Sensitivity of embryonic rat dorsal root ganglia neurons to Clostridium botulinum neurotoxins

Clostridium botulinum neurotoxins (BoNT) are zinc dependent endopeptidases which. once internalised into the neuronal cytosol, block neurotransmission :by proteolysis of membrane-associated proteins putatively involved in syn aptic vesicle docking and fusion with the plasma membrane. Although many st udies have used a variety of cellular systems to study the neurotoxins, mos t require relatively large amounts of toxin dr permeabilisation to internal ise the neurotoxin. We present here a primary culture of embryonic rat dors al root ganglia (DRG) neurons that exhibits calcium-dependent substance P s ecretion when depolarised with elevated extracellular potassium and is natu rally BoNT sensitive. The DRG neurons showed a different IC50 for each of t he toxins tested with a 1000 fold difference between the most and least pot ent neurotoxins (0.05, 0.3,30 and similar to 60 nM for A, C, F and B, respe ctively). BoNT/A cleavage of SNAP-25 was seen as early as 2 h, but substanc e P secretion was not significantly inhibited until 4 h intoxication and th e effects of BoNT/A were observed for as long as 15 days. This primary neur onal culture system represents a new and sensitive cellular model for the i ll vitro study of the botulinum neurotoxins. (C) 1999 Elsevier Science Ltd. All rights reserved.