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

J Comp Neurol. 2015 Dec 15;523(18):2683-97. doi: 10.1002/cne.23810. Epub 2015 Aug 10.


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.

Keywords: AB_2278725; AB_90953; GAD67; GLYT2; auditory pathways; presynaptic terminals; ratiometric analysis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Brain Mapping
  • Channelrhodopsins
  • Female
  • Glutamate Decarboxylase / genetics
  • Glutamate Decarboxylase / metabolism
  • Glycine / metabolism*
  • Glycine Plasma Membrane Transport Proteins / genetics
  • Glycine Plasma Membrane Transport Proteins / metabolism
  • Inferior Colliculi / metabolism*
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Rats
  • Rats, Long-Evans
  • Vesicular Inhibitory Amino Acid Transport Proteins / genetics
  • Vesicular Inhibitory Amino Acid Transport Proteins / metabolism
  • gamma-Aminobutyric Acid / metabolism*


  • Bacterial Proteins
  • Channelrhodopsins
  • Glycine Plasma Membrane Transport Proteins
  • Luminescent Proteins
  • Slc6a5 protein, mouse
  • Vesicular Inhibitory Amino Acid Transport Proteins
  • Viaat protein, mouse
  • yellow fluorescent protein, Bacteria
  • gamma-Aminobutyric Acid
  • Glutamate Decarboxylase
  • glutamate decarboxylase 1
  • Glycine