The effect of monosodium glutamate on parotid salivary flow in comparison to the response to representatives of the other four basic tastes

Parotid salivary flow was recorded from eight fit and healthy subjects using modified Lashley cups connected to an instantaneous flow meter in response to gustatory stimuli. The gustatory stimuli were monosodium glutamate (MSG), sodium chloride, sucrose, magnesium sulphate and citric acid. Stimuli were applied for 30 s, and repeated after the flows had returned to baseline following the rinse. Subjects were a significant source of variation for salivary response to each different test stimuli (p < 0.001). The normalised salivary flow showed a strong correlation to concentration for all test stimuli (p < 0.0001). The parotid salivary flow to MSG (umami) showed a dose-dependant response in which both Na+ and glutamate ions contributed. The overall order of relative salivary flow responses from highest to lowest flows was citric acid (sour) > MSG (umami) > NaCl (salt) > sucrose (sweet) > = magnesium sulphate (bitter). The relative responses of the peak salivary flows showed the same ordered relation. The peak salivary flow provided a greater contribution to the response to citric acid, NaCl and MSG compared to the response to sucrose and magnesium sulphate.