The Journal of General Physiology, Vol 73, 245-263, Copyright © 1979 by The Rockefeller University Press
Reversibility and mode of action of Black Widow spider venom on the vertebrate neuromuscular junction
A Gorio and A Mauro
Black widow spider venom (BWSV) stimulates transmitter release and depletes
synaptic vesicles from muscles bathed in a sodium free medium containing 1
mM EGTA. However, frog neuromuscular junctions treated with BWSV in
glucosamine Ringer's and post-treated with antivenin recover normal
function. This suggests that probably the permanent block of neuromuscular
transmission is due to changes in permeability of the nerve ending plasma
membrane to cations such as Na+. When BWSV is applied in a medium lacking
divalent cations and containing 1 mM EGTA, in most of the cases no effect
is observed. We found that this inhibition can be overcome in three ways:
(a) by adding divalent cations to the medium; (b) by increasing the
tonicity of the medium with sucrose; (c) by raising the temperature of the
medium. These results suggest that the lack of divalent cations influences
the membrane fluidity. Moreover, in view of the report by Yahara and
Kakimoto-Sameshima (1977. Proc. Natl. Acad. Sci. U.S.A. 74:4511--4515) that
hypertonic media induce capping of surface receptors in lymphocytes and
thymocytes, we think that these data further support the hypothesis that
BWSV stimulates release by a dual mode of action; namely, it increases the
nerve ending permeability to cations and also stimulates release directly
via a process of redistribution of membrane components, a process which may
also inhibit vesicle recycling.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
