Autonomic innervation of the tympanic membrane. An immunocytochemical and histofluorescence study.

The innervation of the tympanic membrane of the rat was investigated with respect to noradrenergic and peptide-containing nerve fibres. In sections, most of the nerves in both the flaccida portion and the tensa portion seemed to be of the small, unmyelinated types, though a few larger myelinated nerves were also found. Noradrenergic fibres, exhibiting specific catecholamine fluorescence (CA), were detected along the blood vessels in the pars flaccida and along the vascular network of the annulus fibrosus. In the pars flaccida, fibres exhibiting SP-like, VIP-like- and enkephalin-like immunoreactivity were noted. None of these peptides could be detected in the pars tensa. The exclusive localization of the oedema-provoking peptides, SP and VIP, to the pars flaccida may be of importance with regard to establishing pars flaccida as the initial site of effusion production in experimental secretory otitis media.