1 4848 117 OPIOID-INDUCED STRUCTURAL AND FUNCTIONAL PLASTICITY OF MEDIUM-SPINY NEURONS IN THE NUCLEUS ACCUMBENS. OPIOID USE DISORDER (OUD) IS A CHRONIC RELAPSING CLINICAL CONDITION WITH TREMENDOUS MORBIDITY AND MORTALITY THAT FREQUENTLY PERSISTS, DESPITE TREATMENT, DUE TO AN INDIVIDUAL'S UNDERLYING PSYCHOLOGICAL, NEUROBIOLOGICAL, AND GENETIC VULNERABILITIES. EVIDENCE SUGGESTS THAT THESE VULNERABILITIES MAY HAVE NEUROCHEMICAL, CELLULAR, AND MOLECULAR BASES. KEY NEUROPLASTIC EVENTS WITHIN THE MESOCORTICOLIMBIC SYSTEM THAT EMERGE THROUGH CHRONIC EXPOSURE TO OPIOIDS MAY HAVE A DETERMINATIVE INFLUENCE ON BEHAVIORAL SYMPTOMS ASSOCIATED WITH OUD. IN PARTICULAR, STRUCTURAL AND FUNCTIONAL ALTERATIONS IN THE DENDRITIC SPINES OF MEDIUM SPINY NEURONS (MSNS) WITHIN THE NUCLEUS ACCUMBENS (NAC) AND ITS DOPAMINERGIC PROJECTIONS FROM THE VENTRAL TEGMENTAL AREA (VTA) ARE BELIEVED TO FACILITATE THESE BEHAVIORAL SEQUELAE. ADDITIONALLY, GLUTAMATERGIC NEURONS FROM THE PREFRONTAL CORTEX, THE BASOLATERAL AMYGDALA, THE HIPPOCAMPUS, AND THE THALAMUS PROJECT TO THESE SAME MSNS, PROVIDING AN ENRICHED TARGET FOR SYNAPTIC PLASTICITY. HERE, WE REVIEW LITERATURE RELATED TO NEUROADAPTATIONS IN NAC MSNS FROM DOPAMINERGIC AND GLUTAMATERGIC PATHWAYS IN OUD. WE ALSO DESCRIBE NEW FINDINGS RELATED TO TRANSCRIPTIONAL, EPIGENETIC, AND MOLECULAR MECHANISMS IN MSN PLASTICITY IN THE DIFFERENT STAGES OF OUD. 2021 2 2934 28 GENETIC ADDICTION RISK SCORE (GARS) , A PREDICTOR OF VULNERABILITY TO OPIOID DEPENDENCE. THE INTERACTION OF NEUROTRANSMITTERS AND GENES THAT CONTROL THE RELEASE OF DOPAMINE IS THE BRAIN REWARD CASCADE (BRC). VARIATIONS WITHIN THE BRC, WHETHER GENETIC OR EPIGENETIC, MAY PREDISPOSE INDIVIDUALS TO ADDICTIVE BEHAVIORS AND ALTERED PAIN TOLERANCE. THIS DISCUSSION AUTHORED BY A GROUP OF CONCERNED SCIENTISTS AND CLINICIANS EXAMINES THE GENETIC ADDICTION RISK SCORE (GARS), THE FIRST TEST TO ACCURATELY PREDICT VULNERABILITY TO PAIN, ADDICTION, AND OTHER COMPULSIVE BEHAVIORS, DEFINED AS REWARD DEFICIENCY SYNDROME (RDS). INNOVATIVE STRATEGIES TO COMBAT EPIDEMIC OPIOID, IATROGENIC PRESCRIPTION DRUG ABUSE AND DEATH, BASED ON THE ROLE OF DOPAMINERGIC TONE IN PAIN PATHWAYS, ARE PROPOSED. SENSITIVITY TO PAIN MAY RESIDE IN THE MESOLIMBIC PROJECTION SYSTEM, WHERE GENETIC POLYMORPHISMS ASSOCIATE WITH A PREDISPOSITION TO PAIN VULNERABILITY OR TOLERANCE. THEY PROVIDE UNIQUE THERAPEUTIC TARGETS THAT COULD ASSIST IN THE TREATMENT OF PAIN, AND IDENTIFY RISK FOR SUBSEQUENT ADDICTION. PHARMACOGENOMIC TESTING OF CANDIDATE GENES LIKE CB1, MU RECEPTORS, AND PENK MIGHT RESULT IN PHARMACOGENOMIC, PERSONALIZED SOLUTIONS, AND IMPROVED CLINICAL OUTCOMES. GENETICALLY IDENTIFYING RISK FOR ALL RDS BEHAVIORS, ESPECIALLY IN COMPROMISED POPULATIONS, MAY BE A FRONTLINE TOOL TO ASSIST MUNICIPALITIES TO PROVIDE BETTER RESOURCE ALLOCATION. 2018 3 6352 35 THE ROLE OF GABA(A) RECEPTORS IN THE DEVELOPMENT OF ALCOHOLISM. ALCOHOLISM IS A COMMON, HERITABLE, CHRONIC RELAPSING DISORDER. GABA(A) RECEPTORS UNDERGO ALLOSTERIC MODULATION BY ETHANOL, ANESTHETICS, BENZODIAZEPINES AND NEUROSTEROIDS AND HAVE BEEN IMPLICATED IN THE ACUTE AS WELL AS THE CHRONIC EFFECTS OF ETHANOL INCLUDING TOLERANCE, DEPENDENCE AND WITHDRAWAL. MEDICATIONS TARGETING GABA(A) RECEPTORS AMELIORATE THE SYMPTOMS OF ACUTE WITHDRAWAL. ETHANOL INDUCES PLASTICITY IN GABA(A) RECEPTORS: TOLERANCE IS ASSOCIATED WITH GENERALLY DECREASED GABA(A) RECEPTOR ACTIVATION AND DIFFERENTIALLY ALTERED SUBUNIT EXPRESSION. THE DOPAMINE (DA) MESOLIMBIC REWARD PATHWAY ORIGINATING IN THE VENTRAL TEGMENTAL AREA (VTA), AND INTERACTING STRESS CIRCUITRY PLAY AN IMPORTANT ROLE IN THE DEVELOPMENT OF ADDICTION. VTA GABAERGIC INTERNEURONS ARE THE PRIMARY INHIBITORY REGULATORS OF DA NEURONS AND A SUBSET OF VTA GABA(A) RECEPTORS MAY BE IMPLICATED IN THE SWITCH FROM HEAVY DRINKING TO DEPENDENCE. GABA(A) RECEPTORS MODULATE ANXIETY AND RESPONSE TO STRESS; IMPORTANT ELEMENTS OF SUSTAINED DRINKING AND RELAPSE. THE GABA(A) RECEPTOR SUBUNIT GENES CLUSTERED ON CHROMOSOME 4 ARE HIGHLY EXPRESSED IN THE REWARD PATHWAY. SEVERAL RECENT STUDIES HAVE PROVIDED STRONG EVIDENCE THAT ONE OF THESE GENES, GABRA2, IS IMPLICATED IN ALCOHOLISM IN HUMANS. THE INFLUENCE OF THE INTERACTION BETWEEN ETHANOL AND GABA(A) RECEPTORS IN THE REWARD PATHWAY ON THE DEVELOPMENT OF ALCOHOLISM TOGETHER WITH GENETIC AND EPIGENETIC VULNERABILITIES WILL BE EXPLORED IN THIS REVIEW. 