Central angiotensin II stimulates arteriolar vasomotion in conscious hamsters

The effects of intracerebroventricular (icv) injections of 10 ng angiotensin II (ANG II) on mean arteriolar diameter and spontaneous arteriolar vasomotion were studied in subcutaneous tissue of conscious, restrained hamsters, using the skin fold window chamber preparation. Angiotensin II caused a significant decrease in mean arteriolar diameter which was associated with a significant elevation in the amplitude of vasomotion. The frequency of vasomotion did not change significantly. The central ANG II-induced effects on arteriolar vasomotion were not significantly altered by continuous intravenous (iv) infusion of hexamethonium (1 mg.kg-1.min-1). In contrast, iv bolus injection of the vascular vasopressin receptor antagonist d(CH2)5Tyr(Me)AVP (10 micrograms.kg-1) 5 min prior to icv injection of ANG II significantly attenuated the effects of the neuropeptide on mean arteriolar diameter and the amplitude of vasomotion. These data indicate that central ANG II stimulation enhances arteriolar vasomotion in peripheral subcutaneous tissue of conscious hamsters and that this effect may be mediated by release of vasopressin.