Sympatho-inhibitory effects of gamma-l-glutamyl-l-dopa are not mediated by activation of dopamine-2 receptors in conscious rabbits.
OBJECTIVE
To define the role of dopamine-2 receptors in the sympatho-inhibitory effects of gamma-l-glutamyl-l-dopa in conscious rabbits.


METHODS
gamma-l-glutamyl-l-dopa (gludopa) was infused iv at 25 and 100 micrograms.kg-1.min-1 with and without prior dopamine-2 receptor blockade by YM-09151-2 (50 micrograms.kg-1 iv) in conscious rabbits.


RESULTS
Mean arterial pressure and heart rate remained unchanged while renal plasma flow increased. Arterial norepinephrine (NE) concentration, total and renal NE spillover rate were markedly decreased in a dose-related manner, which were not affected by prior dopamine-2 receptor blockade. Gludopa was detected in the whole brain (92 +/- 112 ng/g wet brain tissue) at the end of experiment although brain tissue levodopa, NE, and dopamine contents were not much different from those in the control group.


CONCLUSIONS
Gludopa decreased dose-dependently plasma NE concentration, and total and renal NE overflow to plasma, which were not mediated by activation of dopamine D2 receptors.
Wang
Z Q
ZQ
University Department of Medicine, Monash Medical Center, Melbourne, Victoria, Australia.
Shimizu
K
K
Way
D
D
Secombe
J
J
McGrath
B P
BP
D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D007262:Infusions, Intravenous; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D011817:Rabbits; D017448:Receptors, Dopamine D2 / Q000502:physiology*
D001549:Benzamides; D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; C017342:gamma-glutamyl DOPA; D004295:Dihydroxyphenylalanine; C030265:nemonapride; D009638:Norepinephrine