Development of acoustically evoked and spontaneous pre- and postsynaptic discharge activity in the anteroventral cochlear nucleus (AVCN) and in the medial nucleus of the trapezoid body (MNTB): An melectrophysiological in vivo study in mice and Mongolian g

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Extracellular electrophysiological in vivo recordings will be performed in second order neurons (AVCN) and third order neurons (MNTB) of the ascending auditory system in mice and Mongolian gerbils between postnatal days 6 and 30. This period includes the time before the onset of acoustically evoked signal processing up to (almost) physiological maturity in central auditory signaling. In both target nuclei, the recordings will enable a differentiation between the presynaptic electrical activity and the postsynaptic activity (EPSP and/or action potential) of the respective principal neurons. The data will allow to scrutinize the postnatal development of (i) spontaneous and (ii) stimulus evoked discharge activity, (iii) changes in the reliability of synaptic transmission and (iv) in the synaptic delay in vivo. Mice were chosen as an experimental animal because of the potential use of genetically manipulated specimen in future experiments, and gerbils are specifically suited because of their distinctly developed sensitivity for low frequencies, which provides the opportunity for precise analysis of temporal aspects of signal processing (e.g. phase locking). Additional recordings on acute brainstem slices by means of multi-electrode arrays (MEA) will be performed from the respective neurons after electrical stimulation of the afferent fibers (i.e. auditory nerve fibers, fibers of the trapezoid body). This preparation allows selective pharmacological manipulations of pre- and postsynaptic discharge activity. This extracellular recording technique will be applied to link the results from the in vivo data to the large body of diverse experimental data obtained by patch clamp recordings.