Regular Contributions
Vascular Areas Where Clonidine Induces Vasodilation in Hypertensive and Normotensive Rats
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JURO IRIUCHIJIMA
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>Physiological Laboratory, Hiroshima Prefectural College of Health and Welfare, Mihara 723-0053
The aim of this study was to find vascular areas where clonidine decreases the regional vascular resistance when this drug lowers arterial pressure in conscious spontaneously hypertensive rats and normotensive control rats. Arterial pressure was observed with an indwelling catheter at a carotid. Blood flow was measured with an electromagnetic flow probe implanted around the renal artery or the superior mesenteric artery. Regional vascular resistance was calculated as arterial pressure divided by blood flow. Intravenous bolus injection of clonidine at a dose to decrease arterial pressure decreased renal resistance and superior mesenteric resistance. Quantitatively, the combined effect of the decrease in these two resistances was enough to account for the decrease in arterial pressure. Although clonidine is thought to inhibit sympathetic nerve activity centrally, the above vasodilator effect is not ascribable to this inhibitory mechanism: Sympathetic activity to be inhibited does not seem to be present in the superior mesenteric area and clonidine similarly decreased renal vascular resistance even after renal denervation.
Key words---
clonidine; renal artery; superior mesenteric artery; SHR; renal nerve
© 1999 Tohoku University Medical Press
Tohoku J. Exp. Med., 1999, 189, 29-36
Address for reprints: Juro Iriuchijima, Physiological Laboratory, Hiroshima Prefectural College of Health and Welfare, Mihara 723-0053, Japan.
e-mail: iriuti@hpc.ac.jp
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