1 2574 110 EPIGENETICS OF DRUG ADDICTION. SUBSTANCE USE DISORDERS (SUDS) ARE CHRONIC BRAIN DISEASES CHARACTERIZED BY TRANSITIONS FROM RECREATIONAL TO COMPULSIVE DRUG USE AND ABERRANT DRUG CRAVING THAT PERSISTS FOR MONTHS TO YEARS AFTER ABSTINENCE IS ACHIEVED. THE TRANSITION TO COMPULSIVE DRUG USE IMPLIES THAT PLASTICITY IS OCCURRING, ALTERING THE PHYSIOLOGY OF THE BRAIN TO PRECIPITATE ADDICTED STATES. EPIGENETIC PHENOMENA REPRESENT A VARIED ORCHESTRA OF TRANSCRIPTIONAL TUNING MECHANISMS THAT, IN RESPONSE TO ENVIRONMENTAL STIMULI, CREATE AND MAINTAIN GENE EXPRESSION-MEDIATED PHYSIOLOGICAL OUTCOMES. THEREFORE, EPIGENETIC MECHANISMS REPRESENT A CONVERGENT REGULATORY FRAMEWORK THROUGH WHICH THE PLASTICITY REQUIRED TO ACHIEVE AN ADDICTED STATE CAN ARISE AND THEN PERSIST LONG AFTER DRUG USE HAS ENDED. IN THE FIRST SECTION, WE WILL INTRODUCE BASIC CONCEPTS IN EPIGENETICS, SUCH AS CHROMATIN ARCHITECTURE, HISTONES AND THEIR POSTTRANSLATIONAL MODIFICATIONS, DNA METHYLATION, NONCODING RNAS, AND TRANSCRIPTION FACTORS, ALONG WITH METHODS FOR THEIR INVESTIGATION. WE WILL THEN EXAMINE THE IMPLICATIONS OF THESE MECHANISMS IN SUDS, WITH A PARTICULAR FOCUS ON COCAINE-MEDIATED NEUROEPIGENETIC PLASTICITY ACROSS MULTIPLE BEHAVIORAL MODELS OF ADDICTION. 2021 2 3094 39 GENOMIC AND PERSONALIZED MEDICINE APPROACHES FOR SUBSTANCE USE DISORDERS (SUDS) LOOKING AT GENOME-WIDE ASSOCIATION STUDIES. DRUG ADDICTION, OR SUBSTANCE USE DISORDER (SUD), IS A CHRONIC, RELAPSING DISORDER IN WHICH COMPULSIVE DRUG-SEEKING AND DRUG-TAKING BEHAVIOUR PERSIST DESPITE SERIOUS NEGATIVE CONSEQUENCES. DRUG ABUSE REPRESENTS A PROBLEM THAT DESERVES GREAT ATTENTION FROM A SOCIAL POINT OF VIEW, AND FOCUSES ON THE IMPORTANCE OF GENETIC STUDIES TO HELP IN UNDERSTANDING THE GENETIC BASIS OF ADDICTION AND ITS MEDICAL TREATMENT. DESPITE THE COMPLEXITY OF DRUG ADDICTION DISORDERS, AND THE HIGH NUMBER OF ENVIRONMENTAL VARIABLES PLAYING A ROLE IN THE ONSET, RECURRENCE, AND DURATION OF THE SYMPTOMS, SEVERAL STUDIES HAVE HIGHLIGHTED THE NON-NEGLIGIBLE ROLE OF GENETICS, AS DEMONSTRATED BY HERITABILITY AND GENOME-WIDE ASSOCIATION STUDIES. A CORRELATION BETWEEN THE RELATIVE RISK OF ADDICTION TO SPECIFIC SUBSTANCES AND HERITABILITY HAS BEEN RECENTLY OBSERVED, SUGGESTING THAT NEUROBIOLOGICAL MECHANISMS MAY BE, AT LEAST IN PART, INHERITED. ALL THESE OBSERVATIONS POINT TOWARDS A SCENARIO WHERE THE CORE NEUROBIOLOGICAL FACTORS OF ADDICTION, INVOLVING THE REWARD SYSTEM, IMPULSIVITY, COMPULSIVITY, STRESS, AND ANXIETY RESPONSE, ARE TRANSMITTED, AND THEREFORE, GENES AND MUTATIONS UNDERLYING THEIR VARIATION MIGHT BE DETECTED. IN THE LAST FEW YEARS, THE DEVELOPMENT OF NEW AND MORE EFFICIENT SEQUENCING TECHNOLOGIES HAS PAVED THE WAY FOR LARGE-SCALE STUDIES IN SEARCHING FOR GENETIC AND EPIGENETIC FACTORS AFFECTING DRUG ADDICTION DISORDERS AND THEIR TREATMENTS. THESE STUDIES HAVE BEEN CRUCIAL TO PINPOINT SINGLE NUCLEOTIDE POLYMORPHISMS (SNPS) IN GENES THAT AFFECT THE REACTION TO MEDICAL TREATMENTS. THIS IS CRITICALLY IMPORTANT TO IDENTIFY