1 803 151 CENTRAL CONTROL OF VISCERAL PAIN AND URINARY TRACT FUNCTION. AFFERENT INPUT FROM ADELTA AND C-FIBRES INNERVATING THE URINARY BLADDER ARE PROCESSED DIFFERENTLY BY THE BRAIN, AND HAVE DIFFERENT ROLES IN SIGNALING BLADDER SENSATION. ADELTA FIBRES THAT SIGNAL BLADDER FILLING ACTIVATE A SPINO-BULBO-SPINAL LOOP, WHICH RELAYS IN THE MIDBRAIN PERIAQUEDUCTAL GREY (PAG) AND PONTINE MICTURITION CENTRE (PMC). THE EXCITABILITY OF THIS CIRCUITRY IS REGULATED BY TONIC GABAERGIC INHIBITORY PROCESSES. IN HUMANS AND SOCIALISED ANIMALS MICTURITION IS NORMALLY UNDER VOLITIONAL CONTROL AND INFLUENCED BY A HOST OF PSYCHOSOCIAL FACTORS. HIGHER NERVOUS DECISION-MAKING IN A SOCIAL CONTEXT TO 'GO NOW' OR 'DO NOT GO' PROBABLY RESIDES IN FRONTAL CORTICAL AREAS, WHICH ACT AS A CENTRAL CONTROL SWITCH FOR MICTURITION. EXPOSURE TO PSYCHOSOCIAL STRESS CAN HAVE PROFOUNDLY DISRUPTIVE INFLUENCE ON THE PROCESS AND LEAD TO MALADAPTIVE CHANGES IN THE BLADDER. DURING SLEEPING THE VOIDING REFLEX THRESHOLD APPEARS TO BE RESET TO A HIGHER LEVEL TO PROMOTE URINARY CONTINENCE. UNDER PHYSIOLOGICAL CONDITIONS C-FIBRE BLADDER AFFERENTS ARE NORMALLY SILENT BUT ARE ACTIVATED IN INFLAMMATORY BLADDER STATES AND BY INTENSE DISTENDING PRESSURE. FOLLOWING PROLONGED STIMULATION VISCERAL NOCICEPTORS SENSITISE, LEADING TO A LOWERED THRESHOLD AND HEIGHTENED SENSITIVITY. IN ADDITION, SENSITIZATION MAY OCCUR WITHIN THE CENTRAL PAIN PROCESSING CIRCUITRY, WHICH OUTLASTS THE ORIGINAL NOCICEPTIVE INSULT. VISCERAL NOCICEPTION MAY ALSO BE INFLUENCED BY GENETIC AND ENVIRONMENTAL INFLUENCES. A PERIOD OF CHRONIC STRESS CAN PRODUCE INCREASED SENSITIVITY TO VISCERAL PAIN THAT LASTS FOR MONTHS. ADVERSE EARLY LIFE EVENTS CAN PRODUCE EVEN LONGER LASTING EPIGENETIC CHANGES, WHICH INCREASE THE INDIVIDUAL'S SUSCEPTIBILITY TO DEVELOPING VISCERAL PAIN STATES IN ADULTHOOD. 2016 2 2509 30 EPIGENETICS AND PAIN: NEW INSIGHTS TO AN OLD PROBLEM. PHYSICIANS AND NEUROSCIENTISTS HAVE LONG OBSERVED THAT FACTORS SUCH AS THOUGHTS, EMOTIONS, AND EXPECTATIONS CAN INFLUENCE THE PERCEPTION OF PAIN. PAIN CAN BE DESCRIBED AS AN UNPLEASANT SENSATION THAT CAUSES PHYSICAL DISCOMFORT AND EMOTIONAL DISTRESS. IT ALERTS AN INDIVIDUAL TO SEEK HELP AND IS THE MAIN COMPLAINT THAT BRINGS INDIVIDUALS TO PHYSICIANS. THOUGH IT IS ASSOCIATED WITH PROBABLE TISSUE DAMAGE, SUCH DAMAGE MAY BE SUBTLE, SOMETIMES INVOLVING THE RELEASE OF ALGESIC CHEMICALS, AND ALSO INFLUENCED BY ATTITUDES, BELIEFS, PERSONALITY, AND SOCIAL FACTORS. THE PERCEPTION OF PAIN MAY VARY DUE TO A MULTITUDE OF THESE FACTORS INFLUENCING THE ASCENDING SENSORY IMPULSE PROPAGATION TO THE PRIMARY SOMATOSENSORY CORTEX. THE GENETICS AND EPIGENETICS OF PAIN MODULATORS HAVE BEEN PREVIOUSLY STUDIED, BUT THERE IS A LACK OF APPLICATION IN THE EVERYDAY MANAGEMENT AND TREATMENT OF PAIN DUE TO THE PAUCITY OF VALID EVIDENCE-BASED DATA. WE USED THE PUBMED DATABASE AS OUR PRIMARY TOOL FOR RESEARCHING CURRENT LITERATURE ON THIS TOPIC. THE MESH TERMS USED INCLUDED: GENE MODIFICATION, EPIGENETICS, GENES, PAIN, ANALGESIA, "TYPES OF PAIN, AND THEORIES OF PAIN. THE RESULTS WERE FILTERED AS FOLLOWS: PUBLICATIONS WITHIN THE LAST 10 YEARS, GENERALIZED PAIN STUDIES REGARDING THE BIOPSYCHOSOCIAL ASPECT OF PAIN, PERTINENT GENES, AND EPIGENETIC MODULATION OF THOSE GENES; 52 PUBLICATIONS WERE SELECTED FOR REVIEW. BY ADDRESSING THE EXTERNAL FACTORIAL CAUSES AND THE APPROPRIATE APPLICATION OF EPIGENETIC PRINCIPLES WHICH AFFECT PAIN PERCEPTION, IT IS HOPED THAT THIS REVIEW WILL MOTIVATE FUTURE ADVANCEMENTS IN THE MANAGEMENT OF ACUTE AND/OR CHRONIC PAIN. 2022 3 6007 37 THE ANATOMY OF PAIN AND SUFFERING IN THE BRAIN AND ITS CLINICAL IMPLICATIONS. PAIN IS AN UNPLEASANT SENSORY AND EMOTIONAL EXPERIENCE ASSOCIATED WITH ACTUAL OR POTENTIAL TISSUE DAMAGE. CHRONIC PAIN, WITH A PREVALENCE OF 20-30 % IS THE MAJOR CAUSE OF HUMAN SUFFERING WORLDWIDE, BECAUSE EFFECTIVE, SPECIFIC AND SAFE THERAPIES HAVE YET TO BE DEVELOPED. IT IS UNEVENLY DISTRIBUTED AMONG SEXES, WITH WOMEN EXPERIENCING MORE PAIN AND SUFFERING. CHRONIC PAIN CAN BE ANATOMICALLY AND PHENOMENOLOGICALLY DISSECTED INTO THREE SEPARABLE BUT INTERACTING PATHWAYS, A LATERAL 'PAINFULNESS' PATHWAY, A MEDIAL 'SUFFERING' PATHWAY AND A DESCENDING PAIN INHIBITORY PATHWAY. ONE MAY HAVE PAIN(FULLNESS) WITHOUT SUFFERING AND SUFFERING WITHOUT PAIN(FULLNESS). PAIN SENSATION LEADS TO