Inputs from three brainstem sources to identified neurons of the mouse inferior colliculus slice

A total of 40 neurons from of the central nucleus of the mouse inferior col liculus (IC) were recorded intracellularly from brain slices to determine i nput properties by electrical stimulation of the ipsilateral lateral lemnis cus (LL), commissure of Probst (CP), and commissure of the IC (CoIC) togeth er with cellular morphology (in 25 neurons) by biocytin injection and stain ing. Nine neurons had oriented (bipolar), 16 neurons non-oriented (multipol ar) dendritic trees of various sizes. Axon collaterals of a given neuron of ten ran in several directions to provide multiple input to adjacent isofreq uency laminae, the lateral nucleus of the IC, the brachium of the IC, the L L, the CP, and the IC commissure. Neurons were classified by spike response patterns to depolarizing current injection into onset- and sustained-spiki ng cells. The former had significantly shorter membrane-time constants, sig nificantly less frequently and smaller hyperpolarizations after spike occur rence, and more Ca2+-humps. These properties and their preferred position i n the dorsolateral ICC suggest a participation in binaural temporal process ing. Almost all oriented cells showed only excitatory post-synaptic potenti als (EPSPs) after LL stimulation, while in non-oriented cells inhibitory po st-synaptic potentials (IPSPs) after the EPSPs were significantly more freq uent. Neurons with largest dendritic trees and many dorsalward projecting a xon collaterals were found in the ventral IC. There, neurons had average 4 ms (two synapses) shorter response latencies to LL stimulation than dorsall y located neurons. Thus, neurons in the central and dorsal IC may receive m ono- and disynaptic input from ventrally located neurons. (C) 1999 Elsevier Science B.V. All rights reserved.