Impact of cochlear ablation on calretinin and synaptophysin in the gerbil anteroventral cochlear nucleus before the hearing onset

Ivonne Bazwinsky-Wutschke; Faramarz Dehghani

doi:10.1016/j.jchemneu.2020.101746

Impact of cochlear ablation on calretinin and synaptophysin in the gerbil anteroventral cochlear nucleus before the hearing onset

J Chem Neuroanat. 2020 Jan 13:104:101746. doi: 10.1016/j.jchemneu.2020.101746. Online ahead of print.

Authors

Ivonne Bazwinsky-Wutschke¹, Faramarz Dehghani²

Affiliations

¹ Department of Biology, University of Leipzig, Talstrasse 33, D-04103 Leipzig, Germany; Department of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Grosse Steinstrasse 52, D-06108 Halle (Saale), Germany. Electronic address: ivonne.bazwinsky@medizin.uni-halle.de.
² Department of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Grosse Steinstrasse 52, D-06108 Halle (Saale), Germany.

PMID: 31945410
DOI: 10.1016/j.jchemneu.2020.101746

Abstract

Mammalian auditory system undergoes many structural and functional modifications during postnatal development, which are dependent on the relationship between auditory nerve fibers and their nuclei. In the present study, the cochlea of Meriones unguiculatus was ablated unilaterally on postnatal day 5 or 9 (P5 or P9), before the onset of hearing. Histochemical analysis of synaptophysin (SYN) and calretinin (CR) in anterior anteroventral cochlear nucleus (AVCN-A) was performed to analyze whether unilateral cochlea ablation induces changes in the auditory terminal endings and somata of spherical bushy cells (SBCs). During the period of postnatal development, CR-labeling was evident in somata of SBCs and in auditory nerve terminals. SYN was most apparent in puncta encircled cell bodies, progressing with age. Cochlear removal at P5 induced a decrease in CR-labeling in SBCs somata 6 h and 48 h post-lesion; whereas, ablation at P9 increased the somatic CR-labeling in the lesioned AVCN-A after 24 and 48 h post-lesion. The SYN-labeled synaptic puncta were remarkably reduced in the AVCN-A of P5- and P9-cochlea-ablated gerbils with stronger effects in P5 animals (a 50% reduction after 48 h). Interestingly, a significant increase in the SYN-immunolabeled puncta was found after 48 h compared to 24 h in the lesioned AVCN-A of P9 gerbils, indicating reactive synaptogenesis. Our study shows, that following the destruction of the cochlea at different postnatal periods, the CR- and SYN-labeling are differentially influenced in the AVCN-A, which in turn coincides with different critical developmental periods before the onset of hearing.

Keywords: Auditory brainstem; Calcium-binding proteins; Cochlear nucleus; Cochlear removal; Sensitive period; Synaptic terminals.