SUFFERING VIA A COGNITIVE, EMOTIONAL AND AUTONOMIC PROCESSING, AND IS EXPRESSED AS ANGER, FEAR, FRUSTRATION, ANXIETY AND DEPRESSION. THE MEDIAL PATHWAY OVERLAPS WITH THE SALIENCE AND STRESS NETWORKS, EXPLAINING THAT BEHAVIOURAL RELEVANCE OR MEANING DETERMINES THE SUFFERING ASSOCIATED WITH PAINFULNESS. GENETIC AND EPIGENETIC INFLUENCES TRIGGER CHRONIC NEUROINFLAMMATORY CHANGES WHICH ARE INVOLVED IN TRANSITIONING FROM ACUTE TO CHRONIC PAIN. BASED ON THE CONCEPT OF THE BAYESIAN BRAIN, PAIN (AND SUFFERING) CAN BE REGARDED AS THE CONSEQUENCE OF AN IMBALANCE BETWEEN THE TWO ASCENDING AND THE DESCENDING PAIN INHIBITORY PATHWAYS UNDER CONTROL OF THE REWARD SYSTEM. THE THERAPEUTIC CLINICAL IMPLICATIONS OF THIS SIMPLE PAIN MODEL ARE OBVIOUS. AFTER CATEGORIZING THE WORKING MECHANISMS OF EACH OF THE AVAILABLE TREATMENTS (PAIN KILLERS, PSYCHOPHARMACOLOGY, PSYCHOTHERAPY, NEUROMODULATION, PSYCHOSURGERY, SPINAL CORD STIMULATION) TO 1 OR MORE OF THE 3 PATHWAYS, A RATIONAL COMBINATION CAN BE PROPOSED OF ACTIVATING THE DESCENDING PAIN INHIBITORY PATHWAY IN COMBINATION WITH INHIBITION OF THE MEDIAL AND LATERAL PATHWAY, SO AS TO REBALANCE THE PAIN (AND SUFFERING) PATHWAYS. 2021 4 6389 34 THE ROLE OF THE ENDOCANNABINOID SYSTEM IN THE BRAIN-GUT AXIS. THE ACTIONS OF CANNABIS ARE MEDIATED BY RECEPTORS THAT ARE PART OF AN ENDOGENOUS CANNABINOID SYSTEM. THE ENDOCANNABINOID SYSTEM (ECS) CONSISTS OF THE NATURALLY OCCURRING LIGANDS N-ARACHIDONOYLETHANOLAMINE (ANANDAMIDE) AND 2-ARACHIDONOYLGLYCEROL (2-AG), THEIR BIOSYNTHETIC AND DEGRADATIVE ENZYMES, AND THE CANNABINOID (CB) RECEPTORS CB1 AND CB2. THE ECS IS A WIDELY DISTRIBUTED TRANSMITTER SYSTEM THAT CONTROLS GUT FUNCTIONS PERIPHERALLY AND CENTRALLY. IT IS AN IMPORTANT PHYSIOLOGIC REGULATOR OF GASTROINTESTINAL MOTILITY. POLYMORPHISMS IN THE GENE ENCODING CB1 (CNR1) HAVE BEEN ASSOCIATED WITH SOME FORMS OF IRRITABLE BOWEL SYNDROME. THE ECS IS INVOLVED IN THE CONTROL OF NAUSEA AND VOMITING AND VISCERAL SENSATION. THE HOMEOSTATIC ROLE OF THE ECS ALSO EXTENDS TO THE CONTROL OF INTESTINAL INFLAMMATION. WE REVIEW THE MECHANISMS BY WHICH THE ECS LINKS STRESS AND VISCERAL PAIN. CB1 IN SENSORY GANGLIA CONTROLS VISCERAL SENSATION, AND TRANSCRIPTION OF CNR1 IS MODIFIED THROUGH EPIGENETIC PROCESSES UNDER CONDITIONS OF CHRONIC STRESS. THESE PROCESSES MIGHT LINK STRESS WITH ABDOMINAL PAIN. THE ECS IS ALSO INVOLVED CENTRALLY IN THE MANIFESTATION OF STRESS, AND ENDOCANNABINOID SIGNALING REDUCES THE ACTIVITY OF HYPOTHALAMIC-PITUITARY-ADRENAL PATHWAYS VIA ACTIONS IN SPECIFIC BRAIN REGIONS, NOTABLY THE PREFRONTAL CORTEX, AMYGDALA, AND HYPOTHALAMUS. AGENTS THAT MODULATE THE ECS ARE IN EARLY STAGES OF DEVELOPMENT FOR TREATMENT OF GASTROINTESTINAL DISEASES. INCREASING OUR UNDERSTANDING OF THE ECS WILL GREATLY ADVANCE OUR KNOWLEDGE OF INTERACTIONS BETWEEN THE BRAIN AND GUT AND COULD LEAD TO NEW TREATMENTS FOR GASTROINTESTINAL DISORDERS. 2016 5 5804 33 STRAIN AND SEX DEPENDENT EFFECTS OF ISOLATION HOUSING RELATIVE TO ENVIRONMENTAL ENRICHMENT ON OPERANT SENSATION SEEKING IN MICE. SENSATION SEEKING IS A MULTIDIMENSIONAL PHENOTYPE THAT PREDICTS THE DEVELOPMENT OF DRUG ADDICTION IN HUMANS AND ADDICTION-LIKE DRUG SEEKING IN RODENTS. SEVERAL LINES OF EVIDENCE SUGGEST THAT CHRONIC STRESS INCREASES SENSATION SEEKING AND ADDICTION-LIKE DRUG SEEKING THROUGH COMMON GENETIC MECHANISMS. DISCOVERY AND CHARACTERIZATION OF THESE MECHANISMS WOULD REVEAL HOW CHRONIC STRESS INTERACTS WITH THE GENOME TO INFLUENCE SENSATION SEEKING AND HOW DRUGS OF ABUSE HIJACK THESE FUNDAMENTAL REWARD MECHANISMS TO DRIVE ADDICTION. TO THIS END, WE TESTED THE HYPOTHESIS THAT CHRONIC ISOLATION HOUSING STRESS (RELATIVE TO ENVIRONMENTAL ENRICHMENT) INFLUENCES OPERANT SENSATION SEEKING AS A FUNCTION OF STRAIN, SEX, OR THEIR INTERACTION. TO DETERMINE IF THE BXD RECOMBINANT INBRED PANEL COULD BE USED TO IDENTIFY GENETIC AND EPIGENETIC MECHANISMS UNDERLYING ANY IDENTIFIED GENE-BY-ENVIRONMENT INTERACTIONS, WE USED MICE FROM THE TWO BXD FOUNDER STRAINS. FOLLOWING 10 WEEKS OF DIFFERENTIAL HOUSING, WE ASSESSED OPERANT SENSATION SEEKING USING SEVERAL REINFORCEMENT SCHEDULES. THE PRIMARY FINDING FROM THIS STUDY WAS THAT DBA/2J BUT NOT C57BL/6J MICE WERE SIGNIFICANTLY VULNERABLE TO AN ISOLATION-INDUCED INCREASE (RELATIVE TO ENVIRONMENTAL ENRICHMENT) IN SENSATION SEEKING DURING EXTINCTION WHEN THE SENSORY REWARD WAS NO LONGER AVAILABLE; THIS EFFECT WAS SIGNIFICANTLY MORE ROBUST IN FEMALES. THESE DATA REVEAL A PREVIOUSLY UNKNOWN ISOLATION-INDUCED EFFECT ON EXTINCTION OF OPERANT SENSATION SEEKING THAT IS SEX-DEPENDENT, ADDICTION-RELEVANT, AND THAT CAN BE DISSECTED USING THE BXD RECOMBINANT INBRED PANEL. 