Structural requirements for 5-HT2A and 5-HT1A serotonin receptor potentiation by the biologically active lipid oleamide

μ-opioid receptor agonists and psychedelics: pharmacological opportunities and challenges

Opioid misuse and opioid-involved overdose deaths are a massive public health problem involving the intertwined misuse of prescription opioids for pain management with the emergence of extremely potent fentanyl derivatives, sold as standalone products or adulterants in counterfeit prescription opioids or heroin. The incidence of repeated opioid overdose events indicates a problematic use pattern consistent with the development of the medical condition of opioid use disorder (OUD). Prescription and illicit opioids reduce pain perception by activating µ-opioid receptors (MOR) localized to the central nervous system (CNS). Dysregulation of meso-corticolimbic circuitry that subserves reward and adaptive behaviors is fundamentally involved in the progressive behavioral changes that promote and are consequent to OUD. Although opioid-induced analgesia and the rewarding effects of abused opioids are primarily mediated through MOR activation, serotonin (5-HT) is an important contributor to the pharmacology of opioid abused drugs (including heroin and prescription opioids) and OUD. There is a recent resurgence of interest into psychedelic compounds that act primarily through the 5-HT2A receptor (5-HT 2A R) as a new frontier in combatting such diseases (e.g., depression, anxiety, and substance use disorders). Emerging data suggest that the MOR and 5-HT2AR crosstalk at the cellular level and within key nodes of OUD circuitry, highlighting a major opportunity for novel pharmacological intervention for OUD. There is an important gap in the preclinical profiling of psychedelic 5-HT2AR agonists in OUD models. Further, as these molecules carry risks, additional analyses of the profiles of non-hallucinogenic 5-HT2AR agonists and/or 5-HT2AR positive allosteric modulators may provide a new pathway for 5-HT2AR therapeutics. In this review, we discuss the opportunities and challenges associated with utilizing 5-HT2AR agonists as therapeutics for OUD.

Brain Metabolomics in Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS)

The course of pathophysiological mechanisms involved in fragile X-associated tremor/ataxia syndrome (FXTAS) remains largely unknown. Previous proteomics and metabolomics studies conducted in blood samples collected from FMR1 premutation carriers with FXTAS reported abnormalities in energy metabolism, and precursors of gluconeogenesis showed significant changes in plasma expression levels in FMR1 premutation carriers who developed FXTAS. We conducted an analysis of postmortem human brain tissues from 44 donors, 25 brains with FXTAS, and 19 matched controls. We quantified the metabolite relative abundance in the inferior temporal gyrus and the cerebellum using untargeted mass spectrometry (MS)-based metabolomics. We investigated how the metabolite type and abundance relate to the number of cytosine-guanine-guanine (CGG) repeats, to markers of neurodegeneration, and to the symptoms of FXTAS. A metabolomic analysis identified 191 primary metabolites, the data were log-transformed and normalized prior to the analysis, and the relative abundance was compared between the groups. The changes in the relative abundance of a set of metabolites were region-specific with some overlapping results; 22 metabolites showed alterations in the inferior temporal gyrus, while 21 showed differences in the cerebellum. The relative abundance of cytidine was decreased in the inferior temporal gyrus, and a lower abundance was found in the cases with larger CGG expansions; oleamide was significantly decreased in the cerebellum. The abundance of 11 metabolites was influenced by changes in the CGG repeat number. A histological evaluation found an association between the presence of microhemorrhages in the inferior temporal gyrus and a lower abundance of 2,5-dihydroxypyrazine. Our study identified alterations in the metabolites involved in the oxidative-stress response and bioenergetics in the brains of individuals with FXTAS. Significant changes in the abundance of cytidine and oleamide suggest their potential as biomarkers and therapeutic targets for FXTAS.

Discovery of Novel Oleamide Analogues as Brain-Penetrant Positive Allosteric Serotonin 5-HT2C Receptor and Dual 5-HT2C/5-HT2A Receptor Modulators

The serotonin 5-HT2A receptor (5-HT2AR) and 5-HT2CR localize to the brain and share overlapping signal transduction facets that contribute to their roles in cognition, mood, learning, and memory. Achieving selective targeting of these receptors is challenged by the similarity in their 5-HT orthosteric binding pockets. A fragment-based discovery approach was employed to design and synthesize novel oleamide analogues as selective 5-HT2CR or dual 5-HT2CR/5-HT2AR positive allosteric modulators (PAMs). Compound 13 (JPC0323) exhibited on-target properties, acceptable plasma exposure and brain penetration, as well as negligible displacement to orthosteric sites of ∼50 GPCRs and transporters. Furthermore, compound 13 suppressed novelty-induced locomotor activity in a 5-HT2CR-dependent manner, suggesting 5-HT2CR PAM, but not 5-HT2AR, activity at the level of the whole organism at the employed doses of 13. We discovered new selective 5-HT2CR PAMs and first-in-class 5-HT2CR/5-HT2AR dual PAMs that broaden the pharmacological toolbox to explore the biology of these vital receptors.

Endocannabinoid System: Chemical Characteristics and Biological Activity

The endocannabinoid system (eCB) has been studied to identify the molecular structures present in Cannabis sativa. eCB consists of cannabinoid receptors, endogenous ligands, and the associated enzymatic apparatus responsible for maintaining energy homeostasis and cognitive processes. Several physiological effects of cannabinoids are exerted through interactions with various receptors, such as CB1 and CB2 receptors, vanilloid receptors, and the recently discovered G-protein-coupled receptors (GPR55, GPR3, GPR6, GPR12, and GPR19). Anandamide (AEA) and 2-arachidoylglycerol (2-AG), two small lipids derived from arachidonic acid, showed high-affinity binding to both CB1 and CB2 receptors. eCB plays a critical role in chronic pain and mood disorders and has been extensively studied because of its wide therapeutic potential and because it is a promising target for the development of new drugs. Phytocannabinoids and synthetic cannabinoids have shown varied affinities for eCB and are relevant to the treatment of several neurological diseases. This review provides a description of eCB components and discusses how phytocannabinoids and other exogenous compounds may regulate the eCB balance. Furthermore, we show the hypo- or hyperfunctionality of eCB in the body and how eCB is related to chronic pain and mood disorders, even with integrative and complementary health practices (ICHP) harmonizing the eCB.

Structure-based discovery of nonhallucinogenic psychedelic analogs

Drugs that target the human serotonin 2A receptor (5-HT_2AR) are used to treat neuropsychiatric diseases; however, many have hallucinogenic effects, hampering their use. Here, we present structures of 5-HT_2AR complexed with the psychedelic drugs psilocin (the active metabolite of psilocybin) and d-lysergic acid diethylamide (LSD), as well as the endogenous neurotransmitter serotonin and the nonhallucinogenic psychedelic analog lisuride. Serotonin and psilocin display a second binding mode in addition to the canonical mode, which enabled the design of the psychedelic IHCH-7113 (a substructure of antipsychotic lumateperone) and several 5-HT_2AR β-arrestin-biased agonists that displayed antidepressant-like activity in mice but without hallucinogenic effects. The 5-HT_2AR complex structures presented herein and the resulting insights provide a solid foundation for the structure-based design of safe and effective nonhallucinogenic psychedelic analogs with therapeutic effects.

The Potential Synergistic Activity of Zolmitriptan Combined in New Self-Nanoemulsifying Drug Delivery Systems: ATR-FTIR Real-Time Fast Dissolution Monitoring and Pharmacodynamic Assessment

Purpose

The current work aimed to overcome the poor permeability and undesirable adverse effects of Zolmitriptan (ZMT) and to increase its efficacy in the treatment of acute migraine by exploiting the synergistic effect of the essential oil, lavender, to fabricate ZMT self-nanoemulsifying drug delivery systems (ZMT-SNEDDS).