2008 4 6912 32 [UNDERSTANDING OF THE PSYCHIATRY IN PALLIATIVE CARE: DYSFUNCTION OF THE REWARDING SYSTEM UNDER THE PAIN STATE ASSOCIATED WITH EXACERBATING PAIN]. RECENT HUMAN BRAIN IMAGING STUDIES HAVE EXAMINED DIFFERENCES IN ACTIVITY IN THE NUCLEUS ACCUMBENS (N.ACC.) IN RESPONSE TO HEAT STIMULI BETWEEN CONTROLS AND PATIENTS WITH CHRONIC PAIN, AND HAVE REVEALED THAT THE N.ACC. PLAYS A ROLE IN PREDICTING THE VALUE OF A NOXIOUS STIMULUS AND ITS OFFSET, AND IN THE CONSEQUENT CHANGES IN THE MOTIVATIONAL STATE. NEVERTHELESS, THE MOLECULAR MECHANISMS OF CHANGE IN THE CIRCUITRY INVOLVED IN EMOTION AND MOTIVATION IN RESPONSE TO CHRONIC PAIN STIMULI WERE NOT FULLY EXPLORED. ON THE OTHER HAND, IT HAS BEEN CONSIDERED THAT MICRO RNAS (MIRNAS) PLAY IMPORTANT ROLES AS KEY MODULATORS OF POST-TRANSCRIPTIONAL GENE EXPRESSION. WE HAVE REPORTED THAT CHANGES IN MIRNAS ARE ASSOCIATED WITH PREDICTED CHANGES IN GENE EXPRESSION OF CANDIDATE TARGETS IN THE N.ACC. UNDER NEUROPATHIC PAIN. THEREFORE, WE HAVE INTRODUCED A NEW INSIGHT INTO AN EPIGENETIC DYSFUNCTION OF "MESOLIMBIC MOTIVATION/VALUATION CIRCUITRY" UNDER A NEUROPATHIC PAIN-LIKE STATE. THESE FINDINGS RAISE INTRIGUING POSSIBILITIES THAT MIRNA-MODULATING CELLULAR EVENTS ALONG WITH EPIGENETIC MODIFICATIONS MAY BE ASSOCIATED WITH NEURAL PLASTICITY AND NEURONAL ADAPTIVE RESPONSES IN MESOLIMBIC MOTIVATION/VALUATION CIRCUITRY UNDER WHICH THE NEUROPATHIC PAIN MAY INDUCE NEGATIVE EMOTIONS, EXACERBATING PAIN. 2013 5 76 30 A NEW ASPECT OF CHRONIC PAIN AS A LIFESTYLE-RELATED DISEASE. PHYSICAL EXERCISE HAS BEEN ESTABLISHED AS A LOW-COST, SAFE, AND EFFECTIVE WAY TO MANAGE CHRONIC INTRACTABLE PAIN. WE INVESTIGATED THE UNDERLYING MECHANISMS OF EXERCISE-INDUCED HYPOALGESIA (EIH) USING A MOUSE MODEL OF NEUROPATHIC PAIN (NPP). EPIGENETIC CHANGES IN ACTIVATED MICROGLIA AND MAINTAINED GABA SYNTHESIS IN THE SPINAL DORSAL HORN MAY CONTRIBUTE TO EIH. VOLUNTARY EXERCISE (VE), A STRONG REWARD FOR ANIMALS, ALSO INDUCED EIH, WHICH MAY BE DUE IN PART TO THE ACTIVATION OF DOPAMINE (DA) NEURONS IN THE VENTRAL TEGMENTAL AREA (VTA). VE INCREASES THE EXPRESSION OF PCREB IN DOPAMINERGIC NEURONS IN THE VTA, WHICH WOULD ENHANCE DOPAMINE PRODUCTION, AND THEREBY CONTRIBUTES TO THE ACTIVATION OF THE MESOLIMBIC REWARD SYSTEM IN NPP MODEL MICE. WE DEMONSTRATED THAT NEURONS IN THE LATERODORSAL TEGMENTAL AND PEDUNCULOPONTINE TEGMENTAL NUCLEI, A MAJOR INPUT SOURCE OF REWARDING STIMULI TO THE VTA, WERE ACTIVATED BY EXERCISE. CHRONIC PAIN IS AT LEAST PARTLY ATTRIBUTED TO SEDENTARY AND INACTIVE LIFESTYLE AS INDICATED BY THE FEAR-AVOIDANCE MODEL. THEREFORE, CHRONIC PAIN COULD BE RECOGNIZED AS A LIFESTYLE-RELATED DISEASE. PHYSICAL ACTIVITY/INACTIVITY MAY BE DETERMINED BY GENETIC/EPIGENETIC AND NEURAL FACTORS ENCODED IN OUR BRAIN. THE HYPOTHALAMUS AND REWARD SYSTEM IS CLOSELY RELATED IN THE AXIS OF FOOD INTAKE, ENERGY METABOLISM AND PHYSICAL ACTIVITY. UNDERSTANDING THE INTERACTIONS BETWEEN THE MESOLIMBIC DA SYSTEM AND THE HYPOTHALAMUS THAT SENSE AND REGULATE ENERGY BALANCE IS THUS OF SIGNIFICANT IMPORTANCE. FOR EXAMPLE, PROOPIOMELANOCORTIN NEURONS AND MELANOCORTIN 4 RECEPTORS MAY PLAY A ROLE IN CONNECTING THESE TWO SYSTEMS. THEREFORE, IN A CERTAIN SENSE, CHRONIC PAIN AND OBESITY MAY SHARE COMMON BEHAVIORAL AND NEURAL PATHOLOGY, I.E. PHYSICAL INACTIVITY, AS A RESULT OF INACTIVATION OF THE MESOLIMBIC DA SYSTEM. EXERCISE AND INCREASING PHYSICAL ACTIVITY IN DAILY LIFE MAY BE IMPORTANT IN TREATING AND PREVENTING CHRONIC PAIN, A LIFE-STYLE RELATED DISEASE. 2017 6 807 28 CHANGE IN MICRORNAS ASSOCIATED WITH NEURONAL ADAPTIVE RESPONSES IN THE NUCLEUS ACCUMBENS UNDER NEUROPATHIC PAIN. NEUROPATHIC PAIN IS THE MOST DIFFICULT TYPE OF PAIN TO CONTROL, AND PATIENTS LOSE THEIR MOTIVATION FOR THE PURPOSIVE PURSUIT WITH A DECREASE IN THEIR QUALITY OF LIFE. USING A FUNCTIONAL MAGNETIC RESONANCE IMAGING ANALYSIS, WE DEMONSTRATED THAT BLOOD OXYGENATION LEVEL-DEPENDENT SIGNAL INTENSITY WAS INCREASED IN THE IPSILATERAL NUCLEUS ACCUMBENS (N.ACC.) FOLLOWING PERIPHERAL NERVE INJURY. MICRORNAS ARE SMALL, NONCODING RNA MOLECULES THAT DIRECT THE POST-TRANSCRIPTIONAL SUPPRESSION OF GENE EXPRESSION, AND PLAY AN IMPORTANT ROLE IN