Evidence for L-dopa systems responsible for cardiovascular control in the nucleus tractus solitarii of the rat.
Microinjections of L-DOPA (10-100 ng) into the medial area of the nucleus tractus solitarii (NTS) led to dose-dependent decreases in arterial blood pressure and heart rate in rats treated with i.p. 3-hydroxybenzylhydrazine, a central inhibitor of DOPA decarboxylase, or similarly with intraventricular 6-hydroxydopamine. D-DOPA, dopamine or noradrenaline (100 ng) produced no effect. L-DOPA methyl ester (1 microgram), a competitive antagonist for L-DOPA, microinjected into NTS, blocked the depressor and bradycardic responses to L-DOPA. High K+ (40 mM) released endogenous DOPA in a Ca(2+)-dependent manner from slices of the rat dorsomedial medulla including NTS. These results support the hypothesis that there exist systems of L-DOPA itself responsible for cardiovascular regulation in NTS of rats. This regulatory action of L-DOPA seems to be postsynaptic in nature.
Kubo
T
T
Department of Pharmacology, Yokohama City University School of Medicine, Japan.
Yue
J L
JL
Goshima
Y
Y
Nakamura
S
S
Misu
Y
Y
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects*; D007980:Levodopa / Q000031:analogs & derivatives / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D007980:Levodopa; D004295:Dihydroxyphenylalanine; C035420:levodopa methyl ester; D002118:Calcium; D004298:Dopamine; D009638:Norepinephrine