1. Isolated hind limbs of rats were perfused and vascular smooth muscle sensitivity to noradrenaline, methoxamine and potassium chloride was measured and dose-response curves were obtained.
2. The sensitivity of vascular smooth muscle to noradrenaline is attenuated by adrenalectomy and low sodium diet; it is enhanced by corticosterone. High sodium diet or administration of deoxycorticosterone did not alter the dose—response curve significantly.
3. The increased sensitivity of vascular smooth muscle after corticosterone treatment is not related to changes in the contractile protein or alterations in the neuronal uptake and extraneuronal metabolism of noradrenaline.
4. These results suggest that the increased sensitivity in corticosterone-treated rats may be due to the number of receptors, receptor affinity to noradrenaline, or changes in the functional link between receptor and contractile apparatus.