Effects of capsaicin pre-treatment in experimentally-induced secretory otitis media

Neurogenic inflammation may play a role in the aetiology of secretory otitis media (SOM). The strongest candidate that initiates the characteristic symptoms of neurogenic inflammation is supposed to be substance P. Capsaicin is a specific antagonist of substance P. The effects of capsaicin on middle ear mucosa have not been studied yet. In an attempt to investigate the effect of pre-treatment with capsaicin on the development of SOM an experimental study was performed. Fourteen Wistar rats were divided into two groups. Seven rats were pre-treated with capsaicin (Group 1) and the others were administered isotonic saline solution (Group 2). Seven days after the third injection rats were operated on and the right tympanal orifice of the Eustachian tube was obstructed. Animals were sacrificed seven days after the operation. Their bullas were excised bilaterally and were studied by light microscopic technique. In Group 1 there was no effusion except for one case. The subepithelial layer was thickened by fibroblast proliferation. Capillary proliferation and some glandular atrophy were observed. In Group 2 the middle ear lumens were filled with effusion. Oedema with dilatation in capillaries and medium-sized vessels of lamina propria was observed as a common feature of the group. Subepithelial fibrosis was found in one case. Capsaicin pre-treatment prevented the formation of effusion in the middle ear lumen in spite of tuba occlusion. The results of this preliminary study lead us to consider that an imbalance in the autonomic innervation of the mucosa of the middle ear may play a role in the aetiology of SOM as in vasomotor rhinitis, and capsaicin may be an alternative in the treatment.