the first 5 weeks of MBSR. However, these benefits were largely preserved after completion of the course. Importantly, increases in dispositional mindfulness predicted lower trauma, complicated grief, and sleep difficulties.

Conclusions

The present findings should be interpreted with caution because they were derived from an uncontrolled, non-randomized trial. However, said findings suggest that MBSR may reduce trauma and improve overall well-being in gun violence victims.

Psychedelic-assisted therapy for functional neurological disorders: A theoretical framework and review of prior reports

Functional neurological disorders (FNDs), which are sometimes also referred to as psychogenic neurological disorders or conversion disorder, are common disabling neuropsychiatric disorders with limited treatment options. FNDs can present with sensory and/or motor symptoms, and, though they may mimic other neurological conditions, they are thought to occur via mechanisms other than those related to identifiable structural neuropathology and, in many cases, appear to be triggered and sustained by recognizable psychological factors. There is intriguing preliminary evidence to support the use of psychedelic‐assisted therapy in a growing number of psychiatric illnesses, including FNDs. We review the theoretical arguments for and against exploring psychedelic‐assisted therapy as a treatment for FNDs. We also provide an in‐depth discussion of prior published cases detailing the use of psychedelics for psychosomatic conditions, analyzing therapeutic outcomes from a contemporary neuroscientific vantage as informed by several recent neuroimaging studies on psychedelics and FNDs.

Biosynthesis and Extracellular Concentrations of N,N-dimethyltryptamine (DMT) in Mammalian Brain

N,N-dimethyltryptamine (DMT), a psychedelic compound identified endogenously in mammals, is biosynthesized by aromatic-L-amino acid decarboxylase (AADC) and indolethylamine-N-methyltransferase (INMT). Whether DMT is biosynthesized in the mammalian brain is unknown. We investigated brain expression of INMT transcript in rats and humans, co-expression of INMT and AADC mRNA in rat brain and periphery, and brain concentrations of DMT in rats. INMT transcripts were identified in the cerebral cortex, pineal gland, and choroid plexus of both rats and humans via in situ hybridization. Notably, INMT mRNA was colocalized with AADC transcript in rat brain tissues, in contrast to rat peripheral tissues where there existed little overlapping expression of INMT with AADC transcripts. Additionally, extracellular concentrations of DMT in the cerebral cortex of normal behaving rats, with or without the pineal gland, were similar to those of canonical monoamine neurotransmitters including serotonin. A significant increase of DMT levels in the rat visual cortex was observed following induction of experimental cardiac arrest, a finding independent of an intact pineal gland. These results show for the first time that the rat brain is capable of synthesizing and releasing DMT at concentrations comparable to known monoamine neurotransmitters and raise the possibility that this phenomenon may occur similarly in human brains.

Redistribution of Mature Smooth Muscle Markers in Brain Arteries in Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

Vascular smooth muscle cells (SMCs) undergo a series of dramatic changes in CADASIL, the most common inherited cause of vascular dementia and stroke. NOTCH3 protein accumulates and aggregates early in CADASIL, followed by loss of mature SMCs from the media of brain arteries and marked intimal proliferation. Similar intimal thickening is seen in peripheral arterial disease, which features pathological intimal cells including proliferative, dedifferentiated, smooth muscle-like cells deficient in SMC markers. Limited studies have been performed to investigate the differentiation state and location of SMCs in brain vascular disorders. Thus, we investigated the distribution of cells expressing SMC markers in a group of genetically characterized, North American CADASIL brains. We quantified brain RNA abundance of these markers in nine genetically verified cases of CADASIL and found that mRNA expression for several mature SMC markers was increased in CADASIL brain compared to age-matched control. Immunohistochemical studies and in situ hybridization localization of mRNA demonstrated loss of SMCs from the arterial media, and SMC marker-expressing cells were instead redistributed into the intima of diseased arteries and around balloon cells of the degenerating media. We conclude that, despite loss of medial smooth muscle cells in diseased arteries, smooth muscle markers are not lost from CADASIL brain, but rather, the localization of cells expressing mature SMC markers changes dramatically.

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

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 INMT were 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.

PACAP-38 is a chemorepellent and an agonist for the lysozyme receptor in tetrahymena thermophila

Pituitary adenylate cyclase activating peptide (PACAP-38) is a peptide hormone which functions in many mammalian systems, including the nervous and digestive systems. Using in vivo behavioral studies, we have found that this hormone functions as a chemore-pellent in Tetrahymena thermophila with an EC50 of 10 nM. Cells previously adapted to PACAP-38 were found to be adapted to lysozyme and vice versa. Furthermore, the in vivo behavioral activity of PACAP-38 was blocked by addition of the anti-lysozyme receptor antibody, 5545. Chemorepellent activity of PACAP-38 was also inhibited by the addition of neomycin sulfate (inhibition constant Ki = 0.080 micromol x l(-1)), a competitive inhibitor of lysozyme binding to its receptor. PACAP-38 is a more potent and specific agonist for the lysozyme receptor than either intact lysozyme or CB2, a 24-amino acid fragment of lysozyme.