RESTORATION OF EXOCYTOSIS OCCURS AFTER INACTIVATION OF INTRACELLULAR TETANUS TOXIN

Tetanus toxin blocks carbachol-stimulated release of noradrenaline from bovine adrenal chromaffin cells in culture, provided it can gain access to the cells. This can be achieved by electropermeabilization of the plasma membrane or by enriching the membrane with exogenous gangliosides which serve as carriers of the toxin. The inhibition of noradrenaline release persists for at least 6 days, even in the presence of specific anti-tetanus toxin antibodies in the culture medium. However, the block is preventable, for the most part, when antibodies enter chromaffin cells during electropermeabilization, before the uptake of the toxin is facilitated by inserting exogenous gangliosides into the plasma membrane 2 days later. This indicates that the antibodies pass into the cells through the physically induced pores and that these intracellular antibodies neutralize incoming tetanus toxin. If, on the other hand, exocytosis has been inhibited by tetanus toxin, it will recover within 3 days, provided specific anti-tetanus toxin antibodies are introduced into the cells by electropermeabilization. The recovery is not linked to a specific route of entry of the toxin. It is concluded that the restoration of noradrenaline release requires not only the intracellular neutralization of tetanus toxin but also the reconstitution of the as yet unknown target molecule of the toxin.