title: Contralateral retinal dopamine decrease and melatonin increase in progression of hemiparkinsonium rat.
abstract: Both dopamine (DA) and melatonin (MLT) are abundant neuromodulators located in vertebrate retina. The retinal DA deficiency and variations in MLT levels have been linked to Parkinson's disease (PD). No studies have investigated the ipsilateral and contralateral DA and MLT in retina and their relationships in 6-hydroxydopamine (6-OHDA) induced hemiparkinsonian rats. We established PD rat model by unilateral injection of 6-OHDA into the right substantia nigra and the right medial forebrain bundle. Eye tissue was collected and the levels of MLT and DA were measured twice daily at 10:00 and 22:00. The concentrations of DA and its metabolites, 3,4-dihydroxyphenylacetic (DOPAC) and homovanillic acid (HVA), as well as MLT were determined by HPLC. The results show that DA levels in the eye contralateral to the side of a unilateral intracerebral 6-OHDA lesion significantly decreased (P < 0.001). Both the ratios of DOPAC/DA and HVA/DA were increased in comparison with the vehicle groups after 3 weeks post-lesion. The concentrations of MLT at 10:00 and 22:00 in both eyes were distinctly increased compared with the vehicle groups (P < 0.05). The change of DA and its metabolites, as well as MLT appeared to correlate well with the rotation behavior of rats. These findings suggest that rats receive a unilateral intracerebral injection of 6-OHDA that mainly causes the contralateral eye destruction of DA-containing neurons. Increased retinal MLT level probably is associated with the progression of PD.
authors.affiliation: Department of Biochemistry and Molecular Biology, Fujian Medical University, Fuzhou 350004, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Meng
authors.forename: Zhi-Hong
authors.initials: ZH
authors.lastname: Zheng
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D018450:Disease Progression; D004298:Dopamine / Q000378:metabolism*; D006719:Homovanillic Acid / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism*; D016627:Oxidopamine / Q000008:administration & dosage; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D012160:Retina / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D015102:3,4-Dihydroxyphenylacetic Acid; D016627:Oxidopamine; D008550:Melatonin; D004298:Dopamine; D006719:Homovanillic Acid