Contractile responses of vascular smooth muscle strips (rabbit aorta) to angiotensin, vasopressin and serotonin are potentiated by amounts of metanephrine, ephedrine or tyramine that produce no contractions by themselves. Epinephrine and norepinephrine contractions of aortic strips are not potentiated. Phentolamine and bretylium prevent this potentiating effect of metanephrine and ephedrine; th...

In a selected group of rhinitis patients with an IgE-mediated allergy to house dust mites the nasal response to insufflation of histamine chloride, methacholine and phentolamine was demonstrated to be higher than in a control group. With the methods used histamine chloride was better at discriminating between healthy subjects and patients than methacholine or phentolamine. This discrimination w...

In the presence of phentolamine, stimulation of the cat splanchnic nerve decreased the resistance of the superior mesenteric arterial bed. This effect was not significantly influenced by sulpiride. Sulpiride, in the presence of phentolamine, did not inhibit the decrease in resistance in animals pretreated with guanethidine but propranolol or ablation of the adrenal glands prevented the effect o...

The effects of endogenous and of exogenous norepinephrine were studied in isolated rings of canine left circumflex coronary artery and its first ventricular branch. Norepinephrine was released from adrenergic nerve endings by transmural electrical stimulation and by tyramine. In rings contracted with prostaglandin F2 alpha, transmural electrical stimulation resulted in frequency-dependent relax...