Ir7a¹ mutant flies show decreased gustatory avoidance to food laced with higher concentrations of acetic acid (ie. no avoidance to 5% and significantly lower avoidance to 10%) but show no changes in gustatory responses to lower concentrations of acetic acid (0.1-1% acetic acid), as compared to controls. These individuals show no gustatory response changes to other acids (0.1-10% glycolic acid, 0.1-15% citric acid, 0.1-20% lactic acid, 0.1-10% tartaric acid, 0.1-10% propionic acid, 0.1-2% butyric acid, or 1-200mM HCl) or other bitter chemicals (1mM quinine, 0.3mM denatonium, 0.3mM lobeline, 0.5mM strychnine, 10mM caffeine, and 0.1mM berberine), as compared to controls. The decreased avoidance to 5% acetic acid ceases to be observed at only slightly acid or neutral pHs (pH 5.0-7.0), as compared to controls. Ir7a¹ mutant flies show significantly decreased preference to lactic acid in a two way lactic acid:acetic acid assay (at 5% and 10% concentrations for both acids), as compared to controls. Ir7a¹ mutant flies display significantly less distaste (i.e. decreased proboscis extension reflex response) for acetic-acid-containing sucrose than control flies when acetic acid is applied to the labellum, but not when applied to the leg, as compared to controls.

In Ir7a¹ flies, GRNs enervating S-type sensilla (S1-S12), but not I-type sensilla (I1-I10) or L-type sensilla (L1-L9) show greatly reduced responses (frequency of spikes) to 1% acetic acid, as compared to controls; GRNs enervating S6 and S10 sensilla show only residual responses to 0.1%, 1%, and 5% acetic acid, but no significant changes in the response to bitter chemicals (1mM quinine, 1mM denatonium, 1mM lobeline, 1mM strychnine, 10mM caffeine, and 0.1mM berberine), as compared to controls; GRNs enervating S5, S6, and S10 sensilla do not show changes in the responses to other acids (1% glycolic acid, 1% tartaric acid, 5% citric acid, 1% propionic acid, 1% butyric acid, 10mM HCl, and 20% lactic acid), as compared to controls; GRNs enervating S3, S5, S6, and S10 sensilla do not show changes in the responses to ethanol (10%) or acetaldehyde (1%), as compared to controls. GRNs enervating L4 and L6 sensilla do not show changes in the responses to acetic acid (0.1-10%), as compared to controls.

Df(1)hl-a/Ir7a¹ flies do not show the expected avoidance to food laced with acetic acid (5%) and GRNs enervating their S3, S5, S6, and S10 sensilla show greatly reduced responses (frequency of spikes) to acetic acid (1%).