Tetanus toxin inhibits depolarization-induced [3H]serotonin release from rat brain cortex synaptosomes

The effect of tetanus toxin on depolarization-induced [³H]serotonin release from superfused rat brain cortex synaptosomes was investigated. Two hours' preincubation of the synaptosomes with tetanus toxin resulted in a concentration-dependent decrease of K⁺-stimulated release, with an IC₅₀ of about 30 nM (4.5 μg/ml); this inhibitory effect was blocked by a previous incubation of the tetanus toxin with antitoxin serum. Tetanus toxin had no effect on reserpine-induced release, a model of Ca²⁺-independent release. These results indicate that tetanus toxin is able to alter the exocytotic machinery of serotoninergic terminals, in agreement with results obtained with other neurotransmitters. They also indicate that serotoninergic terminals possess the receptor for tetanus toxin. These findings are in line with in vivo observations suggesting a role for serotoninergic system in tetanus intoxication.