2021 6 3196 20 HDAC INHIBITORS RESTORE C-FIBRE SENSITIVITY IN EXPERIMENTAL NEUROPATHIC PAIN MODEL. BACKGROUND AND PURPOSE: HYPOESTHESIA IS A CLINICAL FEATURE OF NEUROPATHIC PAIN. THE FEATURE IS PARTLY EXPLAINED BY THE EVIDENCE OF EPIGENETIC REPRESSION OF NAV 1.8 SODIUM CHANNEL IN THE DORSAL ROOT GANGLION (DRG). EXPERIMENTAL APPROACH: WE INVESTIGATED THE POSSIBILITY OF TRICHOSTATIN A (TSA), VALPROIC ACID (VPA) AND SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) TO REVERSE THE UNIQUE C-FIBRE SENSITIVITY OBSERVED FOLLOWING PARTIAL LIGATION OF SCIATIC NERVE IN MICE. KEY RESULTS: NERVE INJURY-INDUCED DOWN-REGULATION OF DRG NAV 1.8 SODIUM CHANNEL AND C-FIBRE-RELATED HYPOESTHESIA WERE REVERSED BY TSA, VPA AND SAHA TREATMENTS, WHICH INHIBIT HISTONE DEACETYLASE (HDAC), AND INCREASE HISTONE ACETYLATION AT THE REGULATORY SEQUENCE OF NAV 1.8. CONCLUSIONS AND IMPLICATIONS: TAKEN TOGETHER, THESE STUDIES PROVIDE THE EVIDENCE THAT HYPOESTHESIA AND UNDERLYING DOWN-REGULATION OF NAV 1.8, NEGATIVE SYMPTOMS OBSERVED IN NERVE INJURY-INDUCED NEUROPATHIC PAIN MODELS ARE REGULATED BY AN EPIGENETIC CHROMATIN REMODELLING THROUGH HDAC-RELATED MACHINERIES. 2013 7 5331 30 PUTTING THE PIECES TOGETHER IN GILLES DE LA TOURETTE SYNDROME: EXPLORING THE LINK BETWEEN CLINICAL OBSERVATIONS AND THE BIOLOGICAL BASIS OF DYSFUNCTION. GILLES DE LA TOURETTE SYNDROME IS A COMPLEX, IDIOPATHIC NEUROPSYCHIATRIC DISORDER WHOSE PATHOPHYSIOLOGICAL MECHANISMS HAVE YET TO BE ELUCIDATED. IT IS PHENOTYPICALLY HETEROGENEOUS AND MANIFESTS MORE OFTEN THAN NOT WITH BOTH MOTOR AND BEHAVIORAL IMPAIRMENT, ALTHOUGH TICS ARE ITS CLINICAL HALLMARK. TICS THEMSELVES PRESENT WITH A COMPLEX PROFILE AS THEY CHARACTERISTICALLY WAX AND WANE AND ARE OFTEN PRECEDED BY PREMONITORY SOMATOSENSORY SENSATIONS TO WHICH IT IS SAID A TIC IS THE RESPONSE. HIGHLY COMORBID WITH OBSESSIVE-COMPULSIVE DISORDER AND ATTENTION DEFICIT-HYPERACTIVITY DISORDER, IT IS PURPORTED TO BE AN EPIGENETIC, NEURODEVELOPMENTAL SPECTRUM DISORDER WITH A COMPLEX GENETIC PROFILE. IT HAS A CHILDHOOD ONSET, OCCURS DISPROPORTIONATELY IN MALES, AND SHOWS SPONTANEOUS SYMPTOMATIC ATTENUATION BY ADULTHOOD IN THE MAJORITY OF THOSE AFFLICTED. ALTHOUGH NOT FULLY UNDERSTOOD, ITS NEUROBIOLOGICAL BASIS IS LINKED TO DYSFUNCTION IN THE CORTICO-BASAL GANGLIA-THALAMO-CORTICAL NETWORK. TREATMENT MODALITIES FOR TOURETTE SYNDROME INCLUDE BEHAVIORAL, PHARMACOLOGICAL AND SURGICAL INTERVENTIONS, BUT THERE IS PRESENTLY NO CURE FOR THE DISORDER. FOR THOSE SEVERELY AFFECTED, DEEP BRAIN STIMULATION (DBS) HAS RECENTLY BECOME A VIABLE THERAPEUTIC OPTION. A KEY FACTOR TO ATTAINING OPTIMAL RESULTS FROM THIS SURGERY IS TARGET SELECTION, A TOPIC STILL UNDER DEBATE DUE TO THE COMPLEX CLINICAL PROFILE PRESENTED BY GTS PATIENTS. DEPENDING ON ITS PHENOTYPIC EXPRESSION AND THE MOST PROBLEMATIC ASPECT OF THE DISORDER FOR THE INDIVIDUAL, ONE OF THREE BRAIN REGIONS IS MOST COMMONLY CHOSEN FOR STIMULATION: THE THALAMUS, GLOBUS PALLIDUS, OR NUCLEUS ACCUMBENS. NEUROPHYSIOLOGICAL ANALYSES OF INTRA- AND POST-OPERATIVE HUMAN ELECTROPHYSIOLOGICAL RECORDINGS FROM CLINICAL DBS STUDIES SUGGEST A LINK BETWEEN TIC BEHAVIOR AND ACTIVITY IN BOTH THE THALAMUS AND GLOBUS PALLIDUS. IN PARTICULAR, CHRONIC RECORDINGS FROM THE THALAMUS HAVE SHOWN A CORRELATION BETWEEN SYMPTOMATOLOGY AND (1) SPECTRAL ACTIVITY IN GAMMA BAND POWER AND (2) THETA/GAMMA CROSS FREQUENCY COHERENCE. THESE RESULTS SUGGEST GAMMA OSCILLATIONS AND THETA/GAMMA CROSS CORRELATION DYNAMICS MAY SERVE AS BIOMARKERS FOR DYSFUNCTION. WHILE ACUTE AND CHRONIC RECORDINGS FROM HUMAN SUBJECTS UNDERGOING DBS HAVE PROVIDED BETTER INSIGHT INTO TIC GENESIS AND THE NEUROPATHOPHYSIOLOGICAL MECHANISMS UNDERLYING TOURETTE SYNDROME, THESE STUDIES ARE STILL SPARSE AND THE FIELD WOULD GREATLY BENEFIT FROM FURTHER INVESTIGATIONS. THIS REVIEW REPORTS DATA AND DISCOVERIES OF SCIENTIFIC AND CLINICAL RELEVANCE FROM A WIDE VARIETY OF METHODS AND PROVIDES UP-TO-DATE INFORMATION ABOUT OUR CURRENT UNDERSTANDING OF THE PATHOMECHANISMS UNDERLYING TOURETTE SYNDROME. IT GIVES A COMPREHENSIVE OVERVIEW OF THE CURRENT STATE OF KNOWLEDGE AND ADDRESSES OPEN QUESTIONS IN THE FIELD. 