Event:

Acoustic trauma induces changes in the receptor properties at excitatory synapses in the lateral superior olive.



As Charles Liberman and colleagues have so elegantly shown, loud sounds (noise) can cause a reduction in the number of peripheral synapses onto inner hair cells. We are interested in what happens further downstream at synapses in the brainstem following noise exposure. Are they also affected by loud sounds and can we measure the impact that this has on auditory processing?
We have characterized the development of excitatory and inhibitory inputs into the mouse lateral superior olive (LSO) from postnatal day 7 (P7) to P96. We then exposed mice to an acoustic trauma and re-examined the properties of these synapses using an in vitro brain slice preparation. We have conducted auditory brainstem response (ABRs) to assess hearing, and correlated the changes caused by acoustic trauma with the synaptic currents measured from identified LSO principal neurons using whole cell patch under voltage-clamp.
In addition, we measured the changes induced in mRNA levels for excitatory and inhibitory amino acid receptor subunits. The results provide a developmental profile of synaptic transmission in the LSO and of how this is integrated for interaural intensity difference (IID) computations. We demonstrate that acoustic trauma causes a long term change in the expression of AMPAR subunits in the LSO, favoring expression of subunits with slower kinetics for several weeks after exposure.