Prostaglandins (PG) E1 and E2 were applied topically to the receptive fields of feline laryngeal and pharyngeal sensory receptors, while action potentials were recorded from single - or few-fiber preparations of the superior laryngeal nerve. When initially dissolved in ethanol, PGs stimulated these sensory receptors. If ethanol was not used as a solvent for the PGs, they did not stimulate the sensory receptors. Similarly, local application of dilute (0.025%, v/v) solutions of ethanol alone excited the receptors, whereas phosphate buffer alone did not. Thus PGE1 and PGE2 do not themselves stimulate sensory receptors in the larynx and pharynx. These findings suggest that irritant properties of PGEs on upper airways are attributable to the ethanol used as a solvent.
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Prostaglandins (PG) El and E2 relax isolated airway smooth muscle in a number of species, including human (l-4), and, when given by aerosol to asthmatic patients as well as normal subjects, improve specific airway conductance and reduce airway resistance (5-7). In clinical trails of aerosols of these PGs as bronchodilators in treatment of asthma, however, they have been reported to cause cough, irritation of the upper airways, including trachea and pharynx, and tightness of the chest in normal as well as asthmatic patients (7-ll), thus limiting the clinical usefulness of these agents. Although the 1. We thank Drs. 14. Wasserman and .I. Pike of the Upjohn Company for the prostaglandins used in this study. This work was supported in part by Pulmonary SCOR Grant HL 19156 from the National Heart, Lung and Blood Institute and gifts from the Upjohn Company and Parker B. Francis Foundation.