title: Tolerance to diacetyl morphine antinociception: effects on brain serotonin.
abstract: The effects of 5 mg kg-1 diacetyl morphine (DAM) on brain serotonin metabolism of rats were investigated following tolerance to the antinociceptive effects of 2.5 mg kg-1 DAM. Brain levels of tryptophan and 5-hydroxy indoleacetic acid (5-HIAA) were higher in the DAM-tolerant rats killed 24 h after last daily administration of 2.5 mg kg-1 DAM. Administration of 5 mg kg-1 DAM produced less antinociception in DAM-tolerant than DAM-naive rats and increased brain tryptophan concentration in both tolerant and naive rats. 5-HIAA concentrations increased only in naive rats. Combined use of drugs interfering with brain 5-HT turnover along with opiates may be of future benefit for the treatment of chronic pain.
authors.affiliation: Department of Biochemistry, University of Karachi, Pakistan.
authors.forename: D J
authors.initials: DJ
authors.lastname: Haleem
authors.forename: A
authors.initials: A
authors.lastname: Zafar
authors.forename: S
authors.initials: S
authors.lastname: Azam
authors.forename: A
authors.initials: A
authors.lastname: Yasmeen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001921:Brain / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D003932:Heroin / Q000494:pharmacology*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009619:Nociceptors / Q000187:drug effects*; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D003932:Heroin; D014364:Tryptophan