Experimental autonomic neuropathy: ultrastructure and immunohistochemical study of a disorder of reflex vasomotor...

Vasomotor function in ear vessels of rabbits was tested in animals with experimental autonomic neuropathy (EAUN), experimental allergic neuritis (EAN), and controls. Reflex vasodilatation was impaired in animals with EAUN but not in EAN or control rabbits. Ultrastructural examination of paravertebral sympathetic chain, perivascular nerves, and perivascular tissue showed similar changes in all animals differing in degree only. Occasional lymphocytes were seen in paravertebral chains of controls but large numbers of lymphocytes and macrophages occurred in EAUN and EAN. No active destruction of myelinated or unmyelinated fibers could be seen. Perivascular nerves showed similar cellular infiltrates and basophils were found in perivascular spaces of ear vessels which were most abundant in animals with EAUN. Fibre-size spectra analysis of unmyelinated fibres in the paravertebral sympathetic chain showed a shift to the left suggesting regeneration of unmyelinated axons in both EAN and EAUN. No specific immunofluorescence against neuronal components could be demonstrated in sensitized animals. It is concluded that the functional disturbance of reflex vasomotion in EAUN is not accompanied by specific ultrastructural lesions nor could neuronal components be immunologically implicated in the disorder. Regeneration of unmyelinated axons and recovery of function after some weeks together with abundance of basophils in perivascular tissue of sensitized animals, suggests that a localized inflammation may have occurred, the basophils interfacing between foreign antigens, the serum cascade systems, and other inflammatory cells. The usefulness of EAUN as a model for acute pandysautonomia in man remains to be determined.