Methods

ZMT-SNEDDS were fabricated based on full factorial design (3²) to statistically assess the impact of oil and surfactant concentrations on the nanoemulsion globule size, zeta potential and percentage drug dissolution efficiency. An ATR-FTIR method was developed and validated for continuous real-time monitoring of ZMT dissolution and permeation. The dose of the optimized ZMT-SNEDDS used in the efficacy study was selected according to the acute toxicity study. The efficacy study was performed on migraineous rats induced by nitroglycerin and was evaluated by the activity cage and thermal tests, electroencephalogram, electroconvulsive stimulation, and biochemical analysis of brain tissue. Finally, histopathological and immunohistochemical examinations of the cerebra were carried out.

Results

Upon dilution, the optimized ZMT-SNEDDS (F5) exhibited nanosized spherical droplets of 19.59±0.17 nm with narrow size distribution, zeta potential (-23.5±1.17mV) and rapid emulsification characteristics. ATR-FTIR spectra elucidated the complete time course of dissolution and permeation, confirming F5 superior performance. Moreover, ZMT-SNEDDS (F5) showed safety in an acute toxicity study. ZMT concentration in rat brain tissues derived from F5 was lower compared to that of ZMT solution, yet its effect was better on the psychological state, algesia, as well as maintaining normal brain electrical activity and delayed convulsions. It counteracted the cerebral biochemical alternations induced by nitroglycerin, which was confirmed by histopathological examination.

Conclusion

In a nutshell, these findings corroborated the remarkable synergistic efficacy and the high potency of lavender oil-based ZMT-SNEDDS in migraine management compared to the traditional zolmitriptan solution.

Cannabinoid Use in a Tertiary Headache Clinic: A Cross-Sectional Survey

OBJECTIVE

This study seeks to determine the prevalence and nature of cannabis use in patients with headache in a tertiary headache clinic and to explore patients' empiric experience in using cannabinoids therapeutically.

BACKGROUND

Many patients with headache report cannabinoid use as an effective abortive and/or preventive therapy. Mounting evidence implicates cannabinoids in pain mechanisms pertaining to migraine and other headache types.

METHODS

A cross-sectional study surveyed 200 patients presenting with any headache disorder to a tertiary headache clinic in Calgary, Alberta. Descriptive analyses were applied to capture information about headache diagnoses and the frequency, doses and methods of cannabinoid delivery employed, as well as patients' perceptions of therapeutic benefit and selected negative side effects.

RESULTS

Active cannabinoid users comprised 34.0% of respondents. Approximately 40% of respondents using cannabinoids engaged in very frequent use (≥300 days/year). Of cannabinoid modalities, liquid concentrates were most popular (39.2%), followed by smoked cannabis (33.3%). Patients endorsed cannabinoid use for both prevention and acute therapy of headaches, often concurrently. Sixty percent of respondents felt cannabinoids reduced headache severity, while 29.2% perceived efficacy in aborting headaches. Nearly 5% of respondents volunteered that they had encountered a serious problem such as an argument, fight, accident, or work issue as a result of their cannabis use. Approximately 35.4% of users had attempted to reduce their use.

CONCLUSION

This survey shows that over one-third of patients with headache disorders in a tertiary headache clinic use cannabis as a treatment for their headaches. Of these, about 25% and 60% perceive improvements in headache frequency and severity, respectively. The results of this survey will aid neurologists and headache specialists in understanding the landscape of cannabinoid use in a more severely affected population and inform future-controlled studies of cannabinoids in headache patients.

Development of a Microfluidic Platform for Trace Lipid Analysis

The inherent trace quantity of primary fatty acid amides found in biological systems presents challenges for analytical analysis and quantitation, requiring a highly sensitive detection system. The use of microfluidics provides a green sample preparation and analysis technique through small-volume fluidic flow through micron-sized channels embedded in a polydimethylsiloxane (PDMS) device. Microfluidics provides the potential of having a micro total analysis system where chromatographic separation, fluorescent tagging reactions, and detection are accomplished with no added sample handling. This study describes the development and the optimization of a microfluidic-laser induced fluorescence (LIF) analysis and detection system that can be used for the detection of ultra-trace levels of fluorescently tagged primary fatty acid amines. A PDMS microfluidic device was designed and fabricated to incorporate droplet-based flow. Droplet microfluidics have enabled on-chip fluorescent tagging reactions to be performed quickly and efficiently, with no additional sample handling. An optimized LIF optical detection system provided fluorescently tagged primary fatty acid amine detection at sub-fmol levels (436 amol). The use of this LIF detection provides unparalleled sensitivity, with detection limits several orders of magnitude lower than currently employed LC-MS techniques, and might be easily adapted for use as a complementary quantification platform for parallel MS-based omics studies.

Serotonin 2A receptors and cannabinoids

Accumulating evidence has proven that both exogenous cannabinoids as well as imbalances in the endocannabinoid system are involved in the onset and development of mental disorders such as anxiety, depression, or schizophrenia. Extensive recent research in this topic has mainly focused on the molecular mechanisms by which cannabinoid agonists may contribute to the pathophysiology of these disorders. Initially, serotonin neurotransmitter garnered most attention due to its relationship to mood disorders and mental diseases, with little attention to specific receptors. To date, the focus has redirected toward the understanding of different serotonin receptors, through a demonstration of its versatile pharmacology and synergy with different modulators. Serotonin 2A receptors are a good example of this phenomenon, and the complex signaling that they trigger appears of high relevance in the context of mental disorders, especially in schizophrenia. This chapter will analyze most relevant attributes of serotonin 2A receptors and the endocannabinoid system, and will highlight the evidence toward the functional bidirectional interaction between these elements in the brain as well as the impact of the endocannabinoid system dysregulation on serotonin 2A receptors functionality.

In Vitro Bioassay-Guided Identification of Anticancer Properties from Moringa oleifera Lam. Leaf against the MDA-MB-231 Cell Line

Moringa oleifera Lam. (MO) is a medicinal plant distributed across the Middle East, Asia, and Africa. MO has been used in the traditional treatment of various diseases including cancer. This study aimed to perform bioassay-guided fractionation and identification of bioactive compounds from MO leaf against MDA-MB-231 breast cancer cells. MO leaf was sequentially extracted with hexane, ethyl acetate (EtOAc), and ethanol. The most effective extract was subjected to fractionation. MO extract and its derived fractions were continuously screened for anti-cancer activities. The strongest fraction was selected for re-fractionation and identification of bioactive compounds using LC-ESI-QTOF-MS/MS analysis. The best anticancer activities were related to the fraction no. 7-derived crude EtOAc extract. This fraction significantly reduced cell viability and clonogenic growth and increased cells apoptosis. Moreover, sub-fraction no. 7.7-derived fraction no. 7 was selected for the identification of bioactive compounds. There were 10 candidate compounds tentatively identified by LC-ESI-QTOF-MS. Three of identified compounds (7-octenoic acid, oleamide, and 1-phenyl-2-pentanol) showed anticancer activities by inducing cell cycle arrest and triggering apoptosis through suppressed Bcl-2 expression which subsequently promotes activation of caspase 3, indicators for the apoptosis pathway. This study identified 10 candidate compounds that may have potential in the field of anticancer substances.

Targeting the 5-HT2C Receptor in Biological Context and the Current State of 5-HT2C Receptor Ligand Development

Serotonin (5-HT) 5-HT2C receptor (5-HT2CR) is recognized as a critical mediator of diseaserelated pathways and behaviors based upon actions in the central nervous system (CNS). Since 5-HT2CR is a class A G protein-coupled receptor (GPCR), drug discovery efforts have traditionally pursued the activation of the receptor through synthetic ligands with agonists proposed for the treatment of obesity, substance use disorders and impulse control disorders while antagonists may add value for the treatment of anxiety, depression and schizophrenia. The most significant agonist discovery to date is the FDAapproved anti-obesity medication lorcaserin. In recent years, efforts towards developing other mechanisms to enhance receptor function have resulted in the discovery of Positive Allosteric Modulators (PAMs) for the 5-HT2CR, with several molecule series now reported. The biological significance and context for signaling and function of the 5-HT2CR, and the current status of 5-HT2CR agonists and PAMs are discussed in this review.

