On the question of permeability of the blood-brain barrier to botulinum toxin.

The clinical symptoms of botulinum intoxication suggest that besides the involvement of the peripheral nervous system, the central nervous system is also affected. Studies were undertaken to determine whether pure toxin of Clostridium botulinum type A could be demonstrated in the brains of poisoned mice. With the aid of autoradiography of the toxin marked with 125-I and indirect fluorescent labeling it was possible to show the presence of the toxin in the parenchyma of the brain.