TTS development and recovery. (A) Development of TTS was determined using 16-kHz ABR threshold measurements by briefly interrupting sustained noise (85 dB, 4–32 kHz, closed-field; K/X/A anesthesia); knockout (P2RX2-null) (n = 3) mice; wild-type (n = 3) age- and strain-matched control mice. Single exponential curve fits for TTS growth; time constant 19.5 min WT; 28.4 min KO. P < 0.001 KO vs. WT; **P = 0.003, ***P < 0.001, two-way ANOVA, Holm–Sidak pairwise comparison. (B) Recovery of TTS in WT, HET [P2RX2(+/−)], and KO littermate mice using broadband noise (4–32 kHz, 30 min, closed-field; n = 6 each group). ABR (16-kHz) threshold measurements. P < 0.001 for KO vs. WT or HET, two-way ANOVA. TTS recovery time constant for WT or HET was 12.3 h.