NERVE MAST-CELL INTERACTION IN NORMAL GUINEA-PIG URINARY-BLADDER

Urinary bladders of normal adult female guinea pigs were analyzed for anatomical evidence of nerve-mast cell interaction using light microsc opy and electron microscopy. Nerves, ganglia, and individual nerve fib ers were visualized on paraffin sections using immunohistochemistry wi th antisera against the neural antigens neurofilament protein and prot ein gene product 9.5, and sections were also immunoreacted with antise ra against the neuropeptides substance P and calcitonin gene-related p eptide. Separate mast cell populations were identified by counterstain ing with toluidine blue and alcian blue. Mast cells of both types were found within nerves and intramural ganglia and were in close contact with individual nerve fibers displaying substance P- and calcitonin ge ne-related peptide-like immunoreactivity. Moreover, serotonin-immunore active mast cells were innervated with nerve fibers that reacted with antiserum against vasoactive intestinal polypeptide. At the ultrastruc tural level, these fibers were almost exclusively identified as unmyel inated primary sensory afferents. Mast cells contacted these fibers wi th lamellipodia that wrapped around and enclosed the fibers deeply wit hin the cell. Close association between mast cells, nerves, and vessel s was common. Ultrastructural evidence suggests that bidirectional com munication occurs between nerve fibers and mast cells. These structure s may participate in axon reflexes that regulate normal vascular and d etrusor smooth muscle function and cause vasodilation, edema, inflamma tion, and bladder hyperreactivity. In summary, a close relationship ex ists between mast cells and peptidergic nerve fibers, including primar y sensory afferents. Results suggest that bidirectional intel action c ould occur between nerves and mast cells. (C) 1995 Wiley-Liss, Inc.