GAMMA-AMINOBUTYRIC ACID METABOLISM AND RADIATION-INDUCED

摘要

Miniature swine convulsed spontaneously within 30 seconds after a 10,000-rad dose of 30 MeV electrons was delivered to the brain. The seizures ended 2 to 5 minutes later. Since alterations in gamma-amino butyric acid (GABA) metabolism occur in and may be an underlying cause of a variety of convulsive disorders, regional brain concentrations of GABA and activities of L-glutamic acid decarboxylase (E. C. 4.1.1.15) (GAD) were determined in control and irradiated miniature swine. The hypothalamus and midbrain had the highest GABA concentration and GAD activity, followed, in de-creasing order of GABA concentration, by the caudate nucleus, thalamus, hippocampus, cerebral cortex and cerebellum. At 4 minutes after irradiation, GABA concentrations did not change significantly in any brain region examined; the largest apparent change was a decline from 2. 31 ± 13 to 2. 04 ± 11 tmoles/g wet weight in the thalamus. Concurrently, GAD activity in the thalamus increased significantly from 238 ± 7 to 315 ± 29 (umoles/h per g protein. Since inhibition of GAD and significant reduction in GABA concentrations are generally associated with convulsive disorders, these data are not consistent with the hypothesis that alterations in brain GABA metabolism play a role in the etiology or course of radiation-induced seizures in miniature swine.