Central Serotonin Deficiency Impairs Recovery of Sensorimotor Abilities After Spinal Cord Injury in Rats

Area of Science:

• Neuroscience
• Regenerative Medicine
• Spinal Cord Injury Research

Background:

• Spinal cord injury (SCI) presents significant rehabilitation challenges, particularly in retraining preserved or rebuilt spinal circuitry.
• The serotonergic system, involving serotonin (5-HT), is increasingly recognized for its role in axonal sprouting and regeneration following central nervous system (CNS) trauma.

Purpose of the Study:

• To investigate the role of the central serotonergic system in sensorimotor function recovery after SCI.
• To compare the functional recovery of tryptophan hydroxylase 2 knockout (TPH2 KO) rats, lacking central serotonin, with wild-type (WT) rats post-SCI.

Main Methods:

• Induction of lateral hemisection SCI at the T8 spinal level in TPH2 KO and WT female rats.
• Assessment of sensorimotor recovery using the tapered beam walking (TBW) and ladder walking (LW) tests.
• Evaluation of hindlimb muscle tone, voluntary movements, and compound muscle action potentials (CMAPs) in gastrocnemius (GM) and tibialis (TA) muscles.

Main Results:

• TPH2 KO rats exhibited significantly greater sensorimotor deficits in TBW and LW tests compared to WT rats during weeks 3 and 4 post-SCI.
• Hindlimb muscle tone and voluntary movement recovery dynamics correlated with motor performance improvements.
• Compound muscle action potential analysis revealed slower recovery of sensorimotor pathways in TPH2 KO rats.

Conclusions:

• Central serotonergic mechanisms are critical for sensorimotor function recovery following SCI.
• The TPH2 KO rat model is valuable for studying the 5-HT system's contribution to neurorehabilitation after spinal cord injury.