EFFECTS OF LOCALLY INFUSED SEROTONIN ON CANINE FORELIMB WEIGHT AND SEGMENTAL VASCULAR RESISTANCES

¹ Department of Physiology, Giltner Hall, Michigan State University, East Lansing, Michigan

The effects of serotonin on canine forelimb weight were studied to determine if intrarterial infusions of serotonin produce marked edema formation as do intra-arterial infusions of bradykinin and histamine. Changes in net fluid filtration were inferred from changes in forelimb lymph flow and small vein pressures whereas changes in protein permeability were inferred from changes in lymph protein concentration. Local infusions of both low (15 µg base/min) and high (150 µ base/min) concentrations of serotonin failed to promote measurable edema formation in the canine forelimb despite evidence for an increased net fluid filtration. Moreover, there was no evidence for a large pressure-independent increase in microvascular premeability to plasma proteins. The failure of significant edema to develop in the forelimb despite evidence for an increased net fluid filtration may be attributed to the effectiveness of lymphaties to immediately drain excess extravascular fluid. These findings contrast dramatically from those of locally administered bradykinin and histamine which cause a marked pressure-independent increase in microvascular premeability to plasma proteins and marked edema formation.

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