Developmental changes in the excitatory short-term plasticity at input synapses in the rat inferior colliculus.

The inferior colliculus (IC) is the primal center of convergence and integration in the auditory pathway. Although extensive functional changes are known to occur at the relay synapses in the auditory brainstem during development, the changes in the IC remain to be investigated. Here, we have measured excitatory postsynaptic currents (EPSCs) of the neurons in the central nucleus of the IC in response to stimulation of either the lateral lemniscus or the commissure of the inferior colliculus. Before hearing onset, the lemniscus inputs exhibited short-term depression, whereas commissural inputs showed facilitation. After hearing onset, the N-methyl-d-aspartate-EPSCs exhibited faster decay for both pathways, whereas the decay of the AMPA-EPSCs were unaltered. Furthermore, the EPSCs showed more constant responses during repetitive stimulation in both pathways. These developmental changes ensure faster and more reliable signal transmission to the inferior colliculus after onset of hearing.