title: Selective 5-HT1B receptor agonist reduces serotonin synthesis following acute, and not chronic, drug administration: results of an autoradiographic study.
abstract: The effects of acute and chronic administration of the serotonin (5-HT)1B agonist CP-93,129, on 5-HT synthesis rates were evaluated using the alpha-[14C]methyl-L-tryptophan (alpha-MTrp) autoradiographic method. In the acute treatment study, CP-93,129 (7 mg/kg) was injected intraperitoneally 30 min before the alpha-MTrp injection (30 microCi over 2 min). A single dose of CP-93,129 caused a significant increase in the synthesis in the median raphe nucleus (MR) without a significant influence on the dorsal raphe nucleus (DR). There was a reduction in 5-HT synthesis in almost all of the projection areas. In the chronic treatment study, CP-93,129 was administered continuously (7 mg/kg/day) for 14 days using an osmotic minipump implanted subcutaneously. The chronic treatment with CP-93,129 did not produce a significant change in 5-HT synthesis in the raphe nuclei nor in the nerve terminal structures, except for the medial frontal bundle and the visual and sensory-motor cortices. The unaltered 5-HT synthesis rates in the chronic treatment study probably reflect a normalization of the synthesis as a result of the desensitization of 5-HT1B autoreceptors and/or heteroreceptors.
authors.affiliation: Cone Neurosurgical Research Laboratory, Department of Neurology and Neurosurgery, and Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Que., Canada H3A 2B4.
authors.forename: Shu
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Arata
authors.initials: A
authors.lastname: Watanabe
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nishi
authors.forename: Khanh Q
authors.initials: KQ
authors.lastname: Nguyen
authors.forename: Mirko
authors.initials: M
authors.lastname: Diksic
mesh_terms: D000818:Animals; D001345:Autoradiography; D001923:Brain Chemistry / Q000187:drug effects*; D002196:Capillaries / Q000378:metabolism; D015918:Infusion Pumps, Implantable; D007700:Kinetics; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology*; D011758:Pyrroles / Q000008:administration & dosage / Q000494:pharmacology*; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D044302:Receptor, Serotonin, 5-HT1B / Q000187:drug effects*; D012701:Serotonin / Q000096:biosynthesis*; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D011725:Pyridines; D011758:Pyrroles; D044302:Receptor, Serotonin, 5-HT1B; D017366:Serotonin Receptor Agonists; C065046:3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo(3,2-b)pyrid-5-one; C020774:alpha-methyltryptophan; D012701:Serotonin; D014364:Tryptophan