Taste reactivity in rats selectively bred for high vs. low saccharin consumption.

Rats selectively bred for high (HiS) vs. low (LoS) saccharin consumption were compared on taste reactivity responses to 0.1% saccharin before and after continuous access to 0.1% saccharin. The rats were also tested with other saccharin concentrations (0.01-0.3%) before and after the consumption test. Finally, all rats were tested for reactivity to 0.1 M sucrose, 0.0001 M quinine hydrochloride, and a sucrose + quinine mixture. HiS rats ingested more saccharin than did LoS rats, but the groups did not differ in total ingestive or total aversive reactivity on any of the taste tests. When aversive reactivity was analyzed further to distinguish passive drip from other, more active responses, HiS rats made more active responses than LoS rats; the latter showed a consistent tendency to passive drip more than HiS rats. Overall, aversive responding decreased and ingestive responding increased as saccharin concentration rose and from the first to the second concentration series. Because the brain stem-mediated hedonic evaluation of tastes by HiS and LoS rats appears to be similar, the difference in saccharin consumption must be mediated by psychological processes whose neural substrates lie above the brain stem.