Fig. 2.

Chorda Tympani (CT) responses to nicotine and quinine in mice. (A) Phasic and tonic CT responses to nicotine (N) were of lower magnitude in a KO (right trace) than in a WT (left trace) mouse. In all CT recordings, water was applied between stimuli as rinse solution (R) and responses were normalized to the mean tonic response obtained with 300 mM NH₄Cl. (B) Tonic responses to nicotine were compared in 3 WT (blue curve, n = 1.44, EC₅₀ = 7.2 mM, R² = 0.96) and 3 KO (red curve, n = 1.5, EC₅₀ = 7.8 mM, R² = 0.99) mice. Significant differences were found for genotype (P < 0.002), nicotine concentration and their interaction (P < 0.0001 for both, 2-way repeated measures ANOVA). Genotype-dependent differences were significant at 20 mM (*, P < 0.05; Bonferroni). (C) Tonic responses to 10 mM quinine were observed in 3 WT mice (Left) but not in 3 KO mice (Right). In KO mice, phasic responses were not different from those obtained with rinse (P > 0.3), whereas, in WT mice, they were significantly higher (**, P < 0.002; paired 2-sample t test).