Intracellular recordings from burst-firing presumed serotonergic neurones in the rat dorsal raphe nucleus in vivo.

Here we report the existence of burst-firing neurones in the rat dorsal raphe as detected in vivo using intracellular electrophysiological techniques. These neurones discharged single action potentials and doublets or triplets of action potentials in a slow and regular pattern. The apparent input resistance, action potential width and firing threshold of these burst-firing raphe neurones were indistinguishable from classical 5-HT neurones. Spike doublets were evoked by depolarising DC currents, but only in burst-firing neurones. These findings provide further evidence to support the hypothesis that 5-HT neurones (or a sub-set of them) are capable of burst-firing activity.