Protection of olfactory responses from inhibition by ethyl bromoacetate, diethylamine, and other chemically active odorants by certain esters and other compounds

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Abstract
Certain vaporous chemicals (chemically active odorants) are capable of both stimulating olfactory responses and reacting with receptors, ion channels, or receptor/ionophore macromolecules to inhibit olfactory responses. We have studied the physiological effects of several chemically active odorants using electrophysiological techniques to record electroolfactogram (EOG) responses from the frog's olfactory mucosa. So far, the most studied agents are ethyl bromoacetate (EBA), an alkylating agent, and diethylamine (DEA), a compound which is one of the strongest neutral organic bases. Certain odorants, or ‘protectants’, when present before, during, and after exposure of the olfactory mucosa to either EBA or DEA have the property of maintaining olfactory responses which would otherwise be inhibited by exposure to the chemically active odorant alone. Protection from inhibition by EBA is conferred by the presence of isoamyl acetate and a few closely-related esters, while protection from inhibition by DEA is produced by the presence of p-dichlorobenzene. Protection from inhibition by DEA is also achieved by lowering the pH of the olfactory mucosa through the simultaneous delivery of CO 2 which produces carbonic acid. The mechanism of protection by esters and p-dichlorobenzene is unknown, but it seems likely that these odorants somehow interfere with the access of the chemically active odorant to a site where it would normally react.