Taste effectiveness of glutamate compounds with different cations in rat

A role of a cation of glutamate compounds for their taste has not been well elucidated yet. In this experiment, the difference of taste quality of glutamate compounds which have a different cation was compared to reveal the role of cations in the glutamate compounds on their characteristics of taste. Monosodium L-glutamate (MSG), monopotassium glutamate (MPG) and monocalcium glutamate (MCG) were used. The preference test in rats revealed that the rate of drinking volume per day was not statistically different among MSG, MPG and MCG. In the next experiment, the conditioned taste aversion test was performed in rats, and rats were conditioned to hate to drink MSG, MPG and MCG respectively by pairing the intraperitoneal injection of LiCl. In the MSG conditioned animals, the drinking rate of MSG decreased, and that of MPG significantly increased, but that of MCG did not change. In the MPG conditioned animals, drinking rate of MPG was strongly depressed, but that of MCG tended to increase, and that of MSG did not change at all. In the MCG conditioned animals, the drinking rate of MCG decreased, but MSG and MPG did not change. The chorda tympani responses to 0.1 M MSG applied to the tongue surface was larger than those to 0.1 M MCG, and the responses to 0.1 M MPG were the smallest out of these three glutamate compounds. The nerve responses of the glossopharyngeal nerve to MSG, MCG and MPG were very similar to each other.(ABSTRACT TRUNCATED AT 250 WORDS)