The modulation of two motor behaviors by persistent sodium currents inXenopus laevistadpoles.
Persistent sodium currents (INaP) are common in neuronal circuitries and have been implicated in several diseases, such as amyotrophic lateral sclerosis (ALS) and epilepsy. However, the role ofINaPin the regulation of specific behaviors is still poorly understood. In this study we have characterizedINaPand investigated its role in the swimming and struggling behavior ofXenopustadpoles.INaPwas 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 expressedINaP, but the currents differed in decay time constants, amplitudes, and the membrane potential at whichINaPpeaked. Low concentrations (1 µM) of theINaPblocker riluzole blockedINaP~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 behavior level, riluzole at 1 µM shortened fictive swimming episodes. It also reduced the number of action potentials neurons fired on each struggling cycle. The results show thatINaPmay play important modulatory roles in motor behaviors.NEW & NOTEWORTHYWe have characterized persistent sodium currents in three groups of spinal neurons and their role in shaping spiking activity in theXenopustadpole. We then attempted to evaluate the role of persistent sodium currents in regulating tadpole swimming and struggling motor outputs by using low concentrations of the persistent sodium current antagonist riluzole.
School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom erik.svensson@neuro.uu.se.
Erik
E
Svensson
School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom.
Hugo
H
Jeffreys
School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom.
Wen-Chang
WC
Li
D000200:Action Potentials; D000818:Animals; D005260:Female; D007814:Larva / Q000502:physiology; D008297:Male; D009043:Motor Activity; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D019782:Riluzole / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D061566:Voltage-Gated Sodium Channels / Q000378:metabolism; D014982:Xenopus laevis
D026941:Sodium Channel Blockers; D061566:Voltage-Gated Sodium Channels; D019782:Riluzole; D012964:Sodium
Xenopus tadpole; motor behavior; riluzole; sodium currents; spinal cord