Heroin Dependence: Strong dependence, both physiological and emotional, upon heroin.Narcotics: Agents that induce NARCOSIS. Narcotics include agents that cause somnolence or induced sleep (STUPOR); natural or synthetic derivatives of OPIUM or MORPHINE or any substance that has such effects. They are potent inducers of ANALGESIA and OPIOID-RELATED DISORDERS.Morphine Derivatives: Analogs or derivatives of morphine.Methadone: A synthetic opioid that is used as the hydrochloride. It is an opioid analgesic that is primarily a mu-opioid agonist. It has actions and uses similar to those of MORPHINE. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1082-3)Self Administration: Administration of a drug or chemical by the individual under the direction of a physician. It includes administration clinically or experimentally, by human or animal.Buprenorphine: A derivative of the opioid alkaloid THEBAINE that is a more potent and longer lasting analgesic than MORPHINE. It appears to act as a partial agonist at mu and kappa opioid receptors and as an antagonist at delta receptors. The lack of delta-agonist activity has been suggested to account for the observation that buprenorphine tolerance may not develop with chronic use.Drug Overdose: Accidental or deliberate use of a medication or street drug in excess of normal dosage.Codeine: An opioid analgesic related to MORPHINE but with less potent analgesic properties and mild sedative effects. It also acts centrally to suppress cough.Street Drugs: Drugs obtained and often manufactured illegally for the subjective effects they are said to produce. They are often distributed in urban areas, but are also available in suburban and rural areas, and tend to be grossly impure and may cause unexpected toxicity.Cocaine-Related Disorders: Disorders related or resulting from use of cocaine.Substance Abuse, Intravenous: Abuse, overuse, or misuse of a substance by its injection into a vein.Behavior, Addictive: The observable, measurable, and often pathological activity of an organism that portrays its inability to overcome a habit resulting in an insatiable craving for a substance or for performing certain acts. The addictive behavior includes the emotional and physical overdependence on the object of habit in increasing amount or frequency.Opioid-Related Disorders: Disorders related or resulting from abuse or mis-use of opioids.Substance Abuse Detection: Detection of drugs that have been abused, overused, or misused, including legal and illegal drugs. Urine screening is the usual method of detection.Substance Withdrawal Syndrome: Physiological and psychological symptoms associated with withdrawal from the use of a drug after prolonged administration or habituation. The concept includes withdrawal from smoking or drinking, as well as withdrawal from an administered drug.Drug and Narcotic Control: Control of drug and narcotic use by international agreement, or by institutional systems for handling prescribed drugs. This includes regulations concerned with the manufacturing, dispensing, approval (DRUG APPROVAL), and marketing of drugs.Naloxone: A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.Opiate Substitution Treatment: Medical treatment for opioid dependence using a substitute opiate such as METHADONE or BUPRENORPHINE.Morphine: The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle.Naltrexone: Derivative of noroxymorphone that is the N-cyclopropylmethyl congener of NALOXONE. It is a narcotic antagonist that is effective orally, longer lasting and more potent than naloxone, and has been proposed for the treatment of heroin addiction. The FDA has approved naltrexone for the treatment of alcohol dependence.Cocaine: An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake.Substance-Related Disorders: Disorders related to substance abuse.Receptors, Opioid, mu: A class of opioid receptors recognized by its pharmacological profile. Mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. They have also been shown to be molecular receptors for morphine.Drug Users: People who take drugs for a non-therapeutic or non-medical effect. The drugs may be legal or illegal, but their use often results in adverse medical, legal, or social consequences for the users.Analgesics, Opioid: Compounds with activity like OPIATE ALKALOIDS, acting at OPIOID RECEPTORS. Properties include induction of ANALGESIA or NARCOSIS.Conditioning, Operant: Learning situations in which the sequence responses of the subject are instrumental in producing reinforcement. When the correct response occurs, which involves the selection from among a repertoire of responses, the subject is immediately reinforced.Crime: A violation of the criminal law, i.e., a breach of the conduct code specifically sanctioned by the state, which through its administrative agencies prosecutes offenders and imposes and administers punishments. The concept includes unacceptable actions whether prosecuted or going unpunished.Nucleus Accumbens: Collection of pleomorphic cells in the caudal part of the anterior horn of the LATERAL VENTRICLE, in the region of the OLFACTORY TUBERCLE, lying between the head of the CAUDATE NUCLEUS and the ANTERIOR PERFORATED SUBSTANCE. It is part of the so-called VENTRAL STRIATUM, a composite structure considered part of the BASAL GANGLIA.Reinforcement (Psychology): The strengthening of a conditioned response.Substance Abuse Treatment Centers: Health facilities providing therapy and/or rehabilitation for substance-dependent individuals. Methadone distribution centers are included.Law Enforcement: Organized efforts to insure obedience to the laws of a community.Gas Chromatography-Mass Spectrometry: A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.Reinforcement Schedule: A schedule prescribing when the subject is to be reinforced or rewarded in terms of temporal interval in psychological experiments. The schedule may be continuous or intermittent.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Extinction, Psychological: The procedure of presenting the conditioned stimulus without REINFORCEMENT to an organism previously conditioned. It refers also to the diminution of a conditioned response resulting from this procedure.Drug Contamination: The presence of organisms, or any foreign material that makes a drug preparation impure.Behavior, Animal: The observable response an animal makes to any situation.Political Systems: The units based on political theory and chosen by countries under which their governmental power is organized and administered to their citizens.Crack Cocaine: The purified, alkaloidal, extra-potent form of cocaine. It is smoked (free-based), injected intravenously, and orally ingested. Use of crack results in alterations in function of the cardiovascular system, the autonomic nervous system, the central nervous system, and the gastrointestinal system. The slang term "crack" was derived from the crackling sound made upon igniting of this form of cocaine for smoking.Rats, Long-Evans: An outbred strain of rats developed in 1915 by crossing several Wistar Institute white females with a wild gray male. Inbred strains have been derived from this original outbred strain, including Long-Evans cinnamon rats (RATS, INBRED LEC) and Otsuka-Long-Evans-Tokushima Fatty rats (RATS, INBRED OLETF), which are models for Wilson's disease and non-insulin dependent diabetes mellitus, respectively.Social Determinants of Health: The circumstances in which people are born, grow up, live, work, and age, as well as the systems put in place to deal with illness. These circumstances are in turn shaped by a wider set of forces: economics, social policies, and politics (http://www.cdc.gov/socialdeterminants/).Needle Sharing: Usage of a single needle among two or more people for injecting drugs. Needle sharing is a high-risk behavior for contracting infectious disease.Flupenthixol: A thioxanthene neuroleptic that, unlike CHLORPROMAZINE, is claimed to have CNS-activating properties. It is used in the treatment of psychoses although not in excited or manic patients. (From Martindale, The Extra Pharmacopoeia, 30th ed, p595)Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.Injections, Intravenous: Injections made into a vein for therapeutic or experimental purposes.Pupil: The aperture in the iris through which light passes.Secobarbital: A barbiturate that is used as a sedative. Secobarbital is reported to have no anti-anxiety activity.Drug-Seeking Behavior: Activities performed to obtain licit or illicit substances.Sweat: The fluid excreted by the SWEAT GLANDS. It consists of water containing sodium chloride, phosphate, urea, ammonia, and other waste products.Receptors, Opioid, delta: A class of opioid receptors recognized by its pharmacological profile. Delta opioid receptors bind endorphins and enkephalins with approximately equal affinity and have less affinity for dynorphins.