Nonneural vascular smooth muscle tone in arterioles of the hamster cheek pouch

The object of the present study was to employ specific pharmacological agents and the chemical sympatholytic drug 6-hydroxydopamine (6-OHDA) to characterize the neural and adrenergic control of vascular smooth muscle tone in arterioles of the hamster cheek pouch. Arteriolar diameters were measured in the superfused cheek pouch of anesthetized male golden hamsters. All orders of arterioles constricted in response to norepinephrine (10(-7) g/ml) and increased superfusion solution PO2, and dilated in response to isoproterenol (10(-7) g/ml) and adenosine (10(-4) M). Tetrodotoxin (10(-6) g/ml), phentolamine (10(-6) g/ml), and propranolol (10(-6) g/ml) had no effect upon arteriolar diameters under resting conditions. However, phentolamine and propranolol completely blocked vessel responses to norepinephrine and isoproterenol, respectively. Arterioles dilated during superfusion with either 6-OHDA (300 micrograms/ml) or its acidic vehicle. However, vessel diameters returned toward control values during the subsequent 2-hr washout period and exhibited no net dilation following recovery from 6-OHDA or its vehicle. This study suggests that neural and adrenergic mechanisms are not the primary determinants of arteriolar tone in the hamster cheek pouch.