AUTHOR=Petersen Anders V. , Jensen Camilla S. , Crépel Valérie , Falkerslev Mathias , Perrier Jean-François 

TITLE=Serotonin Regulates the Firing of Principal Cells of the Subiculum by Inhibiting a T-type Ca2+ Current

JOURNAL=Frontiers in Cellular Neuroscience

VOLUME=11

YEAR=2017

URL=https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2017.00060

DOI=10.3389/fncel.2017.00060

ISSN=1662-5102

ABSTRACT=<p>The subiculum is the main output of the hippocampal formation. A high proportion of its principal neurons fire action potentials in bursts triggered by the activation of low threshold calcium currents. This firing pattern promotes synaptic release and regulates spike-timing-dependent plasticity. The subiculum receives a high density of fibers originating from the raphe nuclei, suggesting that serotonin (5-HT) modulates subicular neurons. Here we investigated if and how 5-HT modulates the firing pattern of bursting neurons. By combining electrophysiological analysis with pharmacology, optogenetics and calcium imaging, we demonstrate that 5-HT<sub>2C</sub> receptors reduce bursting activity by inhibiting a low-threshold calcium current mediated by T-type Ca<sup>2+</sup> channels in principal cells of the subiculum. In addition, we show that the activation of this novel pathway decreases bursting activity and the occurrence of epileptiform discharges induced in <italic>in vitro</italic> models for temporal lobe epilepsy (TLE).</p>