THE CARDIOVASCULAR EFFECTS OF URAPIDIL

  • 1 January 1983
    • journal article
    • research article
    • Vol. 14  (4) , 465-472
Abstract
The cardiovascular effects of urapidil were investigated in the anesthetized rat. The mechanism of the hypotensive action of this drug was tested in vitro on the isolated rat aorta and in vivo by intracerebroventricular injections. The peripheral vasoconstrictor effect was studied in the pithed rat. In the pithed rat, the thoracic part of the spinal cord was electrically stimulated in order to induce a tachycardia. The reduction of this tachycardia by a drug was due to its inhibitory effect on cardiac sympathetic nerves endings. I.v. urapidil produce a significant hypotension without change in heart rate. Directly injected into the brain cavities, urapidil produced a hypotensive effect only at very high doses (1 mg/kg). This hypotensive action of urapidil was apparently mainly of peripheral origin. Urapidil antagonized competitively the contraction of the aorta induced by norepinephrine. The drug had .alpha.-blocking properties which explained its hypotensive action. Urapidil provoked a weak vasoconstrictor effect in the pithed rat and induced a presynaptic inhibition in the heart which apparently explained the lack of heart rate change during the hypotensive effect of the drug. Urapidil may also stimulate post or presynaptic .alpha.2-adrenoceptors.