2017 8 6139 31 THE ETIOLOGICAL CONTRIBUTION OF GABAERGIC PLASTICITY TO THE PATHOGENESIS OF NEUROPATHIC PAIN. NEUROPATHIC PAIN DEVELOPING AFTER PERIPHERAL OR CENTRAL NERVE INJURY IS THE RESULT OF PATHOLOGICAL CHANGES GENERATED THROUGH COMPLEX MECHANISMS. DISRUPTION IN THE HOMEOSTASIS OF EXCITATORY AND INHIBITORY NEURONS WITHIN THE CENTRAL NERVOUS SYSTEM IS A CRUCIAL FACTOR IN THE FORMATION OF HYPERALGESIA OR ALLODYNIA OCCURRING WITH NEUROPATHIC PAIN. THE CENTRAL GABAERGIC PATHWAY HAS RECEIVED ATTENTION FOR ITS EXTENSIVE DISTRIBUTION AND FUNCTION IN NEURAL CIRCUITS, INCLUDING THE GENERATION AND DEVELOPMENT OF NEUROPATHIC PAIN. GABAERGIC INHIBITORY CHANGES THAT OCCUR IN THE INTERNEURONS ALONG DESCENDING MODULATORY AND NOCICEPTIVE PATHWAYS IN THE CENTRAL NERVOUS SYSTEM ARE BELIEVED TO GENERATE NEURONAL PLASTICITY, SUCH AS SYNAPTIC PLASTICITY OR FUNCTIONAL PLASTICITY OF THE RELATED GENES OR PROTEINS, THAT IS THE FOUNDATION OF PERSISTENT NEUROPATHIC PAIN. THE PRIMARY GABAERGIC PLASTICITY OBSERVED IN NEUROPATHIC PAIN INCLUDES GABAERGIC SYNAPSE HOMO- AND HETEROSYNAPTIC PLASTICITY, DECREASED SYNTHESIS OF GABA, DOWN-EXPRESSION OF GLUTAMIC ACID DECARBOXYLASE AND GABA TRANSPORTER, ABNORMAL EXPRESSION OF NKCC1 OR KCC2, AND DISTURBED FUNCTION OF GABA RECEPTORS. IN THIS REVIEW, WE DESCRIBE POSSIBLE MECHANISMS ASSOCIATED WITH GABAERGIC PLASTICITY, SUCH AS CENTRAL SENSITIZATION AND GABAERGIC INTERNEURON APOPTOSIS, AND THE EPIGENETIC ETIOLOGIES OF GABAERGIC PLASTICITY IN NEUROPATHIC PAIN. MOREOVER, WE SUMMARIZE POTENTIAL THERAPEUTIC TARGETS OF GABAERGIC PLASTICITY THAT MAY ALLOW FOR SUCCESSFUL RELIEF OF HYPERALGESIA FROM NERVE INJURY. FINALLY, WE COMPARE THE EFFECTS OF THE GABAERGIC SYSTEM IN NEUROPATHIC PAIN TO OTHER TYPES OF CHRONIC PAIN TO UNDERSTAND THE CONTRIBUTION OF GABAERGIC PLASTICITY TO NEUROPATHIC PAIN. 2019 9 6617 29 UNDERPINNING THE NEUROBIOLOGICAL INTRICACIES ASSOCIATED WITH OPIOID TOLERANCE. THE OPIOID CRISIS IS A MAJOR THREAT OF THE 21ST CENTURY, WITH A REMARKABLE JUXTAPOSITION OF USE AND ABUSE. OPIOIDS ARE THE MOST POTENT AND EFFICACIOUS CLASS OF ANALGESICS, BUT DESPITE THEIR PROVEN THERAPEUTIC EFFICACY, THEY HAVE RECENTLY BEEN DEGRADED TO THIRD-LINE THERAPY FOR THE MANAGEMENT OF CHRONIC PAIN IN CLINICS. THE REASON BEHIND THIS IS THE DEVELOPMENT OF POTENTIAL SIDE EFFECTS AND TOLERANCE AFTER REPEATED DOSING. OPIOID TOLERANCE IS THE MAJOR LIMITING FACTOR LEADING TO THE WITHDRAWAL OF TREATMENT, SEVERE SIDE EFFECTS DUE TO DOSE ESCALATION, AND SOMETIMES EVEN DEATH OF THE PATIENTS. EVERY DAY MORE THAN 90 PEOPLE DIE DUE TO OPIOIDS OVERDOSE IN AMERICA, AND A SIMILAR TREND HAS BEEN SEEN ACROSS THE GLOBE. OVER THE PAST TWO DECADES, RESEARCHERS HAVE BEEN TRYING TO DISSECT THE NEUROBIOLOGICAL MECHANISM OF OPIOID TOLERANCE. RESEARCH ON OPIOID TOLERANCE SHIFTED TOWARD CENTRAL NERVOUS SYSTEM-BASED ADAPTATIONS BECAUSE TOLERANCE IS MUCH MORE THAN JUST A CELLULAR PHENOMENON. THUS, NEUROBIOLOGICAL ADAPTATIONS ASSOCIATED WITH OPIOID TOLERANCE ARE IMPORTANT TO UNDERSTAND IN ORDER TO FIND NEWER PAIN THERAPEUTICS. THESE ADAPTATIONS ARE ASSOCIATED WITH ALTERATIONS IN ASCENDING AND DESCENDING PAIN PATHWAYS, REWARD CIRCUITRY MODULATIONS, RECEPTOR DESENSITIZATION AND DOWN-REGULATION, RECEPTOR INTERNALIZATION, HETERODIMERIZATION, AND ALTERED EPIGENETIC REGULATION. THE PRESENT REVIEW IS FOCUSED ON NOVEL CIRCUITRIES ASSOCIATED WITH OPIOID TOLERANCE IN DIFFERENT AREAS OF THE BRAIN, SUCH AS PERIAQUEDUCTAL GRAY, ROSTRAL VENTROMEDIAL MEDULLA, DORSAL RAPHE NUCLEUS, VENTRAL TEGMENTAL AREA, AND NUCLEUS ACCUMBENS. UNDERSTANDING THE NEUROBIOLOGICAL MODULATIONS ASSOCIATED WITH CHRONIC OPIOID EXPOSURE AND TOLERANCE WILL PAVE THE WAY FOR THE DEVELOPMENT OF NOVEL PHARMACOLOGICAL TOOLS FOR SAFER AND BETTER MANAGEMENT OF CHRONIC PAIN IN PATIENTS. 