Dynamin inhibition by dynasore affects LTP, a type of synaptic plasticity due to sustained activity in hippocampus.

<p><b>A</b>, Dynasore (80 μM, 20 minute perfusion, open triangles) decreases LTP induced by theta-burst stimulation in CA₃–CA₁ synapses compared to vehicle-treated slices (black circles)(F_1,10 = 9.081, <i>p</i> = 0.013). The horizontal bar indicates the period of perfusion with dynasore before tetanic stimulation. <b>B</b>, Post-tetanus dynamin inhibition by dynasore (80 μm, 20 minute perfusion <i>after</i> the tetanus delivery, open triangle) induced by theta-burst stimulation in CA₃–CA₁ synapses compared to vehicle-treated slices (black circles; F_1,7 = 0.209, <i>p</i> = 0.662). The horizontal bar indicates the period of perfusion with dynasore <i>after</i> tetanic stimulation. <b>C</b>, Basal synaptic transmission is unmodified by dynamin inhibition with dynasore. Averaged evoked field potential slopes as a function of stimulation intensity measured in volts (V) at CA₃–CA₁ synapses in slices do not show significant differences between vehicle-treated (black circles) and dynasore (80 μM, open triangles) treated slices (F_1,11 = 40.081, <i>p</i> = 0.7013). <b>D</b>, Dynamin inhibition by dynasore (open triangles; 80 μm, 20 minute perfusion before the tetanus) does not produce changes in solely post-synaptic LTP induced by three tetani at 50 Hz for 1 second, each tetanus separated by 20 seconds, at the CA₃–CA₁ synapse compared to vehicle-treated slices (black circles; F1,8 = 1.538, p = 0.250). The horizontal bar indicates the period of perfusion with dynasore before tetanic stimulation. Error bars indicate SEM.</p

Dynamin inhibition by dynasore increases synaptic fatigue following sustained activity in hippocampus.

<p><b>A</b>, Dynasore treatment (80 μM, open triangles) increases SF in slices that were previously treated with vehicle (black circles) (F_1,12 = 6.395, <i>p</i> = 0.026). The increase is already present at the 10^th pulse during the stimulation (Mann-Whitney U_{69, 36} = 8.00, <i>p</i> = 0.0379). The effect was reversed by washout with vehicle (open squares). SF was induced by high frequency stimulation in the presence of D-APV (100 μM). <b>B</b>, SF was induced by high frequency stimulation (100 Hz, 1 second) in slices containing both D-APV (100 μM) and cyclothiazide (100 μM). Dynasore (80 μM, open triangles) further increases SF compared to fatigue of the same slices in the presence of vehicle (black circles) (F_1,12 = 6.395, <i>p</i> = 0.026). SF increases in dynasore-treated slices already at the 10^th pulse during the tetanus (Mann-Whitney U_{35, 10} = 0.0001, <i>p</i> = 0.0159). The effect is reversed by washout with vehicle (open squares), re-establishing SF to the values obtained prior to dynasore perfusion. <b>C</b>, SF is induced by high frequency stimulation (100 Hz, 1 second) in vehicle-treated slices (black circles) containing both D-APV (100 μM), the GABA_A receptor blocker picrotoxin (30 μM), the GABA_B receptor blocker SCH 50911 (100 μM). Dynasore (80 μM, open triangles) further increases SF compared to fatigue of the same slices in the presence of vehicle (black circles) (F_1,12 = 6.395, <i>p</i> = 0.026). SF increases in dynasore-treated slices already at the 10^th pulse during the tetanus (Mann-Whitney U_{159, 94} = 28.00, <i>p</i> = 0.0356). The effect is reversed by washout with vehicle (open squares), re-establishing SF to the values obtained prior to dynasore perfusion. Data shows dynasore-induced increase in SF is not associated to AMPA receptor desensitization or changes in GABA_A/B responsiveness. Error bars indicate SEM.</p

Selective dynamin 1 inhibition through siRNA impairs both synaptic plasticity and associative memory.

