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Sympathetic responses to stress and rilmenidine in 2K-1C rabbits

Head GA, Burke SL.

Summary

The authors investigated whether sympathetic responses to environmental stressors and the sympathoinhibitory responses to rilmenidine are altered by renovascular hypertension. Hypertensive rabbits (rendered so by clipping of the right renal artery) were given air-jet and loud noise stressors before and after intravenous administration of rilmenidine. Rilmenidine decreased blood pressure more in hypertensive rabbits and markedly reduced increased sympathetic activity during air-jet stress. These studies show that while sympathetic responses to stress were markedly enhanced in renal clip hypertensive rabbits, they did not result in greater pressor responses, thus suggesting that vascular neuroeffector mechanisms were not altered. The authors concluded that sympathoin-hibitory agents such as rilmenidine are very suitable and very effective agents for the treatment of renovascular hypertension.

Hypertension. 2004;43:636-642.

Commentary

The authors subjected renovascular hypertensive rabbits to external stress stimuli according to standard methods. Air-jet stress provoked strongly enhanced renal sympathetic nerve activity, as well as a rise in blood pressure and heart rate. Surprisingly, pressor responses to these external stimuli were not stronger than in normotensive control animals.

Rilmenidine strongly reduced the sympathetic hyperactivity induced by external stimuli, more so in hypertensive than in normotensive animals. These findings indicate that there exists a much greater contribution to the hypertension by the sympathetic nervous system than by other mechanisms. Rilmenidine is a suitable agent to counteract these phenomena. The authors suggest that rilmenidine would be a suitable agent for the treatment of renovascular hypertension, possibly via impaired neural release of renin.