Chemical Senses 12: 295-305,
© 1987
review-article |
Ingestive responses to some heavy metal salts in mice and inhibition of taste nerve responses by metals
Tokyo Metropolitan Institute for Neurosciences Fuchu, Tokyo 183 1Tokyo Metropolitan Hospital of Fuchu Tokyo 183 2Brain Science Foundation Honda Yaesu Bldg, 2-6-20 Yaesu, Chuo-ku, Tokyo 104, Japan
Preference-aversion for heavy metals in ddy mice was examined using the two-bottle preference technique. Mice preferred MnCl2, CoCl2 at certain concentration ranges, but avoided NiCl2, CuCl2, ZnCl2 and CdCl2. The avoidance threshold for the salts became lower in the order of Mn > Co > Ni > Cd > Cu > Zn, though the degree of rejection for CuCl2 was larger than that for ZnCl2. Preferences for sucrose and Na saccharin were reduced by low concentrations of CuCl2 or ZnCl2. However, preference for glycine was scarcely affected by addition of either salt at 1 mM. Electrophysiological experiments in mice on the inhibition by heavy metal salts of chords tympani nerve responses to the four basic taste stimuli revealed that CuCl2 and ZnCl2 at 1 mM inhibited the response to sucrose strongly and those to guinine HCl (QHCl) and NaCl moderately, but had no effect on the HCl response. On the other hand, MnCl2, CoCl2 and NiCl2 at 1 mM scarcely inhibited the response to sucrose but suppressed those to other stimuli. CoCl2 moderately inhibited responses to all the stimuli. In general, metal salts producing a larger inhibition of neural responses to sucrose and QHCL are avoided by mice at a lower concentration.