Orosensory suppression of saccharin drinking in rat: the response, not the taste.

Hungry rats drink saccharin solutions with avidity, but the ingestion is self-limited: rate of lapping slows down progressively. Since postingestive changes do not produce this suppression, it must depend on a feedback signal generated by lapping the fluid. We show that the suppression depends on the number of laps emitted, not on the taste of the fluid; a given number of laps early in the session produces the same suppression later in the session, whether those early laps are accompanied by a moderate saccharin taste, a weak taste, or no sweet taste at all. Therefore, the feedback signal is provided by the act of lapping; taste does not contribute to it. Yet taste does influence amount ingested. Perhaps it provides a feed-forward signal, that in turn sets the amount of feedback required to end the bout.