Receptors, Opioid, kappa: A class of opioid receptors recognized by its pharmacological profile. Kappa opioid receptors bind dynorphins with a higher affinity than endorphins which are themselves preferred to enkephalins.3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer: A non-peptide, kappa-opioid receptor agonist which has also been found to stimulate the release of adrenocorticotropin (ADRENOCORTICOTROPIC HORMONE) via the release of hypothalamic arginine vasopressin (ARGININE VASOPRESSIN) and CORTICOTROPIN-RELEASING HORMONE. (From J Pharmacol Exp Ther 1997;280(1):416-21)Isomerism: The phenomenon whereby certain chemical compounds have structures that are different although the compounds possess the same elemental composition. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Diprenorphine: A narcotic antagonist similar in action to NALOXONE. It is used to remobilize animals after ETORPHINE neuroleptanalgesia and is considered a specific antagonist to etorphine.PyrrolidinesEnkephalin, D-Penicillamine (2,5)-: A disulfide opioid pentapeptide that selectively binds to the DELTA OPIOID RECEPTOR. It possesses antinociceptive activity.Stereoisomerism: The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Analgesics, Non-Narcotic: A subclass of analgesic agents that typically do not bind to OPIOID RECEPTORS and are not addictive. Many non-narcotic analgesics are offered as NONPRESCRIPTION DRUGS.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.Narcotic Antagonists: Agents inhibiting the effect of narcotics on the central nervous system.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.Receptors, Opioid: Cell membrane proteins that bind opioids and trigger intracellular changes which influence the behavior of cells. The endogenous ligands for opioid receptors in mammals include three families of peptides, the enkephalins, endorphins, and dynorphins. The receptor classes include mu, delta, and kappa receptors. Sigma receptors bind several psychoactive substances, including certain opioids, but their endogenous ligands are not known.Benzeneacetamides: Compounds based on benzeneacetamide, that are similar in structure to ACETANILIDES.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.Enkephalin, Ala(2)-MePhe(4)-Gly(5)-: An enkephalin analog that selectively binds to the MU OPIOID RECEPTOR. It is used as a model for drug permeability experiments.Analgesics, Opioid: Compounds with activity like OPIATE ALKALOIDS, acting at OPIOID RECEPTORS. Properties include induction of ANALGESIA or NARCOSIS.Diterpenes, Clerodane: A group of DITERPENES cyclized into 2-rings with a side-chain.alpha-Linolenic Acid: A fatty acid that is found in plants and involved in the formation of prostaglandins.Benzomorphans: Morphine derivatives of the methanobenzazocine family that act as potent analgesics.Receptors, Phencyclidine: Specific sites or molecular structures on cell membranes or in cells with which phencyclidine reacts or to which it binds to elicit the specific response of the cell to phencyclidine. Studies have demonstrated the presence of multiple receptor sites for PCP. These are the PCP/sigma site, which binds both PCP and psychotomimetic opiates but not certain antipsychotics, and the PCP site, which selectively binds PCP analogs.Chromatography, Gas: Fractionation of a vaporized sample as a consequence of partition between a mobile gaseous phase and a stationary phase held in a column. Two types are gas-solid chromatography, where the fixed phase is a solid, and gas-liquid, in which the stationary phase is a nonvolatile liquid supported on an inert solid matrix.Magnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Fatty Acids, Unsaturated: FATTY ACIDS in which the carbon chain contains one or more double or triple carbon-carbon bonds.