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. 2016 May 20;113(23):E3300–E3306. doi: 10.1073/pnas.1605973113

Fig. 4.

Fig. 4.

Odor blocking can occur within the brain. (A–C) HEK293 cells expressing TAAR3, TAAR4, or TAAR5 were tested with different concentrations of their respective ligands (IAA, PEA, or TMA) paired with varied concentrations of odorants that blocked the ligand's behavioral effects. Receptor activation was scored using a cAMP reporter assay that measures SEAP activity. SEAP activity over basal (no odorant) is shown in relative fluorescence units. Error bars indicate SEM (n = 8–24). Responses of TAARs to their cognate ligands were not significantly altered by pairing those ligands with another odorant (two-way ANOVA followed by post hoc Fisher LSD tests). (D) KO mice lacking TAAR5 [Taar5(−/−)] or their WT littermates [Taar5(+/+)] were tested for behavioral attraction or aversion to single or paired odorants using the olfactory preference test (see legend to Fig. 1) [n = 6–10 per condition for Taar5(−/−) mice and n = 5–11 per condition for Taar5(+/+) mice]. Asterisks indicate responses significantly different from responses to water: *P < 0.05; **P < 0.01; ***P < 0.001 (unpaired t test, two tailed). WhereasTaar5(+/+) mice showed a neutral response to TMT+TMA, Taar5(−/−) mice lacking Taar5 showed aversion to TMT+TMA, similar to that seen with TMT alone. Thus, TAAR5 is required for TMA to block aversion to TMT.