title: Enhancement of hepatic tryptophan pyrrolase activity and decreases of open field locomotion following single and repeated administration of high doses of caffeine in rats.
abstract: In view of a possible role of kynurenine in caffeine-induced anxiety syndrome, the effects of single and repeated administration of caffeine on hepatic tryptophan (T)-pyrrolase activity are investigated. Single administration of caffeine at doses of 80 mg/kg decreased open field locomotion and increased hepatic T-pyrrolase activity. Locomotor stimulating effects of 80 mg/kg caffeine, monitored in the home cages of rats, were attenuated following daily administration of caffeine for 5 days. Open field locomotor activity of rats and its caffeine-induced decrement were also attenuated following 5 daily administrations of caffeine on the 6th day. Basal levels of hepatic T-pyrrolase activity increased after 5 daily administrations of caffeine on the 6th day. Acute administration of caffeine did not further elevate hepatic T-pyrrolase activity in 5 day caffeine injected rats. Drug adjuvants decreasing hepatic T-pyrrolase activity may prove valuable for extending the clinical utility of caffeine.
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: Yasmeen
authors.forename: T
authors.initials: T
authors.lastname: Parveen
authors.forename: A
authors.initials: A
authors.lastname: Zafar
mesh_terms: D000818:Animals; D001007:Anxiety / Q000139:chemically induced; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology* / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D007274:Injections, Intraperitoneal; D007737:Kynurenine / Q000502:physiology; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D014366:Tryptophan Oxygenase / Q000096:biosynthesis*
chemical_list: D007737:Kynurenine; D002110:Caffeine; D014366:Tryptophan Oxygenase