Melatonin reverses neurochemical alterations induced by 6-OHDA in rat striatum.
The present work showed that the intrastriatal injection of 6-OHDA significantly decreases DA, DOPAC and HVA levels in that rat brain structure. Although there is also a decrease in 5-HT levels no changes were observed in 5-HIAA levels as compared to controls. On the other hand, melatonin (2, 5, 10 and 25 mg/kg. i.p., daily for 7 days) treatment starting 1 h after 6-OHDA lesions, partially reverses the decreases caused by 6-OHDA lesions on these neurotransmitter levels, and contents were brought to approximately 50% of that observed in the contralateral sides of controls or of melatonin treated group. Melatonin was more efficient at the doses of 5 and 10 mg/kg, i.p., and effects were similar between the lowest and highest doses characteristic of a bell-shaped type of response. The apomorphine-induced rotational behavior (3 mg/kg, i.p.) was blocked by 60, 89, 78 and 47% after the doses of 2, 5, 10 and 25 mg/kg, i.p., respectively. Similarly, in this case the doses of 5 and 10 mg/kg were also more efficient. Melatonin (5 mg/kg) produced an upregulation of D1 receptors associated with a decrease in Kd value. While no change was observed in maximum density of D2 receptors, the Kd value was also decreased.
Aguiar
L M V
LM
Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil.
Vasconcelos
S M M
SM
Sousa
F C F
FC
Viana
G S B
GS
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000008:administration & dosage / Q000494:pharmacology*; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007274:Injections, Intraperitoneal; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000494:pharmacology*; D008845:Microinjections; D016627:Oxidopamine / Q000008:administration & dosage / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism; D013565:Sympatholytics / Q000008:administration & dosage / Q000633:toxicity
D016166:Free Radical Scavengers; D013565:Sympatholytics; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D016627:Oxidopamine; D008550:Melatonin; D004298:Dopamine; D006719:Homovanillic Acid