  Serotonergic neurons of the dorsal raphe nuclei, with their extensive
innervation of nearly the whole brain have important modulatory effects on many
cognitive and physiological processes. They play important roles in clinical
depression and other psychiatric disorders. In order to quantify the effects of
serotonergic transmission on target cells it is desirable to construct
computational models and to this end these it is necessary to have details of
the biophysical and spike properties of the serotonergic neurons. Here several
basic properties are reviewed with data from several studies since the 1960s to
the present. The quantities included are input resistance, resting membrane
potential, membrane time constant, firing rate, spike duration, spike and
afterhyperpolarization (AHP) amplitude, spike threshold, cell capacitance, soma
and somadendritic areas. The action potentials of these cells are normally
triggered by a combination of sodium and calcium currents which may result in
autonomous pacemaker activity. We here analyse the mechanisms of high-threshold
calcium spikes which have been demonstrated in these cells the presence of TTX.
The parameters for calcium dynamics required to give calcium spikes are quite
different from those for regular spiking which suggests the involvement of
restricted parts of the soma-dendritic surface as has been found, for example,
in hippocampal neurons.
