Journal of Neuroscience, Vol 8, 3383-3394, Copyright © 1988 by Society for Neuroscience
Dopaminergic and indoleamine-accumulating amacrine cells express GABA- like immunoreactivity in the cat retina
H Wassle and MH Chun
Max-Planck-Institut fur Hirnforschung, Frankfurt, West Germany.
Colocalization of indoleamine uptake and GABA-like immunoreactivity was
studied in the cat retina. Consecutive, semithin sections were incubated in
antisera to either 5-HT (5-hydroxytryptamine) or GABA. More than 90% of all
5-HT-accumulating amacrine cells expressed GABA- like antigens. With the
same approach, the colocalization of 5-HT uptake and GABA-like
immunoreactivity was studied in rabbit and 75-80% of the 5-HT-accumulating
amacrine cells expressed GABA-like immunoreactivity, thus confirming a
previous study (Osborne and Beaton, 1986). Since, in both cat and rabbit,
endogenous 5-HT could not be found by immunocytochemistry, one must
consider the possibility that some GABAergic amacrine cells take up
indoleamines. In the cat retina, antibodies against tyrosine hydroxylase
(TH) label dopaminergic amacrine cells (Oyster et al., 1985). By incubating
consecutive, semithin sections in antisera to either TH or GABA, it was
found that 84% of the dopaminergic amacrine cells also expressed GABA-like
immunoreactivity. GABA-like immunoreactivity and 3H-muscimol uptake were
found to be colocalized in more than 90% of the amacrine cells labeled.
However, dopaminergic amacrine cells did not accumulate 3H- muscimol.
Evidence is presented from colocalization studies for 2 types of
interplexiform cell in the cat retina. One is stained by GABA-like
immunocytochemistry and by 3H-muscimol uptake. The other is the
dopaminergic amacrine cell, which also expresses GABA-like
immunoreactivity, but does not accumulate 3H-muscimol.
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