REGULATING SYNAPTIC PLASTICITY. IN THIS STUDY, WE FOUND THAT SCIATIC NERVE LIGATION INDUCED A DRASTIC DECREASE IN THE EXPRESSION OF MIR200B AND MIR429 IN N.ACC. NEURONS. THE EXPRESSION OF DNA METHYLTRANSFERASE 3A (DNMT3A), WHICH IS THE ONE OF THE PREDICTED TARGETS OF MIR200B/429, WAS SIGNIFICANTLY INCREASED IN THE LIMBIC FOREBRAIN INCLUDING N.ACC. AT 7 D AFTER SCIATIC NERVE LIGATION. DOUBLE-IMMUNOLABELING WITH ANTIBODIES SPECIFIC TO DNMT3A AND NR1 SHOWED THAT DNMT3A-IMMUNOREACTIVITY IN THE N.ACC. WAS LOCATED IN NR1-LABELED NEURONS, INDICATING THAT INCREASED DNMT3A PROTEINS WERE DOMINANTLY EXPRESSED IN POSTSYNAPTIC NEURONS IN THE N.ACC. AREA UNDER A NEUROPATHIC PAIN-LIKE STATE. THE RESULTS OF THESE ANALYSES PROVIDE NEW INSIGHT INTO AN EPIGENETIC MODIFICATION THAT IS ACCOMPANIED BY A DRAMATIC DECREASE IN MIR200B AND MIR429 ALONG WITH THE DYSFUNCTION OF "MESOLIMBIC MOTIVATION/VALUATION CIRCUITRY" UNDER A NEUROPATHIC PAIN-LIKE STATE. THESE PHENOMENA MAY RESULT IN AN INCREASE IN DNMT3A IN NEURONS OF THE N.ACC. UNDER NEUROPATHIC PAIN, WHICH LEADS TO THE LONG-TERM TRANSCRIPTION-SILENCING OF SEVERAL GENES. 2011 7 4469 39 MOLECULAR NEUROLOGICAL CORRELATES OF ENDORPHINERGIC/DOPAMINERGIC MECHANISMS IN REWARD CIRCUITRY LINKED TO ENDORPHINERGIC DEFICIENCY SYNDROME (EDS). THE CONSENSUS OF THE CURRENT LITERATURE STRONGLY SUPPORTS THE CONCEPT THAT BRAIN NEUROTRANSMITTERS, AND SECOND MESSENGERS INVOLVED IN THE NET RELEASE OF DOPAMINE IN THE MESOLIMBIC REGION, ESPECIALLY THE NUCLEUS ACCUMBENS (NAC), IS DIRECTLY LINKED TO MOTIVATION, ANTI-STRESS, INCENTIVE SALIENCE (WANTING), AND WELL-BEING. THE ROLE OF DOPAMINE IN TERMS OF ALCOHOL WITHDRAWAL SYMPTOMOLOGY, COCAINE CRAVING BEHAVIOR, DOPAMINE -CONDENSATION PRODUCTS (TIQS), AND MORE RECENTLY, THE GENETIC ASPECTS OF DRUG-SEEKING AND PRO-DOPAMINE REGULATION, PROVIDE COMPELLING EVIDENCE OF THE RELEVANT MOLECULAR NEUROLOGICAL CORRELATES OF DOPAMINERGIC /ENDORPHINERGIC MECHANISMS IN REWARD CIRCUITRY DUE TO GENETIC POLYMORPHISMS AND EPIGENETIC INSULTS. IN THE FACE OF AN AMERICANS OPIOID EPIDEMIC, THE CLINICAL CONSENSUS IS TO TREAT OPIOID USE DISORDER (OUD) WITH LIFE-LONG OPIOID SUBSTITUTION THERAPY. HOWEVER, THE AUTHORS SUGGEST A PARADIGM SHIFT INVOLVING NOVEL MODALITIES LIKE TARGETING THE ENDORPHINERGIC SYSTEM LINKED TO DOPAMINE RELEASE AT THE NAC, IN TERMS OF THE INDUCTION OF REQUIRED "DOPAMINE HOMEOSTASIS." UTILIZING THE KNOWN GENETIC - ENVIRONMENTAL INTERACTION THEOREM P = G +E, THE AUTHORS PROVIDE A CLEAR RATIONALE FOR THE ADOPTION OF GENETIC RISK TESTING COUPLED WITH ENDORPHINERGIC/DOPAMINE REGULATION TO ADDRESS DYSFUNCTION ACROSS THE BRAIN REWARD CIRCUITRY. THE GOAL OF ALTERING RESTING-STATE, FUNCTIONAL CONNECTIVITY MAY REQUIRE A GENTLE "NEUROTRANSMITTER FIX" VIS ENKEPHALINASE INHIBITION TO OVERCOME OR COMBAT - SELF-INDUCTION OF ACUTE DOPAMINE RELEASE VIA PSYCHOACTIVE SUBSTANCE MISUSE RESULTING IN CHRONIC DOPAMINE DOWN-REGULATION. AS SUBSETS OF REWARD DEFICIENCY, WE ARE POISED TO PROVIDE NOVEL, GENETICALLY GUIDED THERAPY FOR ENDORPHINERGIC, OPIOIDERGIC, AND DOPAMINERGIC DEFICIENCIES AND RELATED SYNDROMES, UTILIZING "PRECISION ADDICTION MANAGEMENT. 2020 8 4498 32 MORPHINE REGULATES ARGONAUTE 2 AND TH EXPRESSION AND ACTIVITY BUT NOT MIR-133B IN MIDBRAIN DOPAMINERGIC NEURONS. EPIGENETIC CHANGES SUCH AS MICRORNAS (MIRS)/AGO2-INDUCED GENE SILENCING REPRESENT COMPLEX MOLECULAR SIGNATURE THAT REGULATE CELLULAR PLASTICITY. RECENT STUDIES SHOWED INVOLVEMENT OF MIRS AND AGO2 IN DRUG ADDICTION. IN THIS STUDY, WE SHOW THAT CHANGES IN GENE EXPRESSION INDUCED BY MORPHINE AND MORPHINE WITHDRAWAL OCCUR WITH CONCOMITANT EPIGENETIC MODIFICATIONS IN THE MESOLIMBIC DOPAMINERGIC (DA) PATHWAY [VENTRAL TEGMENTAL AREA (VTA)/NUCLEUS ACCUMBENS (NAC) SHELL], WHICH IS CRITICALLY INVOLVED IN DRUG-INDUCED DEPENDENCE. WE FOUND THAT ACUTE OR CHRONIC MORPHINE ADMINISTRATION AS WELL AS MORPHINE WITHDRAWAL DID NOT MODIFY MIR-133B MESSENGER RNA (MRNA) EXPRESSION IN THE VTA, WHEREAS AGO2 PROTEIN LEVELS WERE DECREASED AND INCREASED IN MORPHINE-DEPENDENT RATS AND AFTER MORPHINE WITHDRAWAL, RESPECTIVELY. THESE CHANGES WERE PARALLELED WITH ENHANCED AND DECREASED NAC TYROSINE HYDROXYLASE (TH) PROTEIN (AN EARLY DA MARKER) IN MORPHINE-DEPENDENT RATS AND AFTER WITHDRAWAL, RESPECTIVELY. WE ALSO OBSERVED CHANGES IN TH MRNA EXPRESSION IN THE VTA THAT COULD BE RELATED TO AGO2-INDUCED TRANSLATIONAL REPRESSION OF TH MRNA DURING MORPHINE WITHDRAWAL. HOWEVER, THE VTA NUMBER OF TH-POSITIVE NEURONS SUFFERED NO ALTERATIONS AFTER THE DIFFERENT TREATMENT. ACUTE MORPHINE ADMINISTRATION PRODUCED A MARKED INCREASE IN TH ACTIVITY AND DA TURNOVER IN THE NAC (SHELL). IN CONTRAST, PRECIPITATED MORPHINE WITHDRAWAL DECREASED TH ACTIVATION AND DID NOT CHANGE DA TURNOVER. THESE FINDINGS PROVIDE NEW INFORMATION INTO THE POSSIBLE CORRELATION BETWEEN AGO2/MIRS COMPLEX REGULATION AND DA NEURONS PLASTICITY DURING OPIATE ADDICTION. 