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Development of gaba binding sites in chick embryo optic lobe: Effect of triton X‐100
Author(s) -
Flores Vladimir,
Rios Hugo,
Plazas Sara Fiszer
Publication year - 1986
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/0736-5748(86)90013-4
Subject(s) - incubation , bicuculline , gabaa receptor , hatching , binding site , medicine , biology , endocrinology , receptor , gaba receptor , muscimol , incubation period , stimulation , chemistry , biochemistry , zoology
The temporal course of the development of GABA receptor sites in chick optic lohe was studied as a parameter of neuronal differentiation in the central nervous system. At 10 days of incubation, specific [ 3 H]GABA binding was of 0.08 pmol/optic lobe and increased 7–8 fold between 12 and 16 days of incubation, reaching at 16 days a value of 0.60 pmol/optic lobe. This coincides with the period of arrival of the retinal fibers to the optic lobe. After this stage, the number of GABA binding sites decreased to a value of 0.35 pmol/optic lobe at hatching. After hatching a new increase appeared which reached at 5 days post‐hatching a value of 0.87 pmol/optic lobe. Scatchard analysis of the saturation binding data obtained at 16 days of incubation and at hatching revealed the presence of two binding sites: one with high affinity and the other with low affinity, while at 12 days of incubation, the earliest stage examined, only the low‐affinity binding site appeared. The high‐affinity binding site for [ 3 H]GABA was inhibited by muscimol, GABA, and bicuculline ( ic 50 : 0.006, 0.002 and 10 μM, respectively). These values correspond to the potencies shown by those compounds in the binding to the synaptic GABA receptor. Treatment of the synaptic membranes with Triton X‐100) showed a marked increase in the amount of specific [ 3 H]GABA binding after 16 days of incubation reaching a 3‐fold increase at hatching. These results suggest that endogenous inhibitors of the higher affinity binding site, probably appear during this period.