2020 10 1773 32 EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY AND ANXIETY BEHAVIOR IS REVERSED BY HISTONE DEACETYLASE INHIBITION. STRESSFUL LIFE EVENTS, ESPECIALLY IN CHILDHOOD, CAN HAVE DETRIMENTAL EFFECTS ON HEALTH AND ARE ASSOCIATED WITH A HOST OF PSYCHIATRIC AND GASTROINTESTINAL DISORDERS INCLUDING IRRITABLE BOWEL SYNDROME (IBS). EARLY-LIFE STRESS CAN BE RECAPITULATED IN ANIMALS USING THE MATERNAL SEPARATION (MS) MODEL, EXHIBITING MANY KEY PHENOTYPIC OUTCOMES INCLUDING VISCERAL HYPERSENSITIVITY AND ANXIETY-LIKE BEHAVIORS. THE MOLECULAR MECHANISMS OF MS ARE UNCLEAR, BUT RECENT STUDIES POINT TO A ROLE FOR EPIGENETICS. HISTONE ACETYLATION IS A KEY EPIGENETIC MARK THAT IS ALTERED IN NUMEROUS STRESS-RELATED DISEASE STATES. HERE, WE INVESTIGATED THE ROLE OF HISTONE ACETYLATION IN EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY. INTERESTINGLY, INCREASED NUMBER OF PAIN BEHAVIORS AND REDUCED THRESHOLD OF VISCERAL SENSATION WERE ASSOCIATED WITH ALTERATIONS IN HISTONE ACETYLATION IN THE LUMBOSACRAL SPINAL CORD, A KEY REGION IN VISCERAL PAIN PROCESSING. MOREOVER, WE ALSO INVESTIGATED WHETHER THE HISTONE DEACETYLASE (HDAC) INHIBITOR, SUBEROYLANILIDE HYDROXAMIC ACID (SAHA), COULD REVERSE EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY AND STRESS-INDUCED FECAL PELLET OUTPUT IN THE MS MODEL. SIGNIFICANTLY, SAHA REVERSED BOTH OF THESE PARAMETERS. TAKEN TOGETHER, THESE DATA DESCRIBE, FOR THE FIRST TIME, A KEY ROLE OF HISTONE ACETYLATION IN THE PATHOPHYSIOLOGY OF EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY IN A WELL-ESTABLISHED MODEL OF IBS. THESE FINDINGS WILL INFORM NEW RESEARCH AIMED AT THE DEVELOPMENT OF NOVEL PHARMACEUTICAL APPROACHES TARGETING THE EPIGENETIC MACHINERY FOR NOVEL ANTI-IBS DRUGS. 2015 11 5051 37 PHARMACOLOGICAL RESCUE OF NOCICEPTIVE HYPERSENSITIVITY AND OXYTOCIN ANALGESIA IMPAIRMENT IN A RAT MODEL OF NEONATAL MATERNAL SEPARATION. OXYTOCIN (OT), KNOWN FOR ITS NEUROHORMONAL EFFECTS AROUND BIRTH, HAS RECENTLY BEEN SUGGESTED FOR BEING A CRITICAL DETERMINANT IN NEURODEVELOPMENTAL DISORDERS. THIS HYPOTHALAMIC NEUROPEPTIDE EXERTS A POTENT ANALGESIC EFFECT THROUGH AN ACTION ON THE NOCICEPTIVE SYSTEM. THIS ENDOGENOUS CONTROL OF PAIN HAS AN IMPORTANT ADAPTIVE VALUE BUT MIGHT BE ALTERED BY EARLY LIFE STRESS, POSSIBLY CONTRIBUTING TO ITS LONG-TERM CONSEQUENCES ON PAIN RESPONSES AND ASSOCIATED COMORBIDITIES. WE TESTED THIS HYPOTHESIS USING A RAT MODEL OF NEONATAL MATERNAL SEPARATION (NMS) KNOWN TO INDUCE LONG-TERM CONSEQUENCES ON SEVERAL BRAIN FUNCTIONS INCLUDING CHRONIC STRESS, ANXIETY, ALTERED SOCIAL BEHAVIOR, AND VISCERAL HYPERSENSITIVITY. WE FOUND THAT ADULT RATS WITH A HISTORY OF NMS WERE HYPERSENSITIVE TO NOXIOUS MECHANICAL/THERMAL HOT STIMULI AND TO INFLAMMATORY PAIN. WE FAILED TO OBSERVE OT RECEPTOR-MEDIATED STRESS-INDUCED ANALGESIA AND OT ANTIHYPERALGESIA AFTER CARRAGEENAN INFLAMMATION. THESE ALTERATIONS WERE PARTIALLY RESCUED IF NMS PUPS WERE TREATED BY INTRAPERITONEAL DAILY INJECTION DURING NMS WITH OT OR ITS DOWNSTREAM SECOND MESSENGER ALLOPREGNANOLONE. THE INVOLVEMENT OF EPIGENETIC CHANGES IN THESE ALTERATIONS WAS CONFIRMED SINCE NEONATAL TREATMENT WITH THE HISTONE DEACETYLASE INHIBITOR SAHA, NOT ONLY NORMALIZED NOCICEPTIVE SENSITIVITIES BUT ALSO RESTORED OT RECEPTOR-MEDIATED STRESS-INDUCED ANALGESIA AND THE ENDOGENOUS ANTIHYPERALGESIA IN INFLAMED NMS RATS. THERE IS GROWING EVIDENCE IN THE LITERATURE THAT EARLY LIFE STRESS MIGHT IMPAIR THE NOCICEPTIVE SYSTEM ONTOGENY AND FUNCTION. THIS STUDY SUGGESTS THAT THESE ALTERATIONS MIGHT BE RESTORED WHILE STIMULATING OT RECEPTOR SIGNALING OR HISTONE DEACETYLASE INHIBITORS, USING MOLECULES THAT ARE CURRENTLY AVAILABLE OR PART OF CLINICAL TRIALS FOR OTHER PATHOLOGIES. 2018 12 189 30 ACETYL-L-CARNITINE IN CHRONIC PAIN: A NARRATIVE REVIEW. ACETYL-L-CARNITINE (ALC) IS AN ENDOGENOUS MOLECULE THAT NOT ONLY PLAYS A ROLE IN ENERGY METABOLISM, BUT ALSO HAS ANTIOXIDANT PROPERTIES, PROTECTS FROM OXIDATIVE STRESS, MODULATES BRAIN NEUROTRANSMITTERS SUCH AS ACETYLCHOLINE, SEROTONIN AND DOPAMINE, AND ACTS ON NEUROTROPHIC FACTORS SUCH AS NERVE GROWTH FACTOR (NGF) AND METABOTROPIC GLUTAMATE (MGLU) RECEPTORS BY MEANS OF EPIGENETIC MECHANISMS. IMPORTANTLY, IT INDUCES MGLU2 EXPRESSION AT NERVE TERMINALS, THUS GIVING RISE TO ANALGESIA AND PREVENTING SPINAL SENSITISATION. IT HAS ALSO BEEN FOUND TO HAVE EVEN LONG-TERM NEUROTROPHIC AND ANALGESIC ACTIVITY IN EXPERIMENTAL MODELS OF CHRONIC INFLAMMATORY AND NEUROPATHIC PAIN. THE AIM OF THIS NARRATIVE REVIEW IS TO SUMMARISE THE CURRENT EVIDENCE REGARDING THE USE OF ALC IN PATIENTS WITH CHRONIC PAIN, AND COGNITIVE AND MOOD DISORDERS, AND INVESTIGATE THE RATIONALE UNDERLYING ITS USE IN PATIENTS WITH FIBROMYALGIA SYNDROME, WHICH IS CHARACTERISED BY NOCIPLASTIC CHANGES THAT INCREASE THE SENSITIVITY