GABAρ expression in the medial nucleus of the trapezoid body

Abstract

The Calyx of Held (CoH) synapse is the largest synapse in mammals. It is located in the medial nucleus of the trapezoid body (MNTB) and forms part of the auditory pathway. Modest GABAergic signaling is present in the CoH before hearing onset, when glutamatergic transmission predominates. In mice, after postnatal day 12, the absolute strength of glycinergic transmission increases markedly, while GABAergic signaling remains constant. The persistent GABAergic transmission in the MNTB is mediated by a slowly desensitizing component. In this study we recorded GABA-mediated responses from postsynaptic principal neurons (PPNs) of the MNTB and found that they are sensitive to TPMPA, suggesting the involvement of GABAρ subunits. RT-PCR and immunohistofluorescence in the MNTB confirmed GABAρ expression in PPNs. Interestingly, GABAρ3 was present only before hearing onset, and there was a switch to GABAρ1 and GABAρ2 expression in adult animals.