FIGURE 3.

Nicotine stimulation abolishes synaptic potentiation in hippocampal dentate gyrus of miRNA‐132/212 gene knockout. A, Representative traces of field excitatory postsynaptic potentials (fEPSPs), recorded at baseline conditions and after the application of potentiation‐inducing protocols (Section 2), from untreated hippocampal slices derived from untreated wild‐type controls and untreated miRNA‐132/212^−/− mice. The responses generated after delivery of electrical stimulation were taken at 22.5 min and are indicated as “synaptic potentiation” in the graph. B, Temporal course of the changes in fEPSPs slopes as recorded before and after the application of potentiation‐inducing protocols in hippocampal slices from untreated wild‐type and untreated miRNA‐132/212^−/− mice. No statistically significant differences were observed between the groups. C, Representative traces of fEPSPs, recorded at baseline conditions and after the application of potentiation‐inducing protocols, from untreated hippocampal slices derived from untreated wild‐type controls and untreated miRNA‐132/212^−/− mice. The responses generated after delivery of electrical stimulation are indicated as “synaptic potentiation” in the graph and were obtained after the dual application of 1‐μM nicotine, which was delivered during baseline conditions as described below. D, Temporal course of the changes in fEPSPs slopes as recorded before and after the application of potentiation‐inducing protocols in hippocampal slices from untreated wild‐type (n = 6) and untreated miRNA‐132/212^−/− (n = 5) mice. Two consecutive pulses of 5‐min exposure to 1‐μM nicotine, spaced by a 5‐min washout period, preceded the delivery of the application of potentiation‐inducing protocols as illustrated in the figure in the shadowed box insets. A pronounced and statistically significant enhancement of synaptic potentiation was observed in recordings from wild‐type animals, whereas a virtual abolishment of the potentiation response was detected in slices from miRNA‐132/212^−/− mice. E, Scatter plots showing the field responses after delivering potentiation‐inducing protocols in all four investigated groups at 22.5 min. The high‐frequency stimulation protocol used to induce potentiation was delivered right after the recording obtained at 20 min as indicated in the figure (HFS + arrow). Data are presented as mean ± SEM. Please see details for the statistics on the main text