title: beta-Endorphin-like immunoreactivity in discrete brain regions, spinal cord, pituitary gland and peripheral tissues of U-50,488H-tolerant and -abstinent rats.
abstract: The effect was determined of trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzene- acetamide methane sulfonate (U-50,488H), a kappa opioid agonist, -induced tolerance dependence and abstinence on the levels of beta-endorphin in discrete brain regions, spinal cord, pituitary gland, plasma and peripheral tissues of male Sprague-Dawley rats. The brain regions examined were hypothalamus, hippocampus, amygdala, midbrain, corpus striatum, pons-medulla and cortex. The peripheral tissues included kidneys, spleen, adrenals and heart. Rats were made tolerant dependent on U-50,488H by intraperitoneal injections of the drug (25 mg/kg) twice a day for 4 days. Vehicle-injected rats served as controls. Rats that were labeled as tolerant dependent were injected with U-50,488H (25 mg/kg) on day 5 and killed 1 hr later, whereas those labeled as abstinent were killed without injection of the drug. Rats serving as controls were injected with the vehicle. Tolerance to the analgesic and hypothermic effects of U-50,488H developed, as evidenced by a decrease in the intensity of responses in chronic U-50,488H-treated compared with chronic vehicle-treated rats. In U-50,488H-tolerant rats, the concentration of beta-endorphin was increased in hippocampus, corpus striatum, pituitary gland, plasma, kidneys and adrenals compared with vehicle-injected controls. In U-50,488H-abstinent rats, the concentration of beta-endorphin was increased in pons-medulla and amygdala, whereas the concentration of beta-endorphin did not change in the pituitary gland, plasma and peripheral tissues. In general, chronic treatment with a kappa opioid agonist results in increases in the concentration of beta-endorphin in specific tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmaceutics and Pharmacodynamics, University of Illinois at Chicago.
authors.forename: H N
authors.initials: HN
authors.lastname: Bhargava
authors.forename: G A
authors.initials: GA
authors.lastname: Matwyshyn
authors.forename: A K
authors.initials: AK
authors.lastname: Rattan
authors.forename: K L
authors.initials: KL
authors.lastname: Koo
authors.forename: G A
authors.initials: GA
authors.lastname: Tejwani
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D004361:Drug Tolerance; D008297:Male; D010902:Pituitary Gland / Q000737:chemistry* / Q000187:drug effects; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000737:chemistry* / Q000187:drug effects; D019966:Substance-Related Disorders / Q000378:metabolism*; D001615:beta-Endorphin / Q000032:analysis* / Q000276:immunology
chemical_list: D000700:Analgesics; D011759:Pyrrolidines; D001615:beta-Endorphin; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer