LTPi diffuses to neighboring synapses.

<p>(A, Top) Infrared Differential Interference Contrast (IR-DIC) microphotograph of acute cortical slice showing two adjacent recorded layer 5 P neurons (<50 µm). (A, Middle) Representative eIPSC traces of one test (PN1) and one adjacent P neuron (PN2) in control and after injecting depolarizing voltage steps in PN1. IPSCs were evoked in the two neurons by a single stimulating electrode placed nearby their perisomatic region. Note that LTPi was observed also in PN2, despite only PN1 being depolarized. (B) Same experiment of (A) but on a different pair of P neurons recorded at a farther distance (∼80 µm). Note the absence of spread of LTPi in the second, nondepolarized neuron. Scale bar (A and B), 20 µm. (C) Population data of IPSC time course in tested cells (open circles), cells patched up to 50 µm (solid dark gray circles), and at a distance higher than 50 µm from the test neuron (solid light gray circles). (D) ΔeIPSCs of same data of (D). Data are single values and/or mean and median ± SEM. *<i>p</i><0.05; **<i>p</i><0.001. Numbers 1 and 2 refer to times of trace illustration.