Pharmacological manipulation of the immediate effects of spinal trauma in neonatal rats reveals a crucial role for TRPV4 receptors

Physical trauma to the spinal cord causes a massive depolarising injury potential (DIP), transient spinal hypoxia and extensive cell loss at the injury site, disrupting conduction along white matter tracts. This leads to transient hypotonia and areflexia during the spinal shock phase. The link between DIP magnitude and spinal cord injury progression, as well as potential pharmacological interventions, remains unexplored, especially in neonatal age. To limit DIP peak and accelerate motor reflex response (MRR) recovery, we applied selective neurochemicals targeting mechanosensitive and classical neurotransmitter receptors. These agents were applied during experimental trauma to the mid-thoracic cord of CNS preparations from 0- to 2.5-day-old rats. Continuous lumbar root recordings monitored baseline levels and MRR elicited by electric pulses to sacro-caudal afferents. In uninjured preparations, each agent affected baseline polarisation, synaptic responses and bursting activity, indicating their role in maintaining the functional state of the spinal cord. Neurochemicals targeting glutamatergic, adenosinergic, glycinergic or GABAergic receptors did not impact trauma outcomes (DIP or MRR). Only the transient receptor potential, vanilloid 4 (TRPV4) antagonist RN1734, not TRPA1 antagonist AP18, reduced DIP peak and accelerated MRR recovery following trauma. The protective effect of RN1734 was corroborated by TRPV4 expression in neonatal spinal neurons and glial cells, located in dura and around the central canal. Blocking gap junctions and GABA_A receptors also restored MRR, but less effectively and more slowly than TRPV4 antagonism. Our findings show that blocking mechanosensitive TRPV4 receptors at the moment of impact effectively reduces the immediate pathological effects of a neonatal spinal trauma.