Skeletal muscle interstitial fluid metabolomics at rest and associated with an exercise bout: application in rats and humans

Blood or biopsies are often used to characterize metabolites that are modulated by exercising muscle. However, blood has inputs derived from multiple tissues, biopsies cannot discriminate between secreted and intracellular metabolites, and their invasive nature is challenging for frequent collections in sensitive populations (e.g., children and pregnant women). Thus, minimally invasive approaches to interstitial fluid (IF) metabolomics would be valuable. A catheter was designed to collect IF from the gastrocnemius muscle of acutely anesthetized adult male rats at rest or immediately following 20 min of exercise (~60% of maximal O₂ uptake). Nontargeted, gas chromatography-time-of-flight mass spectrometry analysis was used to detect 299 metabolites, including nonannotated metabolites, sugars, fatty acids, amino acids, and purine metabolites and derivatives. Just 43% of all detected metabolites were common to IF and blood plasma, and only 20% of exercise-modified metabolites were shared in both pools, highlighting that the blood does not fully reflect the metabolic outcomes in muscle. Notable exercise patterns included increased IF amino acids (except leucine and isoleucine), increased α-ketoglutarate and citrate (which may reflect tricarboxylic acid cataplerosis or shifts in nonmitochondrial pathways), and higher concentration of the signaling lipid oleamide. A preliminary study of human muscle IF was conducted using a 20-kDa microdialysis catheter placed in the vastus lateralis of five healthy adults at rest and during exercise (65% of estimated maximal heart rate). Approximately 70% of commonly detected metabolites discriminating rest vs. exercise in rats were also changed in exercising humans. Interstitium metabolomics may aid in the identification of molecules that signal muscle work (e.g., exertion and fatigue) and muscle health.

Chronic Stress Disturbs Metabolome of Blood Plasma and Urine in Diabetic Rats

About 30% of diabetes patients suffer from varying degrees of depression. Diabetes itself is associated with abnormal carbohydrate and energy metabolism. Whether chronic stress-induced depression-like behavior impacts the metabolome of blood plasma and urine in diabetes is not clear. This study aimed to investigate the effect of chronic stress on metabolome of plasma and urine in spontaneously diabetic Goto-Kakizaki (GK) rats. The GK rats were subjected to 8 weeks' chronic unpredictable mild stress (CUMS) to induce depression-like behavior. Metabolome analysis of blood plasma and urine using liquid chromatography mass spectrometry (LC/MS) was performed. Multivariate data analysis was used to evaluate the data. Behavior and biochemical assay confirmed the successful establishment of CUMS-induced depression-like behavior model in rats. Disturbance of 20 plasma metabolites and 16 urine metabolites were altered in CUMS-induced depression GK rats as compared to control ones. These disturbed metabolites were involved in fatty acid metabolism, sphingolipid metabolism, phenylalanine metabolism, citrate cycle, glycolysis, glutathione metabolism, and nicotinate and nicotinamide metabolism. This study suggest that chronic stress-induced depression-like behavior may further disturb diabetes-itself energy metabolome. The plasma and urine lipid metabolites monitoring may be useful for early detection of depression in patients with diabetes mellitus.

Endocannabinoid System and Migraine Pain: An Update

The trigeminovascular system (TS) activation and the vasoactive release from trigeminal endings, in proximity of the meningeal vessels, are considered two of the main effector mechanisms of migraine attacks. Several other structures and mediators are involved, however, both upstream and alongside the TS. Among these, the endocannabinoid system (ES) has recently attracted considerable attention. Experimental and clinical data suggest indeed a link between dysregulation of this signaling complex and migraine headache. Clinical observations, in particular, show that the levels of anandamide (AEA)—one of the two primary endocannabinoid lipids—are reduced in cerebrospinal fluid and plasma of patients with chronic migraine (CM), and that this reduction is associated with pain facilitation in the spinal cord. AEA is produced on demand during inflammatory conditions and exerts most of its effects by acting on cannabinoid (CB) receptors. AEA is rapidly degraded by fatty acid amide hydrolase (FAAH) enzyme and its levels can be modulated in the peripheral and central nervous system (CNS) by FAAH inhibitors. Inhibition of AEA degradation via FAAH is a promising therapeutic target for migraine pain, since it is presumably associated to an increased availability of the endocannabinoid, specifically at the site where its formation is stimulated (e.g., trigeminal ganglion and/or meninges), thus prolonging its action.

An Update on Non-CB1, Non-CB2 Cannabinoid Related G-Protein-Coupled Receptors

The endocannabinoid system (ECS) has been shown to be of great importance in the regulation of numerous physiological and pathological processes. To date, two Class A G-protein-coupled receptors (GPCRs) have been discovered and validated as the main therapeutic targets of this system: the cannabinoid receptor type 1 (CB1), which is the most abundant neuromodulatory receptor in the brain, and the cannabinoid receptor type 2 (CB2), predominantly found in the immune system among other organs and tissues. Endogenous cannabinoid receptor ligands (endocannabinoids) and the enzymes involved in their synthesis, cell uptake, and degradation have also been identified as part of the ECS. However, its complex pharmacology suggests that other GPCRs may also play physiologically relevant roles in this therapeutically promising system. In the last years, GPCRs such as GPR18 and GPR55 have emerged as possible missing members of the cannabinoid family. This categorization still stimulates strong debate due to the lack of pharmacological tools to validate it. Because of their close phylogenetic relationship, the Class A orphan GPCRs, GPR3, GPR6, and GPR12, have also been associated with the cannabinoids. Moreover, certain endo-, phyto-, and synthetic cannabinoid ligands have displayed activity at other well-established GPCRs, including the opioid, adenosine, serotonin, and dopamine receptor families. In addition, the cannabinoid receptors have also been shown to form dimers with other GPCRs triggering cross-talk signaling under specific conditions. In this mini review, we aim to provide insight into the non-CB1, non-CB2 cannabinoid-related GPCRs that have been reported thus far. We consider the physiological relevance of these molecular targets in modulating the ECS.

UHPLC-Q-TOF-MS based serum metabonomics revealed the metabolic perturbations of ischemic stroke and the protective effect of RKIP in rat models

Stroke is one of the most fatal diseases in the world, which is seriously threatening human life. Raf kinase inhibitory protein (RKIP) is involved in the regulation of several signaling pathways and is important for cell growth, proliferation, differentiation and apoptosis. In the present study, the protective effect of RKIP on stroke was investigated by the metabonomics method based on the UHPLC-Q-TOF-MS technique. TTC staining of brain tissues showed that RKIP overexpression by the lentivirus markedly reduced the necrotic area after ischemic stroke. Subsequent metabolomic profiling revealed that the protective effect of RKIP overexpression on ischemic stroke is mainly reflected in the metabolism of energy, amino acids and lipids. Several metabolites involved in purine, pyrimidine and fatty acid metabolism were identified. It was also shown that the protective effect of RKIP on ischemic stroke might be mediated by inhibiting the inflammatory response. The current study provided insight into the molecular mechanism of ischemic stroke and a reliable basis for the development of novel therapeutic targets for the treatment of ischemic stroke.