2015 9 636 42 BIOLOGICAL SUBSTRATES OF ADDICTION. THIS REVIEW IS AN INTRODUCTION TO ADDICTION, THE REWARD CIRCUITRY, AND LABORATORY ADDICTION MODELS. ADDICTION IS A CHRONIC DISEASE HALLMARKED BY A STATE OF COMPULSIVE DRUG SEEKING THAT PERSISTS DESPITE NEGATIVE CONSEQUENCES. MOST OF THE ADVANCES IN ADDICTION RESEARCH HAVE CENTERED ON THE CANONICAL AND CONTEMPORARY DRUGS OF ABUSE; HOWEVER, ADDICTIONS TO OTHER ACTIVITIES AND STIMULI ALSO EXIST. SUBSTANCES OF ABUSE HAVE THE POTENTIAL TO INDUCE LONG-LASTING CHANGES IN THE BRAIN AT THE BEHAVIORAL, CIRCUIT, AND SYNAPTIC LEVELS. ADDICTION-RELATED BEHAVIORAL CHANGES INVOLVE INITIATION, ESCALATION, AND OBSESSION TO DRUG SEEKING AND MUCH OF THE CURRENT RESEARCH IS FOCUSED ON MAPPING THESE MANIFESTATIONS TO SPECIFIC NEURAL PATHWAYS. DRUG ABUSE IS WELL KNOWN TO RECRUIT COMPONENTS OF THE MESOLIMBIC DOPAMINE SYSTEM, INCLUDING THE NUCLEUS ACCUMBENS AND VENTRAL TEGMENTAL AREA. IN ADDITION, ALTERED FUNCTION OF A WIDE VARIETY OF BRAIN REGIONS IS TIGHTLY ASSOCIATED WITH SPECIFIC MANIFESTATIONS OF DRUG ABUSE. THESE REGIONS PERIPHERAL TO THE MESOLIMBIC PATHWAY LIKELY PLAY A ROLE IN SPECIFIC OBSERVED COMORBIDITIES AND ENDOPHENOTYPES THAT CAN FACILITATE, OR BE CAUSED BY, SUBSTANCE ABUSE. ALTERATIONS IN SYNAPTIC STRUCTURE, FUNCTION, AND CONNECTIVITY, AS WELL AS EPIGENETIC AND GENETIC MECHANISMS ARE THOUGHT TO UNDERLIE THE PATHOLOGIES OF ADDICTION. IN PRECLINICAL MODELS, THESE PERSISTENT CHANGES ARE STUDIED AT THE LEVELS OF MOLECULAR PHARMACOLOGY AND BIOCHEMISTRY, EX VIVO AND IN VIVO ELECTROPHYSIOLOGY, RADIOGRAPHY, AND BEHAVIOR. COORDINATING RESEARCH EFFORTS ACROSS THESE DISCIPLINES AND EXAMINING CELL TYPE- AND CIRCUIT-SPECIFIC PHENOMENA ARE CRUCIAL COMPONENTS FOR TRANSLATING PRECLINICAL FINDINGS TO VIABLE MEDICAL INTERVENTIONS THAT EFFECTIVELY TREAT ADDICTION AND RELATED DISORDERS. WIRES COGN SCI 2014, 5:151-171. DOI: 10.1002/WCS.1273 CONFLICT OF INTEREST: THE AUTHORS HAVE DECLARED NO CONFLICTS OF INTEREST FOR THIS ARTICLE. FOR FURTHER RESOURCES RELATED TO THIS ARTICLE, PLEASE VISIT THE WIRES WEBSITE. 2014 10 4327 35 MICRORNAS MODULATE INTERACTIONS BETWEEN STRESS AND RISK FOR COCAINE ADDICTION. EXPOSURE TO STRESS INCREASES VULNERABILITY TO DRUG ABUSE, AS WELL AS RELAPSE LIABILITY IN ADDICTED INDIVIDUALS. CHRONIC DRUG USE ALTERS STRESS RESPONSE IN A MANNER THAT INCREASES DRUG SEEKING BEHAVIORS AND RELAPSE. DRUG EXPOSURE AND WITHDRAWAL HAVE BEEN SHOWN TO ALTER STRESS RESPONSES, AND CORTICOSTEROID MEDIATORS OF STRESS HAVE BEEN SHOWN TO IMPACT ADDICTION-RELATED BRAIN FUNCTION AND DRUG-SEEKING BEHAVIOR. DESPITE THE DOCUMENTED INTERPLAY BETWEEN STRESS AND SUBSTANCE ABUSE, THE MECHANISMS BY WHICH STRESS EXPOSURE AND DRUG SEEKING INTERACT REMAIN LARGELY UNKNOWN. RECENT STUDIES INDICATE THAT MICRORNAS (MIRNA) PLAY A SIGNIFICANT ROLE IN STRESS MODULATION AS WELL AS ADDICTION-RELATED PROCESSES INCLUDING NEUROGENESIS, SYNAPSE DEVELOPMENT, PLASTICITY, DRUG ACQUISITION, WITHDRAWAL AND RELAPSE. MIRNAS ARE SHORT NON-CODING RNAS THAT FUNCTION AS BIDIRECTIONAL EPIGENETIC MODULATORS OF GENE EXPRESSION THROUGH IMPERFECT SEQUENCE TARGETED DEGRADATION AND/OR TRANSLATIONAL REPRESSION OF MRNAS. THEY SERVE AS DYNAMIC REGULATORS OF CNS PHYSIOLOGY AND PATHOPHYSIOLOGY, AND FACILITATE RAPID AND LONG-LASTING CHANGES TO COMPLEX SYSTEMS AND BEHAVIORS. MIRNAS FUNCTION IN GLUCOCORTICOID SIGNALING AND THE MESOLIMBIC DOPAMINE REWARD SYSTEM, AS WELL AS MOOD DISORDERS RELATED TO DRUG WITHDRAWAL. THE LITERATURE SUGGESTS MIRNAS PLAY A PIVOTAL ROLE IN THE INTERACTION BETWEEN EXPOSURES TO STRESS, ADDICTION-RELATED PROCESSES, AND NEGATIVE AFFECTIVE STATES RESULTING FROM EXTENDED DRUG WITHDRAWAL. THIS MANUSCRIPT REVIEWS RECENT EVIDENCE FOR THE ROLE OF MIRNAS IN THE MODULATION OF STRESS AND COCAINE RESPONSES, AND DISCUSSES POTENTIAL MEDIATION OF THE INTERACTION OF THESE SYSTEMS BY MIRNAS. UNCOVERING THE MECHANISM BEHIND THE ASSOCIATION OF STRESS AND DRUG TAKING HAS THE POTENTIAL TO IMPACT THE TREATMENT OF DRUG ABUSE AND PREVENTION OF RELAPSE. FURTHER COMPREHENSION OF THESE COMPLEX INTERACTIONS MAY PROVIDE PROMISING NEW TARGETS FOR THE TREATMENT OF DRUG ADDICTION. 