Two patterns of neuronal firing, bursting and regular spiking, are obs
erved in the somatosensory cortex of anesthetized rats. The effects of
excitatory amino acid receptor agonists and antagonists on these disc
harge types have been examined in vivo, in order to assess their invol
vement in the generation of such firing patterns. The analysis of inte
rspike interval histograms indicates that N-methyl-D-aspartate (NMDA)
receptors are involved in the generation of bursting responses while n
on-NMDA receptors mediate the regular spiking pattern of firing in ind
ividual neurons. It is also suggested that a basal level of ongoing ne
uronal excitation via the activation of non-NMDA receptors is required
for bursting to be evoked through NMDA receptors.