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Characterization of Na + ‐Independent GABA and Flunitrazepam Binding Sites in Preparations of Synaptic Membranes and Postsynaptic Densities Isolated from Canine Cerebral Cortex and Cerebellum
Author(s) -
Carlin Richard K.,
Siekevitz Philip
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb12837.x
Subject(s) - cerebellum , inhibitory postsynaptic potential , cerebral cortex , excitatory postsynaptic potential , postsynaptic potential , biophysics , flunitrazepam , binding site , membrane , chemistry , postsynaptic density , cerebellar cortex , neuroscience , biology , biochemistry , receptor , gabaa receptor
The binding of [ 3 H]GABA and [ 3 H]flunitrazepam was performed with synaptic membranes and postsynaptic densities (PSDs) isolated from canine cerebral cortex and cerebellum. Two GABA binding sites were found with cerebral cortex membranes but only one with cerebellar membranes. PSDs isolated from these showed only single binding sites, with cerebellar PSDs exhibiting lower K D values and a larger concentration of sites than did cerebral cortex PSDs. In the case of flunitrazepam, only one binding site was found for all four preparations, with cerebellar PSDs having twice the concentration of sites of cerebral PSDs. Photoaffinity labeling of the flunitrazepam receptor in PSDs resulted in the binding to a 51,000 M r protein in both cases, with cerebellar PSDs again showing an increased concentration over that found in cerebral cortex PSDs. Based on this work, and on earlier work of ourselves and of others, we conclude that both populations of isolated PSDs contain inhibitory sites, but that the intact PSDs in both preparations are derived from Gray type I, probably excitatory, synapses, and that the inhibitory sites are found in the broken‐up material in the PSD fractions which are derived from Gray type II, probably inhibitory, synapses.