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Regional differences in GABA and GAD immunoreactivity in rabbit horizontal cells
1Department of Neuroscience, University of Pennsylvania, Philadelphia 19104-6058, USA.
Visual Neuroscience
|July 31, 1998
Summary
Rabbit horizontal cells are confirmed to be GABAergic, expressing glutamic acid decarboxylase (GAD). Different GAD isoforms (GAD65 and GAD67) are found in distinct cell parts, suggesting varied GABA release mechanisms.
Area of Science:
- Neuroscience
- Retinal Physiology
Background:
- Mammalian horizontal cells are generally considered GABAergic, based on GABA and glutamic acid decarboxylase (GAD) presence.
- Previous studies in adult rabbits showed inconsistent GABA and GAD immunoreactivity in horizontal cells, questioning their GABAergic nature.
Purpose of the Study:
- To investigate the GABAergic status of horizontal cells in the adult rabbit retina.
- To identify the specific isoforms of GAD present in rabbit horizontal cells and their cellular localization.
Main Methods:
- Immunohistochemistry was used to detect GAD65 and GAD67 isoforms in rabbit horizontal cells.
- Calbindin immunoreactivity identified type A horizontal cell somas and dendrites in the visual streak.
- Double-labeling experiments combined GAD65 and GABA staining.
Main Results:
- All horizontal cell terminals (type A and B) immunostained for GAD67.
- Type A horizontal cell somas and dendrites in the visual streak immunostained for GAD65.
- All cells positive for GAD65 were also positive for GABA.
Conclusions:
- Rabbit horizontal cells express GAD67 in terminals and GAD65 in somas/dendrites, confirming they are GABAergic.
- The distinct localization of GAD isoforms suggests compartmentalized GABA synthesis and release.
- This compartmentalization may indicate different release mechanisms for GABA from different cellular compartments.