Propyl ether. I. Interaction with the sensory irritant receptor.

The sensory irritating response of propyl ether, measured as a decrease in respiratory rate in mice, faded within one minute. The threshold was 620 p.p.m., calculated from the concentration-response curve, which had a low slope. The sensory irritating level depressing the respiratory rate to 50 per cent (RD-50 = 89,000 p.p.m.) could not be reached with saturated vapour at 20 degrees. The thermodynamic activity corresponding to the RD-50 was about 0.6, a rather high value. The low slope and high thermodynamic activity may be explained by steric hindrance of the oxygen atom and thereby decreasing the receptor-activating capacity and/or the stability of the active receptor conformation. A specific effect beyond the receptor offers another explanation.