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The solubilization and partial purification from rat brain cortex homogenates of ["H]y-aminobutyric acid (GABA) and ["Hldiazepam recognition sites and of their endogenous modulators (GABAmodulin and an endogenous compound which displaces specifically bound ["Hldiazepam) are reported. A high percentage of GABA binding sites (virtually free of benzodiazepine binding sites) was solubilized from homogenates of rat brain cortex incubated at 0°C with 1% Triton X-100 and a mixture of protease inhibitors. A large proportion of benzodiazepine binding sites was solubilized in the absence of apparent GABA binding capacity by incubating crude synaptic membrane preparations at 37°C with 0.05% Triton X-100. The characteristics of these two solubilized binding sites resemble those of the membrane-bound binding sites. However, unlike the membrane-bound sites, solubilized GABA and benzodiazepine recognition sites have lost the ability to cross-react. Hence, solubilized benzodiazepine binding sites are insensitive to GABA stimulation, while solubilized GABA binding sites are no longer protected by the benzodiazepines against heat inactivation. These results indicate that GABA and benzodiazepine recognition sites reside in two different molecules which, when bound to membranes, can interact reciprocally and modulate their binding affinity for specific ligands.

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Abstract— The distribution of taurine was investigated in 16 areas of the brain, in cats transected either at collicular or at midpontine level. A comparison was also made between the content in the same areas of the cerebral cortex of the two groups of cats showing respectively either a synchronized or an activated electrocorticogram. Taurine was determined in picric acid extracts by means of column chromatography followed by thin layer chromatography of the eluates. The levels of taurine were fairly uniform in all areas investigated with the exception of the lateral geniculate bodies, the pituitary gland and the pineal gland where the levels were higher than in all other regions. The taurine content of the cortex of cats showing a synchronized EEG pattern was higher than in the cortex of cats showing an activated pattern. The results are discussed in the light of the limited information available on the possible role of taurine in the CNS.

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