Question

I've been reading about Dorsal Raphe Nucleus, a serotonin- richpart of the brain. I noticed mentioning of "tonic activity" -regular pulsing that releases neurotransmitters. On top of this"tone" the nucleus can fire bursts of spikes(action potentials?)that further increase neurotransmitter concentrations for a shorttime.

Is this kind of tonic firing common throughout thebrain, or is it DRN specific?