Journal of Neurophysiology, Vol 58, Issue 2 319-326, Copyright © 1987 by APS
Effect of a spider toxin (JSTX) on excitatory postsynaptic current at neuromuscular synapse of spiny lobster
A. Miwa, N. Kawai, M. Saito, H. Pan-Hou and M. Yoshioka
Department of Neurobiology, Tokyo Metropolitan Institute for Neurosciences, Japan.
1. We studied the blocking properties of a spider (Nephila clavata) toxin
(JSTX) purified from venom on the spiny lobster neuromuscular junction. 2.
When a small amount of JSTX was applied to the neuromuscular junction, the
excitatory postsynaptic potential (EPSP) was partially suppressed. The
amplitude of EPSPs remained at a steady level for several hours during the
washing of the preparation, showing that the action of JSTX is
irreversible. 3. We recorded the excitatory postsynaptic current (EPSC)
from synaptic site using a macro-patch electrode. The amplitude of EPSC
increased linearly with hyperpolarization of the membrane potential in the
presence and absence of JSTX. 4. The decay phase time constant of EPSC and
spontaneous EPSC was decreased by hyperpolarizing the membrane potential
both in the absence and in the presence of JSTX. The relationship between
the decay time constant and the membrane potential was not modified by
JSTX. 5. It is suggested that JSTX irreversibly blocks EPSC by acting on
the site that is apart from the ionic channel of the glutamate receptor
molecule.