2016 11 2398 27 EPIGENETIC REPROGRAMMING OF CORTICAL NEURONS THROUGH ALTERATION OF DOPAMINERGIC CIRCUITS. ALTERATIONS OF THE DOPAMINERGIC SYSTEM ARE ASSOCIATED WITH THE COGNITIVE AND FUNCTIONAL DYSFUNCTIONS THAT CHARACTERIZE COMPLEX NEUROPSYCHIATRIC DISORDERS. WE MODELED A DYSFUNCTIONAL DOPAMINERGIC SYSTEM USING MICE WITH TARGETED ABLATION OF DOPAMINE (DA) D2 AUTORECEPTORS IN MESENCEPHALIC DOPAMINERGIC NEURONS. LOSS OF D2 AUTORECEPTORS ABOLISHES D2-MEDIATED CONTROL OF DA SYNTHESIS AND RELEASE. HERE, WE SHOW THAT THIS MUTATION LEADS TO A PROFOUND ALTERATION OF THE GENOMIC LANDSCAPE OF NEURONS RECEIVING DOPAMINERGIC AFFERENTS AT DISTAL SITES, SPECIFICALLY IN THE PREFRONTAL CORTEX. INDEED, WE OBSERVED A REMARKABLE DOWNREGULATION OF GENE EXPRESSION IN THIS AREA OF ~2000 GENES, WHICH INVOLVES A WIDESPREAD INCREASE IN THE HISTONE REPRESSIVE MARK H3K9ME2/3. THIS REPROGRAMMING PROCESS IS COUPLED TO PSYCHOTIC-LIKE BEHAVIORS IN THE MUTANT MICE. IMPORTANTLY, CHRONIC TREATMENT WITH A DA AGONIST CAN REVERT THE GENOMIC PHENOTYPE. THUS, CORTICAL NEURONS UNDERGO A PROFOUND EPIGENETIC REPROGRAMMING IN RESPONSE TO DYSFUNCTIONAL D2 AUTORECEPTOR SIGNALING LEADING TO ALTERED DA LEVELS, A PROCESS THAT MAY UNDERLIE A NUMBER OF NEUROPSYCHIATRIC DISORDERS. 2014 12 3314 40 HIPPOCAMPAL CANNABINOID 1 RECEPTORS ARE MODULATED FOLLOWING COCAINE SELF-ADMINISTRATION IN MALE RATS. COCAINE ADDICTION IS A COMPLEX PATHOLOGY INDUCING LONG-TERM NEUROPLASTIC CHANGES THAT, IN TURN, CONTRIBUTE TO MALADAPTIVE BEHAVIORS. THIS BEHAVIORAL DYSREGULATION IS ASSOCIATED WITH TRANSCRIPTIONAL REPROGRAMMING IN BRAIN REWARD CIRCUITRY, ALTHOUGH THE MECHANISMS UNDERLYING THIS MODULATION REMAIN POORLY UNDERSTOOD. THE ENDOGENOUS CANNABINOID SYSTEM MAY PLAY A ROLE IN THIS PROCESS IN THAT CANNABINOID MECHANISMS MODULATE DRUG REWARD AND CONTRIBUTE TO COCAINE-INDUCED NEURAL ADAPTATIONS. IN THIS STUDY, WE INVESTIGATED WHETHER COCAINE SELF-ADMINISTRATION INDUCES LONG-TERM ADAPTATIONS, INCLUDING TRANSCRIPTIONAL MODIFICATIONS AND ASSOCIATED EPIGENETIC PROCESSES. WE FIRST EXAMINED ENDOCANNABINOID GENE EXPRESSION IN REWARD-RELATED BRAIN REGIONS OF THE RAT FOLLOWING SELF-ADMINISTERED (0.33 MG/KG INTRAVENOUS, FR1, 10 DAYS) COCAINE INJECTIONS. INTERESTINGLY, WE FOUND INCREASED CNR1 EXPRESSION IN SEVERAL STRUCTURES, INCLUDING PREFRONTAL CORTEX, NUCLEUS ACCUMBENS, DORSAL STRIATUM, HIPPOCAMPUS, HABENULA, AMYGDALA, LATERAL HYPOTHALAMUS, VENTRAL TEGMENTAL AREA, AND ROSTROMEDIAL TEGMENTAL NUCLEUS, WITH MOST PRONOUNCED EFFECTS IN THE HIPPOCAMPUS. ENDOCANNABINOID LEVELS, MEASURED BY MASS SPECTROMETRY, WERE ALSO ALTERED IN THIS STRUCTURE. CHROMATIN IMMUNOPRECIPITATION FOLLOWED BY QPCR IN THE HIPPOCAMPUS REVEALED THAT TWO ACTIVATING HISTONE MARKS, H3K4ME3 AND H3K27AC, WERE ENRICHED AT SPECIFIC ENDOCANNABINOID GENES FOLLOWING COCAINE INTAKE. TARGETING CB1 RECEPTORS USING CHROMOSOME CONFORMATION CAPTURE, WE HIGHLIGHTED SPATIAL CHROMATIN RE-ORGANIZATION IN THE HIPPOCAMPUS, AS WELL AS IN THE NUCLEUS ACCUMBENS, SUGGESTING THAT DESTABILIZATION OF THE CHROMATIN MAY CONTRIBUTE TO NEURONAL RESPONSES TO COCAINE. OVERALL, OUR RESULTS HIGHLIGHT A KEY ROLE FOR THE HIPPOCAMPUS IN COCAINE-INDUCED PLASTICITY AND BROADEN THE UNDERSTANDING OF NEURONAL ALTERATIONS ASSOCIATED WITH ENDOCANNABINOID SIGNALING. THE LATTER SUGGESTS THAT EPIGENETIC MODIFICATIONS CONTRIBUTE TO MALADAPTIVE BEHAVIORS ASSOCIATED WITH CHRONIC DRUG USE. 2022 13 2670 34 ETHANOL ACTIONS ON THE VENTRAL TEGMENTAL AREA: NOVEL POTENTIAL TARGETS ON REWARD PATHWAY NEURONS. THE VENTRAL TEGMENTAL AREA (VTA) EVALUATES SALIENCE OF ENVIRONMENTAL STIMULI AND PROVIDES DOPAMINERGIC INNERVATION TO MANY BRAIN AREAS AFFECTED BY ACUTE AND CHRONIC ETHANOL EXPOSURE. WHILE PRIMARILY ASSOCIATED WITH REWARDING AND REINFORCING STIMULI, RECENT EVIDENCE INDICATES A ROLE FOR THE VTA IN AVERSION AS