PHARMACOGENOMIC APPROACHES FOR SUBSTANCE USE DISORDER, SUCH AS OPRM1 SNPS AND METHADONE REQUIRED DOSES FOR MAINTENANCE TREATMENT (MMT). NEVERTHELESS, DESPITE THE PROMISING RESULTS OBTAINED BY GENOME-WIDE ASSOCIATION AND PHARMACOGENOMIC STUDIES, SPECIFIC STUDIES RELATED TO POPULATION GENETICS DIVERSITY ARE LACKING, UNDERMINING THE OVERALL APPLICABILITY OF THE PRELIMINARY FINDINGS, AND THUS POTENTIALLY AFFECTING THE PORTABILITY AND THE ACCURACY OF THE GENETIC STUDIES. IN THIS REVIEW, FOCUSING ON CANNABIS, COCAINE AND HEROIN USE, WE REPORT THE STATE-OF-THE-ART GENOMICS AND PHARMACOGENOMICS OF SUDS, AND THE POSSIBLE FUTURE PERSPECTIVES RELATED TO MEDICAL TREATMENT RESPONSE IN PEOPLE THAT ASK FOR ASSISTANCE IN SOLVING DRUG-RELATED PROBLEMS. 2021 3 3774 26 INTERACTION OF GONADAL HORMONES, DOPAMINERGIC SYSTEM, AND EPIGENETIC REGULATION IN THE GENERATION OF SEX DIFFERENCES IN SUBSTANCE USE DISORDERS: A SYSTEMATIC REVIEW. SUBSTANCE USE DISORDER (SUD) IS A CHRONIC CONDITION CHARACTERIZED BY PATHOLOGICAL DRUG-TAKING AND SEEKING BEHAVIORS. REMARKABLY DIFFERENT BETWEEN MALES AND FEMALES, SUGGESTING THAT DRUG ADDICTION IS A SEXUALLY DIFFERENTIATED DISORDER. THE NEUROBIOLOGICAL BASES OF SEX DIFFERENCES IN SUD INCLUDE SEX-SPECIFIC REWARD SYSTEM ACTIVATION, INFLUENCED BY INTERACTIONS BETWEEN GONADAL HORMONE LEVEL CHANGES, DOPAMINERGIC REWARD CIRCUITS, AND EPIGENETIC MODIFICATIONS OF KEY REWARD SYSTEM GENES. THIS SYSTEMATIC REVIEW, ADHERING TO PICOS AND PRISMA-P 2015 GUIDELINES, HIGHLIGHTS THE SEX-DEPENDENT ROLES OF ESTROGENS, PROGESTERONE, AND TESTOSTERONE IN SUD. IN PARTICULAR, ESTRADIOL ELEVATES AND PROGESTERONE REDUCES DOPAMINERGIC ACTIVITY IN SUD FEMALES, WHILST TESTOSTERONE AND PROGESTERONE AUGMENT SUD BEHAVIOR IN MALES. FINALLY, SUD IS ASSOCIATED WITH A SEX-SPECIFIC INCREASE IN THE RATE OF OPIOID AND MONOAMINERGIC GENE METHYLATION. THE STUDY REVEALS THE NEED FOR DETAILED RESEARCH ON GONADAL HORMONE LEVELS, DOPAMINERGIC OR REWARD SYSTEM ACTIVITY, AND EPIGENETIC LANDSCAPES IN BOTH SEXES FOR EFFICIENT SUD THERAPY DEVELOPMENT. 2023 4 6155 36 THE GENETIC EPIDEMIOLOGY OF SUBSTANCE USE DISORDER: A REVIEW. BACKGROUND: SUBSTANCE USE DISORDER (SUD) REMAINS A SIGNIFICANT PUBLIC HEALTH ISSUE. A GREATER UNDERSTANDING OF HOW GENES AND ENVIRONMENT INTERACT TO REGULATE PHENOTYPES COMPRISING SUD WILL FACILITATE DIRECTED TREATMENTS AND PREVENTION. METHODS: THE LITERATURE STUDYING THE NEUROBIOLOGICAL CORRELATES OF SUD WITH A FOCUS ON THE GENETIC AND ENVIRONMENTAL INFLUENCES UNDERLYING THESE MECHANISMS WAS REVIEWED. RESULTS FROM TWIN/FAMILY, HUMAN GENETIC ASSOCIATION, GENE-ENVIRONMENT INTERACTION, EPIGENETIC LITERATURE, PHENOME-WIDE ASSOCIATION STUDIES ARE SUMMARIZED FOR ALCOHOL, NICOTINE, CANNABINOIDS, COCAINE, AND OPIOIDS. RESULTS: THERE ARE SUBSTANTIAL GENETIC INFLUENCES ON SUD THAT ARE EXPECTED TO INFLUENCE MULTIPLE NEUROTRANSMISSION PATHWAYS, AND THESE INFLUENCES ARE PARTICULARLY IMPORTANT WITHIN THE DOPAMINERGIC SYSTEM. GENETIC INFLUENCES INVOLVED IN OTHER ASPECTS OF SUD ETIOLOGY INCLUDING DRUG