The Use of Cannabis for Headache Disorders

Headache disorders are common, debilitating, and, in many cases, inadequately managed by existing treatments. Although clinical trials of cannabis for neuropathic pain have shown promising results, there has been limited research on its use, specifically for headache disorders. This review considers historical prescription practices, summarizes the existing reports on the use of cannabis for headache, and examines the preclinical literature exploring the role of exogenous and endogenous cannabinoids to alter headache pathophysiology. Currently, there is not enough evidence from well-designed clinical trials to support the use of cannabis for headache, but there are sufficient anecdotal and preliminary results, as well as plausible neurobiological mechanisms, to warrant properly designed clinical trials. Such trials are needed to determine short- and long-term efficacy for specific headache types, compatibility with existing treatments, optimal administration practices, as well as potential risks.

Clinical Endocannabinoid Deficiency Reconsidered: Current Research Supports the Theory in Migraine, Fibromyalgia, Irritable Bowel, and Other Treatment-Resistant Syndromes

Medicine continues to struggle in its approaches to numerous common subjective pain syndromes that lack objective signs and remain treatment resistant. Foremost among these are migraine, fibromyalgia, and irritable bowel syndrome, disorders that may overlap in their affected populations and whose sufferers have all endured the stigma of a psychosomatic label, as well as the failure of endless pharmacotherapeutic interventions with substandard benefit. The commonality in symptomatology in these conditions displaying hyperalgesia and central sensitization with possible common underlying pathophysiology suggests that a clinical endocannabinoid deficiency might characterize their origin. Its base hypothesis is that all humans have an underlying endocannabinoid tone that is a reflection of levels of the endocannabinoids, anandamide (arachidonylethanolamide), and 2-arachidonoylglycerol, their production, metabolism, and the relative abundance and state of cannabinoid receptors. Its theory is that in certain conditions, whether congenital or acquired, endocannabinoid tone becomes deficient and productive of pathophysiological syndromes. When first proposed in 2001 and subsequently, this theory was based on genetic overlap and comorbidity, patterns of symptomatology that could be mediated by the endocannabinoid system (ECS), and the fact that exogenous cannabinoid treatment frequently provided symptomatic benefit. However, objective proof and formal clinical trial data were lacking. Currently, however, statistically significant differences in cerebrospinal fluid anandamide levels have been documented in migraineurs, and advanced imaging studies have demonstrated ECS hypofunction in post-traumatic stress disorder. Additional studies have provided a firmer foundation for the theory, while clinical data have also produced evidence for decreased pain, improved sleep, and other benefits to cannabinoid treatment and adjunctive lifestyle approaches affecting the ECS.

Passiflora incarnata attenuation of neuropathic allodynia and vulvodynia apropos GABA-ergic and opioidergic antinociceptive and behavioural mechanisms

Background

Passiflora incarnata is widely used as an anxiolytic and sedative due to its putative GABAergic properties. Passiflora incarnata L. methanolic extract (PI-ME) was evaluated in an animal model of streptozotocin-induced diabetic neuropathic allodynia and vulvodynia in rats along with antinociceptive, anxiolytic and sedative activities in mice in order to examine possible underlying mechanisms.

Methods

PI-ME was tested preliminary for qualitative phytochemical analysis and then quantitatively by proximate and GC-MS analysis. The antinociceptive property was evaluated using the abdominal constriction assay and hot plate test. The anxiolytic activity was performed in a stair case model and sedative activity in an open field test. The antagonistic activities were evaluated using naloxone and/or pentylenetetrazole (PTZ). PI-ME was evaluated for prospective anti-allodynic and anti-vulvodynic properties in a rat model of streptozotocin induced neuropathic pain using the static and dynamic testing paradigms of mechanical allodynia and vulvodynia.

Results

GC-MS analysis revealed that PI-ME contained predominant quantities of oleamide (9-octadecenamide), palmitic acid (hexadecanoic acid) and 3-hydroxy-dodecanoic acid, among other active constituents. In the abdominal constriction assay and hot plate test, PI-ME produced dose dependant, naloxone and pentylenetetrazole reversible antinociception suggesting an involvement of opioidergic and GABAergic mechanisms. In the stair case test, PI-ME at 200 mg/kg increased the number of steps climbed while at 600 mg/kg a significant decrease was observed. The rearing incidence was diminished by PI-ME at all tested doses and in the open field test, PI-ME decreased locomotor activity to an extent that was analagous to diazepam. The effects of PI-ME were antagonized by PTZ in both the staircase and open field tests implicating GABAergic mechanisms in its anxiolytic and sedative activities. In the streptozotocin-induced neuropathic nociceptive model, PI-ME (200 and 300 mg/kg) exhibited static and dynamic anti-allodynic effects exemplified by an increase in paw withdrawal threshold and paw withdrawal latency. PI-ME relieved only the dynamic component of vulvodynia by increasing flinching response latency.

Conclusions

These findings suggest that Passiflora incarnata might be useful for treating neuropathic pain. The antinociceptive and behavioural findings inferring that its activity may stem from underlying opioidergic and GABAergic mechanisms though a potential oleamide-sourced cannabimimetic involvement is also discussed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1048-6) contains supplementary material, which is available to authorized users.

Differential proteomic analysis of the anti-depressive effects of oleamide in a rat chronic mild stress model of depression

Depression is a complex psychiatric disorder, and its etiology and pathophysiology are not completely understood. Depression involves changes in many biogenic amine, neuropeptide, and oxidative systems, as well as alterations in neuroendocrine function and immune-inflammatory pathways. Oleamide is a fatty amide which exhibits pharmacological effects leading to hypnosis, sedation, and anti-anxiety effects. In the present study, the chronic mild stress (CMS) model was used to investigate the antidepressant-like activity of oleamide. Rats were exposed to 10weeks of CMS or control conditions and were then subsequently treated with 2weeks of daily oleamide (5mg/kg, i.p.), fluoxetine (10mg/kg, i.p.), or vehicle. Protein extracts from the hippocampus were then collected, and hippocampal maps were generated by way of two-dimensional gel electrophoresis (2-DE). Altered proteins induced by CMS and oleamide were identified through mass spectrometry and database searches. Compared to the control group, the CMS rats exhibited significantly less body weight gain and decreased sucrose consumption. Treatment with oleamide caused a reversal of the CMS-induced deficit in sucrose consumption. In the proteomic analysis, 12 protein spots were selected and identified. CMS increased the levels of adenylate kinase isoenzyme 1 (AK1), nucleoside diphosphate kinase B (NDKB), histidine triad nucleotide-binding protein 1 (HINT1), acyl-protein thioesterase 2 (APT-2), and glutathione S-transferase A4 (GSTA4). Compared to the CMS samples, seven spots changed significantly following treatment with oleamide, including GSTA4, glutathione S-transferase A6 (GSTA6), GTP-binding nuclear protein Ran (Ran-GTP), ATP synthase subunit d, transgelin-3, small ubiquitin-related modifier 2 (SUMO2), and eukaryotic translation initiation factor 5A-1 (eIF5A1). Of these seven proteins, the level of eIF5A1 was up-regulated, whereas the remaining proteins were down-regulated. In conclusion, oleamide has antidepressant-like properties in the CMS rat model. The identification of proteins altered by CMS and oleamide treatment provides support for targeting these proteins in the development of novel therapies for depression.

Sulfonyl fluoride inhibitors of fatty acid amide hydrolase

Sulfonyl fluorides are known to inhibit esterases. Early work from our laboratory has identified hexadecyl sulfonylfluoride (AM374) as a potent in vitro and in vivo inhibitor of fatty acid amide hydrolase (FAAH). We now report on later generation sulfonyl fluoride analogs that exhibit potent and selective inhibition of FAAH. Using recombinant rat and human FAAH, we show that 5-(4-hydroxyphenyl)pentanesulfonyl fluoride (AM3506) has similar inhibitory activity for both the rat and the human enzyme, while rapid dilution assays and mass spectrometry analysis suggest that the compound is a covalent modifier for FAAH and inhibits its action in an irreversible manner. Our SAR results are highlighted by molecular docking of key analogs.

