Oscillatory firing is an important process in neural system for presenting, integrating and synchronizing neuronal signals.Though most pyramidal neurons are able to oscillate at a broad band, only a few specific neurons in brain can generate oscillation spontaneously.Here we report a novel oscillation elicited by glutamate applied to the apical dendrite of pyramidal neuron.We found that glutamate-elicited oscillation was dependent on activation of NMDA receptor and was evoked only in apical dendrite but not in soma.The firing is an intrinsic property of individual neuron and depends on extracellular Mg2+ and Ca2+.A parallel change between intracellular Ca2+ and oscillating membrane potential was clearly observed during oscillation, with much stronger calcium oscillation in dendrite than that in soma.Further study showed that two calcium-activated currents SK and AHP current underlie the repolarization phase of the firing.And the frequency of the oscillation is dominated by HCN channel, a channel increasingly distributed along dendrite.Dopamine was found to modulate the firing by prolonging the firing duration and increasing oscillation frequency.However, in cocaine withdrawal rats, dopamine application still produced prolonged duration but with decreased frequency.By the use of single unit recording techniques and spectral analysis, we also proved that in vivo slow oscillation shares similar mechanisms of the dendritically induced oscillation, thus indicating possible existence of the firing under physiological condition.These data demonstrate an interesting oscillatory coding mechanism in the apical dendrite and shed light on potential coding changes by addictive drugs.