Abstract

The rise in arterial blood pressure caused by the intravenous injection of tetrahydrozoline was accompanied by a slowing of the heart rate, decrease in cardiac minute-volume and increase in peripheral vascular resistance. Following the pressor response of tetrahydrozoline, the blood pressure fell below the control levels although the peripheral resistance remained elevated.

The cardiac rates of bilaterally vagotomized cats were reduced by small doses of tetrahydrozoline, while the rates of spinal cats were unaffected. The drug also depressed the pressor responses to electrical stimulation of the vasomotor center in cats under pentobarbital anesthesia.

Tetrahydrozoline prevented epinephrine-induced automaticity of isolated papillary muscles in concentrations which did not lower excitability. The incidence of ventricular fibrillation after harman methosulfate and epinephrine was also reduced by tetrahydrozoline.