Cytotoxic and antibacterial beilschmiedic acids from a Gabonese species of Beilschmiedia

High-throughput natural products chemistry methods have facilitated the isolation of eight new (1-8) and two known (9 and 10) beilschmiedic acid derivatives from the leaves of a Gabonese species of Beilschmiedia. Compounds 3-10 were isolated in microgram quantities, and the NMR data for structure elucidation and dereplication were acquired utilizing a Bruker BioSpin TCI 1.7 mm MicroCryoProbe. All of the compounds were screened for cytotoxic and antibacterial activity against NCI-H460 human lung cancer cells and a clinical isolate of methicillin-resistant Staphylococcus aureus, respectively. This is the first report of cytotoxic activity for the endiandric/beilschmiedic acid class of compounds.

α-Ketoheterocycle-based Inhibitors of Fatty Acid Amide Hydrolase (FAAH)

A summary of the initial discovery and characterization of the enzyme fatty acid amide hydrolase (FAAH), and the subsequent advancement of an important class of competitive, reversible, potent and selective inhibitors is presented. Initially explored using substrate-inspired inhibitors bearing electrophilic carbonyls, the examination of α-ketoheterocyle-based inhibitors of FAAH with the benefit of a unique activity-based protein-profiling (ABPP)-based proteome-wide selectivity assay, a powerful in vivo biomarker-based in vivo screen, and subsequent retrospective X-ray co-crystal structures with the enzyme, is summarized. These efforts defined the impact of the central activating heterocycle and its key substituents, provided key simplifications in the C2 acyl side chain and clear interpretations for the unique role and subsequent optimization of the central activating heterocycle, and established the basis for the recent further conformational constraints in the C2 acyl side chain, providing potent, long-acting, orally-active FAAH inhibitors.

Electrospray ionization and collision induced dissociation mass spectrometry of primary fatty acid amides

Primary fatty acid amides are a group of bioactive lipids that have been linked with a variety of biological processes such as sleep regulation and modulation of monoaminergic systems. As novel forms of these molecules continue to be discovered, more emphasis will be placed on selective, trace detection. Currently, there is no published experimental determination of collision induced dissociation of PFAMs. A select group of PFAM standards, 12 to 22 length carbon chains, were directly infused into an electrospray ionization source Quadrupole Time of Flight Mass Spectrometer. All standards were monitored in positive mode using the [M + H](+) peak. Mass Hunter Qualitative Analysis software was used to calculate empirical formulas of the product ions. All PFAMs showed losses of 14 m/z indicative of an acyl chain, while the monounsaturated group displayed neutral losses corresponding to H(2)O and NH(3). The resulting spectra were used to propose fragmentation mechanisms. Isotopically labeled PFAMs were used to validate the proposed mechanisms. Patterns of saturated versus unsaturated standards were distinctive, allowing for simple differentiation. This determination will allow for fast, qualitative identification of PFAMs. Additionally, it will provide a method development tool for selection of unique product ions when analyzed in multiple reaction monitoring mode.

Fatty acid amide signaling molecules

Key studies leading to the discovery and definition of the role of endogenous fatty acid amide signaling molecules are summarized.

Oleamide administered into the nucleus accumbens shell regulates feeding behaviour via CB1 and 5-HT2C receptors

The central nervous system control of food intake has been extensively studied, hence, several neurotransmitter systems regulating this function are now clearly identified, for example, the endocannabinoid and serotoninergic systems. The former stimulates feeding while the latter inhibits it. Oleamide (Ole) is a cannabimimetic molecule affecting both systems. In this work, we tested the orexigenic and anorectic potential of Ole when administered into the nucleus accumbens shell (NAcS), a brain region that has been related to the orexigenic effects of cannabinoids. Additionally, we tested if Ole administered into this nucleus affects the activity of the hypothalamic nuclei involved in feeding behaviour, just as other cannabinoids do. We found a hyperphagic effect of Ole that is mediated through CB1 activation. The combination of Ole and the CB1 antagonist, AM251, produced a hypophagia that was fully blocked by SB212084, a 5-HT2C receptor antagonist. We also show that blockade of 5-HT2C and 5-HT2A receptors in the NAcS stimulates food intake. Finally, the combination of Ole and AM251 activates hypothalamic nuclei, an effect also blocked by SB242084. In conclusion, we show, for the first time, that Ole administered into the NAcS has a dual effect on feeding behaviour, acting through cannabinoid and serotonin receptors. These effects probably result from a downstream interaction with the hypothalamus.

Effect of the CB(1) receptor antagonists rimonabant and AM251 on the firing rate of dorsal raphe nucleus neurons in rat brain slices

BACKGROUND AND PURPOSE

Previous studies have suggested a regulation of 5-hydroxytryptamine (5-HT) neurons by the endocannabinoid system. The aim of our work was to examine the effect of two CB(1) receptor antagonists, SR141716A (rimonabant, Sanofi-Synthélabo Recherche, Montpellier, France) and N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251, Tocris Cookson, Bristol, UK), on the firing rate of dorsal raphe nucleus (DRN) neurons.

EXPERIMENTAL APPROACH

Single-unit extracellular recordings were performed to study the effect of CB(1) receptor antagonists in slices of the DRN from rat brain.

KEY RESULTS

Rimonabant (1 microM) and AM251 (1 microM) decreased the firing rate of about 50% of all the recorded DRN 5-HT cells. The GABA(A)receptor antagonist picrotoxin (20 microM) (Sigma) prevented and also reversed the inhibitory effect of rimonabant (1 microM) and AM251 (1 microM), suggesting that CB(1) receptors regulate 5-HT neurons through the GABAergic system. However, the CB(1)/CB(2) receptor agonist R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)-methyl]pyrrolol[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl) methanone mesylate salt (10 microM) (WIN55212-2, Sigma, St. Louis, MO, USA) failed to change the firing activity of non-5-HT (presumably GABAergic) neurons in the DRN. The endocannabinoid N-(2-hydroxyethyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (anandamide, Tocris Cookson) (10 microM) also inhibited the firing activity of a number of 5-HT neurons, but this inhibition was not blocked by rimonabant (1 microM) or AM251 (1 microM), and the stable analogue R-(+) N-(2-hydroxy-1methylethyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (methanandamide, Tocris Cookson) (10 microM) did not mimic this effect. The selective CB(1) receptor agonist arachidonoyl-2-chloroethylamide (ACEA) (1 microM) only slightly increased the firing rate of DRN 5-HT cells.

CONCLUSIONS AND IMPLICATIONS

These results suggest a tonic/constitutive regulation of DRN 5-HT neurons by the endocannabinoid system, which may occur through a CB(1) receptor-mediated inhibition of the GABAergic system. The inhibitory effect of anandamide may be mediated through a CB(1) receptor-independent mechanism.

Properties of gap junction blockers and their behavioural, cognitive and electrophysiological effects: animal and human studies

Gap junctions play an important role in brain physiology. They synchronize neuronal activity and connect glial cells participating in the regulation of brain metabolism and homeostasis. Gap junction blockers (GJBs) include various chemicals that impair gap junction communication, disrupt oscillatory neuronal activity over a wide range of frequencies, and decrease epileptic discharges. The behavioural and clinical effects of GJBs suggest that gap junctions can be involved in the regulation of locomotor activity, arousal, memory, and breathing. Severe neuropsychiatric side effects suggest the involvement of gap junctions in mechanisms of consciousness. Unfortunately, the available GJBs are not selective and can bind to targets other than gap junctions. Other problems in behavioural studies include the possible adverse effects of GJBs, for example, retinal toxicity and hearing disturbances, changes in blood-brain transport, and the metabolism of other drugs. Therefore, it is necessary to design experiments properly to avoid false, misleading or uninterpretable results. We review the pharmacological properties and electrophysiological, behavioural and cognitive effects of the available gap junction blockers, such as carbenoxolone, glycyrrhetinic acid, quinine, quinidine, mefloquine, heptanol, octanol, anandamide, fenamates, 2-APB, several anaesthetics, retinoic acid, oleamide, spermine, aminosulfonates, and sodium propionate. It is concluded that despite a number of different problems, the currently used gap junction blockers could be useful tools in pharmacology and neuroscience.

