GTTR fluorescence in the lateral semicircular canal (LSC) peaked 3 hours after a single systemic injection of GTTR.

<p>At 0.5 hours, intense fluorescent puncta were readily seen in dark cells (A1) and transitional cells (A2), with less intense puncta seen in sensory epithelia (A3). Low intensity diffuse GTTR fluorescence was also detected in dark cells (A1) and transitional cells (A2), with weaker fluorescence in supporting cells and sensory hair cells in the sensory epithelia of the LSC crista (A3). At 1 hour, dark cells (B1), transitional cells (B2), and sensory epithelia (B3) had increased numbers of puncta and higher fluorescence intensity compared to at 0.5 hours (A1-A3). Increased intensity of diffuse cytosolic GTTR fluorescence was also observed in dark cells (B2), transitional cells (B2), and sensory epithelia (B3). Two hours after GTTR injection, increased cytosolic GTTR fluorescence was apparent in dark cells (C2), but less so in transitional cells (C2) and sensory epithelia (C3). Also, increased numbers of fluorescent puncta were found in dark cells (C1), transitional cells (C2), and sensory epithelia (C3), compared to earlier time points (A1-B3). Fluorescent intensity peaked at 3 hours, and declined by 4 hours (E1-E3), in all three regions. Mice injected with hydrolyzed Texas Red for 2 hours showed negligible fluorescence in all three vestibular regions (F1-F3). Scale bar in A3 = 20 <i>μ</i>m.