WELL. ETHANOL ACTIONS IN THE VTA MAY TRIGGER NEUROADAPTATION RESULTING IN REDUCTION OF THE AVERSIVE RESPONSES TO ALCOHOL AND A RELATIVE INCREASE IN THE REWARDING RESPONSES. IN SEARCHING FOR EFFECTIVE PHARMACOTHERAPIES FOR THE TREATMENT OF ALCOHOL ABUSE AND ALCOHOLISM, RECOGNITION OF THIS IMBALANCE MAY REVEAL NOVEL STRATEGIES. IN ADDITION TO CONVENTIONAL RECEPTOR/ION CHANNEL PHARMACOTHERAPIES, EPIGENETIC FACTORS THAT CONTROL NEUROADAPTATION TO CHRONIC ETHANOL TREATMENT CAN BE TARGETED AS AN AVENUE FOR DEVELOPMENT OF THERAPEUTIC APPROACHES TO RESTORE THE BALANCE. FURTHERMORE, WHEN EXPLORING THERAPIES TO ADDRESS REWARD/AVERSION IMBALANCE IN THE ACTION OF ALCOHOL IN THE VTA, SEX DIFFERENCES HAVE TO BE TAKEN INTO ACCOUNT TO ENSURE EFFECTIVE TREATMENT FOR BOTH MEN AND WOMEN. THESE PRINCIPLES APPLY TO A VTA-CENTRIC APPROACH TO THERAPIES, BUT SHOULD HOLD TRUE WHEN THINKING ABOUT THE OVERALL APPROACH IN THE DEVELOPMENT OF NEUROACTIVE DRUGS TO TREAT ALCOHOL USE DISORDERS. ALTHOUGH THE FUNCTIONS OF THE VTA ITSELF ARE COMPLEX, IT IS A USEFUL MODEL SYSTEM TO EVALUATE THE REWARD/AVERSION IMBALANCE THAT OCCURS WITH ETHANOL EXPOSURE AND COULD BE USED TO PROVIDE NEW LEADS IN THE EFFORTS TO DEVELOP NOVEL DRUGS TO TREAT ALCOHOLISM. 2018 14 5819 28 STRESS CHANGES AMPHETAMINE RESPONSE, D2 RECEPTOR EXPRESSION AND EPIGENETIC REGULATION IN LOW-ANXIETY RATS. THE AIM OF THIS STUDY WAS TO ASSESS THE INFLUENCE OF CHRONIC RESTRAINT STRESS ON AMPHETAMINE (AMPH)-RELATED APPETITIVE 50-KHZ ULTRASONIC VOCALISATIONS (USVS) IN RATS DIFFERING IN FREEZING DURATION IN A CONTEXTUAL FEAR TEST (CFT), I.E. HR (HIGH-ANXIETY RESPONSIVE) AND LR (LOW-ANXIETY RESPONSIVE) RATS. THE LR AND THE HR RATS, PREVIOUSLY EXPOSED TO AN AMPH BINGE EXPERIENCE, DIFFERED IN SENSITIVITY TO AMPH'S REWARDING EFFECTS, MEASURED AS APPETITIVE VOCALISATIONS. MOREOVER, CHRONIC RESTRAINT STRESS ATTENUATED AMPH-RELATED APPETITIVE VOCALISATIONS IN THE LR RATS BUT HAD NO INFLUENCE ON THE HR RATS' BEHAVIOUR. TO SPECIFY, THE RESTRAINT LR RATS VOCALISED APPETITIVELY LESS IN THE AMPH-ASSOCIATED CONTEXT AND AFTER AN AMPH CHALLENGE THAN THE CONTROL LR RATS. THIS PHENOMENON WAS ASSOCIATED WITH A DECREASE IN THE MRNA LEVEL FOR D2 DOPAMINE RECEPTOR IN THE AMYGDALA AND ITS PROTEIN EXPRESSION IN THE BASAL AMYGDALA (BA) AND OPPOSITE CHANGES IN THE NUCLEUS ACCUMBENS (NAC) - AN INCREASE IN THE MRNA LEVEL FOR D2 DOPAMINE RECEPTOR AND ITS PROTEIN EXPRESSION IN THE NAC SHELL, COMPARED TO CONTROL CONDITIONS. MOREOVER, WE OBSERVED THAT CHRONIC RESTRAINT STRESS INFLUENCED EPIGENETIC REGULATION IN THE LR AND THE HR RATS DIFFERENTLY. THE CONTRASTING CHANGES WERE OBSERVED IN THE DENTATE GYRUS (DG) OF THE HIPPOCAMPUS - THE LR RATS PRESENTED A DECREASE, BUT THE HR RATS SHOWED AN INCREASE IN H3K9 TRIMETHYLATION. THE RESTRAINT LR RATS ALSO SHOWED HIGHER MIR-494 AND MIR-34C LEVELS IN THE NAC THAN THE CONTROL LR GROUP. OUR STUDY PROVIDES BEHAVIOURAL AND BIOCHEMICAL DATA CONCERNING THE ROLE OF DIFFERENCES IN FEAR-CONDITIONED RESPONSE IN STRESS VULNERABILITY AND AMPH-ASSOCIATED APPETITIVE BEHAVIOUR. THE LR RATS WERE LESS SENSITIVE TO THE REWARDING EFFECTS OF AMPH WHEN PREVIOUSLY EXPOSED TO CHRONIC STRESS THAT WAS ACCOMPANIED BY CHANGES IN D2 DOPAMINE RECEPTOR EXPRESSION AND EPIGENETIC REGULATION IN MESOLIMBIC AREAS. 2019 15 4846 28 OPIATE ADDICTION AND COCAINE ADDICTION: UNDERLYING MOLECULAR NEUROBIOLOGY AND GENETICS. ADDICTIVE DISEASES, INCLUDING ADDICTION TO HEROIN, PRESCRIPTION OPIOIDS, OR COCAINE, POSE MASSIVE PERSONAL AND PUBLIC HEALTH COSTS. ADDICTIONS ARE CHRONIC RELAPSING DISEASES OF THE BRAIN CAUSED BY DRUG-INDUCED DIRECT EFFECTS AND PERSISTING NEUROADAPTATIONS AT THE EPIGENETIC, MRNA, NEUROPEPTIDE, NEUROTRANSMITTER, OR PROTEIN LEVELS. THESE NEUROADAPTATIONS, WHICH CAN BE SPECIFIC TO DRUG TYPE, AND THEIR RESULTANT BEHAVIORS ARE MODIFIED BY VARIOUS INTERNAL AND EXTERNAL ENVIRONMENTAL FACTORS, INCLUDING STRESS RESPONSIVITY, ADDICT MINDSET, AND SOCIAL SETTING. SPECIFIC GENE VARIANTS, INCLUDING VARIANTS ENCODING PHARMACOLOGICAL TARGET PROTEINS OR GENES MEDIATING NEUROADAPTATIONS, ALSO MODIFY VULNERABILITY AT PARTICULAR STAGES OF ADDICTION. GREATER UNDERSTANDING OF THESE INTERACTING FACTORS THROUGH LABORATORY-BASED AND TRANSLATIONAL STUDIES HAVE THE POTENTIAL TO OPTIMIZE EARLY INTERVENTIONS FOR THE THERAPY OF CHRONIC ADDICTIVE DISEASES AND TO REDUCE THE BURDEN OF RELAPSE. HERE, WE REVIEW THE MOLECULAR NEUROBIOLOGY AND GENETICS OF OPIATE ADDICTION, INCLUDING HEROIN AND PRESCRIPTION OPIOIDS, AND COCAINE ADDICTION. 