Mapping kainate activation of inner neurons in the rat retina.
Kainate receptors mediate fast, excitatory synaptic transmission for a range of inner neurons in the mammalian retina. However, allocation of functional kainate receptors to known cell types and their sensitivity remains unresolved. Using the cation channel probe 1-amino-4-guanidobutane agmatine (AGB), we investigated kainate sensitivity of neurochemically identified cell populations within the structurally intact rat retina. Most inner retinal neuron populations responded to kainate in a concentration-dependent manner. OFF cone bipolar cells demonstrated the highest sensitivity of all inner neurons to kainate. Immunocytochemical localization of AGB and macromolecular markers confirmed that type 2 bipolar cells were part of this kainate-sensitive population. The majority of amacrine (ACs) and ganglion cells (GCs) showed kainate responses with different sensitivities between major neurochemical classes (γ-aminobutyric acid [GABA]/glycine ACs > glycine ACs > GABA ACs; glutamate [Glu]/weakly GABA GCs > Glu GCs). Conventional and displaced cholinergic ACs were highly responsive to kainate, whereas dopaminergic ACs do not appear to express functional kainate receptors. These findings further contribute to our understanding of neuronal networks in complex multicellular tissues.
School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, 2052, Australia.
Lisa
L
Nivison-Smith
Daniel
D
Sun
Erica L
EL
Fletcher
Robert E
RE
Marc
Michael
M
Kalloniatis
D000376:Agmatine / Q000494:pharmacology; D025042:Amacrine Cells / Q000187:drug effects; D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D019084:Fluorescent Antibody Technique, Indirect; D018755:GABA Agonists / Q000494:pharmacology*; D018698:Glutamic Acid / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D007150:Immunohistochemistry; D007608:Kainic Acid / Q000494:pharmacology*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051245:Retinal Bipolar Cells / Q000187:drug effects / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology; D016610:Tissue Embedding / Q000379:methods; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018755:GABA Agonists; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D000376:Agmatine; D007608:Kainic Acid; D005998:Glycine