Dataset Information

Differential distribution of GABA and glycine terminals in the inferior colliculus of rat and mouse.

ABSTRACT: The inferior colliculus (IC), the midbrain component of the auditory pathway, integrates virtually all inputs from the auditory brainstem. These are a mixture of excitatory and inhibitory ascending inputs, and the inhibitory transmitters include both gamma-aminobutyric acid (GABA) and glycine (GLY). Although the presence of these inhibitory inputs is well established, their relative location in the IC is not, and there is little information on the mouse. Here, we study the distribution of glutamic acid decarboxylase (GAD)67 and GLY transporter 2 (T2) in axonal terminals to better understand the relative contributions of these inputs. Large-scale mosaic composite images of immunohistochemistry sections of rat and mice were used to isolate the signals related to the concentrations of these axonal terminals in the tissue, and the ratio of GLYT2/GAD67 in each pixel was calculated. GLYT2 was seen only in the central nucleus of the IC (ICC), whereas GAD67 was seen throughout the IC. The map of the GAD67 and GLYT2 axonal distribution revealed a gradient that runs from ventrolateral to dorsomedial along the axis of the laminae of the ICC and perpendicular to the tonotopic axis. Although anatomically different, both the mouse and the rat had relatively more GAD67 dorsomedially in the ICC and relatively more GLYT2 ventrolaterally. This organization of GABA and GLY inputs may be related to functional zones with different properties in ICC that are based, in part, on different sets of inhibitory inputs to each zone.

SUBMITTER: Choy Buentello D

PROVIDER: S-EPMC4607567 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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Publications

Differential distribution of GABA and glycine terminals in the inferior colliculus of rat and mouse.

Choy Buentello David D Bishop Deborah C DC Oliver Douglas L DL

The Journal of comparative neurology 20150810 18

The inferior colliculus (IC), the midbrain component of the auditory pathway, integrates virtually all inputs from the auditory brainstem. These are a mixture of excitatory and inhibitory ascending inputs, and the inhibitory transmitters include both gamma-aminobutyric acid (GABA) and glycine (GLY). Although the presence of these inhibitory inputs is well established, their relative location in the IC is not, and there is little information on the mouse. Here, we study the distribution of glutam ...[more]

PMID: 25976159

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Project description:The corelease of several neurotransmitters from a single synaptic vesicle has been observed at many central synapses. Nevertheless, the signaling synergy offered by cotransmission and the mechanisms that maintain the optimal release and detection of neurotransmitters at mixed synapses remain poorly understood, thus limiting our ability to interpret changes in synaptic signaling and identify molecules important for plasticity. In the brainstem and spinal cord, GABA and glycine cotransmission is facilitated by a shared vesicular transporter VIAAT (also named VGAT), and occurs at many immature inhibitory synapses. As sensory and motor networks mature, GABA/glycine cotransmission is generally replaced by either pure glycinergic or GABAergic transmission, and the functional role for the continued corelease of GABA and glycine is unclear. Whether or not, and how, the GABA/glycine content is balanced in VIAAT-expressing vesicles from the same terminal, and how loading variability effects the strength of inhibitory transmission is not known. Here, we use a combination of loose-patch (LP) and whole-cell (WC) electrophysiology in cultured spinal neurons of GlyT2:eGFP mice to sample miniature inhibitory post synaptic currents (mIPSCs) that originate from individual GABA/glycine co-releasing synapses and develop a modeling approach to illustrate the gradual change in mIPSC phenotypes as glycine replaces GABA in vesicles. As a consistent GABA/glycine balance is predicted if VIAAT has access to both amino-acids, we test whether vesicle exocytosis from a single terminal evokes a homogeneous population of mixed mIPSCs. We recorded mIPSCs from 18 individual synapses and detected glycine-only mIPSCs in 4/18 synapses sampled. The rest (14/18) were co-releasing synapses that had a significant proportion of mixed GABA/glycine mIPSCs with a characteristic biphasic decay. The majority (9/14) of co-releasing synapses did not have a homogenous phenotype, but instead signaled with a combination of mixed and pure mIPSCs, suggesting that there is variability in the loading and/or storage of GABA and glycine at the level of individual vesicles. Our modeling predicts that when glycine replaces GABA in synaptic vesicles, the redistribution between the peak amplitude and charge transfer of mIPSCs acts to maintain the strength of inhibition while increasing the temporal precision of signaling.

Dataset Information

Differential distribution of GABA and glycine terminals in the inferior colliculus of rat and mouse.

Publications

Differential distribution of GABA and glycine terminals in the inferior colliculus of rat and mouse.

Similar Datasets

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