Persistent sodium currents (INaP) are common in neuronal circuitries and they have been implicated in several diseases like amyotrophic lateral sclerosis (ALS) and epilepsy. However, the role of INaP in the regulation of specific behaviours is still poorly understood. Here we have characterized INaP and investigated its role in the swimming and struggling behaviour of Xenopus tadpoles. INaP was identified in three groups of neurons, namely sensory Rohon-Beard neurons (RB neurons), descending interneurons (dINs), and non-dINs (neurons rhythmically active in swimming). All groups of neurons expressed INaP but the currents differed in decay time constants, amplitudes, and the membrane potential where INaP peaked. Low concentrations (1 µM) of the INaP blocker, riluzole, blocked INaP for ~ 30 % and decreased the excitability of the three neuron groups without affecting spike amplitudes or cellular input resistances. Riluzole reduced the number of rebound spikes in dINs and depressed repetitive firing in RB neurons and non-dINs. At the behaviour level, riluzole at 1 µM shortened fictive swimming episodes. It also reduced the number of action potentials neurons fire on each struggling cycle. The results show that INaP may play important modulatory roles in motor behaviours.
- Xenopus tadpole
- motor behaviour
- spinal cord
- sodium currents
- Copyright © 2016, Journal of Neurophysiology