Journal of Neuroscience, Vol 11, 111-122, Copyright © 1991 by Society for Neuroscience
Acetylcholine release from the rabbit retina mediated by kainate receptors
DM Linn, C Blazynski, DA Redburn and SC Massey
Sensory Sciences Center, Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston 77030.
The cholinergic amacrine cells of the rabbit retina may be labeled with
3H-choline (3H-Ch), and the activity of the cholinergic population may be
monitored by following the release of 3H-ACh. Glutamate analogs caused
massive ACh release, up to 50 times the basal efflux, with the following
rank order of potency: alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic
acid (AMPA) greater than quisqualate (QQ) = kainate (KA) much greater than
NMDA (in magnesium-free medium) much greater than glutamate greater than
aspartate. In contrast, the release of 3H- Ch was unchanged. Submaximal
doses of each agonist were used to establish the specifity of glutamate
antagonists. Kynurenic acid was selective for KA much greater than QQ, and
6,7-dinitroquinoxaline-2,3- dione (DNQX) was selective for KA greater than
QQ much greater than NMDA. At low doses, which selectively blocked the
response to KA, both antagonists blocked the light-evoked release of ACh.
These results suggest that ACh release may be produced via several
glutamate receptors, but the physiological input to the cholinergic
amacrine cells is mediated by KA receptors. Because these cells receive
direct input from cone bipolar cells, this work supports previous evidence
that the bipolar cell transmitter is glutamate.