Lemniscal input to identified neurons of the central nucleus of mouse inferior colliculus: an intracellular brain slice study.

Intracellular recordings were performed in 34 neurons in the central nucleus of the inferior colliculus in brain slice preparations of the mouse. Sixteen neurons recorded were stained intracellularly by injection of biocytin and identified as multipolar. After electrical stimulation of the lateral lemniscus, 32 of 34 neurons exhibited postsynaptic potentials (PSPs). Onset latencies of the PSPs were 5.0 +/- 2.8 ms (range 2-12 ms), presumably reflecting the lack of a significant monosynaptic input to most of the neurons recorded. An excitatory PSP (EPSP), often followed by a late inhibitory PSP (IPSP), was present in all neurons which received synaptic input. The IPSPs usually had a reversal potential positive to the cell's resting membrane potential, thus working as shunting inhibitors. Superfusion of the slice with the GABAA antagonist bicuculline resulted in blockade of the IPSP and pronounced prolongation of the EPSP. In 50% of these cases, paroxysmal depolarizing shifts were observed in the presence of bicuculline. Blocking the non-NMDA glutamate receptors with 6,7-dinitroquinoxaline-2,3-dione resulted not only in the total disappearance of EPSPs but also of late IPSPs, indicating that the latter depend on the glutamatergic EPSPs. Furthermore, all neurons recorded must receive substantial innervation from sources within the inferior colliculus, together constituting a complex neuronal network in the inferior colliculus with an important role of the inhibitory neurotransmitter GABA in controlling network properties.