[Increase in glutamate decarboxylase activity in the synaptosomes after treatment with tetanus toxin]

The tetanus toxin (TT) action on crude glutamic acid decarboxylase (GAD) preparation and GAD activity of synaptosomes were studied. TT was not found to affect GAD, but the GAD activity of synaptosomes isolated from the rat brain cortex increased by 46% after 15 min of incubation in the presence of a dose of 0.1 DLM TT. In some experiments, the GAD activity of a crude synaptosomal fraction isolated from TT affected lumbar segments of the rat spinal cord 48 hours after 0.2 DLM TT injection into the m. gastrocnemius was higher than in the control. If the GAD activity was evaluated in the presence of saturating concentrations of pyridoxal-5-phosphate, the difference in the GAD activities between the control and TT-affected synaptosomes (in vivo and in vitro) was not revealed. These findings allow the suggestion that the TT influences on GABA synthesis are mediated by membrane processes and that they occur at the level of the cofactor and apoenzyme interaction.