PROCESSING AND METABOLISM ARE ALSO IDENTIFIED. STUDIES OF GENE-ENVIRONMENT INTERACTION EMPHASIZE THE IMPORTANCE OF ENVIRONMENTAL CONTEXT IN SUD. EPIGENETIC STUDIES INDICATE DRUG-SPECIFIC CHANGES IN GENE EXPRESSION AS WELL AS DIFFERENCES IN GENE EXPRESSION RELATED TO THE USE OF MULTIPLE SUBSTANCES. FURTHER, GENE EXPRESSION IS EXPECTED TO DIFFER BY STAGE OF SUD SUCH AS SUBSTANCE INITIATION VERSUS CHRONIC SUBSTANCE USE. WHILE A SUBSTANTIAL LITERATURE HAS DEVELOPED FOR ALCOHOL AND NICOTINE USE DISORDERS, THERE IS COMPARATIVELY LESS INFORMATION FOR OTHER COMMONLY ABUSED SUBSTANCES. CONCLUSIONS: A BETTER UNDERSTANDING OF GENETICALLY-MEDIATED MECHANISMS INVOLVED IN THE NEUROBIOLOGY OF SUD PROVIDES INCREASED OPPORTUNITY TO DEVELOP BEHAVIORAL AND BIOLOGICALLY BASED TREATMENT AND PREVENTION OF SUD. 2017 5 1671 27 DRD2 METHYLATION IS ASSOCIATED WITH EXECUTIVE CONTROL NETWORK CONNECTIVITY AND SEVERITY OF ALCOHOL PROBLEMS AMONG A SAMPLE OF POLYSUBSTANCE USERS. CHRONIC EXPOSURE TO ALCOHOL AND OTHER DRUGS OF ABUSE HAS BEEN ASSOCIATED WITH DELETERIOUS CONSEQUENCES, INCLUDING FUNCTIONAL CONNECTIVITY DEFICITS WITHIN NEURAL NETWORKS ASSOCIATED WITH EXECUTIVE CONTROL. ALTERED FUNCTIONAL CONNECTIVITY WITHIN THE EXECUTIVE CONTROL NETWORK (ECN) MIGHT UNDERLIE THE PROGRESSIVE INABILITY TO CONTROL CONSUMPTION OF ALCOHOL AND OTHER DRUGS AS SUBSTANCE USE DISORDERS PROGRESS. GENETIC AND EPIGENETIC FACTORS HAVE BEEN ASSOCIATED WITH SUBSTANCE USE DISORDERS (SUDS). FOR EXAMPLE, DOPAMINE RECEPTOR 2 (DRD2) FUNCTIONING HAS BEEN ASSOCIATED WITH ALCOHOL USE DISORDER (AUD) AND RELATED PHENOTYPES, INCLUDING CORRELATES OF EXECUTIVE FUNCTIONING. THE PRESENT STUDY AIMS TO EXPLORE THE RELATIONSHIP BETWEEN A CONTINUOUS MEASURE OF ALCOHOL-RELATED PROBLEMS, EPIGENETIC MARKERS (METHYLATION) WITHIN THE DRD2 GENE, AND FUNCTIONAL CONNECTIVITY WITHIN THE ECN AMONG A SAMPLE OF POLYSUBSTANCE USERS. A COMMUNITY SAMPLE OF 658 SUBJECTS, WHOSE CONSUMPTION OF ALCOHOL, NICOTINE, AND CANNABIS SPAN ACROSS A SPECTRUM OF QUANTITY AND FREQUENCY OF USE, WERE OBTAINED ACROSS PREVIOUS STUDIES IN POLYSUBSTANCE USING POPULATIONS. RESTING STATE FUNCTIONAL MAGNETIC RESONANCE IMAGING WAS ANALYZED TO IDENTIFY INTRINSIC CONNECTIVITY NETWORKS USING A PRIORI REGIONS OF INTEREST. METHYLATION MEASUREMENT OF FUNCTIONALLY RELEVANT SITES WITHIN THE DRD2 GENE WAS ACHIEVED VIA PYROSEQUENCING. REGRESSION-BASED MODELS, INCLUDING MEDIATION AND MODERATION MODELS, TESTED THE ASSOCIATION BETWEEN DRD2 METHYLATION, FUNCTIONAL CONNECTIVITY WITHIN INTRINSIC NEURAL NETWORKS (INCLUDING THE ECN), AND SEVERITY OF ALCOHOL PROBLEMS. RESULTS SUGGEST THAT AVERAGE DRD2 METHYLATION WAS NEGATIVELY ASSOCIATED WITH RIGHT ECN (RECN) AND LEFT ECN (LECN) CONNECTIVITY, BUT NOT ASSOCIATED WITH OTHER NETWORKS TESTED, AND DRD2 METHYLATION WAS SIGNIFICANTLY ASSOCIATED WITH ALCOHOL PROBLEMS SEVERITY. MEDIATION MODELS WERE NOT SUPPORTED, ALTHOUGH MODERATION MODELS SUGGESTED THAT CONNECTIVITY BETWEEN EDGES WITHIN THE RECN MODERATED THE RELATIONSHIP BETWEEN DRD2 METHYLATION AND AUD SEVERITY. RESULTS SUPPORT A THEORETICAL MODEL IN WHICH EPIGENETIC FACTORS ARE ASSOCIATED WITH NEUROBIOLOGICAL CORRELATES OF ALCOHOL CONSUMPTION AMONG A SAMPLE OF POLYSUBSTANCE USERS. 