The Effect of Menthol on the Thermoreceptors

Abstract

Summary.: The discharge of specific cold and warm fibres in the lingual nerve of the cat has been studied in response to the application of menthol solutions and to exactly defined thermal stimuli on the tongue. Aqueous menthol solutions of 1: 10,000 lead to strong stationary discharge of the tongue's cold receptors at constant warm temperatures at which there without menthol is no discharge. At lower temperatures at which the cold receptors are stationary discharging without menthol, this substance produces a great increase of the stationary cold impulse frequency. The effect of menthol can be completely compensated for by sudden heating or by keeping the tongue at a constant higher temperature as these measures can cause the cold impulses elicited by menthol to disappear entirely. Thus it is not simply the question of a chemical “inadequate” stimulation of the cold receptors but of a sensitization of the thermal effect. Our experiments have not given any evidence that menthol exerts any corresponding action on the warm receptors. The threshold of the menthol effect lies between a concentration 1: 1,000,000 and 1: 500,000. It is thus likely that the action of menthol concerns some enzymatic process in the cold receptors.