2012 16 4643 33 NEUROPATHIC PAIN AS A TRIGGER FOR HISTONE MODIFICATIONS IN LIMBIC CIRCUITRY. CHRONIC PAIN INVOLVES BOTH CENTRAL AND PERIPHERAL NEURONAL PLASTICITY THAT ENCOMPASSES CHANGES IN THE BRAIN, SPINAL CORD, AND PERIPHERAL NOCICEPTORS. WITHIN THE FOREBRAIN, MESOCORTICOLIMBIC REGIONS ASSOCIATED WITH EMOTIONAL REGULATION HAVE RECENTLY BEEN SHOWN TO EXHIBIT LASTING GENE EXPRESSION CHANGES IN MODELS OF CHRONIC PAIN. TO BETTER UNDERSTAND HOW SUCH ENDURING TRANSCRIPTIONAL CHANGES MIGHT BE REGULATED WITHIN BRAIN STRUCTURES ASSOCIATED WITH PROCESSING OF PAIN OR AFFECT, WE EXAMINED EPIGENETIC MODIFICATIONS INVOLVED WITH ACTIVE OR PERMISSIVE TRANSCRIPTIONAL STATES (HISTONE H3 LYSINE 4 MONO AND TRIMETHYLATION, AND HISTONE H3 LYSINE 27 ACETYLATION) IN PERIAQUEDUCTAL GRAY (PAG), LATERAL HYPOTHALAMUS (LH), NUCLEUS ACCUMBENS (NAC), AND VENTRAL TEGMENTAL AREA (VTA) 5 WEEKS AFTER SCIATIC NERVE INJURY IN MICE TO MODEL CHRONIC PAIN. FOR BOTH MALE AND FEMALE MICE IN CHRONIC PAIN, WE OBSERVED AN OVERALL TREND FOR A REDUCTION OF THESE EPIGENETIC MARKERS IN PERIAQUEDUCTAL GRAY, LH, AND NAC, BUT NOT VTA. MOREOVER, WE DISCOVERED THAT SOME EPIGENETIC MODIFICATIONS EXHIBITED CHANGES ASSOCIATED WITH PAIN HISTORY, WHILE OTHERS WERE ASSOCIATED WITH INDIVIDUAL DIFFERENCES IN PAIN SENSITIVITY. WHEN TAKEN TOGETHER, THESE RESULTS SUGGEST THAT NERVE INJURY LEADS TO CHRONIC CHROMATIN-MEDIATED SUPPRESSION OF TRANSCRIPTION IN KEY LIMBIC BRAIN STRUCTURES AND CIRCUITS, WHICH MAY UNDERLIE ENDURING CHANGES IN PAIN PROCESSING AND SENSITIVITY WITHIN THESE SYSTEMS. 2023 17 2773 40 EXTRACELLULAR SIGNAL-REGULATED PROTEIN KINASES 1 AND 2 ACTIVATION BY ADDICTIVE DRUGS: A SIGNAL TOWARD PATHOLOGICAL ADAPTATION. ADDICTION IS A CHRONIC AND RELAPSING PSYCHIATRIC DISORDER THAT IS THOUGHT TO OCCUR IN VULNERABLE INDIVIDUALS. SYNAPTIC PLASTICITY EVOKED BY DRUGS OF ABUSE IN THE SO-CALLED NEURONAL CIRCUITS OF REWARD HAS BEEN PROPOSED TO UNDERLIE BEHAVIORAL ADAPTATIONS THAT CHARACTERIZE ADDICTION. BY INCREASING DOPAMINE IN THE STRIATUM, ADDICTIVE DRUGS ALTER THE BALANCE OF DOPAMINE AND GLUTAMATE SIGNALS CONVERGING ONTO STRIATAL MEDIUM-SIZED SPINY NEURONS (MSNS) AND ACTIVATE INTRACELLULAR EVENTS INVOLVED IN LONG-TERM BEHAVIORAL ALTERATIONS. OUR LABORATORY CONTRIBUTED TO THE IDENTIFICATION OF SALIENT MOLECULAR CHANGES INDUCED BY ADMINISTRATION OF ADDICTIVE DRUGS TO RODENTS. WE PIONEERED THE OBSERVATION THAT A COMMON FEATURE OF ADDICTIVE DRUGS IS TO ACTIVATE, BY A DOUBLE TYROSINE/THREONINE PHOSPHORYLATION, THE EXTRACELLULAR SIGNAL-REGULATED KINASES 1 AND 2 (ERK1/2) IN THE STRIATUM, WHICH CONTROL A PLETHORA OF SUBSTRATES, SOME OF THEM BEING CRITICALLY INVOLVED IN COCAINE-MEDIATED MOLECULAR AND BEHAVIORAL ADAPTATIONS. HEREIN, WE REVIEW HOW THE INTERPLAY BETWEEN DOPAMINE AND GLUTAMATE SIGNALING CONTROLS COCAINE-INDUCED ERK1/2 ACTIVATION IN MSNS. WE EMPHASIZE THE KEY ROLE OF N-METHYL-D-ASPARTATE RECEPTOR POTENTIATION BY D1 RECEPTOR TO TRIGGER ERK1/2 ACTIVATION AND ITS SUBSEQUENT NUCLEAR TRANSLOCATION WHERE IT MODULATES BOTH EPIGENETIC AND GENETIC PROCESSES ENGAGED BY COCAINE. WE DISCUSS HOW COCAINE-INDUCED LONG-TERM SYNAPTIC AND STRUCTURAL PLASTICITY OF MSNS, AS WELL AS BEHAVIORAL ADAPTATIONS, ARE INFLUENCED BY ERK1/2-CONTROLLED TARGETS. WE CONCLUDE THAT A BETTER KNOWLEDGE OF MOLECULAR MECHANISMS UNDERLYING ERK1/2 ACTIVATION BY DRUGS OF ABUSE AND/OR ITS ROLE IN LONG-TERM NEURONAL PLASTICITY IN THE STRIATUM MAY PROVIDE A NEW ROUTE FOR THERAPEUTIC TREATMENT IN ADDICTION. 