Distribution of tetanus toxin in rat peripheral nerve trunks during the development of local tetanus

Summary Mouse bioassay studies were made on the tetanus toxin content of three different segments of both sciatic nerve trunks after unilateral gastrocnemius muscle injections. Multiple toxin dosages, sampling times, nerve transections, and nerve dissections to produce three samples per segment (undissected nerve, epineurium, and perineurium plus endoneurium) were used.The results showed that after i.m. injections a dosage dependent bilateral toxin distribution could be detected in the undissected nerve or its epineurium. The characteristics of this epineurial toxin distribution are discussed.A unilateral toxin distribution was detected only in the stripped (perineurium plus endoneurium) nerve segment from the injected extremity. This unilateral toxin distribution had the characteristics of centripetal toxin transport along the tissue spaces or axons to the spinal cord. This unilateral centripetal toxin gradient was temporally related to the onset of local tetanus. Both the toxin gradient pattern and local tetanus due to i.m. injected toxin could be prevented by nerve transection.These data suggest that peripheral nerves do transport tetanus toxin to the spinal cord and that this transport in an important factor in the pathogenesis of local tetanus.