OF THE NERVOUS SYSTEM TO PAIN. 2021 13 5831 44 STRESS-INDUCED CHRONIC VISCERAL PAIN OF GASTROINTESTINAL ORIGIN. VISCERAL PAIN IS GENERALLY POORLY LOCALIZED AND CHARACTERIZED BY HYPERSENSITIVITY TO A STIMULUS SUCH AS ORGAN DISTENSION. IN CONCERT WITH CHRONIC VISCERAL PAIN, THERE IS A HIGH COMORBIDITY WITH STRESS-RELATED PSYCHIATRIC DISORDERS INCLUDING ANXIETY AND DEPRESSION. THE MECHANISMS LINKING VISCERAL PAIN WITH THESE OVERLAPPING COMORBIDITIES REMAIN TO BE ELUCIDATED. EVIDENCE SUGGESTS THAT LONG TERM STRESS FACILITATES PAIN PERCEPTION AND SENSITIZES PAIN PATHWAYS, LEADING TO A FEED-FORWARD CYCLE PROMOTING CHRONIC VISCERAL PAIN DISORDERS SUCH AS IRRITABLE BOWEL SYNDROME (IBS). EARLY LIFE STRESS (ELS) IS A RISK-FACTOR FOR THE DEVELOPMENT OF IBS, HOWEVER THE MECHANISMS RESPONSIBLE FOR THE PERSISTENT EFFECTS OF ELS ON VISCERAL PERCEPTION IN ADULTHOOD REMAIN INCOMPLETELY UNDERSTOOD. IN RODENT MODELS, STRESS IN ADULT ANIMALS INDUCED BY RESTRAINT AND WATER AVOIDANCE HAS BEEN EMPLOYED TO INVESTIGATE THE MECHANISMS OF STRESS-INDUCE PAIN. ELS MODELS SUCH AS MATERNAL SEPARATION, LIMITED NESTING, OR ODOR-SHOCK CONDITIONING, WHICH ATTEMPT TO MODEL EARLY CHILDHOOD EXPERIENCES SUCH AS NEGLECT, POVERTY, OR AN ABUSIVE CAREGIVER, CAN PRODUCE CHRONIC, SEXUALLY DIMORPHIC INCREASES IN VISCERAL SENSITIVITY IN ADULTHOOD. CHRONIC VISCERAL PAIN IS A CLASSIC EXAMPLE OF GENE X ENVIRONMENT INTERACTION WHICH RESULTS FROM MALADAPTIVE CHANGES IN NEURONAL CIRCUITRY LEADING TO NEUROPLASTICITY AND ABERRANT NEURONAL ACTIVITY-INDUCED SIGNALING. ONE POTENTIAL MECHANISM UNDERLYING THE PERSISTENT EFFECTS OF STRESS ON VISCERAL SENSITIVITY COULD BE EPIGENETIC MODULATION OF GENE EXPRESSION. WHILE THERE ARE RELATIVELY FEW STUDIES EXAMINING EPIGENETICALLY MEDIATED MECHANISMS INVOLVED IN VISCERAL NOCICEPTION, STRESS-INDUCED VISCERAL PAIN HAS BEEN LINKED TO ALTERATIONS IN DNA METHYLATION AND HISTONE ACETYLATION PATTERNS WITHIN THE BRAIN, LEADING TO INCREASED EXPRESSION OF PRO-NOCICEPTIVE NEUROTRANSMITTERS. THIS REVIEW WILL DISCUSS THE POTENTIAL NEURONAL PATHWAYS AND MECHANISMS RESPONSIBLE FOR STRESS-INDUCED EXACERBATION OF CHRONIC VISCERAL PAIN. ADDITIONALLY, WE WILL REVIEW THE IMPORTANCE OF SPECIFIC EXPERIMENTAL MODELS OF ADULT STRESS AND ELS IN ENHANCING OUR UNDERSTANDING OF THE BASIC MOLECULAR MECHANISMS OF PAIN PROCESSING. 2017 14 4645 32 NEUROPATHIC PAIN: FROM MECHANISMS TO TREATMENT. NEUROPATHIC PAIN CAUSED BY A LESION OR DISEASE OF THE SOMATOSENSORY NERVOUS SYSTEM IS A COMMON CHRONIC PAIN CONDITION WITH MAJOR IMPACT ON QUALITY OF LIFE. EXAMPLES INCLUDE TRIGEMINAL NEURALGIA, PAINFUL POLYNEUROPATHY, POSTHERPETIC NEURALGIA, AND CENTRAL POSTSTROKE PAIN. MOST PATIENTS COMPLAIN OF AN ONGOING OR INTERMITTENT SPONTANEOUS PAIN OF, FOR EXAMPLE, BURNING, PRICKING, SQUEEZING QUALITY, WHICH MAY BE ACCOMPANIED BY EVOKED PAIN, PARTICULAR TO LIGHT TOUCH AND COLD. ECTOPIC ACTIVITY IN, FOR EXAMPLE, NERVE-END NEUROMA, COMPRESSED NERVES OR NERVE ROOTS, DORSAL ROOT GANGLIA, AND THE THALAMUS MAY IN DIFFERENT CONDITIONS UNDERLIE THE SPONTANEOUS PAIN. EVOKED PAIN MAY SPREAD TO NEIGHBORING AREAS, AND THE UNDERLYING PATHOPHYSIOLOGY INVOLVES PERIPHERAL AND CENTRAL SENSITIZATION. MALADAPTIVE STRUCTURAL CHANGES AND A NUMBER OF CELL-CELL INTERACTIONS AND MOLECULAR SIGNALING UNDERLIE THE SENSITIZATION OF NOCICEPTIVE PATHWAYS. THESE INCLUDE ALTERATION IN ION CHANNELS, ACTIVATION OF IMMUNE CELLS, GLIAL-DERIVED MEDIATORS, AND EPIGENETIC REGULATION. THE MAJOR CLASSES OF THERAPEUTICS INCLUDE DRUGS ACTING ON ALPHA(2)DELTA SUBUNITS OF CALCIUM CHANNELS, SODIUM CHANNELS, AND DESCENDING MODULATORY INHIBITORY PATHWAYS. 2021 15 4615 28 NERVE INJURY DIMINISHES OPIOID ANALGESIA THROUGH LYSINE METHYLTRANSFERASE-MEDIATED TRANSCRIPTIONAL REPRESSION OF MU-OPIOID RECEPTORS IN PRIMARY SENSORY NEURONS. THE MU-OPIOID RECEPTOR (MOR, ENCODED BY OPRM1) AGONISTS ARE THE MAINSTAY ANALGESICS FOR TREATING MODERATE TO SEVERE PAIN. NERVE INJURY CAUSES DOWN-REGULATION OF MORS IN THE DORSAL ROOT GANGLION (DRG) AND DIMINISHES THE OPIOID EFFECT ON NEUROPATHIC PAIN. HOWEVER, THE EPIGENETIC MECHANISMS UNDERLYING THE DIMINISHED MOR EXPRESSION CAUSED BY NERVE INJURY ARE NOT CLEAR. G9A (ENCODED BY EHMT2), A HISTONE 3 AT LYSINE 9 METHYLTRANSFERASE, IS A KEY CHROMATIN REGULATOR RESPONSIBLE FOR GENE SILENCING. IN THIS STUDY, WE DETERMINED THE ROLE OF