In Vitro Characterization of Botulinum Toxin Types A, C and D Action on Human Tissues: Combined Electrophysiologic, Pharmacologic and Molecular Biologic Approaches

摘要: Human exposure to botulinum toxin typically occurs in two settings: 1) as an etiologic agent the disease botulism and 2) a therapeutic for treatment of dystonia. Epidemiologic studies on suggest that human nervous system is susceptible five serotypes (A, B, E, F G) resistant (C D). In past, these epidemiologic findings have been used basis selecting should be tested agents data utilized because there are no neurotoxin action isolated nerves. present study, electrophysiologic techniques were monitor effects neuromuscular transmission surgically excised pyramidalis muscles, ligand binding done detect characterize receptors nerve membrane preparations, molecular biologic isolate sequence gene encodes substrate neurotoxin. The results demonstrated stable resting potentials (−61.5 mV; S.E.M. ± 0.7) maintained individual fibers muscle up 6 hr at 33°C. rate spontaneous miniature endplate was low physiologic solution (0.14 sec −1 ) but increased response elevations extracellular potassium concentration. keeping with findings, type A (10 −8 M) paralyzed preparations ( ca. 90 min). contrast serotype C also tissues 65 Iodinated displayed high-affinity (serotype site: K d = 0.3 nM, B max 0.78 pmol/mg protein; 1.96 8.9 protein). addition, found encode polypeptides substrates types (synaptosomal-associated protein M r 25,000) (syntaxin 1A). These important implications bearing on: development administration vaccines against testing