• acceptor;
  • clostridial neurotoxins;
  • immunocytochemistry;
  • nerve terminals;
  • rat brain


Clostridial neurotoxins (tetanus and botulinum toxins) are potent blockers of neurotransmitter release. These toxins act specifically on the nervous system by interacting with still non-identified protein receptors together with gangliosides. Whereas many biochemical data are available on their binding properties to neuronal membranes in vitro, there is poor morphological evidence of their binding to mammalian central nervous system. In the present study, the binding of tetanus and botulinum neurotoxin type A to rat brain sections is reported. Both toxins bound to nerve terminals with a broad distribution in brain. Tetanus toxin additionally bound to nerve fibres. The staining patterns were clearly shown to be due to the interaction of the heavy chains, which contain the binding moiety, with the tissue. In an attempt to investigate the nature of the acceptors present in the tissue, some sections were pre-incubated with periodic acid. This treatment resulted in the additional binding of botulinum neurotoxin type A to nerve fibres. Since the extended staining of nerve terminals was not modified by this pretreatment, it is suggested that protein receptors of clostridial neurotoxins are located at the nerve terminals, which may be common constituents of the synapses.