The complications of promiscuity: endocannabinoid action and metabolism

In this review, we present our understanding of the action and metabolism of endocannabinoids and related endogenous molecules. It is clear that the interactions between the multiple endocannabinoid-like molecules (ECLs) are highly complex, both at the level of signal transduction and metabolism. Thus, ECLs are a group of ligands active at 7-transmembrane and nuclear receptors, as well as transmitter-gated and ion channels. ECLs and their metabolites can converge on common endpoints (either metabolic or signalling) through contradictory or reinforcing pathways. We highlight the complexity of the endocannabinoid system, based on the promiscuous nature of ECLs and their metabolites, as well as the synthetic modulators of the endocannabinoid system.

The Future of Cannabinoids as Analgesic Agents: A Pharmacologic, Pharmacokinetic, and Pharmacodynamic Overview

For thousands of years, physicians and their patients employed cannabis as a therapeutic agent. Despite this extensive historical usage, in the Western world, cannabis fell into disfavor among medical professionals because the technology available in the 1800s and early 1900s did not permit reliable, standardized preparations to be developed. However, since the discovery and cloning of cannabinoid receptors (CB1 and CB2) in the 1990s, scientific interest in the area has burgeoned, and the complexities of this fascinating receptor system, and its endogenous ligands, have been actively explored. Recent studies reveal that cannabinoids have a rich pharmacology and may interact with a number of other receptor systems-as well as with other cannabinoids-to produce potential synergies. Cannabinoids-endocannabinoids, phytocannabinoids, and synthetic cannabinoids-affect numerous bodily functions and have indicated efficacy of varying degrees in a number of serious medical conditions. Nevertheless, despite promising preclinical and early clinical data, particularly in the areas of inflammation and nociception, development challenges abound. Tetrahydrocannabinol (THC) and other CB1 receptor agonists can have an undesirable CNS impact, and, in many cases, dose optimization may not be realizable before onset of excessive side effects. In addition, complex botanically derived cannabinoid products must satisfy the demanding criteria of the U.S. Food and Drug Association's approval process. Recent agency guidance suggests that these obstacles are not insurmountable, although cannabis herbal material ("medical marijuana") may present fatal uncertainties of quality control and dosage standardization. Therefore, formulation, composition, and delivery system issues will affect the extent to which a particular cannabinoid product may have a desirable risk-benefit profile and acceptable abuse liability potential. Cannabinoid receptor agonists and/or molecules that affect the modulation of endocannabinoid synthesis, metabolism, and transport may, in the future, offer extremely valuable tools for the treatment of a number of currently intractable disorders. Further research is warranted to explore the therapeutic potential of this area.

Structure-activity relationships of alpha-ketooxazole inhibitors of fatty acid amide hydrolase

A systematic study of the structure-activity relationships of 2b (OL-135), a potent inhibitor of fatty acid amide hydrolase (FAAH), is detailed targeting the C2 acyl side chain. A series of aryl replacements or substituents for the terminal phenyl group provided effective inhibitors (e.g., 5c, aryl = 1-napthyl, Ki = 2.6 nM), with 5hh (aryl = 3-ClPh, Ki = 900 pM) being 5-fold more potent than 2b. Conformationally restricted C2 side chains were examined, and many provided exceptionally potent inhibitors, of which 11j (ethylbiphenyl side chain) was established to be a 750 pM inhibitor. A systematic series of heteroatoms (O, NMe, S), electron-withdrawing groups (SO, SO2), and amides positioned within and hydroxyl substitutions on the linking side chain were investigated, which typically led to a loss in potency. The most tolerant positions provided effective inhibitors (12p, 6-position S, Ki = 3 nM, or 13d, 2-position OH, Ki = 8 nM) comparable in potency to 2b. Proteome-wide screening of selected inhibitors from the systematic series of >100 candidates prepared revealed that they are selective for FAAH over all other mammalian serine proteases.

Oleamide: A Fatty Acid Amide Signaling Molecule in the Cardiovascular System?

Oleamide (cis-9,10-octadecenoamide), a fatty acid primary amide discovered in the cerebrospinal fluid of sleep-deprived cats, has a variety of actions that give it potential as a signaling molecule, although these actions have not been extensively investigated in the cardiovascular system. The synthetic pathway probably involves synthesis of oleoylglycine and then conversion to oleamide by peptidylglycine alpha-amidating monooxygenase (PAM); breakdown of oleamide is by fatty acid amide hydrolase (FAAH). Oleamide interacts with voltage-gated Na(+) channels and allosterically with GABA(A) and 5-HT(7) receptors as well as having cannabinoid-like actions. The latter have been suggested to be due to potentiation of the effects of endocannabinoids such as anandamide by inhibiting FAAH-mediated hydrolysis. This might underlie an "entourage effect" whereby co-released endogenous nonagonist congeners of endocannabinoids protect the active molecule from hydrolysis by FAAH. However, oleamide has direct agonist actions at CB(1) cannabinoid receptors and also activates the TRPV1 vanilloid receptor. Other actions include inhibition of gap-junctional communication, and this might give oleamide a role in myocardial development. Many of these actions are absent from the trans isomer of 9,10-octadecenoamide. One of the most potent actions of oleamide is vasodilation. In rat small mesenteric artery the response does not involve CB(1) cannabinoid receptors but another pertussis toxin-sensitive, G protein-coupled receptor, as yet unidentified. This receptor is sensitive to rimonabant and O-1918, an antagonist at the putative "abnormal-cannabidiol" or endothelial "anandamide" receptors. Vasodilation is mediated by endothelium-derived nitric oxide, endothelium-dependent hyperpolarization, and also through activation of TRPV1 receptors. A physiological role for oleamide in the heart and circulation has yet to be demonstrated, as has production by cells of the cardiovascular system, but this molecule has a range of actions that could give it considerable modulatory power.

Potent and selective alpha-ketoheterocycle-based inhibitors of the anandamide and oleamide catabolizing enzyme, fatty acid amide hydrolase

A study of the structure-activity relationships (SAR) of 2f (OL-135), a potent inhibitor of fatty acid amide hydrolase (FAAH), is detailed, targeting the 5-position of the oxazole. Examination of a series of substituted benzene derivatives (12-14) revealed that the optimal position for substitution was the meta-position with selected members approaching or exceeding the potency of 2f. Concurrent with these studies, the effect of substitution on the pyridine ring of 2f was also examined. A series of small, nonaromatic C5-substituents was also explored and revealed that the K(i) follows a well-defined correlation with the Hammett sigma(p) constant (rho = 3.01, R2 = 0.91) in which electron-withdrawing substituents enhance potency, leading to inhibitors with K(i)s as low as 400 pM (20n). Proteomic-wide screening of the inhibitors revealed that most are exquisitely selective for FAAH over all other mammalian proteases, reversing the 100-fold preference of 20a (C5 substituent = H) for the enzyme TGH.

