Monosodium Glutamate (MSG) Promotes the Contraction of Duodenal Visceral Smooth Muscle Ex Vivo in Rat

Monosodium glutamate (MSG), popularly trading in the name of AJI-NO-MOTO, is one of the world’s most extensively used taste enhancing food additive. It is used in cooking as a flavor enhancer with an umami taste that intensifies the meaty and savory flavor of food. Thus, humans are often exposed to MSG through consumption of MSG tainted food stuffs and the small intestine gets primarily exposed to it. In order to examine any effect of MSG on the contractile activity of the small intestinal visceral smooth muscle (SiVSM), the movement of the duodenum ex vivo in response to MSG in single dose experiments have been recorded using an isotonic transducer (IT-2245) coupled with an RMS-Polyrite D machine (RMS, Chandigarh, India). Significant increase in the amplitude and frequency of contraction of the duodenum in comparison with control tracings in a dose-response manner were observed. From the results, it can be suggested that MSG potentiates the contractile activity of duodenal visceral smooth muscle probably by increasing the amplitude and frequency of the contractions of the visceral smooth muscle located in the wall structure of the duodenum, probably by facilitating the activity of excitatory intrinsic cholinergic efferents and/or inhibiting the activity of inhibitory adrenergic or nitrergic myenteric efferents. The MSG induced impairment in the contraction of the dVSM results in impaired digestive and absorptive functions of the duodenum (small intestine).