Time-dependent plasticity of synaptic transmission produced by long-term potentiation of C-fiber evoked field potentials in rat spinal dorsal horn

Our previous work has shown that repetitive stimulation of Ab-fibers depres ses long-term potentiation (LTP) of C-fiber evoked field potentials in spin al dorsal horn. Here, we tested the effects of the A delta stimulation on t he spinal LTP at different time points following LTP induction. Fifteen min utes after LTP induction A delta stimulation depressed LTP by 44.1 +/- 4.2% (mean SEM, n = 7) for 69.3 +/- 18.5 min and 1 h after LTP the same A delta stimulation depressed spinal LTP by only 16.9 +/- 3.1% for 21.9 +/- 2.0 mi n In 7). Three hours after LTP, however, the A delta stimulation produced a further potentiation (31.9 +/- 6.3%, n = 7) lasting for all the recording periods (1-3 h). These data indicate that the effects of repetitive stimula tion of A delta -fibers on established spinal LTP of C-fiber evoked field p otentials is time-dependent. (C) 2001 Elsevier Science Ireland Ltd. All rig hts reserved.