A PHARMACOLOGICAL AND HISTOLOGICAL INVESTIGATION OF THE INVOLVEMENT OF MAST CELLS IN CUTANEOUS AXON REFLEX VASODILATATION

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Abstract
Arteriolar vasodilatation following injury to the pinna of the left ear was measured thermometrically in 43 rats. Quantitative histological assessments were made of the intact and degranulating dermal mast cells in the left and right ears of the animals. Vasodilatation, with associated increased proportions of degranulating mast cells, was found only in animals in which the sensory innervation of the left ear was intact, allowing the occurrence of axon reflexes.In rats depleted of mast cells by treatment for 5 days with compound 48/80, axon reflex vasodilatation was suppressed, indicating that mast cells are essential for the development of the flare in the triple response. Vasodilatation was also suppressed in animals injected with aspirin 20—30 min prior to injury. In these latter rats, there was no increase in the proportion of degranulating dermal mast cells It is suggested that aspirin protects the mast cells from the degranulating effect of axon reflexes.These results indicate that the arteriolar flare around the site of a cutaneous injury is mediated by the action of axon reflexes upon dermal mast cells. This conclusion is discussed in relation to other observations on vasodilatation in injured and diseased skin.

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