The recovery period of the taste responses of rat chorda tympani after application of toothpaste.

The recovery period of the taste responses of rat chorda tympani after application of toothpaste was examined. The response observations of four kinds of essential taste stimuli, 0.1 M sodium chloride, 0.005 M quinine hydrochloride, 1.0 M sucrose, and 0.05 M tartaric acid, were repeated every 2 or 5 minutes. After five observations of summated responses of the chorda tympani with each taste stimulus, a toothpaste solution diluted 3 to 1 was applied to rat tongues for 3 minutes and then they were washed with distilled water for 1.5 minutes. Thereafter, observations of the responses to each taste stimulus were repeated at 2 or 5 minute intervals for 30 or 60 minutes. The responses caused by four kinds of essential taste stimuli became smaller immediately after application of toothpaste, and then gradually returned to normal. The same experimental procedure was also applied using an application of distilled water instead of an application of toothpaste to rat tongues. A t-test was performed between the response ratios after application of toothpaste and those after application of distilled water. Significant differences disappeared at 18 minutes after application on the 0.1 M sodium chloride stimulus, at 23 minutes on the 0.005 M quinine hydrochloride stimulus, at 15 minutes on the 1.0 M sucrose stimulus, and at 15 minutes on the 0.05 M tartaric acid stimulus. The authors estimated that all kinds of taste responses recovered within at least 50 minutes.