Autonomic stimulation, osmolarity and prostaglandin effects in the Eustachian tube.

Stimulation of the vidian nerve in the dog induced an apparent vasodilation in the mucosa of the Eustachian tube. It is presumed that these parasympathetic fibers course from the greater petrosal nerve through the vidian to the sphenopalatine ganglion. The pharyngeal nerve arises from the ganglion and innervates the mucosa of the tube. Perfusion of the dog's Eustachian tube with solutions of various osmolarities caused a shrinking or swelling of the tube mucosa. Ten percent alterations in the concentration of saline, Ringer's or isotonic KCl produced a hypo- or hypertonic effect. Systemic administration of osmotic diuretics was shown to remove water from normal and edematous tubal mucosa. An agent in human middle ear effusions was found to contract smooth muscle. The behavior of this agent in pharmacological tests suggested the presence of prostaglandins (PG). The effusions were tested for the presence of other inflammatory mediators such as bradykinin, acetylcholine and histamine. These were felt to be absent or present in small amounts. A radioimmune assay of pooled samples of middle ear effusions revealed the presence of several PG, notably PGF2alpha and PGE2. There appeared to be a higher concentration of PG in mucoid effusions than serous effusions. The inflammatory capabilities of these agents are mentioned.