Volume electron microscopy reveals age-related circuit remodeling in the auditory brainstem

CHEQUER CHARAN DM; BOERGENS KM; HUANG W; GOMEZ-CASATI ME; ELGOYHEN AB; CHEQUER CHARAN DM, HUANG W, GÓMEZ-CASATI ME, WEDEMEYER C, ELGOYHEN AB, HUA Y & DI GUILMI MN; DI GUILMI MN

Buenos Aires

Congreso; XXXVII Annual Meeting of the Argentine Society for Neuroscience; 2022

Sociedad Argentina de Investigacion en Neurociencias

Medial nucleus of the trapezoid body (MNTB) neurons are an integral component of the auditory brainstem circuitry involved in sound localization. In order to study how neural connectivity is refined post-hearing onset in this nucleus, we used serial block-face electron microscopy (SBEM) in mice at different ages (3 weeks, 6 and 18 months). We acquired circuitry-level data volumes of the MNTB neurons which allows a comprehensive neuro-morphological investigation of age-related changes. We found that the total number of MNTB cells is reduced with age. Moreover, the accumulation of age pigment on MNTB cells increased with age. The morphology of the presynaptic terminal, the calyx of Held, was heterogeneous independently of age but degenerated terminals were strongly evident in older animals along the tonotopic axes. Interestingly, poly-innervated MNTB cells were present not only in young but also in older animals being more frequent in the low frequency region. This last observation demonstrates that the multiple innervations of the MNTB is not only restricted to the developmental critical period, but that it is also present throughout life. As a conclusion, our data supports the notion that age-related hearing impairments can be in part a direct consequence of several morphological alterations at the brainstem level.