The reflex secretion of parotid saliva was utilized to evaluate the stimulatory action of various taste mixtures on human gustatory chemoreceptors. Test solutions consisted of citric acid, sucrose, and sodium citrate. Rates of secretion were determined by measuring the volume produced by a standardized application procedure. The response elicited by the different solutions was determined. The effect of one modality upon another was then studied by combining two solutions at each of four concentrations. Results showed that the addition of citric acid or sodium citrate to sucrose produced a response equal to the sum of the separate constituents. The flow rate obtained from mixtures of citric acid and sodium citrate was less than the sum of the individual components. This apparently was due to the buffering effect causing a decreased hydrogen ion concentration. Although the hydrogen ion concentration decreased to sub-threshold levels, the salivary gland secretion rate was still responsive to variations in hydrogen ion concentration, indicating a synergistic effect when hydrogen and sodium ions were present in the same solution.
gustation; taste; gustatory-salivary reflex; parotid gland secretion
Submitted on October 1, 1964
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