Figure 6.

Adaptation and cross-adaptation of psychophysical responses elicited by the sulfonyl amides and aristolochic acid. In the beginning of the experiment, the subjects rated the bitterness of all four solutions after 15 sec. Then, they took up the primary bitter solution for prolonged times and rated its bitterness at the indicated times. After the panelists spat off the primary bitter solution, they sequentially tasted the other three test solutions and rated their bitter intensity after 15 sec. To assess reversibility, the subjects sequentially rated 30 min later the bitterness of all four test solutions after 15 sec. a, Adaptation to the bitterness of salicin used as a control compound and lack of cross-adaptation with responses to saccharin, acesulfame K, and aristolochic acid. b, Adaptation to the bitter response of aristolochic acid and cross-adaptation with those of both sulfonyl amide sweeteners. Note that the response to salicin was not affected. c, Adaptation to the bitter taste of saccharin and cross-adaptation with those of acesulfame K and aristolochic acid. d, Adaptation to the bitter taste of acesulfame K and cross-adaptation with those of saccharin and aristolochic acid. AA, aristolochic acid; Ace K, acesulfame K; Sac, saccharin; Sal, salicin.