An electron microscopical observation of the endoneurial mast cells of the laboratory musk shrew: Suncus murinus).

Histochemical and ultrastructural properties of endoneurial mast cells of the normal and histamine liberator Compound 48/80 (48/80)--injected musk shrew, Suncus murinus (Suncus) were examined by light and electron microscopies. It was observed that the normal mast cells contained numerous cytoplasmic granules, with dense and irregular dense cores, covered at times with slender microvilli. The cells were diffusely located within the endoneurial sheath of the peripheral nerve fibers and in the intercellular spaces of the spinal ganglion cells. Histochemically, histamine, 5-hydroxytryptamine and heparin were observed in mast cell granules. Biochemical analysis also indicated a relatively high content of histamine in the suncus peripheral nerve. A single intradural-injection of 48/80 resulted in the degranulation of endoneurial mast cells and revealed peculiar axoplasmic changes make up of neurofilament-mitochondrial complexes in the peripheral nerve fibers. No remarkable histochemical and ultrastructural differences were observed between the endoneurial mast cells and the connective tissue mast cells in the suncus. The significance of these findings is discussed with regard to previous studies of the endoneurial mast cells in other laboratory animals.