The Effect of Umami Stimulation on Salivary Secretion Rate and Duration

Purpose: Umami reportedly promotes salivation. We aimed to investigate the effects of taste stimuli on slow and fast salivary secretion in humans using umami, sweet, and sour stimuli. Methods: Eight healthy women participated between 14:00 and 15:00, taking the circadian rhythm of salivary secretion into account. The types and concentrations of the taste solutions were glutamic acid (1.7 × 10−3 M), inosinic acid (9.8 × 10−3 M), and guanylic acid (9.8 × 10−3 M) for umami stimulation, citric acid (6.5 × 10−3 M) for acidity stimulation, and sucrose (1.6 × 10−2 M) for sweetness stimulation. First, the unstimulated salivary flow rate was measured. Then, 3 ml of a flavor solution was dropped under the tongue using a syringe. The saliva was expelled into an aluminum cup every minute and weighed. The first minute’s value minus 3 ml flavor solution was the stimulated salivary secretion rate produced by each flavor. The time-to-return to the initial unstimulated salivary flow rate was the duration of the stimulated saliva secretion rate. Results: The mean unstimulated salivary flow rate across participants was 0.64 ± 0.25 ml/min (range: 0.23 - 1.03 ml/min). The highest amount of saliva was induced by citric acid. There were significant differences between citric acid and the other flavor solutions (p < 0.05 for glutamic acid, inosinic acid, and sucrose;p < 0.01 for guanylic acid). There were no significant differences in duration of salivation between the flavor solutions. When the participants were divided into slow (0.45 ± 0.16 ml/min) and fast groups (0.83 ± 0.15 ml/min) based on their median resting salivary secretion rate, there were no significant differences between the two groups in the amount of saliva secreted at 1 minute after stimulation and the duration of the salivary secretion rate. Conclusion: Umami stimulation was effective in slowing salivary secretion and sustaining salivary secretion after stimulation.

Effects of Chinese herbs on salivary fluid secretion by isolated and perfused rat submandibular glands

AIM： TO determine whether Chinese herbs （CHs） relieve xerostomia （dry mouth） by increasing salivary secretion. METHODS： The submandibular glands of Wistar rats were surgically isolated and perfused arterially with buffered salt solution. After control perfusion, recording started 5 min prior to the start of stimulation. After fluid secretion was induced by 0.2 μmol/L carbamylcholine （CCh） in the perfusate for 10 min, Chinese herb （CH） was added in the perfusion for 5 min. CCh was then overloaded at 0.2 μmol/L in the perfusion for 20 min. The volume of salivary fluid secretion was recorded by a computer-controlled balance system. RESULTS： Saliva secretion formed an initial ephemeral peak at 30 s followed by a gradual increase to a sustained level. CH alone induced no or little saliva in all types of CH selected. During perfusion with CH,overloading of CCh promoted fluid secretion in 1S of 20 CHs. This promotion was classified into four patterns, which were eventually related to the categories of CH： Overall sustained phase was continuously raised （Yin-nourishing, fluid production-promoting and heatclearing agents）; The sustained secretion rose to reach a maximum then decreased （Qi-enhancing agent）; Sustained secretion rose to reach the highest maximum and was then sustained with a slight decline （swelling-reducing, phlegm-resolving and pus-expelling agents）; Stimulation of salivary secretion without any added stimulants. Addition of CCh raised the fluid secretion to reach the highest maximum then sharply decreased to a lower sustained level （blood activating agent）. CONCLUSION： The present findings lead to the conclusion that various CHs have different promotional effects directly on the salivary gland.