2014 18 4440 22 MOLECULAR GENETIC TESTING IN PAIN AND ADDICTION: FACTS, FICTION AND CLINICAL UTILITY. THE BRAIN REWARD CASCADE (BRC) IS AN INTERACTION OF NEUROTRANSMITTERS AND THEIR RESPECTIVE GENES TO CONTROL THE AMOUNT OF DOPAMINE RELEASED WITHIN THE BRAIN. ANY VARIATIONS WITHIN THIS PATHWAY, WHETHER GENETIC OR ENVIRONMENTAL (EPIGENETIC), MAY RESULT IN ADDICTIVE BEHAVIORS AS WELL AS ALTERED PAIN TOLERANCE. WHILE THERE ARE MANY STUDIES CLAIMING A GENETIC ASSOCIATION WITH ADDICTION AND OTHER BEHAVIORAL INFRACTIONS, DEFINED AS REWARD DEFICIENCY SYNDROME (RDS), NOT ALL ARE SCIENTIFICALLY ACCURATE AND IN SOME CASE JUST WRONG. ALBEIT OUR BIAS, WE DISCUSS HEREIN THE FACTS AND FICTIONS BEHIND MOLECULAR GENETIC TESTING IN RDS (INCLUDING PAIN AND ADDICTION) AND THE SIGNIFICANCE BEHIND THE DEVELOPMENT OF THE GENETIC ADDICTION RISK SCORE (GARSPREDX), THE FIRST TEST TO ACCURATELY PREDICT ONE'S GENETIC RISK FOR RDS. 2015 19 1677 32 DRUG ADDICTION: HYPERKATIFEIA/NEGATIVE REINFORCEMENT AS A FRAMEWORK FOR MEDICATIONS DEVELOPMENT. COMPULSIVE DRUG SEEKING THAT IS ASSOCIATED WITH ADDICTION IS HYPOTHESIZED TO FOLLOW A HEURISTIC FRAMEWORK THAT INVOLVES THREE STAGES (BINGE/INTOXICATION, WITHDRAWAL/NEGATIVE AFFECT, AND PREOCCUPATION/ANTICIPATION) AND THREE DOMAINS OF DYSFUNCTION (INCENTIVE SALIENCE/PATHOLOGIC HABITS, NEGATIVE EMOTIONAL STATES, AND EXECUTIVE FUNCTION, RESPECTIVELY) VIA CHANGES IN THE BASAL GANGLIA, EXTENDED AMYGDALA/HABENULA, AND FRONTAL CORTEX, RESPECTIVELY. THIS REVIEW FOCUSES ON NEUROCHEMICAL/NEUROCIRCUITRY DYSREGULATIONS THAT CONTRIBUTE TO HYPERKATIFEIA, DEFINED AS A GREATER INTENSITY OF NEGATIVE EMOTIONAL/MOTIVATIONAL SIGNS AND SYMPTOMS DURING WITHDRAWAL FROM DRUGS OF ABUSE IN THE WITHDRAWAL/NEGATIVE AFFECT STAGE OF THE ADDICTION CYCLE. HYPERKATIFEIA PROVIDES AN ADDITIONAL SOURCE OF MOTIVATION FOR COMPULSIVE DRUG SEEKING VIA NEGATIVE REINFORCEMENT. NEGATIVE REINFORCEMENT REFLECTS AN INCREASE IN THE PROBABILITY OF A RESPONSE TO REMOVE AN AVERSIVE STIMULUS OR DRUG SEEKING TO REMOVE HYPERKATIFEIA THAT IS AUGMENTED BY GENETIC/EPIGENETIC VULNERABILITY, ENVIRONMENTAL TRAUMA, AND PSYCHIATRIC COMORBIDITY. NEUROBIOLOGICAL TARGETS FOR HYPERKATIFEIA IN ADDICTION INVOLVE NEUROCIRCUITRY OF THE EXTENDED AMYGDALA AND ITS CONNECTIONS VIA WITHIN-SYSTEM NEUROADAPTATIONS IN DOPAMINE, ENKEPHALIN/ENDORPHIN OPIOID PEPTIDE, AND GAMMA-AMINOBUTYRIC ACID/GLUTAMATE SYSTEMS AND BETWEEN-SYSTEM NEUROADAPTATIONS IN PROSTRESS CORTICOTROPIN-RELEASING FACTOR, NOREPINEPHRINE, GLUCOCORTICOID, DYNORPHIN, HYPOCRETIN, AND NEUROIMMUNE SYSTEMS AND ANTISTRESS NEUROPEPTIDE Y, NOCICEPTIN, ENDOCANNABINOID, AND OXYTOCIN SYSTEMS. SUCH NEUROCHEMICAL/NEUROCIRCUITRY DYSREGULATIONS ARE HYPOTHESIZED TO MEDIATE A NEGATIVE HEDONIC SET POINT THAT GRADUALLY GAINS ALLOSTATIC LOAD AND SHIFTS FROM A HOMEOSTATIC HEDONIC STATE TO AN ALLOSTATIC HEDONIC STATE. BASED ON PRECLINICAL STUDIES AND TRANSLATIONAL STUDIES TO DATE, MEDICATIONS AND BEHAVIORAL THERAPIES THAT RESET BRAIN STRESS, ANTISTRESS, AND EMOTIONAL PAIN SYSTEMS AND RETURN THEM TO HOMEOSTASIS WOULD BE PROMISING NEW TARGETS FOR MEDICATION DEVELOPMENT. SIGNIFICANCE STATEMENT: THE FOCUS OF THIS REVIEW IS ON NEUROCHEMICAL/NEUROCIRCUITRY DYSREGULATIONS THAT CONTRIBUTE TO HYPERKATIFEIA, DEFINED AS A GREATER INTENSITY OF NEGATIVE EMOTIONAL/MOTIVATIONAL SIGNS AND SYMPTOMS DURING WITHDRAWAL FROM DRUGS OF ABUSE IN THE WITHDRAWAL/NEGATIVE AFFECT STAGE OF THE DRUG ADDICTION CYCLE AND A DRIVING FORCE FOR NEGATIVE REINFORCEMENT IN ADDICTION. MEDICATIONS AND BEHAVIORAL THERAPIES THAT REVERSE HYPERKATIFEIA BY RESETTING BRAIN STRESS, ANTISTRESS, AND EMOTIONAL PAIN SYSTEMS AND RETURNING THEM TO HOMEOSTASIS WOULD BE PROMISING NEW TARGETS FOR MEDICATION DEVELOPMENT. 2021 20 2259 30 EPIGENETIC PRIMING IN DRUG ADDICTION. DRUG ADDICTION IS A CHRONIC RELAPSING BRAIN DISORDER THAT IS CHARACTERIZED BY COMPULSIVE DRUG SEEKING AND CONTINUED USE DESPITE NEGATIVE OUTCOMES. CURRENT PHARMACOLOGICAL THERAPIES TARGET NEURONAL RECEPTORS OR TRANSPORTERS UPON WHICH DRUGS OF ABUSE ACT INITIALLY, YET THESE TREATMENTS REMAIN INEFFECTIVE FOR MOST INDIVIDUALS AND DO NOT PREVENT DISEASE RELAPSE AFTER ABSTINENCE. DRUGS OF ABUSE, IN ADDITION TO THEIR ACUTE EFFECTS, CAUSE PERSISTENT PLASTICITY AFTER REPEATED USE, INVOLVING DYSREGULATED GENE EXPRESSION IN THE BRAIN'S REWARD REGIONS, WHICH ARE THOUGHT TO MEDIATE THE PERSISTENT BEHAVIORAL ABNORMALITIES THAT CHARACTERIZE ADDICTION. EMERGING EVIDENCE IMPLICATES EPIGENETIC PRIMING AS A KEY MECHANISM THAT UNDERLIES THE LONG-LASTING ALTERATIONS IN NEURONAL GENE REGULATION, WHICH CAN REMAIN LATENT UNTIL TRIGGERED BY RE-EXPOSURE TO DRUG-ASSOCIATED STIMULI OR THE DRUG ITSELF. THUS, TO EFFECTIVELY TREAT DRUG ADDICTION, WE MUST IDENTIFY THE PRECISE EPIGENETIC MECHANISMS THAT ESTABLISH AND PRESERVE THE DRUG-INDUCED PATHOLOGY OF THE BRAIN REWARD CIRCUITRY. 2018