Biophysical properties and computational modeling of calcium spikes in serotonergic neurons of the dorsal raphe nucleus

TL;DR

This paper reviews biophysical properties and models of calcium spikes in serotonergic neurons of the dorsal raphe nucleus, highlighting mechanisms underlying their firing behavior and implications for computational modeling.

Contribution

It provides a comprehensive synthesis of biophysical data and analyzes calcium spike mechanisms, aiding the development of accurate computational models of these neurons.

Findings

Calcium spikes involve distinct parameters from regular spiking.

High-threshold calcium spikes may involve restricted soma-dendritic regions.

Serotonergic neuron properties support autonomous pacemaker activity.

Abstract

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.