<p><b>A</b>, siRNA specific for murine dynamin 1 reduces protein expression. An example of western blot showing that Penetratin 1- conjugated dynamin 1 siRNA reduces protein expression. Cells are lysed 48 hours after the treatment with siRNA. Dynamin 1 is detected using a rabbit polyclonal anti-dynamin1 antibody. Penetratin 1- conjugated Control siRNA, that does not affect dynamin 1 expression, does not change protein levels. n = 3 for each group. <b>B</b>, Penetratin 1- conjugated dynamin 1 siRNA (open bars) (80 nM in a final volume of 1.5 μl over 1 minute, bilateral injections twice a day for 3 days) impairs contextual fear memory compared to control siRNA infused mice (grey bars) (Mann-Whitney U_{150, 126} = 21.00, <i>p</i> = 0.0089). Moreover, control siRNA infused mice show similar amount of freezing as vehicle-infused animals (black bars). <b>C</b>, Penetratin 1- conjugated dynamin 1 siRNA (open bars) does not modify cued fear memory compared to Penetratin 1- conjugated Control siRNA (grey bars) (Mann-Whitney U_{99, 90} = 44.50, <i>p</i> = 1.00) in mice previously tested for contextual fear conditioning at 24 hours after the shock. <b>D</b>, Bilateral infusions of Penetratin 1- conjugated dynamin 1 siRNA (open triangles) (80 nM in a final volume of 1.5 μl over 1 minute, repeated 2 times a day for three days) into dorsal hippocampi decrease LTP compared to Penetratin 1- conjugated Control siRNA treatment (grey squares) (F_1,9 = 5.578, <i>p</i> = 0.001). As an internal control, slices from vehicle-infused animals (black circles) show similar amounts of potentiation as those from Penetratin 1- conjugated Control siRNA treated animals. Error bars indicate SEM.</p

Dynamin inhibition affects presynaptic mechanisms underlying synaptic plasticity evoked by sustained activity.

<p><b>A</b>, Tetanic efficiency, expressed as percent in evoked potential area across a train of 10 bursts at 5 Hz, each consisting of 4 pulses at 100 Hz, is reduced by dynasore (80 μM, open bars) with respect to percent response area in vehicle-treated slices (black bars) (F_1,9 = 12.071, <i>p</i> = 0.007). The reduction reaches statistical significance at the third burst (Mann-Whitney U_{51, 15} = 0.00001, <i>p</i> = 0.0043); <b>B</b>, Dynasore (80 μM, open bars) already produces a partial reduction of the area within the first group of 4 pulses at 100 Hz compared to vehicle-treated slices (black bars); <b>C</b>, Raw <i>f</i>EPSP signals recorded during tetanic stimulation in vehicle-treated and dynasore (80 μM, 20 minutes before tetanus)-treated hippocampal slices. Calibration: 0.5 mV, 2 ms;. <b>D</b>, Perfusion of hippocampal slices with dynasore (80 μM) in the presence of D-APV (100 μM) for 20 minutes prior to theta-burst stimulation diminishes PTP to about 50% of the values obtained with vehicle perfusion (F_1,12 = 6.924, <i>p</i> = 0.022). The effect was reversed by washout with vehicle. Error bars indicate SEM.</p

Dynamin inhibition with dynasore does not affect paired-pulse facilitation, a type of synaptic plasticity that is not linked with sustained activity.

<p>Paired-pulse-induced change is calculated as the ratio of the slope of the second evoked field potential to the first one at different interpulse intervals (1–1000 ms). Paired-pulse ratio is not modified in dynasore (80 μM, open triangles) treated slices with respect to vehicle-treated slices (black circles)(F1,12 = 0.339, p = 0.914). No effect is observed by subsequent washout with ACSF (open squares). Error bars indicate SEM.</p

Dynamin inhibition by dynasore impairs associative memory.

<p><b>A</b>, Schematic representation of the hippocampi bilaterally implanted with cannulas. <b>B</b>, Bilateral injections of dynasore (80 μM in a final volume of 1.5 μl over 1 minute) into dorsal hippocampi, 20 minutes before training, dramatically impairs contextual fear memory (open bars) compared to vehicle treated mice (black bars) (Mann-Whitney U_{137, 73} = 18.00, <i>p</i> = 0.00147). <b>C</b>, Mice do not show changes in cued fear conditioning following dynasore infusions (open bars) compared to vehicle-treated animals (black bars) (Mann-Whitney U_{121, 89} = 34.00, <i>p</i> = 0.2412). Each bar represents the average percent of time spent in freezing posture. Error bars indicate SEM. <b>D</b>, Sensory threshold was not affected regardless of treatment (n = 10).</p