Journal of Neuroscience, Vol 6, 1621-1627, Copyright © 1986 by Society for Neuroscience
Localization of 3H-GABA, -muscimol, and -glycine in goldfish retinas stained for glutamate decarboxylase
AK Ball and C Brandon
Glutamic acid decarboxylase (GAD), the synthesizing enzyme for the
neurotransmitter GABA, has been localized in goldfish retina using a new
antiserum. We observed at least six types of GAD-immunoreactive amacrine
cells, one of which was large and pyriform (Ab type). In addition,
immunoreactive synaptic terminals were located throughout the inner
plexiform layer (IPL). Amacrine cells that were GAD- immunoreactive also
had high-affinity uptake mechanisms for both 3H- GABA and 3H-muscimol that
were detectable autoradiographically. Type Ab pyriform amacrine cells were
heavily labeled because of 3H-GABA uptake and were GAD-immunoreactive.
Other types of GAD-immunoreactive amacrine cells, including a subpopulation
of Ab amacrines, were lightly labeled because of 3H-GABA uptake. Because
the same neurons that were GAD- immunoreactive also accumulated 3H-GABA and
3H-muscimol, these three are appropriate markers for GABAergic cells in the
goldfish retina. However, the uptake of 3H-muscimol by many
non-GAD-immunoreactive cells, detectable at longer autoradiographic
exposure times, indicates that this label must be used with caution. Thirty
percent of goldfish retinal amacrine cells are GABAergic, and their
processes are distributed throughout all levels of the IPL. Few
GAD-immunoreactive amacrine cells accumulated 3H-glycine, so the goldfish
retina contains distinct populations of glycinergic and GABAergic amacrine
cells.