Sympatho-inhibitory effects of gamma-l-glutamyl-l-dopa are not mediated by activation of dopamine-2 receptors in conscious rabbits.

AIM

To define the role of dopamine-2 receptors in the sympatho-inhibitory effects of gamma-l-glutamyl-l-dopa in conscious rabbits.

METHOD

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.

CONCLUSION

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.