1. Presynaptic Miniature Gabaergic Currents in Developing Interneurons
Federico F. Trigo, Brice Bouhours, Philippe Rostaing, George Papageorgiou, John E.T. Corrie, Antoine Triller, David Ogden, Alain Marty 
Neuron 
Volume 66, Issue 2, Pages (April 2010)
DOI: /j.neuron
Copyright © 2010 Elsevier Inc. Terms and Conditions

2. Figure 1 Two Classes of Miniature Currents in Cerebellar Interneurons
(A) Sample recordings of miniature currents (membrane potential: −70 mV) in a cerebellar interneuron reveal small events (red crosses) in addition to the large (≥30 pA) events described earlier (which are truncated here).
(B) Examples of individual large events (left) and small events (center). Right: averages of the two classes of events (insert, after normalization).
(C) Peak amplitude histogram showing two components, with values of 13.3 ± 5.4 pA and 170 ± 67 pA (mean ± SD; 314 events; recording time, 4 min). Most small events fall below a cutoff of 30 pA (dashed line).
(D) A plot of the 20%–80% rise time of individual events as a function of peak amplitude (recording time, 2 min) shows that small events have a longer rise time than large events (2.5 ± 1.7 ms versus 0.51 ± 0.46 ms; mean ± SD; n = 111; p < 0.01, Student's t test).
Neuron  , DOI: ( /j.neuron )
Copyright © 2010 Elsevier Inc. Terms and Conditions

3. Figure 2
Small Miniature Currents Are Sensitive to Washout, to Intracellular BAPTA, and to Membrane Potential
(A) Sample traces from one cell early and late during whole-cell recording, showing ordinary miniature currents (truncated) as well as smaller miniature currents.
(B) Frequency plot from the same cell showing that smaller minis (labeled “preminis”; red) run down during whole-cell recording, whereas the frequency of ordinary minis is stable (black). The two mini classes were separated using an amplitude cutoff of 30 pA.
(C) Summary plot from 10 cells comparing, in each case, the relative frequency of large and small events for time windows of 0–10 and 30–40 min of whole-cell recording. The frequency ratio for small events (red) is significantly smaller than 1 (p < 0.01).
(D) Sample traces for 2 cells at 9 min of whole-cell recording, one with the “low EGTA” solution (containing 50 μM EGTA) and the other with a solution containing a strong Ca2+ buffer (10 mM BAPTA).
(E) Summary data comparing the frequencies of smaller events for the two conditions (n = 10 each) as a function of time in whole-cell recording. Event frequency is initially lower and decays more rapidly with whole-cell recording time in the presence of 10 mM BAPTA than in the control. Single and double stars indicate significant differences using Student's t test at p < 0.05 and at p < 0.01 level, respectively.
(F) Summary data from the same cells showing that ordinary mini frequency is not affected by BAPTA.
(G) Representative traces showing a selective increase in the frequency of smaller events at −50 mV compared to −80 mV.
(H) Rise time versus peak amplitudes plots (104 s duration each) show that events with peak amplitude values < 30 pA and 20%–80% rise time values > 0.7 ms (“preminis”; see dotted lines) are selectively increased by depolarization (0.92 versus 0.14 Hz); by contrast, the frequency of events with amplitudes > 30 pA and rise times < 0.7 ms was not sensitive to potential (0.29 Hz at −50 mV and 0.24 Hz at −80 mV).
(I) Summary data from five experiments showing that premini frequency significantly increases with depolarization while that of minis is not significantly changed. All data from this figure are from PN 11–15 animals. Error bars display ± SEM.
Neuron  , DOI: ( /j.neuron )
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4. Figure 3 Age Dependence of Preminis
(A) Left: sample recordings from a PN 20 MLI at −55 and −80 mV, illustrating a lack of increase in the frequency of preminis at depolarized potentials, in contrast to the results illustrated in Figure 2G for the PN 11–15 age group. Right, rise time versus peak amplitude plots for the same cell (90 s recordings at each potential). Only 3 and 1 preminis were found at −80 and at −55 mV, respectively. There are 26 and 17 other events (minis) at −80 and at −55 mV.
(B) Summary results showing the ratio of all events (preminis + minis) at depolarized (either −50 or −55 mV; the latter value was preferred for cells where recordings at −50 mV were considered too noisy) over hyperpolarized (−80 mV) potential. This ratio is larger than 1 at PN 12–14 (p < 0.05) but not at PN 19 to 20.
(C) Summary results comparing the relative frequency of preminis in the two age groups, at a holding potential of −70 mV. Here, preminis are defined as events that have a peak amplitude smaller than 30 pA and a 20%–80% rise time longer than 0.7 ms (upper left rectangles in the rise time versus amplitude plots illustrated in (A). Data were collected in the first 10 min of whole-cell recording in all cases. Error bars display ± SEM.