2020 6 747 25 CANNABIS-INDUCED HYPODOPAMINERGIC ANHEDONIA AND COGNITIVE DECLINE IN HUMANS: EMBRACING PUTATIVE INDUCTION OF DOPAMINE HOMEOSTASIS. OVER YEARS, THE REGULAR USE OF CANNABIS HAS SUBSTANTIALLY INCREASED AMONG YOUNG ADULTS, AS INDICATED BY THE RISE IN CANNABIS USE DISORDER (CUD), WITH AN ESTIMATED PREVALENCE OF 8. 3% IN THE UNITED STATES. RESEARCH SHOWS THAT EXPOSURE TO CANNABIS IS ASSOCIATED WITH HYPODOPAMINERGIC ANHEDONIA (DEPRESSION), COGNITIVE DECLINE, POOR MEMORY, INATTENTION, IMPAIRED LEARNING PERFORMANCE, REDUCED DOPAMINE BRAIN RESPONSE-ASSOCIATED EMOTIONALITY, AND INCREASED ADDICTION SEVERITY IN YOUNG ADULTS. THE ADDICTION MEDICINE COMMUNITY IS INCREASING CONCERN BECAUSE OF THE HIGH CONTENT OF DELTA-9-TETRAHYDROCANNABINOL (THC) CURRENTLY FOUND IN ORAL AND VAPING CANNABIS PRODUCTS, THE COGNITIVE EFFECTS OF CANNABIS MAY BECOME MORE PRONOUNCED IN YOUNG ADULTS WHO USE THESE CANNABIS PRODUCTS. PRELIMINARY RESEARCH SUGGESTS THAT IT IS POSSIBLE TO INDUCE 'DOPAMINE HOMEOSTASIS,' THAT IS, RESTORE DOPAMINE FUNCTION WITH DOPAMINE UPREGULATION WITH THE PROPOSED COMPOUND AND NORMALIZE BEHAVIOR IN CHRONIC CANNABIS USERS WITH CANNABIS-INDUCED HYPODOPAMINERGIC ANHEDONIA (DEPRESSION) AND COGNITIVE DECLINE. THIS PSYCHOLOGICAL, NEUROBIOLOGICAL, ANATOMICAL, GENETIC, AND EPIGENETIC RESEARCH ALSO COULD PROVIDE EVIDENCE TO USE FOR THE DEVELOPMENT OF AN APPROPRIATE POLICY REGARDING THE DECRIMINALIZATION OF CANNABIS FOR RECREATIONAL USE. 2021 7 1091 26 COGNITIVE ENHANCERS AS A TREATMENT FOR HEROIN RELAPSE AND ADDICTION. HEROIN ADDICTION IS A DISORDER THAT STEMS FROM MALADAPTIVE PLASTICITY WITHIN NEURAL CIRCUITS AND PRODUCES BROAD COGNITIVE DEFICITS. DESPITE CONSIDERABLE ADVANCES IN PSYCHOTHERAPY AND PHARMACOTHERAPY FOR HEROIN RELAPSE AND ADDICTION, EFFECTIVE TREATMENTS FOR HEROIN USE DISORDER ARE STILL LACKING. INCREASING PRECLINICAL EVIDENCE INDICATES THAT HEROIN SEEKING BEHAVIOR IS PERSISTENT AFTER WITHDRAWAL, WHILE COGNITIVE DYSFUNCTIONS ASSOCIATED WITH CHRONIC HEROIN USE ARE AN IMPORTANT CONTRIBUTING FACTOR TO RISK OF HEROIN RELAPSE AND ADDICTION. COGNITIVE ENHANCERS MAY BE USED TO STIMULATE TREATMENT SUCCESS AND ENHANCE TREATMENT EFFICACY. THE PURPOSE OF THIS REVIEW IS TO OUTLINE THE LITERATURE THAT DEMONSTRATES THE COGNITIVE DEFICITS DURING THE DEVELOPMENT OF HEROIN ADDICTION AND WITHDRAWAL PROCESS, AND SEVERAL FACTORS THAT UNDERLINE THE EFFICACY OF COGNITIVE ENHANCERS FOR HEROIN USE DISORDERS. THE REVIEW, THEN, EXAMINES THE POTENTIAL USE AND PHARMACOLOGICAL MECHANISMS OF COGNITIVE ENHANCERS THAT ACT ON CHOLINERGIC, GLUTAMATERGIC, DOPAMINERGIC OR ADRENERGIC PATHWAYS. IT ALSO EXAMINES THE EFFECTS OF COMPOUNDS THAT ALTER CREB SIGNALING AND EPIGENETIC MECHANISMS IN ANIMAL MODEL OF HEROIN RELAPSE. THE CURRENT BODY OF RESEARCH REVEALS THE NEW INSIGHTS INTO THE PHARMACOLOGICAL MECHANISMS UNDERLYING