Synaptic Effects of Systemic -Amino Butyric Acid in Cortical Regions of Increased Vascular Permeability

Abstract

The effects of systemically administered gamma-amino butyric acid (GABA) on spontaneous and evoked responses are compared in normal cortical regions and regions of local blood-brain barrier destruction produced by topical application of ethyl chloride or chloroform-methanol. In the latter regions, injected GABA (8 to 50 mg/kg) rapidly inactivates surface evoked dendritic post synathic potentials, whereas simultaneously evoked axo-somatic synaptic activity is unaffected. Low frequency paroxysmal discharges developing in regions of barrier destruction are abolished by systemic GABA (30 to 50 mg/kg). No electrophysiological effects are detectable in normal cortex. It is concluded that the effects produced by systemic administration of GABA in regions of blood-brain barrier loss are qualitatively similar to those produced by topical applications of the amino acid. Under ordinary conditions, GABA does not effectively penetrate the blood-brain barrier.