G9A IN DIMINISHED MOR EXPRESSION AND OPIOID ANALGESIC EFFECTS IN ANIMAL MODELS OF NEUROPATHIC PAIN. WE FOUND THAT NERVE INJURY IN RATS INDUCED A LONG-LASTING REDUCTION IN THE EXPRESSION LEVEL OF MORS IN THE DRG BUT NOT IN THE SPINAL CORD. NERVE INJURY CONSISTENTLY INCREASED THE ENRICHMENT OF THE G9A PRODUCT HISTONE 3 AT LYSINE 9 DIMETHYLATION IN THE PROMOTER OF OPRM1 IN THE DRG. G9A INHIBITION OR SIRNA KNOCKDOWN FULLY REVERSED MOR EXPRESSION IN THE INJURED DRG AND POTENTIATED THE MORPHINE EFFECT ON PAIN HYPERSENSITIVITY INDUCED BY NERVE INJURY. IN MICE LACKING EHMT2 IN DRG NEURONS, NERVE INJURY FAILED TO REDUCE THE EXPRESSION LEVEL OF MORS AND THE MORPHINE EFFECT. IN ADDITION, G9A INHIBITION OR EHMT2 KNOCKOUT IN DRG NEURONS NORMALIZED NERVE INJURY-INDUCED REDUCTION IN THE INHIBITORY EFFECT OF THE OPIOID ON SYNAPTIC GLUTAMATE RELEASE FROM PRIMARY AFFERENT NERVES. OUR FINDINGS INDICATE THAT G9A CONTRIBUTES CRITICALLY TO TRANSCRIPTIONAL REPRESSION OF MORS IN PRIMARY SENSORY NEURONS IN NEUROPATHIC PAIN. G9A INHIBITORS MAY BE USED TO ENHANCE THE OPIOID ANALGESIC EFFECT IN THE TREATMENT OF CHRONIC NEUROPATHIC PAIN. 2016 16 6536 30 TRANSCRIPTIONAL REGULATION OF TYPE-2 METABOTROPIC GLUTAMATE RECEPTORS: AN EPIGENETIC PATH TO NOVEL TREATMENTS FOR CHRONIC PAIN. ACTIVATION OF METABOTROPIC GLUTAMATE 2 (MGLU2) RECEPTORS INHIBITS PAIN TRANSMISSION AT THE SYNAPSES BETWEEN PRIMARY AFFERENT FIBERS AND NEURONS IN THE DORSAL HORN OF THE SPINAL CORD. IN ADDITION, MGLU2 RECEPTORS ARE FOUND IN PERIPHERAL NOCICEPTORS, AND IN PAIN-REGULATORY CENTERS OF THE BRAIN STEM AND FOREBRAIN. MGLU2 RECEPTOR AGONISTS PRODUCE ANALGESIA IN MODELS OF INFLAMMATORY AND NEUROPATHIC PAIN, BUT THEIR USE IS LIMITED BY THE DEVELOPMENT OF TOLERANCE. A NEW THERAPEUTIC STRATEGY COULD BE BASED ON THE TRANSCRIPTIONAL REGULATION OF MGLU2 RECEPTORS VIA THE ACETYLATION-PROMOTED ACTIVATION OF THE P65/RELA TRANSCRIPTION FACTOR. "EPIGENETIC" DRUGS THAT INCREASE MGLU2 RECEPTOR EXPRESSION, INCLUDING L-ACETYLCARNITINE AND INHIBITORS OF HISTONE DEACETYLASES, HAVE A DIFFERENT ANALGESIC PROFILE WITH NO TOLERANCE TO THE THERAPEUTIC EFFECT AFTER REPEATED DOSING. 2010 17 4619 26 NERVE TRAUMA-CAUSED DOWNREGULATION OF OPIOID RECEPTORS IN PRIMARY AFFERENT NEURONS: MOLECULAR MECHANISMS AND POTENTIAL MANAGEMENTS. NEUROPATHIC PAIN IS THE MOST COMMON CLINICAL DISORDER DESTROYING THE QUALITY OF PATIENT LIFE AND LEADING TO A MARKED ECONOMIC AND SOCIAL BURDEN. OPIOIDS ARE STILL LAST OPTION FOR PHARMACOLOGICAL TREATMENT OF THIS DISORDER, BUT THEIR ANTINOCICEPTIVE EFFECTS ARE LIMITED IN PART DUE TO THE DOWNREGULATION OF OPIOID RECEPTORS IN THE PRIMARY AFFERENT NEURONS AFTER PERIPHERAL NERVE TRAUMA. HOW THIS DOWNREGULATION OCCURS IS NOT COMPLETELY UNDERSTOOD, BUT RECENT STUDIES HAVE DEMONSTRATED THAT PERIPHERAL NERVE TRAUMA DRIVES THE ALTERATIONS IN EPIGENETIC MODIFICATIONS (INCLUDING DNA METHYLATION, HISTONE METHYLATION AND MCIRORNAS), EXPRESSION OF TRANSCRIPTION FACTORS, POST-TRANSCRIPTIONAL MODIFICATIONS (E.G., RNA METHYLATION) AND PROTEIN TRANSLATION INITIATION IN THE NEURONS OF NERVE TRAUMA-RELATED DORSAL ROOT GANGLION (DRG) AND THAT THESE ALTERNATIONS MAY BE ASSOCIATED WITH NERVE TRAUMA-CAUSED DOWNREGULATION OF DRG OPIOID RECEPTORS. THIS REVIEW PRESENTS HOW OPIOID RECEPTORS ARE DOWNREGULATED IN THE DRG AFTER PERIPHERAL NERVE TRAUMA, SPECIFICALLY FOCUSING ON DISTINCT MOLECULAR MECHANISMS UNDERLYING TRANSCRIPTIONAL AND TRANSLATIONAL PROCESSES. THIS REVIEW ALSO DISCUSSES HOW THIS DOWNREGULATION CONTRIBUTES TO THE INDUCTION AND MAINTENANCE OF NEUROPATHIC PAIN. A DEEPER UNDERSTANDING OF THESE MOLECULAR MECHANISMS LIKELY PROVIDES A NOVEL AVENUE FOR PREVENTION AND/OR TREATMENT OF NEUROPATHIC PAIN. 2021 18 2321 26 EPIGENETIC REGULATION OF GENES THAT MODULATE CHRONIC STRESS-INDUCED VISCERAL PAIN IN THE PERIPHERAL NERVOUS SYSTEM. BACKGROUND & AIMS: CHRONIC STRESS ALTERS THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS, INCREASES GUT MOTILITY, AND INCREASES THE PERCEPTION OF VISCERAL PAIN. WE INVESTIGATED WHETHER EPIGENETIC MECHANISMS REGULATE CHRONIC STRESS-INDUCED VISCERAL PAIN IN THE PERIPHERAL NERVOUS SYSTEMS OF RATS. METHODS: MALE RATS WERE SUBJECTED TO 1 HOUR OF WATER AVOIDANCE STRESS EACH DAY, OR GIVEN DAILY SUBCUTANEOUS INJECTIONS OF CORTICOSTERONE, FOR 10 CONSECUTIVE DAYS. L4-L5 AND L6-S2 DORSAL ROOT GANGLIA (DRG) WERE