HEROIN ADDICTION AND HOLDS A SIGNIFICANT PROMISE FOR COGNITIVE ENHANCERS AS AN IMPROVED APPROACH TO TREAT HEROIN USE DISORDER IN A MORE EFFICIENT AND PERSISTENT WAY. 2019 8 4846 25 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 9 5035 28 PHARMACOEPIGENOMICS OF OPIATES AND METHADONE MAINTENANCE TREATMENT: CURRENT DATA AND PERSPECTIVES. CURRENT TREATMENTS OF OPIOID ADDICTION INCLUDE PRIMARILY MAINTENANCE MEDICATIONS SUCH AS METHADONE. CHRONIC EXPOSURE TO OPIATE AND/OR LONG-LASTING MAINTENANCE TREATMENT INDUCE MODULATIONS OF GENE EXPRESSION IN BRAIN AND PERIPHERAL TISSUES. THERE IS INCREASING EVIDENCE THAT EPIGENETIC MODIFICATIONS UNDERLIE THESE MODULATIONS. THIS REVIEW SUMMARIZES PUBLISHED RESULTS ON OPIOID-INDUCED EPIGENETIC CHANGES IN ANIMAL MODELS AND IN PATIENTS. THE EPIGENETIC MODIFICATIONS OBSERVED WITH OTHER DRUGS OF ABUSE OFTEN USED BY OPIATE ABUSERS ARE ALSO OUTLINED. SPECIFIC METHADONE MAINTENANCE TREATMENT INDUCED EPIGENETIC MODIFICATIONS AT DIFFERENT TREATMENT STAGES MAY BE COMBINED WITH THE ONES RESULTING FROM PATIENTS' SUBSTANCE USE HISTORY. THEREFORE, RESEARCH COMPARING GROUPS OF ADDICTS WITH SIMILAR HISTORY AND SUBSTANCES USE DISORDERS BUT CONTRASTING FOR WELL-CHARACTERIZED TREATMENT PHENOTYPES SHOULD BE ENCOURAGED. 2017 10 2259 36 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 11 2934 22 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 12 1252 38 CURRENT PERSPECTIVES ON THE NEUROBIOLOGY OF DRUG ADDICTION: A FOCUS ON GENETICS AND FACTORS REGULATING GENE EXPRESSION. DRUG ADDICTION IS A CHRONIC, RELAPSING DISORDER DEFINED BY CYCLIC PATTERNS OF COMPULSIVE DRUG SEEKING AND TAKING INTERSPERSED WITH EPISODES OF ABSTINENCE. WHILE GENETIC VARIABILITY MAY INCREASE THE RISK OF ADDICTIVE BEHAVIOURS IN AN INDIVIDUAL, EXPOSURE TO A DRUG RESULTS IN NEUROADAPTATIONS IN INTERCONNECTED BRAIN CIRCUITS WHICH, IN SUSCEPTIBLE INDIVIDUALS, ARE BELIEVED TO UNDERLIE THE TRANSITION TO, AND MAINTENANCE OF, AN ADDICTED STATE. THESE ADAPTATIONS CAN OCCUR AT THE CELLULAR, MOLECULAR, OR (EPI)GENETIC LEVEL AND ARE ASSOCIATED WITH SYNAPTIC PLASTICITY AND ALTERED GENE EXPRESSION, THE LATTER BEING MEDIATED VIA BOTH FACTORS AFFECTING TRANSLATION (EPIGENETICS) AND TRANSCRIPTION (NON CODING MICRORNAS) OF THE DNA OR RNA ITSELF. NEW ADVANCES USING TECHNIQUES SUCH AS OPTOGENETICS HAVE THE POTENTIAL TO INCREASE OUR UNDERSTANDING OF THE MICROCIRCUITRY MEDIATING ADDICTIVE BEHAVIOURS. HOWEVER, THE PROCESSES LEADING TO ADDICTION ARE COMPLEX AND MULTIFACTORIAL AND THUS WE FACE A MAJOR CONTEMPORARY CHALLENGE TO ELUCIDATE THE FACTORS IMPLICATED IN THE DEVELOPMENT AND MAINTENANCE OF AN ADDICTED STATE. 