Supplementary Information
Supplementary Methods
Reliability of the noise analysis Small dendritic arborization of RGCs in Xenopus tadpole
before 46 stage (usually less than 100 μm in the size of the arbor1), the low series resistance (<
20 MΩ), and high input resistance (0.5 – 1 GΩ) make these RGCs electrotonically compact for
space clamp2, as indicated by the observation that the rise time and decay time of sEPSCs is
amplitude independent (see Supplementary Fig. 3a). Further support for the reliability of the
noise analysis came from the partial AMPA receptor blockade experiments (see Supplementary
Fig. 3b and 3c). We found that when functional AMPA receptors were reduced in number by a
low concentration of CNQX (0.05 – 0.15 μM), noise analysis indeed yielded significant
reduction in the receptor number (N) associated with sEPSCs, but not the channel conductance
(gs) and channel open probability (p0).
1. Sakaguchi, D. S., Murphey, R. K. & Tompkins, R. The development of retinal ganglion
cells in a tetraploid strain of Xenopus laevis: a morphological study utilizing intracellular
dye injection. J. Comp. Neurol. 224, 231-251 (1984).
2. Tian, N., Hwang, T. N. & Copenhagen, D. R. Analysis of excitatory and inhibitory
spontaneous synaptic activity in mouse retinal ganglion cells. J. Neurophysio1. 80, 132740 (1998).
Supplementary Figure Legends
Figure 1. Dose-dependence of BDNF effects on light-evoked excitatory CSCs in RGCs.
Experiments were performed in the similar manner as in Fig. 2c,d, except that different total
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amounts of BDNF (0.4 ng, 4 ng, 40 ng or 400 ng, dissolved in 15 μl 0.1% BSA) were applied.
The number of experiments is shown in the parenthesis (* p < 0.01, paired Student’s t-test).
Figure 2. Absence of potentiation of light-evoked CSCs in RGCs following tectal application of
NGF (a and b) or NT-3 (c and d) (marked by the bar). Changes in the ON and OFF component
of light-evoked excitatory CSCs with time are shown in left and right, respectively. a-d, Top,
An example of data recorded from a RGC (Vc = - 65 mV) in a stage 44 tadpole (a and b) or a
RGC (Vc = - 70 mV) in a stage 43 tadpole (c and d). Sample responses are obtained at the time
marked by arrows and corresponding ON or OFF responses are shown at a higher time
resolution. Scales: 50 pA, 4 s or 300 ms. Bottom, Summary of results from all RGCs studied.
Figure 3. Characterization of sEPSCs and noise analysis under partial blockade of sEPSCs. a,
The rise time and decay time of sEPSCs were independent of the amplitude. The data were
obtained from a RGC (Vc = - 65 mV) in a stage 43 tadpole. Experiments were performed in the
similar manner as in Fig 2c, d, except that at 50 min after the onset of BDNF application at the
tectum, CNQX (0.1 μM) was added to the external solution to partially suppress sEPSCs. Top,
Examples of recordings before (“Control”), 40 min after the onset of BDNF application, and 20
min after the addition of CNQX. Scales: 20 pA, 2s. Middle & Bottom, Plots of peak
amplitudes against 10-90% rise times (middle) or decay times (bottom) of sEPSCs, which were
obtained during 10 min window before (left), 40 min after (middle) the onset of the BDNF
application and 20 min after CNQX addition (right), respectively. The plots are fitted with leastsquare linear regression (gray dashed line). b, Noise analysis of the decay phase of sEPSCs
shown in a. c, Scatter data of N (left), gs (middle), and p0 (right) associated with sEPSCs
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obtained from four RGCs before (“Control”) and after the BDNF application, and after the
CNQX addition. Values derived from the same RGC are connected by lines (*p < 0.05, paired
Student’s t-test).
Figure 4. Enhanced light-evoked spiking activity of RGCs by tectal application of BDNF. a,b,
Cell-attached recording of light-evoked action potentials showed potentiation of ON (a) and OFF
(b) responses of RGCs following tectal application of BDNF. Experiments were performed in
the similar manner as in Fig. 2c,d. The data shown on the top were obtained from a RGC in a
stage 44 tadpole. Scales: 80 pA, 2 s or 80 ms. Summary plots show increased spiking for both
ON and OFF responses (filled symbols) as well as results from experiments in which the optic
nerve of the recorded retina was severed (open symbols). c, Summary histograms of ON and
OFF light responses of RGCs, showing increased spiking frequency and spike number without
significant change in the duration of the spike train following the BDNF application, for the
same data set as in a,b. The average values represent data obtained during a 20-min period
before (“control”) and 60 min after the BDNF application (* p < 0.01, paired Student’s t-test)
Figure 5. Enhanced spontaneous spiking activity of RGCs by tectal application of BDNF. a.
An example of the changes in spontaneous spiking of a RGC in a stage 44 tadpole monitored by
cell-attached patch recording before and after BDNF application in the tectum. Top, Raster plots
showing 4-min continuous recordings of spontaneous spiking activity before (“Control”) and 60
min after the BDNF application. Dots above indicate bursting events, with the inter-spikeinterval (ISI) < 50 ms. Note the increase in the burst number after the BDNF application. Scale:
5 s. A sample burst is shown at a higher time resolution below (scale: 60 ms). Bottom, ISI
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histograms (line) and corresponding cumulative distributions (dashed line) derived from
spontaneous spiking activity (of the same RGC as that shown on the top) over a 20-min period
before (thin) and 60 min after (thick) the BDNF application. Both ISI histograms were
normalized by the total number of spikes. b, Summary of data showing increased mean
frequency of spontaneous spikes (top) and bursts (middle) following the BDNF application.
Data over 10-min bins are normalized to the mean value before BDNF application. Filled
symbols: Results identical to that shown in a. Open symbols: with optic nerve severed. Bottom:
Percentage changes in the mean frequency of spikes, frequency of bursts, and number of spikes
per burst, recorded at 60 - 80 min after the BDNF application, as compared to the mean values
before the BDNF application (*p < 0.01, paired Student’s t-test).
Figure 6. Intracellular inclusion of k252a (200 nM) abolished the retrograde synaptic
modification induced by tectal application of BDNF. Changes in the ON and OFF component of
light-evoked excitatory CSCs with time are shown in left and right, respectively. a, b, An
example of pair recording on the effect of intracellular loading with k252a (200 nM) (a) or
normal internal solution (b) on the BDNF-induced potentiation of RGC light responses. The
data were simultaneously obtained from two RGCs (Vc = - 65 mV) in a stage 43 tadpole 15 - 20
min after establishing perforated recording. Sample responses at the time marked by arrows and
corresponding ON or OFF responses are shown at a higher time resolution. Scales: 50 pA, 4 s,
300 ms. c, Summary data from all 5 pair recordings. Filled symbols: control; Open symbols:
k252a included in the internal solution.
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