Housley, G. D. | Search bioRxiv

bioRxiv2021

Association of cochlear outer hair cell - type II spiral ganglion afferents with protection from noise-induced hearing loss

The medial olivocochlear (MOC) efferent feedback circuit projecting to the cochlear outer hair cells (OHCs) confers protection from noise-induced hearing loss and is generally thought to be driven by inner hair cell (IHC) - type I spiral ganglion afferent (SGN) input. Knockout of the Prph gene (PrphKO) encoding the peripherin type III intermediate filament disrupted the OHC - type II SGN innervation and virtually eliminated MOC - mediated contralateral suppression from noise delivered to the opposite ear, measured as a reduction in cubic distortion product otoacoustic emissions. Electrical stimulation of the MOC pathway elicited contralateral suppression indistinguishable between wildtype (WT) and PrphKO mice, indicating that the loss of contralateral suppression was not due to disruption of the efferent arm of the circuit; IHC - type I SGN input was also normal, based on auditory brainstem responses. High-intensity, broadband noise (108 dB SPL, 1 hour) produced permanent hearing loss in PrphKO mice, but not in WT littermates. These findings associate OHC-type II input with MOC efferent - based otoprotection at loud sound levels.

neuroscience↗

bioRxiv2018

Conditional upregulation of KCC2 selectively enhances neuronal inhibition during seizures

Abstract/SummaryEfficacious neuronal inhibition is sustained by the neuronal K+Cl- co-transporter KCC2, and loss of KCC2 function through injury or mutation is associated with altered GABAergic signalling and neuronal seizures. Here we report a transgenic mouse with conditional KCC2 overexpression that results in increased membrane transport function. Increased KCC2 has little impact on behavioural and in vitro assays of neuronal excitability and GABAA receptor responses under resting conditions. In contrast, increased KCC2 imparts resistance to seizure-like neuronal activity in hippocampal slices and prevents the progression of mice into behavioural status epilepticus following multiple kainic acid doses. Our results demonstrate a transgenic mouse to facilitate investigations into the role of KCC2 in brain function, and provide a proof of principle that targeting KCC2 may be an effective way to selectively enhance neuronal inhibition to mitigate against diseases that involve an imbalance between excitation and inhibition.

neuroscience↗