2012 13 2513 31 EPIGENETICS AND PSYCHOSTIMULANT ADDICTION. CHRONIC DRUG EXPOSURE ALTERS GENE EXPRESSION IN THE BRAIN AND PRODUCES LONG-TERM CHANGES IN NEURAL NETWORKS THAT UNDERLIE COMPULSIVE DRUG TAKING AND SEEKING. EXACTLY HOW DRUG-INDUCED CHANGES IN SYNAPTIC PLASTICITY AND SUBSEQUENT GENE EXPRESSION ARE TRANSLATED INTO PERSISTENT NEUROADAPTATIONS REMAINS UNCLEAR. EMERGING EVIDENCE SUGGESTS THAT COMPLEX DRUG-INDUCED NEUROADAPTATIONS IN THE BRAIN ARE MEDIATED BY HIGHLY SYNCHRONIZED AND DYNAMIC PATTERNS OF GENE REGULATION. RECENTLY, IT HAS BECOME CLEAR THAT EPIGENETIC MECHANISMS CONTRIBUTE TO DRUG-INDUCED STRUCTURAL, SYNAPTIC, AND BEHAVIORAL PLASTICITY BY REGULATING EXPRESSION OF GENE NETWORKS. HERE WE REVIEW HOW ALTERATIONS IN HISTONE MODIFICATIONS, DNA METHYLATION, AND MICRORNAS REGULATE GENE EXPRESSION AND CONTRIBUTE TO PSYCHOSTIMULANT ADDICTION WITH A FOCUS ON THE EPIGENETIC MECHANISMS THAT REGULATE BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) EXPRESSION FOLLOWING CHRONIC COCAINE EXPOSURE. IDENTIFYING EPIGENETIC SIGNATURES THAT DEFINE PSYCHOSTIMULANT ADDICTION MAY LEAD TO NOVEL, EFFICACIOUS TREATMENTS FOR DRUG CRAVING AND RELAPSE. 2013 14 4441 38 MOLECULAR GENETICS OF COCAINE USE DISORDERS IN HUMANS. DRUG ADDICTION, ONE OF THE MAJOR HEALTH PROBLEMS WORLDWIDE, IS CHARACTERIZED BY THE LOSS OF CONTROL IN DRUG INTAKE, CRAVING, AND WITHDRAWAL. AT THE INDIVIDUAL LEVEL, DRUGS OF ABUSE PRODUCE SERIOUS CONSEQUENCES ON HEALTH AND HAVE A NEGATIVE IMPACT ON THE FAMILY ENVIRONMENT AND ON INTERPERSONAL AND WORK RELATIONSHIPS. AT A WIDER SCALE, THEY HAVE SIGNIFICANT SOCIO-ECONOMIC AND PUBLIC HEALTH CONSEQUENCES AND THEY CAUSE DELINQUENCY AND CITIZEN INSECURITY. COCAINE, A PSYCHOSTIMULANT SUBSTANCE, IS ONE OF THE MOST USED ILLICIT DRUGS, ESPECIALLY IN AMERICA, WESTERN EUROPE, AND AUSTRALIA. COCAINE USE DISORDERS (CUD) ARE COMPLEX MULTIFACTORIAL CONDITIONS DRIVEN BY BOTH GENETIC AND ENVIRONMENTAL INFLUENCES. IMPORTANTLY, NOT ALL PEOPLE WHO USE COCAINE DEVELOP CUD, AND THIS IS DUE, AT LEAST IN PART, TO BIOLOGICAL FACTORS THAT ARE ENCODED IN THE GENOME OF INDIVIDUALS. ACUTE AND REPEATED USE OF COCAINE INDUCES EPIGENETIC AND GENE EXPRESSION CHANGES RESPONSIBLE FOR THE NEURONAL ADAPTATIONS AND THE REMODELING OF BRAIN CIRCUITS THAT LEAD TO THE TRANSITION FROM USE TO ABUSE OR DEPENDENCE. THE PURPOSE OF THIS REVIEW IS TO DELINEATE SUCH FACTORS, WHICH SHOULD EVENTUALLY HELP TO UNDERSTAND THE INTER-INDIVIDUAL VARIABILITY IN THE SUSCEPTIBILITY TO COCAINE ADDICTION. HERITABILITY ESTIMATES FOR CUD ARE HIGH AND GENETIC RISK FACTORS FOR COCAINE ADDICTION HAVE BEEN INVESTIGATED BY CANDIDATE GENE ASSOCIATION STUDIES (CGAS) AND GENOME-WIDE ASSOCIATION STUDIES (GWAS), REVIEWED HERE. ALSO, THE HIGH COMORBIDITY THAT EXISTS BETWEEN CUD AND SEVERAL OTHER PSYCHIATRIC DISORDERS IS WELL KNOWN AND INCLUDES PHENOTYPES LIKE SCHIZOPHRENIA, AGGRESSION, ANTISOCIAL OR RISK-TAKING BEHAVIORS. SUCH COMORBIDITIES ARE ASSOCIATED WITH A WORSE LIFETIME TRAJECTORY, AND HERE WE REPORT SHARED GENETIC FACTORS THAT MAY CONTRIBUTE TO THEM. GENE EXPRESSION CHANGES AND EPIGENETIC MODIFICATIONS INDUCED BY COCAINE USE AND CHRONIC ABUSE IN HUMANS ARE ADDRESSED BY REVIEWING TRANSCRIPTOMIC STUDIES PERFORMED ON NEURONAL CELLS AND ON POSTMORTEM BRAINS. WE REPORT SOME GENES WHICH EXPRESSION IS ALTERED BY COCAINE THAT ALSO BEAR GENETIC RISK VARIANTS FOR THE DISORDER. FINALLY, WE HAVE A GLANCE TO THE PHARMACOGENETICS OF CUD TREATMENTS, STILL IN EARLY STAGES. A BETTER UNDERSTANDING OF THE GENETIC UNDERPINNINGS OF CUD WILL FOSTER THE SEARCH OF EFFECTIVE TREATMENTS AND HELP TO MOVE FORWARD TO PERSONALIZED MEDICINE. 