The Journal of Neuroscience, July 12, 2006, ():
The Role of Nitric Oxide and GluR1 in Presynaptic and Postsynaptic Components of Neocortical Potentiation
J. Neurosci. Hardingham and Fox
26: 7395
Supplemental data
Files in this Data Supplement:
- supplemental material
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Supplementary Figure 1. Unitary EPSPs correlate with peak separation in amplitude histogram.
Left column (a-c) : an example of amplitude histograms for evoked EPSPs (a) and monoquantal EPSPs produced by asychronous release (b) are compared for the same connection (c). The monoquantal EPSPs were obtained by producing asynchronous release with extracellular Strontium (2mM) and looking at EPSPs on the tail of the main evoked EPSP ( see f).
d, The peak separation observed in the evoked amplitude histograms (Q evoked) is plotted against the mean monoquantal EPSP for each neuron (Q Strontium). Points lie close to the identity line indicating a close correspondance between the two and demonstrating that the peak separation is a good indicator of quantal size (R2 = 0.61). e, Mean quantal size estimated using peak separation of the amplitude histogram for evoked activity (Qe = 404 ?V) or monoquantal EPSPs (QSr = 363 ?V) in Strontium are almost identical (t(10) = 2.1, p=0.49) . f, An example of an evoked EPSP in the presence of Strontium. Note the two monoquantal EPSPs on the tail of the evoked EPSP (arrows).
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Supplementary Figure 2. Stability of quantal variables following induction of LTP.
Two wild-type examples of stable periods used for quantal analysis are shown. b, f and e are amplitude histograms of the baseline recordings made before induction of LTP and c, and f the periods immediately following spike pairing.shows the next 30 minutes of recording after inducing LTP. a-c: there is a moderate increase in Q from 470?V (b) to 660?V (c). In this case Q increases without much change in Pr. d-f In this example, Q increases from 540?V (i) to 840?V (j) without any significant change in Pr. Consequently, as shown in d, the SD increases substantially following induction of LTP (as it is proportional to Q). The numbers inset with the histograms indicate the response numbers included in the analysis e.g 1-50, and correspond to the period indicated in the mean amplitude (x) and standard deviation (SD) plots shown above in a and d. Stimuli were delivered at a rate of 1 every 7 seconds.
For wild-types, we used minimal stimulation in 40 cases, of which 24 exhibited stable periods before and after inducing LTP, as judged by the mean and standard deviation remaining constant within prescribed limits (see Methods). The stable control periods were between 6 and 18 minutes duration (average 9.8) and the test periods during LTP were between 12 and 36 minutes duration (average 16 minutes). Of these 24 cases, 11 passed the autocorrelation test for resolvable peaks that could not be accounted for by chance (GUT; Monte Carlo simulation; alpha=0.05). The measurements of the potentiated period began at least 6 minutes after induction of LTP apart from one case. The longest duration stable period was 36 minutes and that ranged from 6 minutes to 41 minutes post pairing.
For GluR-1 knockouts, we used minimal stimulation in 30 cases of which 18 exhibited stable periods before and after inducing LTP as judged by the mean amplitude and standard deviation remaining constant within the prescribed limits (see Methods). The stable control periods were between 6 and 12 minutes duration (average 9.4 minutes) and the test periods during LTP were between 12 and 29.2 minutes duration (average 19.6 minutes). Of these 18 cases, 7 passed the autocorrelation test for resolvable peaks that could not be accounted for by chance (GUT; Monte Carlo simulation; alpha=0.05).
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Supplementary Figure 3. Stability of quantal variables with time.
a,e show the means (x) and standard deviation (SD) plots for two examples taken from wild-type recordings not involving LTP induction. b, the entire period of 250 trials is represented and shows peaks with a Q value of 670?V. The stability of these cases were tested by analysing the first and second 125 responses separately as shown in c and d respectively. Similar peaks are present in both halves of the 30 minute period and Q varies little between first (690 ?V) and second half (670 ?V). f, Similarly, in the other example, the peaks present in the overall amplitude histogram are present in the first and second halves of the 30 minute period shown in g and h respectively. In total, we examined 314 cases where we had used minimal stimulation in experiments that did not involve an LTP protocol. Of these we found 163 that exhibited stable periods over at least 30 minutes as judged by the mean and standard deviation remaining constant within the prescribed limits (see Methods). The stable periods were between 30 and 93 minutes duration (average 34 minutes). Of these 163, 65 cases showed peaks in the amplitude histograms from visual inspection and 28 passed the autocorrelation test for resolvable peaks that could not be accounted for by chance (GUT; Monte Carlo simulation; alpha=0.05).
