title: Antidepressant-like effect of agmatine and its possible mechanism.
abstract: In mammalian brain, agmatine is an endogenous neurotransmitter and/or neuromodulator, which is considered as an endogenous ligand for imidazoline receptors. In this study, the antidepressant-like action of agmatine administered p.o. or s.c. was evaluated in three behavioral models in mice or rats. Agmatine at doses 40 and 80 mg/kg (p.o.) reduced immobility time in the tail suspension test and forced swim test in mice or at dose 20 mg/kg (s.c.) in the forced swim test. Agmatine also reduced immobility time at 10 mg/kg (p.o.) or at 1.25, 2.5 and 5 mg/kg (s.c.) in the forced swim test in rats. These results firstly indicated that agmatine possessed an antidepressant-like action. With 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and lactic dehydrogenase (LDH) assay, 1, 10 and 100 microM agmatine or a classical antidepressant, 2.5 and 10 microM desipramine, protected PC12 cells from the lesion induced by 300 microM N-methyl-D-aspartate (NMDA) treatment for 24 h. Using high-performance liquid chromatography with electrochemical detection (HPLC-ECD), it was found that the levels of monoamines including norepinephrine, epinephrine, dopamine or 5-hydroxytryptamine (5-HT) in PC12 cells decreased after the treatment with 200 microM NMDA for 24 h, while in the presence of 1 and 10 microM agmatine or 1 and 5 microM desipramine, the levels of norepinephrine, epinephrine or dopamine were elevated significantly while 5-HT did not change. Moreover, norepinephrine, 5-HT or dopamine had the same cytoprotective effect as agmatine at doses 0.1, 1 and 10 microM. In the fura-2/AM (acetoxymethyl ester) labeling assay, 1 and 10 microM agmatine, 1 and 5 microM desipramine or monoamines norepinephrine, 5-HT at doses 0.1 and 1 microM attenuated the intracellular Ca(2+) overloading induced by 200 microM NMDA treatment for 24 h in PC12 cells. In summary, we firstly demonstrated that agmatine has an antidepressant-like effect in mice and rats. A classical antidepressant, desipramine, as well as agmatine or monoamines protect the PC12 cells from the lesion induced by NMDA treatment. Agmatine reverses the NMDA-induced intracellular Ca(2+) overloading and the decrease of monoamines (including norepinephrine, epinephrine or dopamine) contents in PC12 cells, indicating that agmatine's antidepressant-like action may be related to its modulation of NMDA receptor activity and/or reversal of the decrease of monoamine contents and Ca(2+) overloading induced by NMDA.
authors.affiliation: Division of Psychopharmacology, Beijing Institute of Pharmacology and Toxicology, 27 Taiping Road, Beijing 100850, China. LYF619@yahoo.com.cn
authors.forename: Yun Feng
authors.initials: YF
authors.lastname: Li
authors.forename: Zheng Hua
authors.initials: ZH
authors.lastname: Gong
authors.forename: Jiang Bei
authors.initials: JB
authors.lastname: Cao
authors.forename: Heng Lin
authors.initials: HL
authors.lastname: Wang
authors.forename: Zhi Pu
authors.initials: ZP
authors.lastname: Luo
authors.forename: Jin
authors.initials: J
authors.lastname: Li
mesh_terms: D000376:Agmatine / Q000627:therapeutic use*; D000818:Animals; D000928:Antidepressive Agents / Q000627:therapeutic use*; D015306:Biogenic Monoamines / Q000378:metabolism; D003863:Depression / Q000188:drug therapy* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007103:Immobilization / Q000502:physiology; D008297:Male; D051379:Mice; D016716:PC12 Cells; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000928:Antidepressive Agents; D015306:Biogenic Monoamines; D000376:Agmatine