5-HT1A receptors are involved in the anxiolytic effect of Delta9-tetrahydrocannabinol and AM 404, the anandamide transport inhibitor, in Sprague-Dawley rats

The mechanism mediating the effects of cannabinoids on anxiety-related responses appear to involve cannabinoid CB1 and non-CB1 receptors. However, other neurotransmitters may play a role in such effect. This study shows evidence of an interaction between endocannabinoid system and serotonin (5-HT), 1A receptor subtype on anxiety-like behavior in Sprague-Dawley rats. The exogenous cannabinoid agonist, Delta9-tetrahydrocannabinol (THC), and N-(4-hydroxyphenyl)-arachidonylamide, the anandamide transporter inhibitor (AM 404) were evaluated in the elevated plus maze test. THC (0.075-0.75 mg/kg i.p.), given 30 min and AM 404 (0.75-1.25 mg/kg i. p.), given 60 min before the test, exhibited a dose-response anxiolytic effect evaluated in terms of increase in the percentage of total entries and time spent in the open and decrease of total entries and time spent in the closed arms. The anxiolytic effect obtained with the maximal active dose of both THC (0.75 mg/kg) and AM 404 (1.25 mg/kg) was blocked by the 5-HT1A receptor antagonist, N-[2-[4-(2-methoxyphenyl) piperazin-1-yl]ethyl]-N-pyridin-2-yl-cyclohexanecarboxamide dihydro chloride (WAY-100635 (300 microg/kg, s.c.), given 30 min before THC or 15 min before AM 404. The combination of an ineffective dose of THC (0.015 mg/kg) or AM 404 (0.015 mg/kg) on anxiety-related responses with an ineffective dose of the 5HT(1A) receptor agonist, 8-Hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT) (7.5 microg/kg, i.p.), led to a synergistic effect. No interference with spontaneous motor activity, evaluated in an activity cage for 5 min, in rats given the drugs alone or in combination, was found. These data suggest that the anxiolytic effect produced by endo- and eso-cannabinoids is modulated by 5-HT1A receptors.

Enhanced radiosensitization of p53 mutant cells by oleamide

PURPOSE

Effect of oleamide, an endogenous fatty-acid primary amide, on tumor cells exposed to ionizing radiation (IR) has never before been explored.

METHODS AND MATERIALS

NCI H460, human lung cancer cells, and human astrocytoma cell lines, U87 and U251, were used. The cytotoxicity of oleamide alone or in combination with IR was determined by clonogenic survival assay, and induction of apoptosis was estimated by FACS analysis. Protein expressions were confirmed by Western blotting, and immunofluorescence analysis of Bax by use of confocal microscopy was also performed. The combined effect of IR and oleamide to suppress tumor growth was studied by use of xenografts in the thighs of nude mice.

RESULTS

Oleamide in combination with IR had a synergistic effect that decreased clonogenic survival of lung-carcinoma cell lines and also sensitized xenografts in nude mice. Enhanced induction of apoptosis of the cells by the combined treatment was mediated by loss of mitochondrial membrane potential, which resulted in the activation of caspase-8, caspase-9, and caspase-3 accompanied by cytochrome c release and Bid cleavage. The synergistic effects of the combined treatment were more enhanced in p53 mutant cells than in p53 wild-type cells. In p53 wild-type cells, both oleamide and radiation induced Bax translocation to mitochondria. On the other hand, in p53 mutant cells, radiation alone slightly induced Bax translocation to mitochondria, whereas oleamide induced a larger translocation.

CONCLUSIONS

Oleamide may exhibit synergistic radiosensitization in p53 mutant cells through p53-independent Bax translocation to mitochondria.

Sample preparation and gas chromatography of primary fatty acid amides

A method for the isolation of bio-active primary fatty acid amides (PFAM's) from total lipid extract by solid-phase extraction (SPE) was developed and validated. The lowest mass of amide to be loaded and recovered by this method was detected as 0.5 microg using 500 mg of normal phase adsorbent. The isolated PFAM's were separated and quantified by GC/MS and percent recoveries were calculated. An HP-5MS column was able to provide base line separation between the saturated and unsaturated PFAM's whereas clear resolution between geometric and positional isomers having the same number of carbons was obtained using a BPX70 column. The separated amides were all 18 carbon analogs of cis-9-octadecenoamide (oleamide). Detection limits in the single ion monitoring mode were found to be on the order of 10 pg in a 1 microl injection. Solid phase extraction of amides from total lipid extract before GC/MS analysis provides clean detection and interference free analysis.

Time course of opioid and cannabinoid gene transcription alterations induced by repeated administration with fluoxetine in the rat brain

This study examined the time course effects (8, 16 and 31 days) of fluoxetine administration (1 mg/kg, p.o./day) on serotonin transporter (5-HTT), opioid, tyrosine hydroxylase (TH) and cannabinoid CB1 receptor gene expressions in selected regions of the rat brain. Treatment with fluoxetine progressively decreased (35-55%) 5-HTT gene expression in dorsal raphe nucleus at 8, 16 and 31 days. The results revealed that fluoxetine administration decreased (30%) proenkephalin gene expression in nucleus accumbens shell (AcbS) and caudate-putamen (CPu) (31 days) but was without effect in nucleus accumbens core AcbC. A pronounced and time related decrease (25-65%) in prodynorphin gene expression was detected in AcbC, AcbS, CPu, hypothalamic supraoptic and paraventricular nuclei at all time points as well as in proopiomelanocortin gene expression (20-30%) in the arcuate nucleus (ARC) of the hypothalamus. On days 16 and 31, tyrosine hydroxylase gene expression in ventral tegmental area and substantia nigra and cannabinoid CB1 receptor gene expression in the CPu decreased (approximately 45-50% from vehicle). In conclusion, fluoxetine by inhibiting the reuptake of serotonin produced pronounced and time related alterations in genes involved in the regulation of emotional behaviour, suggesting that these neuroplastic changes may be involved, at least in part, in the clinical efficacy of this drug in neuropsychiatric disorders.

Agonistic Properties of Cannabidiol at 5-HT1a Receptors

Cannabidiol (CBD) is a major, biologically active, but psycho-inactive component of cannabis. In this cell culture-based report, CBD is shown to displace the agonist, [3H]8-OH-DPAT from the cloned human 5-HT1a receptor in a concentration-dependent manner. In contrast, the major psychoactive component of cannabis, tetrahydrocannabinol (THC) does not displace agonist from the receptor in the same micromolar concentration range. In signal transduction studies, CBD acts as an agonist at the human 5-HT1a receptor as demonstrated in two related approaches. First, CBD increases [35S]GTPgammaS binding in this G protein coupled receptor system, as does the known agonist serotonin. Second, in this GPCR system, that is negatively coupled to cAMP production, both CBD and 5-HT decrease cAMP concentration at similar apparent levels of receptor occupancy, based upon displacement data. Preliminary comparative data is also presented from the cloned rat 5-HT2a receptor suggesting that CBD is active, but less so, relative to the human 5-HT1a receptor, in binding analyses. Overall, these studies demonstrate that CBD is a modest affinity agonist at the human 5-HT1a receptor. Additional work is required to compare CBD's potential at other serotonin receptors and in other species. Finally, the results indicate that cannabidiol may have interesting and useful potential beyond the realm of cannabinoid receptors.

Bilateral organization of unilaterally generated activity in lumbar spinal motoneurons of the rat

The spinal nucleus of the bulbocavernosus (SNB) is a medially located, bilaterally organized sexually dimorphic motor nucleus in the lumbar spinal cord of the male rat. To begin to assess the potential functional significance of this bilateral organization, we recorded ipsi- and contralateral SNB motor nerve activity following unilateral spinal stimulation and examined the timing, pattern, and recruitment of population motoneuron activity. A possible mechanism for bilateral communication, gap junctional intercellular communication, was also investigated because dye coupling experiments indicate an extensive syncytium in which SNB motoneurons are coupled with each other and neighboring interneurons. An in vivo peripheral nerve recording paradigm was used: a bipolar stimulating electrode was placed on dorsal root L6, and bipolar recording electrodes were placed bilaterally on the SNB motor nerves. All processes were severed distal to electrode placement to isolate the central preparation; recruitment curves of motoneuronal activity were then generated. Amplitude of peak to peak recruitment was greater in the contralateral motor nerve than in the ipsilateral nerve. Response latency, Fourier transform and spike counts showed no evidence of ipsi/contralateral asymmetry. Recruitment was attenuated both ipsi- and contralaterally after pharmacological gap junction blockade, but antidromic stimulation could not drive activity in contralateral motor axons. These results indicate that unilateral input to the SNB may be differentially modulated to produce functionally distinct output in the two separate halves of the nucleus. We also discuss the potential modulatory role of gap junctions in the activity of the SNB.

