Sympathetic Influence on the Normal Eustachian Tube: An Experimental Study in the Rat

Abstract

A new variant of the inflation test of the Eustachian tube is presented; a constant air flow generator was constructed with minimal sensitivity to counterpressure, and variations in air pressure were measured, reflecting variations in Eustachian tube patency. By means of this test the effect of Otrivin (a₂-receptor stimulation) and Timacar (β-receptor blocking) on the Eustachian tube was investigated with saline serving as reference. The following results were obtained: A) Otrivin lowers the opening pressure and the steady state pressure, and reduces the pressure drop during active opening. B) Timacar alone has no statistically significant effect on the Eustachian tube, but the combined effect of the two drugs is a more pronounced decrease in steady state pressure than the decrease seen following a₂-adrenergic stimulation alone. An explanation could be an a₂-receptor modulation by the β-blocking agent. Consequently, autonomous regulation should be further studied in the search for a better understanding of Eustachian tube physiology.

Key Words:

• Eustachian tube function
• inflation test
• autonomous regulation
• Otrivin
• Timacar