Interaction between enkephalin and gamma-aminobutyric acid in the chicken retina: a double-label immunoelectron microscopic analysis.
In the present study, double-label immunoelectron microscopy was used to examine the synaptic relationships between amacrine cell populations in the chicken retina that contain either enkephalin or gamma-aminobutyric acid (GABA) or both enkephalin and GABA. The objectives of the present study were twofold. First, the ultrastructural features and synaptic organization of enkephalin and enkephalin/GABA amacrine cells were compared. Second, the synaptic interactions between these populations and the population of GABA amacrine cells were examined. A total of 475 synaptic arrangements were observed to involved enkephalin or enkephalin/GABA amacrine cell processes. The synaptic relationships of enkephalin and enkephalin/GABA amacrine cells were quite similar. Each population was pre- and postsynaptic to amacrine cells, postsynaptic to bipolar cells, and presynaptic to processes possibly originating from ganglion cells. A substantial percentage of each population's pre- and postsynaptic relationships were with the processes of GABAergic amacrine cells. Moreover, when enkephalin and enkephalin/GABA amacrine cell processes were postsynaptic to bipolar cells, their dyadic partner was observed frequently to be a GABA amacrine cell process. The present study suggests a diversity in the population of chicken enkephalin amacrine cells with respect to their expression of the classical inhibitory transmitter GABA. Moreover, a functional relationship between enkephalinergic and GABAergic pathways is indicated by studies showing that both enkephalin and enkephalin/GABA amacrine cells exhibit substantial synaptic interaction with GABA amacrine cells.
Watt
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CB
Alice R. McPherson Laboratory of Retina Research, Baylor College of Medicine, The Woodlands, Texas 77381.
Glazebrook
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PA
D000818:Animals; D002645:Chickens / Q000378:metabolism*; D004745:Enkephalins / Q000378:metabolism*; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D012160:Retina / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D004745:Enkephalins; D005680:gamma-Aminobutyric Acid