Effect of diphenylhydantoin on blood pressure of spontaneously hypertensive rats

Diphenylhydantoin (DPH) has been shown to elicit direct peripheral vasodilatory effects in anaesthetised animals. Since spontaneously hypertensive (SH) rats exhibit many features similar to human essential hypertension, the effect of DPH on blood pressure of these rats was studied. DPH given orally for 5 days elicited dose-dependent fall in systolic blood pressure in conscious SH rats. In addition, repeated administrations of DPH increased the noradrenaline concentration in the hypothalamus. These results suggest that the central noradrenergic mechanisms might be involved in the hypotensive action of DPH in SH rats, probably at the supramedullary level.