2022 15 4848 26 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 16 5855 26 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 17 1677 28 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 18 4650 29 NEUROPLASTICITY IN ADDICTION: CELLULAR AND TRANSCRIPTIONAL PERSPECTIVES. DRUG ADDICTION IS A CHRONIC, RELAPSING BRAIN DISORDER WHICH CONSISTS OF COMPULSIVE PATTERNS OF DRUG-SEEKING AND TAKING THAT OCCURS AT THE EXPENSE OF OTHER ACTIVITIES. THE TRANSITION FROM CASUAL TO COMPULSIVE DRUG USE AND THE ENDURING PROPENSITY TO RELAPSE IS THOUGHT TO BE UNDERPINNED BY LONG-LASTING NEUROADAPTATIONS IN SPECIFIC BRAIN CIRCUITRY, ANALOGOUS TO THOSE THAT UNDERLIE LONG-TERM MEMORY FORMATION. RESEARCH SPANNING THE LAST TWO DECADES HAS MADE GREAT PROGRESS IN IDENTIFYING CELLULAR AND MOLECULAR MECHANISMS THAT CONTRIBUTE TO DRUG-INDUCED CHANGES IN PLASTICITY AND BEHAVIOR. ALTERATIONS IN SYNAPTIC TRANSMISSION WITHIN THE MESOCORTICOLIMBIC AND CORTICOSTRIATAL PATHWAYS, AND CHANGES IN THE TRANSCRIPTIONAL POTENTIAL OF CELLS BY EPIGENETIC MECHANISMS ARE TWO IMPORTANT MEANS BY WHICH DRUGS OF ABUSE CAN INDUCE LASTING CHANGES IN BEHAVIOR. IN THIS REVIEW WE PROVIDE A SUMMARY OF MORE RECENT RESEARCH THAT HAS FURTHERED OUR UNDERSTANDING OF DRUG-INDUCED NEUROPLASTIC CHANGES BOTH AT THE LEVEL OF THE SYNAPSE, AND ON A TRANSCRIPTIONAL LEVEL, AND HOW THESE CHANGES MAY RELATE TO THE HUMAN DISEASE OF ADDICTION. 2012 19 242 35 ADOLESCENT CANNABINOID EXPOSURE MODULATES THE VULNERABILITY TO COCAINE-INDUCED CONDITIONED PLACE PREFERENCE AND DNMT3A EXPRESSION IN THE PREFRONTAL CORTEX IN SWISS MICE. RATIONALE: CANNABIS SATIVA IS THE MOST WIDELY USED DRUG BY ADOLESCENTS GLOBALLY. THE RECREATIONAL USE OF SYNTHETIC CANNABINOIDS BY TEENAGERS HAS ALSO GROWN IN RECENT YEARS. DESPITE THE WRONG PERCEPTION THAT EXPOSURE TO THESE DRUGS DOES NOT CAUSE HARM, REPEATED EXPOSURE TO CANNABINOIDS AT EARLY STAGES OF LIFE COMPROMISES IMPORTANT MATURATION PROCESSES AND BRAIN DEVELOPMENT. CHRONIC EARLY CANNABINOID USE HAS BEEN RELATED TO A HIGHER RISK OF PSYCHIATRIC OUTCOMES, INCLUDING COCAINE ADDICTION. EVIDENCE SUGGESTS THAT EXPOSURE TO NATURAL AND SYNTHETIC CANNABINOIDS DURING ADOLESCENCE MODIFIES MOLECULAR AND BEHAVIORAL EFFECTS OF COCAINE IN ADULTHOOD. RESPONSES TO COCAINE ARE REGULATED BY EPIGENETIC MECHANISMS, SUCH AS DNA METHYLATION, IN THE BRAIN'S REWARD REGIONS. HOWEVER, THE INVOLVEMENT OF THESE PROCESSES IN MODULATION OF THE VULNERABILITY TO THE EFFECTS OF COCAINE INDUCED BY PRIOR EXPOSURE TO CANNABINOIDS REMAINS POORLY UNDERSTOOD. OBJECTIVES: INVESTIGATE WHETHER EXPOSURE TO THE SYNTHETIC CANNABINOID WIN55,212-2 DURING ADOLESCENCE MODULATES ANXIETY- AND DEPRESSION-LIKE BEHAVIOR, MEMORY, AND COCAINE REWARD IN ADULT MICE. WE ALSO EVALUATED WHETHER EXPOSURE TO CANNABINOIDS DURING ADOLESCENCE MODULATES THE