Noradrenaline does not change the mode of discharge of auditory cortex neurons

The mode of discharge of auditory cortex cells was studied during iontophor etic application of noradrenaline (NA). Only seven of 190 cells showed chan ges in interspike interval distribution during NA application. A similar co nclusion was drawn when the analysis focused on 68 cells classified as burs ting (n = 15), regular spiking (n = 49) or thin spike (n = 4) cells. Only t wo bursting cells showed changes in their ISI distribution. The effects on the mode of discharge were independent of the effect on the spike rate and were not a function of cortical depth. These results suggest that the chang es in firing mode previously described in vitro occur for a limited percent age of cells and/or for cell types not very often recorded in vivo. NeuroRe port 11:23-26 (C) 2000 Lippincott Williams & Wilkins.