Fig. 4.

Spontaneous excitatory synaptic inputs are not responsible for the tonic firing of cholinergic interneurons in vitro. A, B, Cell-attached voltage-clamp recordings show that pharmacological blockade of AMPA and NMDA receptors had no obvious effect on the spike rate or pattern.C, D, Application of CNQX (20 μm) and CPP (50 μm) did not produce any change in the ISI histogram (bin width = 10 msec; 2 min sample), and accordingly the firing frequency and CV were unaltered. Control data are in C. E, F, Group data illustrate that spontaneous excitatory inputs do not have any detectable effect on the firing rate (E; control = 1.25 ± 0.98 Hz; CNQX + CPP = 1.46 ± 1.04 Hz;n = 17; p > 0.2) or CV (F; control = 0.703 ± 0.373; CNQX + CPP = 0.595 ± 0.334; n = 17;p > 0.2).