Local and commissural IC neurons make axosomatic inputs on large GABAergic tectothalamic neurons
Tetsufumi Ito1, Douglas L Oliver
1Department of Anatomy, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, Japan; Research and Education Program for Life Science, University of Fukui, Fukui, Japan.
The Journal of Comparative Neurology
|May 7, 2014
Summary
Local excitatory neurons in the inferior colliculus (IC) provide glutamate inputs to large GABAergic (LG) neurons. These findings reveal local circuit integration within the IC.
Area of Science:
- Neuroscience
- Cell Biology
- Auditory System Research
Background:
- Large GABAergic (LG) neurons in the inferior colliculus (IC) receive input via vesicular glutamate transporter 2 (VGLUT2)-containing terminals.
- The origin of these VGLUT2+ axosomatic terminals on LG neurons remains unidentified.
Purpose of the Study:
- To investigate the source of glutamatergic axosomatic inputs onto LG neurons within the IC.
- To test the hypothesis that local IC glutamatergic neurons provide these inputs.
Main Methods:
- Recombinant viral tracer injection into the IC for Golgi-like labeling (GFP) of neurons and their axons.
- Immunohistochemical analysis for VGLUT2 and GFP co-localization on axosomatic terminals of LG neurons.
Main Results:
- Co-localization of GFP and VGLUT2 (GFP+/VGLUT2+) confirmed glutamatergic axosomatic terminals on LG neurons.
- Terminals originated from nearby local IC neurons, forming 1-6 contacts per LG cell body.
- A single glutamatergic neuron could contact multiple LG neurons (9-30) within a localized axonal plexus.
Conclusions:
- Local excitatory IC neurons extensively innervate LG neuron cell bodies.
- LG neurons are significantly influenced by the activity of nearby laminar glutamatergic neurons in the IC.
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