EXPRESSION OF ENZYMES THAT ARE INVOLVED IN DNA METHYLATION. RESULTS: EXPOSURE TO WIN55,212-2 DURING ADOLESCENCE DID NOT ALTER ANXIETY- OR DEPRESSIVE-LIKE BEHAVIOR. HOWEVER, PRIOR EXPOSURE TO CANNABINOIDS INHIBITED COCAINE-INDUCED CONDITIONED PLACE PREFERENCE WITHOUT MODULATING COCAINE-INDUCED HYPERLOCOMOTION, ACCOMPANIED BY AN INCREASE IN EXPRESSION OF THE ENZYME DNA METHYLTRANSFERASE 3A (DNMT3A) IN THE PREFRONTAL CORTEX. CONCLUSIONS: OUR FINDINGS SUGGEST THAT EXPOSURE TO WIN55,212-2 DURING ADOLESCENCE LEADS TO CHANGES IN DNMT3A EXPRESSION, AND THIS PATHWAY APPEARS TO BE RELEVANT TO MODULATING THE REWARDING EFFECTS OF COCAINE. 2021 20 3203 27 HDAC3 ACTIVITY WITHIN THE NUCLEUS ACCUMBENS REGULATES COCAINE-INDUCED PLASTICITY AND BEHAVIOR IN A CELL-TYPE-SPECIFIC MANNER. EPIGENETIC MECHANISMS REGULATE PROCESSES OF NEUROPLASTICITY CRITICAL TO COCAINE-INDUCED BEHAVIORS. THIS INCLUDES THE CLASS I HISTONE DEACETYLASE (HDAC) HDAC3, KNOWN TO ACT AS A NEGATIVE REGULATOR OF COCAINE-ASSOCIATED MEMORY FORMATION WITHIN THE NUCLEUS ACCUMBENS (NAC). DESPITE THIS, IT REMAINS UNKNOWN HOW COCAINE ALTERS HDAC3-DEPENDENT MECHANISMS. HERE, WE PROFILED HDAC3 EXPRESSION AND ACTIVITY IN TOTAL NAC MOUSE TISSUE FOLLOWING COCAINE EXPOSURE. ALTHOUGH CHRONIC COCAINE DID NOT AFFECT EXPRESSION OF HDAC3 WITHIN THE NAC, CHRONIC COCAINE DID AFFECT PROMOTER-SPECIFIC CHANGES IN HDAC3 AND H4K8AC OCCUPANCY. THESE CHANGES IN PROMOTER OCCUPANCY CORRELATED WITH COCAINE-INDUCED CHANGES IN EXPRESSION OF PLASTICITY-RELATED GENES. TO CAUSALLY DETERMINE WHETHER COCAINE-INDUCED PLASTICITY IS MEDIATED BY HDAC3'S DEACETYLASE ACTIVITY, WE OVEREXPRESSED A DEACETYLASE-DEAD HDAC3 POINT MUTANT (HDAC3-Y298H-V5) WITHIN THE NAC OF ADULT MALE MICE. WE FOUND THAT DISRUPTING HDAC3'S ENZYMATIC ACTIVITY ALTERED SELECTIVE CHANGES IN GENE EXPRESSION AND SYNAPTIC PLASTICITY FOLLOWING COCAINE EXPOSURE, DESPITE HAVING NO EFFECTS ON COCAINE-INDUCED BEHAVIORS. IN FURTHER ASSESSING HDAC3'S ROLE WITHIN THE NAC, WE OBSERVED THAT CHRONIC COCAINE INCREASES HDAC3 EXPRESSION IN DRD1 BUT NOT DRD2-CELLS OF THE NAC. MOREOVER, WE DISCOVERED THAT HDAC3 ACTS SELECTIVELY WITHIN D1R CELL-TYPES TO REGULATE COCAINE-ASSOCIATED MEMORY FORMATION AND COCAINE-SEEKING. OVERALL, THESE RESULTS SUGGEST THAT COCAINE INDUCES CELL-TYPE-SPECIFIC CHANGES IN EPIGENETIC MECHANISMS TO PROMOTE PLASTICITY IMPORTANT FOR DRIVING COCAINE-RELATED BEHAVIORS.SIGNIFICANCE STATEMENT DRUGS OF ABUSE ALTER MOLECULAR MECHANISMS THROUGHOUT THE REWARD CIRCUITRY THAT CAN LEAD TO PERSISTENT DRUG-ASSOCIATED BEHAVIORS. EPIGENETIC REGULATORS ARE CRITICAL DRIVERS OF DRUG-INDUCED CHANGES IN GENE EXPRESSION. HERE, WE DEMONSTRATE THAT THE ACTIVITY OF AN EPIGENETIC ENZYME PROMOTES NEUROPLASTICITY WITHIN THE NUCLEUS ACCUMBENS (NAC) CRITICAL TO COCAINE ACTION. IN ADDITION, WE DEMONSTRATE THAT THESE CHANGES IN EPIGENETIC ACTIVITY DRIVE COCAINE-SEEKING BEHAVIORS IN A CELL-TYPE-SPECIFIC MANNER. THESE FINDINGS ARE KEY IN UNDERSTANDING AND TARGETING COCAINE'S IMPACT OF NEURAL CIRCUITRY AND BEHAVIOR. 2021