Figure 4. Non-stationary noise analysis of ‘slow’ bursts with large mIPSC amplitude variance recorded in the absence of external Ca²⁺.

A, example of a ‘slow’ burst recorded in the absence of external Ca²⁺. B, 25 consecutive mIPSCs occurring within the burst shown in A (filter cut-off frequency, 1 kHz; V_H, −50 mV). C, the amplitude distribution of the detected events had a CV of 0.34 and a mean of 103.6 pA. The coefficient of skewness (C_s) was 0.16 (bin width, 10 pA; n = 67). The insert shows the distribution of the basal current noise giving a s.d. noise of 1 pA. D, correlation plot between 20–80 % rise times and mIPSC amplitudes. No significant correlation was found (Spearman rank order test P > 0.1). E, correlation plot between mIPSC half-widths and amplitudes. No significant correlation was found between these parameters (Spearman rank order test P > 0.1). Non-stationary analysis was performed on all events. F, plot of the mean variance versus the mean amplitude. Note that this plot deviates from the predicted parabolic function as shown in Fig. 3, indicating that the mIPSC amplitude variance cannot be explained only by intrinsic channel activity fluctuation. G, plot of the mean variance versus the mean amplitude of responses normalised with respect to their mean amplitude. The data points were fitted by a parabola allowing to extract the elementary current generated by a single GlyR channel giving an elementary conductance (γ) of 48.6 pS.