Serotonin differentially modulates the intrinsic properties of spinal motoneurons from the adult turtle

doi:10.1113/jphysiol.2007.145706

Serotonin differentially modulates the intrinsic properties of spinal motoneurons from the adult turtle

¹Institute of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark ²Neurobiologie des Signaux Intercellulaires, Université Pierre et Marie Curie, 7 quai Saint Bernard, F-75252 Paris, France

Corresponding author J.-F. Perrier: Institute of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark. Email: perrier{at}mfi.ku.dk

Abstract

This report considers serotonergic (5-HT) effects on spinal motoneurons, reviewing previous data and presenting a new study showing distinct effects of two 5-HT receptor subtypes. We previously investigated the effects of 5-HT on motoneurons in a slice preparation from the spinal cord of the adult turtle. In agreement with previous studies, we had found that 5-HT applied to the extracellular medium promoted a voltage sensitive plateau potential. However, we also reported that this effect was only observed in half of the motoneurons; 5-HT inhibited the firing of the other half of the motoneurons recorded from. To investigate the reasons for this, we applied 5-HT focally by means of the microiontophoresis technique. Facilitation of plateau potentials was observed when 5-HT was released at sites throughout the somatodendritic region. However, motoneurons were inhibited by 5-HT when selectively applied in the perisomatic region. These two effects could be induced in the same motoneuron. With pharmacological tools, we demonstrate here that the facilitation of plateau potentials is mediated by 5-HT₂ receptors and the inhibitory effect is due to the activation of 5-HT_1A/7 receptors.

Footnotes

(Received 27 September 2007; accepted after revision 26 November 2007; first published online 20 December 2007)
This report was presented at The Journal of Physiology Symposium on The cortex, interneurones and motoneurones in the control of movement, IBRO World Congress of Neuroscience, Darwin, Australia, 19 July 2007. It was commissioned by the Editorial Board and reflects the views of the authors.