The data shows that much larger quantities of VGLUT3 mRNA are being produced in the rescued as compared to the WT mice (Figure 1C, RT-PCR data) and suggests, though does not prove, an association between increased mRNA levels and vesicle number. We believe that circular vesicles represent properly packaged vesicles, while the elongated vesicles are improperly packaged vesicles. Perhaps continuous

production of VGLUT3 by the constitutive CBA promoter driving transfected VGLUT3 production prevents the IHC from properly packaging the vesicles at a normal rate, leading to a higher number as well as a mixture of regular and irregular-appearing vesicles. Another possibility is that the incomplete selleck compound transfection rate of IHCs (40% of IHCs labeled at the doses used for these morphology studies) led to the heterogeneity of the ribbon morphology seen. The observed growth on behavioral and electrical measures seen with bilateral, as opposed to unilateral, rescue (RWM delivery at P10–P12; Figure 4) was an unexpected finding. While none of the animals had complete normalization of ABR amplitude and startle-response levels, the amplitude growth does imply that

bilateral input increases the auditory response centrally. An analogous phenomenon is seen with “binaural summation” and clinically in patients who wear two hearing aids as opposed to one and report lower levels of amplification required (Noble, 2010 and Steven Colburn et al., 2006) and suggests that

the response seen in these studies is physiologic. ABT-199 cell line Recent studies have localized VGLUT3 to various structures in the brainstem, including cochlear nucleus (Fyk-Kolodziej et al., 2011) as well as the LSO and MNTB (Lee et al., 2011). It is certainly possible that deficits within auditory brainstem signal pathways could be contributing Dipeptidyl peptidase to the inability to restore the startle response to WT levels. The failure of the technique to reverse the spiral ganglion cell loss seen in the VGLUT3 KO mice when delivered at P10–P12 is not surprising (Figure 5), given that hair cell activity and afferent stimulation can provide a trophic effect on SG survival. This is probably at least partly due to the fact that virus was delivered at ∼P10 with subsequent ABR threshold recovery at ∼P17–P24, after spiral ganglion neuronal degradation has begun (Seal et al., 2008). This also implies that in order for SG neurons to be preserved at normal levels, intervention would probably have to occur earlier. Further, with only ∼40% of IHCs expressing VGLUT3 (using the lower concentration of virus, delivered at P10–P12), there are still many spiral ganglion neurons not receiving afferent input, which also probably impacts this result as well. We were thus surprised that even earlier delivery of virus, at P1–P3, which resulted in relatively early onset of hearing, measureable by P14, with 100% of IHC expressing VGLUT3, also did not lead to restoration of SG cell counts to WT levels.