Effect of norepinephrine and 5-hydroxytryptamine on the pulmonary circulation of the spinal dog

¹ From the Centre Chirurgical Marie Lannelongue, Paris, France, and the Department of Physiology of the University of Minnesota, Minneapolis, Minnesota

One microgram of norepinephrine per kilogram of body weight injected in a 1-ml volume into the right atrium had little direct effect on the mean pulmonary artery pressure of dogs with intact nerve supply. The changes observed occurred simultaneously with systemic changes. In the spinal vagotomized dog, a similar dose produced a rise in mean pulmonary artery pressure which preceded any other pressure change. The isolated pulmonary hypertension produced in the intact animal by an identical dose of 5 HT is not modified after vagotomy or spinal section.