Enhancement of Neural and Thermal Vasoconstriction by Prostaglandin B1

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Abstract
The vascular effects of prostaglandin B1 (PGB1) were studied during constant-flow perfusion of the canine hindpaw. The effects of PGB1 (50-200 ng/kg/min ia) on systemic and hindpaw perfusion pressures and on responses to local cooling (4 degrees C for 90 sec) and local heating (45 degrees C for 60 sec) were measured in 15 dogs. PGB1 (50-100 ng/kg/min) decreased perfusion pressure without any significant effect on systemic arterial pressure. Higher concentrations of PGB1 (200 ng/kg/min) elevated perfusion pressure to control values. The pressor responses to local cooling were increased from 11 to 32 mmHg while the dilator responses to local heating and nitroglycerin were reduced during infusions of PGB1. PGB1 also enhanced the pressor responses to norepinephrine or tyramine. These findings support the conclusions that (1) low concentrations of prostaglandin B1 enhance neurotransmitter release with minimal effects on vascular smooth muscle cells and (2) these effects are not secondary to increased perfusion pressures or vascular wall stresses since infusions of PGB1 resulted in vasodilation.