title: Long term exposure to norharman exacerbates 6-hydroxydopamine-induced parkinsonism: possible involvement of L-type Ca2+ channels.
abstract: beta-Carbolines (BCs) are considered as endogenous neurotoxins that may contribute to the pathogenesis of Parkinson's disease (PD). However, several lines of evidences show that these compounds have neuroprotective effect. This study was designed to assess effect of long term exposure to norharman, a BC compound which in mammalian brain occurs at high levels in the substantia nigra, on the progress of parkinsonism induced by 6-hydroxydopamine (6-OHDA). Animals were daily treated by norharman at doses 100, 200 and 1000microg/kg (i.p.) just before to four weeks after the intrastriatal injection of 6-OHDA. Statistical analysis of apomorphine-induced rotation tests demonstrates that treatment by norharman at doses 200 and 1000microg/kg for four weeks exacerbates significantly behavioral symptoms of the parkinsonism. To explore mechanisms by which norharman affects nigral dopaminergic cells, we studied the role of L-type Ca2+ channels. For this purpose, animals were daily treated with either L-type Ca2+ channel blocker of nifedipine at doses 2 and 5mg/kg (i.p.) or nifedipine together with norharman before to four weeks after the 6-OHDA injection. While treatment with nifedipine improved behavioral symptoms of the parkinsonism, treatment with both nifedipine and norharman had no affect on these symptoms. This data indicates that long term exposure to BCs promote nigral dopaminergic cell death possibly through L-type Ca2+ channels.
authors.affiliation: Department of Physiology and Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Bahonar St., Qazvin 3419759811, Iran. hhaghdoost@yahoo.com
authors.forename: Hashem
authors.initials: H
authors.lastname: Haghdoost-Yazdi
authors.forename: Sedighe-Sadat
authors.initials: SS
authors.lastname: Hosseini
authors.forename: Ayda
authors.initials: A
authors.lastname: Faraji
authors.forename: Delaram
authors.initials: D
authors.lastname: Nahid
authors.forename: Hassan
authors.initials: H
authors.lastname: Jahanihashemi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002243:Carbolines; D006247:Harmine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D016627:Oxidopamine; D010302:Parkinson Disease, Secondary / Q000139:chemically induced / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002243:Carbolines; D006247:Harmine; D016627:Oxidopamine; C010262:norharman; D009543:Nifedipine