SOME EVIDENCE FOR A MECHANICAL RECEPTOR IN OLFACTORY FUNCTION

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Abstract
In dogs and monkeys with chronically implanted electrodes, bursts of electrical activity were recorded in the olfactory structures including the olfactory bulb, olfactory striae, amygdala, and pyriform cortex. These waves of 20-40 cps were synchronous with inspiration in the monkey and with inspiration and expiration in dogs. The phenomena were predominantly ipsilateral. Electrical activity of similar frequencies could be elicited by blowing room air, various gases and solutions into the nostril. It appeared that a mechanical component was involved in these phenomena. Therefore studies in acute dogs given local anesthesia and immobilized with decamethonium and placed on artificial respiration were undertaken. With the use of a gas purification system evidence was obtained that in about 50% of the dogs studied electrical discharges were recorded in the olfactory bulb to odor-free O2, N2, and CO2 passed through the ipsilateral nostril. The electrical discharges in the olfactory bulb to odor-free gases were dependent upon the velocity of gas flow. The areas in the olfactory bulb where mechanical responses were obtained were relatively few compared to those areas responding to odors. In all of the animals studied the electrical responses to all odors including tobacco smoke were enhanced with increasing flows of O2 when the flow of the odoriferous material was kept constant. Thus the concentration of odor per unit volume of gas was actually decreased at a time when the olfactory bulb responses were markedly enhanced. It is concluded that preliminary evidence has been obtained for the existence of a mechanical receptor in olfactory function.