Institut de Neurosciences Cognitives et Intégratives d'Aquitaine (UMR5287)

Aquitaine Institute for Cognitive and Integrative Neuroscience



INCIA - UMR 5287- CNRS
Université de Bordeaux

Zone nord Bat 2 2ème étage
146, rue Léo Saignat
33076 Bordeaux cedex
France

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CNRS Ecole Pratique des Hautes Etudes Université de Bordeaux

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Serotonergic modulation of sacral dorsal root stimulation-induced locomotor output in newborn rat./ Neuropharmacology. 2019 Oct 18:107815. doi: 10.1016/j.neuropharm.2019.107815. [Epub ahead of print]

by Loïc Grattier - published on , updated on

Oueghlani Z1, Juvin L1, Lambert FM1, Cardoit L1, Courtand G1, Masmejean F1, Cazalets JR1, Barrière G2.

Author information

1
CNRS (UMR 5287 - INCIA), Université de Bordeaux, 146 rue Léo Saignat, 33076, Bordeaux, France.
2
CNRS (UMR 5287 - INCIA), Université de Bordeaux, 146 rue Léo Saignat, 33076, Bordeaux, France. Electronic address: gregory.barriere@u-bordeaux.fr.

Abstract
Descending neuromodulators from the brainstem play a major role in the development and regulation of spinal sensorimotor functions. Here, the contribution of serotonergic signaling in the lumbar spinal cord was investigated in the context of the generation of locomotor activity. Experiments were performed on in vitro spinal cord preparations from newborn rats (0-5 days). Rhythmic locomotor episodes (fictive locomotion) triggered by tonic electrical stimulations (2Hz, 30s) of a single sacral dorsal root were recorded from bilateral flexor-dominated (L2) and extensor-dominated (L5) ventral roots. We found that the activity pattern induced by sacral stimulation evolves over the 5 post-natal (P) day period. Although alternating rhythmic flexor-like motor bursts were expressed at all ages, the locomotor pattern of extensor-like bursting was progressively lost from P1 to P5. At later stages, serotonin (5-HT) and quipazine (5-HT2A receptor agonist) at concentrations sub-threshold for direct locomotor network activation promoted sacral stimulation-induced fictive locomotion. The 5-HT2A receptor antagonist ketanserin could reverse the agonist’s action but was ineffective when fictive locomotion was already expressed in the absence of 5-HT (mainly before P2). Although inhibiting 5-HT7 receptors with SB266990 did not affect locomotor pattern organization, activating 5-HT1A receptors with 8-OH-DPAT specifically deteriorated extensor phase motor burst activity. We conclude that during the first 5 post-natal days in rat, serotonergic signaling in the lumbar cord becomes increasingly critical for the expression of fictive locomotion. Our findings therefore further underline the importance of both descending serotonergic and sensory afferent pathways in shaping locomotor activity during postnatal development.