γ‐AMINOBUTYRTC ACID RECEPTORS IN CEREBELLAR MEMBRANES OF RAT BRAIN AFTER A TREATMENT WITH TRITON X‐100¹

Abstract

Abstract— The treatment of cerebellar membranes of rat brain with a low concentration of Triton X‐100 followed by sufficient washing results in an increase of the Na + ‐independent binding of [ 3 H]GABA and a total loss of the Na + ‐dependent binding of [ 3 H]GABA. The Na + ‐independent binding of [ 3 H]GABA was more abundant in membranes of cerebellum than in membranes of other rat brain regions and mainly localized in the synaptic membrane fraction of a cerebellar homogenate. In the Triton‐treated membranes, the Na + ‐independent binding of [ 3 H]GABA was a saturable process, which could be resolved into two components, a high and a low affinity component with dissociation constants of 4.5 and 30 n m , respectively. The neurophysiological agonists, muscimol, GABA, and imidazole acetic acid, and the antagonist, bicuculline, inhibited the high affinity Na + ‐independent binding of [ 3 H]GABA by 50% at 0.003, 0.012, 0.3 and 10 μ m respectively. These data suggest that the Na + ‐independent binding of [ 3 H]GABA in the Triton‐treated cerebellar membranes represents the synaptic receptors of GABA. It is emphasized that extensive washing of the membranes after a Triton treatment is necessary in order to detect the high affinity Na + ‐independent binding of [ 3 H]GABA.