Differential effects of the sleep-inducing lipid oleamide and cannabinoids on the induction of long-term potentiation in the CA1 neurons of the rat hippocampus in vitro

Cannabinoids have been shown to impair cognition in vivo and block long-term potentiation (LTP), a candidate experimental model of learning and memory in vitro, via cannabinoid receptor (CB1) activation. cis-Oleamide (cOA) is an endogenous sleep-inducing lipid with putative cannabinomimetic properties. We hypothesise that cOA is cannabinomimetic and perform a comparative study with synthetic and endogenous cannabinoids on their effects on synaptic conditioning via two different patterns of stimulation in the hippocampal slice. CB1 agonists, R(+)-WIN55212-2 and anandamide, but not cOA blocked high frequency stimulation (HFS)-LTP. R(+)-WIN55212-2 and cOA (stereoselectively) attenuated responses to theta-burst-LTP, while anandamide did not. The anandamide transport inhibitor, AM404, attenuated HFS-LTP, an effect reversed by the CB1 receptor antagonist SR141716A but not mimicked by the vanilloid receptor agonist capsaicin. TFNO, an inhibitor of fatty acid amide hydrolase (FAAH), the enzyme responsible for degrading anandamide, failed to block HFS-LTP alone or in combination with cOA. On the contrary, this combination was as effective as cOA on its own in attenuating theta-burst-LTP. cOA effects on theta-burst-LTP were prevented in the presence of the GABA(A) receptor blocker picrotoxin, but not by pretreatment with SR141716A. These findings suggest that cOA neither directly activates CB1 receptors nor acts via the proposed "entourage" effect [Nature 389 (1997) 25] to increase titres of anandamide through FAAH inhibition. The selective effects of cOA on theta-burst-conditioning may reflect modulation of GABAergic transmission. Anandamide uptake inhibition, but not blockade of FAAH, effectively increases synaptic concentrations of endocannabinoids.

The sleep inducing brain lipid cis-oleamide (cOA) does not modulate serotonergic transmission in the CA1 pyramidal neurons of the hippocampus in vitro

cis-Oleamide (cOA) is a novel sleep inducing brain lipid with an unknown mechanism of action. High affinity interactions with metabotropic 5-HT receptors (2A/C and 1A subtypes) in frog oocytes and expression systems have been reported, but functional in vitro evidence for the modulatory effect is still lacking. Here, we addressed the ability of cOA to modulate 5-HT-induced cellular actions in the CA1 neurons of the rat hippocampal slice.5-HT (0.1-100 microM) concentration dependently reduced the amplitude of the evoked field population spike (fPS), and produced a hyperpolarising shift in the resting membrane potential (Vr) and a drop in input resistance (R in). The effects of a low dose of 5-HT (3.2 microM) on fPS, Vr and R in were reversed by the specific 5-HT(1A)-receptor antagonist WAY 100135 (10 microM). cOA (1 microM) failed to potentiate 5-HT1A receptor mediated effects on fPS, Vr or R in. High doses of 5-HT also recruited both 5-HT2 and 5-HT3 receptors, causing an increase in the rate and amplitude of sIPSCs. cOA (1 microM), in the presence of Y 25130, failed to potentiate the 5-HT2 receptor induced enhancement of sIPSCs. In summary, cis-oleamide failed to modulate metabotropic responses to exogenous 5-HT in this microelectrode study at concentrations well in excess of those reported to modulate 5-HT1A and 5-HT2A/C systems in earlier studies.

Selective effect of oleamide, an endogenous sleep-inducing lipid amide, on pentylenetetrazole-induced seizures in mice

The anti-seizure effect of oleamide, an endogenous sleep-inducing fatty acid amide, was studied in mice. Oleamide, in the dose range 43.7-700.0 mg kg(-1), significantly and dose-dependently inhibited the seizures induced by pentylenetetrazole. However, oleamide showed no inhibitory action on the seizures induced by picrotoxin, strychnine, caffeine or semicarbazide. These results provide the first evidence for the anti-seizure effect of oleamide, and suggest that this effect may be selective to the seizure model induced by pentylenetetrazole.

No hypothermic response to serotonin in 5-HT7 receptor knockout mice

With data from recently available selective antagonists for the 5-HT(7) receptor, it has been hypothesized that 5-hydroxytryptamine (5-HT)-induced hypothermia is mediated by the 5-HT(7) receptor, an effect previously attributed to other receptor subtypes. It has been established that the biologically active lipid oleamide allosterically interacts with the 5-HT(7) receptor to regulate its transmission. The most well characterized effects of oleamide administration are induction of sleep and hypothermia. Here, we demonstrate, by using mice lacking the 5-HT(7) receptor, that 5-HT-induced hypothermia is mediated by the 5-HT(7) receptor. Both 5-HT and 5-carboxamidotryptamine, a 5-HT(1) and 5-HT(7) receptor agonist, in physiological doses fail to induce hypothermia in 5-HT(7) knockout mice. In contrast, oleamide was equally effective in inducing hypothermia in mice lacking the 5-HT(7) receptors as in wild-type mice. When administered together, 5-HT and oleamide showed additive or greater than additive effects in reducing body temperature. Taken together, the results show that 5-HT-induced hypothermia is mediated by the 5-HT(7) receptor, and that oleamide may act through an independent mechanism as well as at an allosteric 5-HT(7) receptor site to regulate body temperature.

The sleep hormone oleamide modulates inhibitory ionotropic receptors in mammalian CNS in vitro

1. We examine the sensitivity of GABA(A) and glycine receptors (same ionotropic superfamily) to oleamide. We address subunit-dependence/modulatory mechanisms and analogies with depressant drugs. 2. Oleamide modulated human GABA(A) currents (alpha(1)beta(2)gamma(2L)) in oocytes (EC(50), 28.94+/-s.e.mean of 1.4 microM; Maximum 216%+/-35 of control, n=4). Modulation of human alpha1 glycine homo-oligomers (significant), was less marked, with a lower EC(50) (P<0.05) than GABA receptors (EC(50), 22.12+/-1.4 microM; Maximum 171%+/-30, n=11). 3. Only the hypnogenic cis geometric isomer enhanced glycine currents (without altering slope or maximal current, it reduced the glycine EC(50) from 322 to 239 microM: P<0.001). Modulation was not voltage-dependent or associated with a shift in E(r). 4. beta 1 containing GABA(A) receptors (insensitive to many depressant drugs) were positively modulated by oleamide. Oleamide efficacy was circa 2x greater at alpha(1)beta(1)gamma(2L) than alpha(1)beta(2)gamma(2L) (P=0.007). Splice variation in gamma subunits did not alter oleamide sensitivity. 5. cis-9,10-Octadecenoamide had no effect on the equilibrium binding of [(3)H]-muscimol or [(3)H]-EBOB to mouse brain membranes. It does not directly mimic GABA, or operate as a neurosteroid-, benzodiazepine- or barbiturate-like modulator of GABA(A)-receptors. 6. The transport of [(3)H]-GABA into mouse brain synaptoneurosomes was unaffected by high micromolar concentrations of cis-9,10-octadecenoamide. Oleamide does not enhance GABA-ergic currents or prolong IPSCs by inhibiting GABA transport. 7. Oleamide is a non-selective modulator of inhibitory ionotropic receptors. The sleep lipid exerts its effects indirectly, or at a novel recognition site on the GABA(A) complex.