Abstracts: 33 Effect of afferent vagal stimulation through oral exposure to a sour or a salty taste on gastric myoelectrical activity evaluated by means of multi-channel electrogastrography

Aim:To determine if sensory stimulation with a salty or a sour taste would affect the interdigestive gastric myoelectrical activity (GMA) in humans. Methods:Eighteen healthy volunteers (10 F, 8 M) were subjected on two separate days to four-channel electrogastrographic recordings divided into consecutive 35 min periods: (i) basal fasted; (ii) a stimulation epoch while a subject was chewing an agar cube soaked with a taste-delivering substance (Sodium chloride for the salty taste, citric acid for the sour taste) and (iii) a post-stimulatory (recovery) epoch. An electrocardiogram was simultaneously registered for the purpose of the heart rate variability (HRV) analysis. Results:Exposure to the salty taste increased both the power of the low frequency (LF: 0.04-0.15 Hz) band and the low to high frequency (LF/HF) power ratio of the power spectrum-analysed HRV data. The sour taste did not affect the HRV. During the stimulation and the recovery epoch either in the case of the salty or the sour taste a statistically significant augmentation in the relative time share of tachygastria within the multi-channel electrogastrogram was observed. Exposure to the salty taste resulted in a statistically significant decrease in the fraction of the coupled gastric slow waves. Moreover, the time-share of bradygastria rose slightly but statistically significantly in response to the stimulation with the salty taste. On the other hand, the sour taste elicited a significant decline in the dominant power of the gastric slow waves. Conclusions:(i) Oral exposure to a salty taste elicits a sympathetic arousal reflected by an increase in the LF power and the LF/HF power ratio, whereas a sour taste does not change the balance between the parasympathetic and the sympathetic constituent of the autonomous nervous system; (ii) the increment in tachygastria appears to be an unspecific phenomenon because it was evoked by stimulation with either the salty or the sour taste and (iii) the inhibitory effect on the GMA of the exposure to the sour taste is reflected by a dumping of the dominant power, whereas the stimulation with the salty taste is followed by an uncoupling of the gastric slow waves and an increase in bradygastria.