Figure 12.

Synaptic activation was necessary for associative plasticity. Kynurenic acid (glutamatergic receptor antagonist) or CNQX (AMPA receptor antagonist) were injected into the L4 level of the spinal cord. Both molecules blocked the late components of either nCAP or sCAP. A, Vehicle control (no drug). Sciatic nerve stimulation (top) or spinal stimulation (bottom) induces a biphasic potential. B, The second wave (marked by asterisks in A) is synaptically mediated, because it disappeared after injection of kynurenic acid or CNQX (data not shown). C, An example of associative stimulation-induced potential overlaid with single-pulse-induced potential, showing that SSA stimulation is not effective in amplifying potentials in the presence of kynurenic acid. D, Summary plot showing that SSA stimulation was not effective at ISIs of 0, 4, 8, 12, and 16 ms.