COLLECTED AND COMPARED BETWEEN STRESSED AND CONTROL RATS (PLACED FOR 1 HOUR EACH DAY IN A TANK WITHOUT WATER). LEVELS OF CANNABINOID RECEPTOR 1 (CNR1), DNA (CYTOSINE-5-)-METHYLTRANSFERASE 1 (DNMT1), TRANSIENT RECEPTOR POTENTIAL VANILLOID TYPE 1 (TRPV1), AND EP300 WERE KNOCKED DOWN IN DRG NEURONS IN SITU WITH SMALL INTERFERING RNAS. WE MEASURED DNA METHYLATION AND HISTONE ACETYLATION AT GENES ENCODING THE GLUCOCORTICOID RECEPTOR (NR3C1), CNR1, AND TRPV1. VISCERAL PAIN WAS MEASURED IN RESPONSE TO COLORECTAL DISTENTION. RESULTS: CHRONIC STRESS WAS ASSOCIATED WITH INCREASED METHYLATION OF THE NR3C1 PROMOTER AND REDUCED EXPRESSION OF THIS GENE IN L6-S2, BUT NOT L4-L5, DRGS. STRESS ALSO WAS ASSOCIATED WITH UP-REGULATION IN DNMT1-ASSOCIATED METHYLATION OF THE CNR1 PROMOTER AND DOWN-REGULATION OF GLUCOCORTICOID-RECEPTOR-MEDIATED EXPRESSION OF CNR1 IN L6-S2, BUT NOT L4-L5, DRGS. CONCURRENTLY, CHRONIC STRESS INCREASED EXPRESSION OF THE HISTONE ACETYLTRANSFERASE EP300 AND INCREASED HISTONE ACETYLATION AT THE TRPV1 PROMOTER AND EXPRESSION OF THE TRPV1 RECEPTOR IN L6-S2 DRG NEURONS. KNOCKDOWN OF DNMT1 AND EP300 IN L6-S2 DRG NEURONS OF RATS REDUCED DNA METHYLATION AND HISTONE ACETYLATION, RESPECTIVELY, AND PREVENTED CHRONIC STRESS-INDUCED INCREASES IN VISCERAL PAIN. CONCLUSIONS: CHRONIC STRESS INCREASES DNA METHYLATION AND HISTONE ACETYLATION OF GENES THAT REGULATE VISCERAL PAIN SENSATION IN THE PERIPHERAL NERVOUS SYSTEM OF RATS. BLOCKING EPIGENETIC REGULATORY PATHWAYS IN SPECIFIC REGIONS OF THE SPINAL CORD MIGHT BE DEVELOPED TO TREAT PATIENTS WITH CHRONIC ABDOMINAL PAIN. 2015 19 5855 32 SUBSTANCE USE DISORDER A BIO-DIRECTIONAL SUBSET OF REWARD DEFICIENCY SYNDROME. THIS COMMENTARY IS TO INFORM CLINICIANS CHALLENGED WITH AN INCREASE IN PEOPLE SEEKING TREATMENT FOR SUBSTANCE USE DISORDER (SUD), THAT THE NINETY PERCENT REVOLVING DOOR, IS, IN PART, DUE TO POST-WITHDRAWAL, UNTREATED NEUROTOXICITY. THIS IMPAIRMENT ATTENUATES NEUROTRANSMITTER SIGNALING AND COMPROMISES RESTING STATE FUNCTIONAL CONNECTIVITY, LEADING TO UNWANTED SEQUELAE INCLUDING DEPRESSION, SLEEP DISTURBANCES, SENSATION SEEKING, LACK OF SATISFACTION AND IMPULSIVITY. NEUROIMAGING STUDIES INDICATE THAT NEUROBIOLOGICAL RECOVERY CAN TAKE YEARS. LIKE A "DOUBLE EDGE SWORD" SUD HAS A BIOLOGICAL BI -DIRECTIONAL (BIO-DIRECTIONAL) EFFECT ON THE BRAIN REWARD CIRCUITRY. THE ACUTE INTAKE OF PSYCHOACTIVE DRUGS RESULTS IN HEIGHTENED DOPAMINERGIC ACTIVITY, WHILE, THE OPPOSITE, HYPODOPAMINERGIA OCCURS FOLLOWING CHRONIC ABUSE. INDIVIDUALS WITH SUD CAN HAVE A GENETIC PREDISPOSITION, COMPOUNDED BY STRESS AND NEUROTOXICALLY INDUCED, EPIGENETIC INSULTS THAT IMPACT RECOVERY FROM PROTRACTED ABSTINENCE. FOLLOW-UP POST -SHORT-TERM RECOVERY USUALLY INCLUDES SUPPORTIVE THERAPIES AND PROGRAMS LIKE 12 -STEPS AND OTHER FELLOWSHIPS. HOWEVER, RELAPSE WILL USUALLY OCCUR IF POST -SHORT-TERM RECOVERY HYPODOPAMINERGIA IS NOT TREATED WITH ATTEMPTS AT EPIGENETIC MANIPULATION OF COMPROMISED BRAIN NEUROCHEMISTRY USING SOME MANNER OF PRO-DOPAMINE REGULATION. 2017 20 4518 18 MULTI-OMICS FOR BIOMARKER APPROACHES IN THE DIAGNOSTIC EVALUATION AND MANAGEMENT OF ABDOMINAL PAIN AND IRRITABLE BOWEL SYNDROME: WHAT LIES AHEAD. RELIABLE BIOMARKERS FOR COMMON DISORDERS OF GUT-BRAIN INTERACTION CHARACTERIZED BY ABDOMINAL PAIN, INCLUDING IRRITABLE BOWEL SYNDROME (IBS), ARE CRITICALLY NEEDED TO ENHANCE CARE AND DEVELOP INDIVIDUALIZED THERAPIES. THE DYNAMIC AND HETEROGENEOUS NATURE OF THE PATHOPHYSIOLOGICAL MECHANISMS THAT UNDERLIE VISCERAL HYPERSENSITIVITY HAVE CHALLENGED SUCCESSFUL BIOMARKER DEVELOPMENT. CONSEQUENTLY, EFFECTIVE THERAPIES FOR PAIN IN IBS ARE LACKING. HOWEVER, RECENT ADVANCES IN MODERN OMICS TECHNOLOGIES OFFER NEW OPPORTUNITIES TO ACQUIRE DEEP BIOLOGICAL INSIGHTS INTO MECHANISMS OF PAIN AND NOCICEPTION. NEWER METHODS FOR LARGE-SCALE DATA INTEGRATION OF COMPLEMENTARY OMICS APPROACHES HAVE FURTHER EXPANDED OUR ABILITY TO BUILD A HOLISTIC UNDERSTANDING OF COMPLEX BIOLOGICAL NETWORKS AND THEIR CO-CONTRIBUTIONS TO ABDOMINAL PAIN. HERE, WE REVIEW THE MECHANISMS OF VISCERAL HYPERSENSITIVITY, FOCUSING ON IBS. WE DISCUSS CANDIDATE BIOMARKERS FOR PAIN IN IBS IDENTIFIED THROUGH SINGLE OMICS STUDIES AND SUMMARIZE EMERGING MULTI-OMICS APPROACHES FOR DEVELOPING NOVEL BIOMARKERS THAT MAY TRANSFORM CLINICAL CARE FOR PATIENTS WITH IBS AND ABDOMINAL PAIN. 2023