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.
Mizoguchi
K
K
Department of Pharmacology, Kurume University School of Medicine, Japan.
Yokoo
H
H
Yoshida
M
M
Tanaka
T
T
Tanaka
M
M
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