Effect of Plasmodium yoelii infection on GABA metabolism of mouse brain.

Plasmodium yoelii infection in albino mice decreased the activity of brain glutamic acid decarboxylase (GAD) by about 30 and 48% in crude homogenate and its synaptosomal fraction, respectively. The decrease was evident from 20% parasitemia and remained more or less constant up to 80% parasitemia. The Km values of GAD in normal and infected animals were 1.2 x 10(-2) and 3.3 x 10(-2) mM, respectively, indicating a decrease in enzyme substrate affinity due to infection. The lowered GAD activity rose to slightly above normal by treatment of infected animals with chloroquine. Decrease in GAD activity reflected lower gamma-aminobutyric acid (GABA) levels in the infected brain; however, GABA-transaminase activity was not significantly influenced by infection. It has been proposed that impaired GABA synthesis may be due to hypoxia induced by malarial infection.