Motoneuron uptake from the circulation of the binding fragment of tetanus toxin
P. S. Fishman and D. R. Carrigan
Department of Neurology, University of Maryland School of Medicine, Baltimore 21201.
Tetanus toxin enters the central nervous system from the systemic
circulation after it is internalized by motoneuron terminals at the
neuromuscular junction. We have demonstrated that the atoxic binding
fragment (C-fragment) of tetanus toxin is internalized preferentially by
motoneurons. We examined the distribution of C-fragment after intravenous
injection in the nervous systems of mice by immunohistochemical methods.
All animals remained asymptomatic until killed one to two days after
injection. C-fragment was found only within neurons with processes outside
the blood-brain barrier. Large motoneurons of the spinal cord showed the
greatest accumulation of C-fragment. Motoneurons of brain-stem nuclei
(particularly facial and trigeminal), also showed substantial label of
C-fragment. Small amounts of C-fragment were detected in dorsal root
ganglion cells. Affinity of a systemically distributed substance for
synaptic components, as well as an inability to cross the blood-brain
barrier, may lead to its preferential localization in motoneurons.
