Brain ischemia increased high affinity binding of [3H]muscimol into synaptic plasma membrane receptor

Abstract

The authors investigated the high affinity binding of [3H]muscimol to the receptor of synaptic plasma membranes (SPM) isolated from a normoxic and ischemic brain. Brain ischemia enhanced the [3H] muscimol binding to the receptor, located in native (Triton X-100 untreated) membranes. Scatchard’s analysis showed that the total number of binding sites [B(MAX)] and the K(D) value increased by about 60 percent. The higher K(D) value persisted during 20 min of the reperfusion period. Concomitantly, ischemia stimulated the activity of phospholipase C and phospholipase A(2), acting against phosphatidylinositol (PI). The degradation of PI and a transient accumulation of docosahexaenoic and arachidonic acids may be important factors involved in the modification of high affinity agonist binding to the GABAA receptor of SPM isolated from the brain submitted to ischemia.