[Tetanus toxin disturbance of 3H-GABA transport in the synaptosomes]

Synaptosomes isolated from the rat brain cortex were made use of to study the effect of tetanus toxin (TT) in doses of 1000-1200 MTD/ml (for rats) on 3H-GABA uptake and GABA and 3H-GABA release. After 15 minutes of incubating synaptosomes with TT, partial suppression of 3H-GABA release induced by K+-depolarization (30 and 40 mMK+) was discovered. TT did not suppress GABA release from synaptosomes (35-minute incubation), induced by ouabain (0.5 mM). Incubation of synaptosomes with TT in a Ca2+-containing medium for 2.5 h led to a noticeable (40%) suppression of their ability to accumulate 3H-GABA. Tetrodotoxin (10(-6)-10(-7)lg/1) increased 3H-GABA uptake but did not eliminate differences in the mediator uptake by poisoned and control synaptosomes. Incubation of synaptosomes with TT in media containing no Ca2+ was not followed by suppression of 3H-GABA uptake. The amount of 3H-GABA released during K+-depolarization by synaptosomes incubated with TT for 2.5 h was found to be less (with regard to the absolute magnitudes and proportion of 3H-GABA taken up) than in control.