Table 1.

Deducing the location of activity sensors that trigger synaptic plasticity at the NMJ

Step	TTX Cuff	BTX
Presynaptic action potentials	Blocked	Unchanged
Acetylcholine binding to acetylcholine receptors during evoked release	Blocked	Blocked
Acetylcholine binding to acetylcholine receptors during spontaneous release	Unchanged	Blocked
Postsynaptic action potentials	Blocked	Blocked
Probability of release (p)	Increased	Unchanged
Number of releasable vesicles (n)	Unchanged	Increased

Steps in synaptic transmission that are blocked by placement of a tetrodotoxin (TTX) cuff on the nerve (TTX cuff) or injection of α-bungarotoxin (BTX) into the muscle to block acetylcholine receptors. In the last two rows are the changes in the synaptic parameters p and n triggered by TTX cuff or BTX injection.