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Pharmacologic profile of urapidil
1Division of Pharmacotherapy, University of Amsterdam, The Netherlands.
The American Journal of Cardiology
|August 15, 1989
Summary
Urapidil lowers blood pressure by blocking alpha 1-adrenoceptors. Its central hypotensive effects are not due to alpha 2-adrenoceptor agonism, but may involve 5-HT 1A agonism.
Area of Science:
- Pharmacology
- Cardiovascular Medicine
Background:
- Urapidil is a phenylpiperazine derivative of uracil.
- It acts as a selective alpha 1-adrenoceptor antagonist, reducing blood pressure and peripheral resistance.
- Urapidil exhibits significant central hypotensive activity.
Purpose of the Study:
- To investigate the central hypotensive mechanism of urapidil.
- To determine if urapidil's central effects are mediated by alpha 2-adrenoceptor agonism, similar to clonidine.
Main Methods:
- Radioligand binding studies to assess urapidil's affinity for alpha 2 adrenoceptors.
- In vivo experiments involving injection of urapidil into feline vertebral arteries.
- Administration of alpha 2-adrenoceptor blocking agents (yohimbine, rauwolscine) to assess their effect on urapidil's central hypotensive activity.
Main Results:
- Urapidil demonstrated no affinity for alpha 2 adrenoceptors in binding studies.
- The central hypotensive effect of urapidil in cats was not antagonized by yohimbine or rauwolscine.
- Experimental evidence suggests a potential role for 5-hydroxytryptamine (5-HT 1A) agonistic activity in urapidil's central effects.
Conclusions:
- Urapidil's central hypotensive activity is not mediated by alpha 2-adrenoceptor agonism.
- The precise central mechanism remains under investigation, with 5-HT 1A agonism being a plausible explanation.
- Presynaptic alpha 2-agonistic activity and weak beta 1-adrenoceptor activity are unlikely to significantly contribute to urapidil's hypotensive effects.