title: Local administration of L-DOPA in the chicken ventromedial hypothalamus increases dopamine release in a dose-dependent manner.
abstract: L-DOPA induced extracellular dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in the ventromedial hypothalamus (VMH) of chickens were measured by in vivo microdialysis. Several doses of 3,4-dihydroxy-l-phenylalanine (l-DOPA) were administered locally through the microdialysis probe into the VMH of chickens for 10 min. Local perfusion of l-DOPA increased the extracellular levels of DA. The increased DA was dose-related and was significantly higher compared to the baseline and control group. The maximal level of DA was 212% and 254%, respectively, of the baseline following administration of 1 and 2 μg/ml l-DOPA. There were no changes in NE and 5-HT levels from baseline after l-DOPA perfusion. l-DOPA (1 μg/ml) was mixed with Ca(2+)-free Ringer, tetrodotoxin (TTX) (2 μM) and high K(+) and was perfused for 30 min into the chicken VMH. TTX and Ca(2+)-free Ringer's solution inhibited the effectiveness of l-DOPA in increasing DA release. The NE and 5-HT levels were significantly lower than the baseline. After administration of K(+) a significant increase of DA, NE and 5-HT was observed. The microdialysis results are consistent with our objective that l-DOPA induced extracellular DA increases in the VMH in a dose-dependent manner and the released DA, NE and 5-HT within the dialysate were related to neuronal activity.
authors.affiliation: United Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
authors.forename: Mohammad Rashedul
authors.initials: MR
authors.lastname: Alam
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Yoshizawa
authors.forename: Kunio
authors.initials: K
authors.lastname: Sugahara
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry; D002414:Cations, Monovalent; D002645:Chickens; D004298:Dopamine / Q000378:metabolism*; D015259:Dopamine Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D007552:Isotonic Solutions / Q000737:chemistry / Q000494:pharmacology; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D017551:Microdialysis; D009638:Norepinephrine / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D000077331:Ringer's Solution; D012701:Serotonin / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D002414:Cations, Monovalent; D015259:Dopamine Agents; D007552:Isotonic Solutions; D012701:Serotonin; D013779:Tetrodotoxin; D007980:Levodopa; D011189:Potassium Chloride; D000077331:Ringer's Solution; D002118:Calcium; D004298:Dopamine; D009638:Norepinephrine