Dopamine formation from L-dopa administered exogenously is independent of dopaminergic neuronal activity: studies with in vivo microdialysis.
Extracellular dopamine (DA) levels in the steady state were not detected in the hippocampus of rats where sparse dopaminergic innervations were demonstrated. However, following L-DOPA (100 mg/kg i.p.) administration, extracellular DA was detected. Although tetrodotoxin (TTX, 1 microM) failed to prevent this phenomenon, the striatal DA peak disappeared with the addition of TTX (5 microM) into the perfusate and reappeared following L-DOPA (100 mg/kg i.p.) administration. These findings suggest that DA synthesis from L-DOPA, administered exogenously, is independent of the existence of dopaminergic neurons and that outflow of newly synthesized DA into the extracellular space is not coupled to neuronal activity.
Department of Pharmacology, Kurume University School of Medicine, Japan.
K
K
Mizoguchi
H
H
Yokoo
M
M
Yoshida
T
T
Tanaka
M
M
Tanaka
D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism*; D003956:Dialysis; D004298:Dopamine / Q000378:metabolism* / Q000502:physiology; D006624:Hippocampus / Q000378:metabolism*; D007980:Levodopa / Q000378:metabolism*; D008297:Male; D008846:Micromanipulation; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D007980:Levodopa; D004298:Dopamine