TETANUS TOXIN MECHANISM OF ACTION IN TORPEDO ELECTROMOTOR SYSTEM - A STUDY ON DIFFERENT STEPS IN THE INTOXICATION PROCESS

The mechanism of action of tetanus toxin was characterized in the elec tromotor system of Torpedo marmorata either at peripheral and central nervous system. The consecutive steps of the intoxication pathway were observed: (i) [I-125]tetanus toxin specifically bound to neuronal pla sma membranes isolated both from electric organ and electric lobe of T orpedo, exhibiting one and two binding sites respectively; (ii) [I-125 ]tetanus toxin was internalized into nerve terminals and retrogradely transported to the electric lobe after its injection in the electric o rgan; (iii) finally, intracellular effect of tetanus toxin was studied either at electric organ and electric lobe membrane fractions. In bot h preparations tetanus toxin cleaved synaptobrevin, as detected by imm unoblotting methods. In conclusion, our findings exhibit the presence of two different populations of acceptors for tetanus toxin in central and peripheral nervous system and show that synaptobrevin cleavage ma y account for intracellular toxicity in Torpedo.