The central dopaminergic receptor is believed to suppress the cardiovacular svstem. So, it may be involved in the blood pressure regulation. But, it's action is still controversial. Furthermore, the mechanisms involved in the central dopaminergic
receptor-induced blood pressure regulation is unclear. So, present study was performed in order to clarify the effects of central dopaminergic receptor and to investigate the mechanisms involved in it. Lisuride, a D-receptor agonist, and
clonidine,
aα2-receptor agonist, were administered into lateral ventricle in rat and the changes of blood pressure were compared.
The results as follows;
1. Intracerebroventricular administration of lisuride and clonidine from 0.3μg to 10μg elicited dose related decrease of blood pressure and heart rate. The potencies were similar in both drugs.
2. Contrally administered sulpiride, a D2-antagonist, blocked only the lisuride-induced hypotension, while the clonidine-induced hypotension was blocked only by centrally administered tolazoline a α2-receptor agonist, were administered into
lateral
ventricle in rat and the changes of blood pressure were compared.
3. After desipramine pretreatment, which increases the norepinephrine concentration, lisuride elicited somewhat further decrease of blood pressure.
4. After chemical sympathectomy by 6-hydroxydopamine, lisuride administration still elicited strong suppression of blood pressure.
From these above results, it is concluded that central dopaminergic receptor activation decrease the blood pressure. Suppression of the norepinephrine release at the sympathetic nerve terminal is not related with central dopaminergic
receptor-induced
hypotension.
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