Two Classes of GABAergic Neurons in the Inferior Colliculus

Abstract

The inferior colliculus (IC) is unique, having both glutamatergic and GABAergic projections ascending to the thalamus. Although subpopulations of GABAergic neurons in the IC have been proposed, criteria to distinguish them have been elusive and specific types have not been associated with specific neural circuits. Recently, the largest IC neurons were found to be recipients of somatic terminals containing vesicular glutamate transporter 2 (VGLUT2). Here, we show with electron microscopy that VGLUT2-positive (VGLUT2

Auditory System

“…3, 23, 27 and 28;González-Hernández et al, 1991;Peruzzi et al, 1997;Oliver et al, 1999;Ito et al, 2009;Ito and Oliver, 2012) and descending projections to the superior olivary complex and the cochlear nuclear complex (Fig. 29;Warr, 1992;Caicedo and Herbert, 1993;Saldaña, 1993;Vetter et al, 1993).…”

“…The CIC has also a weaker projection to the medial and dorsal divisions. The CIC projections originate from both the F and LF neurons (Peruzzi et al, 1997;Oliver et al, 1999;Ito et al, 2009;Ito and Oliver, 2012).…”

Effects of Pulse Phase Duration and Location of Stimulation Within the Inferior Colliculus on Auditory Cortical Evoked Potentials in a Guinea Pig Model

“…None of the cases produced any significant trends (P≫0.05) for latency shifts as a function of stimulation location. For more details on the analysis method, see Results: "Latency versus location" 2005) and/or within the medial geniculate nucleus (Winer et al 1996;Peruzzi et al 1997;Bartlett et al 2000;Ito et al 2009;Lee and Sherman 2010) that may not sufficiently respond to the artificially synchronized activation of groups of neurons induced by electrical stimulation. There is some evidence in the cat that greater inhibitory patterns are observed in caudal ICC regions compared to more rostral regions in response to ipsilateral pure tone stimulation based on 2-deoxyglucose mapping (Webster et al 1984).…”

“…Furthermore, the largest tectothalamic neurons are inhibitory (i.e., GABAergic), represent up to 45% (in rat; 20% in cat) of the ascending projections, and provide fast transmission to the medial geniculate nucleus that can precede the excitatory tectothalamic input (Winer et al 1996;Peruzzi et al 1997;Ito et al 2009). Although these inhibitory projections do not appear to be clustered only within the caudal ICC, it is possible that a specific inhibitory circuitry within the medial geniculate nucleus suppresses thalamic activity to electrical stimulation of the caudal ICC.…”

Postnatal development of synaptic properties of the GABAergic projection from the inferior colliculus to the auditory thalamus

“…However, the MGB also receives a unique, feedforward, monosynaptic, GABAergic input from the IC, which constitutes approximately one-third of the total projections from the IC to the rat and cat MGB (Bartlett and Smith 1999;Peruzzi et al 1997;. The IC-MGB inhibitory connection consists predominantly of large GABAergic neurons in the central nucleus of the IC, dorsal and lateral cortices on the input side (Geis and Borst 2012;Ito et al 2009;Ito and Oliver 2012;Peruzzi et al 1997), that project to thalamocortical relay neurons mainly in the MGB ventral (MGBv) and dorsal (MGBd) subdivisions (Bartlett and Smith 1999;Lee and Sherman 2010;Peruzzi et al 1997). These are the two largest subdivisions in MGB and are considered to be lemniscal and nonlemniscal, respectively (Anderson and Linden 2011;Bordi and LeDoux 1994;Calford 1983;Calford and Aitkin 1983;Edeline et al 1999;Morel et al 1987).…”