Modulation of taste reactivity by intestinal distension in rats

Discomfort created by intestinal distension may play a role in controlling intake behavior. We analyzed these effects in details by the taste reactivi ty test in Long-Evans rats. A balloon inserted into a separated Thiry-Vella intestinal loop was distended with different volumes of water (0.05, 0.09, 0.12, and 0.28 mt, respectively). Saccharin solution (0.001 M) was infused into the mouth via an implanted oral cannula nine times for 30 s, with 5-m in intertrial intervals. The balloon was distended after the second and rel eased following the seventh trial. Taste reactivity (TR) elements were vide otaped and later analyzed for appetitive and aversive responses. The number of appetitive responses decreased after gut distension, whereas aversive e lements were unfrequent and stable. It is suggested that pleasantness of th e taste stimulus decreased independently of the discomfort, which remained mild but steady; that is, sweet taste gradually lost its hedonic value but was not accompanied by an acquired aversion of the same taste. This finding may point to the difference of the motivational and discriminative effects of the internal stimuli. (C) 1999 Elsevier Science Inc.