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. Author manuscript; available in PMC: 2010 Sep 15.
Published in final edited form as: Neuroscience. 2009 May 14;162(4):989–1000. doi: 10.1016/j.neuroscience.2009.05.016

Figure 2. In tonic firing neurons block of BK channels increases firing rate and promotes bursting.

Figure 2

A, Extracellular recordings from a Purkinje neuron which fired tonically under control conditions in the presence of synaptic blockers (left trace). Superfusion with iberiotoxin (100 nM) caused the cell to fire irregularly (right trace). B, Left panel: Average firing rate vs. time from the neuron discussed in A. Right panel: Cumulative probability distributions of interspike intervals in the presence of iberiotoxin (thick traces) and in control conditions (thin traces) show that iberiotoxin shifted the distribution to shorter intervals (higher firing rate). C, Left panel: Average firing rate vs. time from another tonically firing Purkinje neuron. Superfusion with iberiotoxin increased the firing rate and induced the trimodal pattern of activity. Right panel: Cumulative probability distributions of interspike intervals in the presence of iberiotoxin (thick traces) and in control conditions (thin traces). D, Mean predominant and maximum firing rates for cells in which iberiotoxin caused irregular bursting (left panel) and for cells in which iberiotoxin caused the trimodal pattern of activity (middle panel). In irregular bursting cells block of BK channels significantly increased the predominant firing rate from 61 (± 10) spikes/s in control conditions (C) to 268 (± 87) in iberiotoxin (I) and the maximum firing rate from 102 (± 29) spikes/s to 536 (± 36) spikes/s. In Neurons which acquired the trimodal pattern, block of BK channels significantly increased the predominant firing rate from 55 (± 3) spikes/s to 102 (± 29) and the maximum firing rate from 66 (± 4) spikes/s to 173 (± 28) spikes/s. Values in iberiotoxin were significantly different from control for (*) p<=0.05 and (**) p<= 0.005 (One-way ANOVA). Error bars are mean ± S.E.M. (n=5 for each type of neuron). E, For cells in which iberiotoxin induced a trimodal pattern of firing, the coefficient of variation (CV) for interspike intervals was measured under control conditions and in the presence of iberiotoxin during a period of the tonic phase of the trimodal pattern. Block of BK channels increased the CV from 0.066 (± 0.01) to 0.11 (± 0.03). Error bars are ± S.E.M. (n=5).