Neuron  , DOI: ( /j.neuron )
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5. Figure 4
Coincidence of Preminis with Postsynaptic Minis in Paired Recordings
(A) Pre- and postsynaptic current traces in response to a short depolarizing pulse to the presynaptic cell. The inset shows the presynaptic trace on a different scale to clearly illustrate the action-potential-induced autoreceptor current.
(B) Simultaneous pre- and postsynaptic recordings from the same cells after washing in TTX and verifiying that evoked transmission was abolished. Small inward currents (four in the trace shown; onsets marked by vertical dashed lines) appear in the presynaptic trace in register with some of the postsynaptically recorded minis. Lower panel: the four individual currents, as well as their mean, are displayed after alignment with the foot of the corresponding postsynaptic events.
(C) Black: average of all aligned presynaptic traces from the same experiment (from 232 postsynaptic minis with amplitude > 50 pA). Red: corresponding average of postsynaptic minis. Lowest panel: normalized averages showing exact coincidence between onset times of preminis and postsynaptic minis.
Neuron  , DOI: ( /j.neuron )
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6. Figure 5 Axotomized Cells Have No Preminis
(A) Axotomized cells occur spontaneously in slices due to the cutting procedure. In the example shown (Aa; cell reconstruction following infusion with Alexa 488), a short axon stump (in red) terminated near the slice surface (arrow). In this cell, the capacitive current response to a hyperpolarizing voltage pulse (from −60 mV to −80 mV) displayed a single fast exponential component (Ab). In the presence of TTX, axotomized cells failed to display any premini (Ac, from another cell).
(B) Cells with intact axons (Ba; axon extended beyond the upper left corner of the displayed field) have a biphasic capacitive current (Bb). They display both preminis (Bc, from another cell; frequency of 0.42 Hz) and minis (frequency of 0.03 Hz).
(C) Summary data showing that axotomized cells (defined as having a monoexponential capacitance current) have very few or no preminis (frequencies of 0.02 Hz or less), whereas intact cells (slow capacitance component ranging from 4.8 to 14.8 pF) have a sizable premini frequency (range, 0.07 to 2.1 Hz).
(D) Axotomized cells and intact cells have similar mini frequencies. Error bars represent SEM.
Neuron  , DOI: ( /j.neuron )
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7. Figure 6
Morphological and Functional Evidence for the Presence of Axonal GABAARs
(A) Left: an Alexa-filled MLI (PN12) was stimulated at two dendritic (white arrowheads) and two axonal locations (red arrowheads), with focused 0.1 ms-long laser flashes that locally delivered GABA from its photolabile precursor DPNI-GABA (1 mM). Center: sample traces at the four locations. Right: cell reconstruction with somatodendritic compartment in black and axon in red (note that axon extended upwards beyond drawing limits).
(B) Superimposed responses for locations 1 and 4 before and after normalization. Respective 20%–80% rise time values were 1.6 and 7.4 ms.
(C) Summary data (mean ± SEM) from 27 dendritic trials and 61 axonal trials gathered on 7 MLIs (PN 12–15). Open symbols, 0.3 ms-long flashes; closed symbols, 0.1 ms-long flashes.
Neuron  , DOI: ( /j.neuron )
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8. Figure 7 Subcellular Location of Presynaptic GABAARs
(A) Examples of GABAAR α1-associated gold particles at basket to Purkinje cell synapses associated with the post- (arrowheads) or pre- (arrows) synaptic side (PN 12).
(B and C) Quantification of location for 173 particles from 36 synapses. (B) Histogram of the distance of particles from the center of the cleft, measured along the direction orthogonal to that of the cleft (negative values correspond to the presynaptic side). (C) Histograms of the distance of particles measured along the direction of the cleft from nearest synaptic border (dotted line; the portions on the right are intrasynaptic) in pre- (C1) and postsynaptic (C2) elements.
Neuron  , DOI: ( /j.neuron )
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9. Figure 8
Calculation of somatic currents associated with axonal current injection
(A) Calculated somatic current associated with the injection of an exponentially decaying current (instantaneous rise, unitary amplitude, decay time constant 20 ms) at various axonal locations. These locations are expressed as reduced distances from the soma (physical distance from the soma divided by the length constant of the axon, X = x / λ) and range from 0.01 to The calculation treats the axon as a cable with a reduced length of 0.55 and with a membrane time constant of 32 ms. These assumptions are derived from a previous analysis of the passive properties of MLI axons (Mejia-Gervacio et al., 2007). The equations used to calculate the current are derived from Rall and Segev (1985). They only require the knowledge of the axon length constant and of its membrane time constant.
(B) Peak amplitudes of the curves in (A), as a function of X.
(C) Current integral.
(D) 20%–80% rise time.
(E) 37% decay time.
Neuron  , DOI: ( /j.neuron )
Copyright © 2010 Elsevier Inc. Terms and Conditions