Development of chorda tympani nerve taste responses in the hamster

To determine whether changes in salt and sugar responses occur during development in the hamster, multifiber responses were recorded from the chorda tympani nerve while stimulating the anterior tongue of preweanling, early postweanling, and adult hamsters. Gustatory stimuli included 0.1 and 0.5 M solutions of NH4Cl, NaCl, LiCl, and KCl, and concentration series (0.01-1.0 M) of glucose, fructose, sucrose, maltose, lactose, and (0.0005-0.01 M) saccharin. Dramatic alterations in hamster peripheral gustatory sensitivities occurred with age, with the direction and magnitude of change dependent on the specific stimulus. Response magnitudes to 0.1 M solutions of NaCl and LiCl decreased with age compared to the NH4Cl response, whereas responses to all other salt stimuli remained constant during development. Responses to all sugars and saccharin compared to the NH4Cl response increased during development across a large concentration range; however, the age at which mature responses were achieved depended on the specific "sweet" stimulus. Whereas these findings demonstrate that the hamster peripheral gustatory system is dynamic during postnatal development, the hamster has a unique developmental pattern of salt taste development compared to other species. Specifically, the effectiveness of NaCl and LiCl decrease during development compared to NH4Cl in the hamster, but increase dramatically in the rat and sheep. Thus, the developmental patterns are opposite in direction for the hamster compared to the rat and sheep and may relate to the environmental pressures imposed upon each species.