Fig. 3: Strong tetanization lowers LTP induction threshold in neighbouring synapses.

a A weak tetanus protocol (short-term potentiation (STP), 14 pulses at 100 Hz) applied to S2 (blue circles) induced a transient potentiation that returned to baseline level within 30 min (n = 10 slices from 5 animals). b STP (14 pulses) applied to S2 (blue circles) followed by STET applied to S1 (red circles) at a 1 h interval did not affect the STP-induced potentiation (n = 8 slices from 4 animals). c When STET was induced in S1 (red circles) followed by STP (14 pulses) in S2 (blue circles), the STP induced a long-lasting potentiation that sustained throughout the recording period (n = 7 slices from 3 animals). d Similar experiment as in c, except that the STP was replaced with an even weaker tetanus (11 pulses at 100 Hz). The STP-induced potentiation did not transform into a long-term potentiation in this case (n = 8 slices from 3 animals). Analogue traces show typical fEPSP of S1 (red) and S2 (blue) at 15 min of baseline (dotted line), 10 min after LTP induction (dashed line), and at the end of the recording (solid line). Scale bar for all traces: 3 mV/5 ms. Three red arrows represent STET, whereas single blue arrow represents STP (11 or 14 pulses). All data are represented as mean ± SEM.