Local administration of l-DOPA in the chicken ventromedial hypothalamus increases dopamine release in a dose-dependent manner

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 Ca2+-free Ringer, tetrodotoxin (TTX) (2 μM) and high K+ and was perfused for 30 min into the chicken VMH. TTX and Ca2+-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.

► In vivo microdialysis showed the effect of l-DOPA on extracellular DA levels in chick VMH. ► Extracellular DA levels increased significantly in the VMH after l-DOPA perfusion. ► l-DOPA has no effect on NE and 5-HT during microdialysis. ► The DA, NE and 5-HT within the dialysate were related to neural activity.