GABA release mechanism in the golden hamster retina.
High K+ medium and glutamate elicited a significant [3H]-GABA release in the golden hamster retina. High K+ -induced GABA release was largely calcium-dependent, while the effect of glutamate was Ca2+ -independent. After replacing Na+ by Li+, glutamate-evoked [3H]-GABA release was abolished, while high K+ -evoked release remained unchanged. The effect of glutamate was completely blocked by DNQX but not by APV. Furthermore, kainate induced [3H]-GABA release, whereas NMDA was ineffective. Assessment of endogenous GABA efflux further confirmed results obtained for [3H]-GABA. GABA-like immunoreactivity was observed in amacrine cells, in neurons localized in ganglion cell layer, as well as in fibers and terminals at the inner plexiform layer. In addition a few horizontal cells showed GABA-like immunolabeling. The present results suggest the existence of at least two pools of GABA in the hamster retina, compatible with both vesicular and carrier-mediated mechanisms of transmitter release, being the amacrine cells the main gabaergic source in this tissue.
Instituto de Biología Celular y Neurociencia, Prof. Eduardo De Robertis, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
J J
JJ
López-Costa
J
J
Goldstein
J
J
Pecci-Saavedra
V M
VM
Della Maggiore
M A
MA
De Las Heras
M I
MI
Sarmiento
R E
RE
Rosenstein
D000818:Animals; D006224:Cricetinae; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D008297:Male; D011188:Potassium / Q000494:pharmacology; D017470:Receptors, Glutamate / Q000187:drug effects; D012160:Retina / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D005680:gamma-Aminobutyric Acid; D011188:Potassium