EFFECTS OF PROSTAGLANDINS B₁ AND B₂ ON VASOCONSTRICTOR RESPONSES OF THE CANINE HINDPAW

¹ Division of Clinical Pharmacology, Departments of Medicine and Pharmacology, College of Medicine, University of Iowa, Iowa City, Iowa

The effects of prostaglandin B₁ (PGB₁) and prostagiandin B₂ (PGB₂) on the responses of the canine perfused hindpaw to adrenergic nerve stimulation and the pressor responses to intra-arterial injections of tymamine and norepineprhine were studied in 32 dogs. intra-arterial infusions of PGB₂(50-200 ng/kg/min) produced concentration-dependent increases in the pressor responses to adrenergic nerve stimulation. The shift of the adrenergic nerve stimulation curve to the left during PGB₂ infusion did not deviate from parallelism at either the low or high concentrations of PGB₂. The pressor responses of the denervated paw to tyramine and norepinephrine were not altered during infusions of PGB₂. Intra-arterial infusions of PGB₁ produced effects similar to that of PGB₂ but were less potent. Since PGB₂ and PGB₁ enhance the pressor responses to nerve stimulation, but not those to tyramine or norepinephrine, the data are consistent with the conclusion that PGB compounds facilitate release of the neurotransmitter from the norepinephrine pool uilized by the nerve action potential. In addition, the results suggest that the perfused canine hindpaw has a large propensity for vasoconstriction.