The Response Speetrum of Taste Fibres in the Cat: A Single Fibre Analysis

Abstract

Summary. 1. Taste receptors in the cat's tongue were analyzed by recording from single afferent chorda tympani nerve fibres while applying various sapid solutions to the tongue. 2. Single fibres were observed which responded to the flow of distilled water over the tongue. The activity of these “water” fibres was depressed by various inorganic salt solutions with an anion concentration above 0.03 M. Organic sodium salts, in contrast, stimulated this fibre type in a manner similar to distilled water. 3. The “water” fibres were also stimulated by quinine hydro‐chloride and mineral acids below pH 2.5. 4. Single “salt” fibres were observed which responded to various salts above 0.1 M concentration. These fibres were also stimulated by acid. 5. Another fibre type responded primarily to quinine chloride and very little if at all to strong acid. The “quinine” fibre was not. stimulated by hypertonic salt solutions or by distilled water. 6. The fourth fibre type found responded only to acids below pH 2.5. 7. It is proposed that the presence of the “water” fibre extends the sensitivity to salt solutions beyond the concentration limits served by the “salt” fibres thus enabling discrimination of salt concentration over the entire physiologically significant saline range. 8. The importance of impulse pattern is discussed and a scheme presented illustrating the possible relationship between afferent impulse pattern and the evoked taste sensation. 9. The possible mechanism of stimulation by water is discussed and a view presented that the outward flow of anions across the receptor membrane stimulates while an inward flow depresses (“water”) fibre activity.