The absence of resurgent sodium current in mouse spinal neurons

• Published in: Brain research 1999-12, Vol.849 (1), p.162-168
• Main Authors: Pan, Fei, Beam, Kurt G.
• Format: Article
• Language: English
• Subjects: Action Potentials; Animals; Animals, Newborn; Biological and medical sciences; Cells, Cultured; Central nervous system; Cerebellum - cytology; Cerebellum - physiology; Electrophysiology; Fundamental and applied biological sciences. Psychology; Mice; Motor Neurons - cytology; Motor Neurons - physiology; NAV1.6 Voltage-Gated Sodium Channel; Nerve Tissue Proteins - physiology; Neurons - cytology; Neurons - physiology; Patch-Clamp Techniques; Purkinje Cells - cytology; Purkinje Cells - physiology; Resurgent current; Scn8a; Scn8a gene; Sodium channel; Sodium Channels - physiology; Spinal Cord - cytology; Spinal Cord - physiology; Spinal motoneuron; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(99)02060-0

The Scn8a gene encodes a neuronal, voltage-gated sodium channel, which is highly expressed in both cerebellar Purkinje neurons and spinal motoneurons [D.L. Burgess, D.C. Kohrman, J. Galt, N.W. Plummer, J.M. Jones, B. Spear, M.H. Meisler, Mutation of a new sodium channel gene, Scn8a, in the mouse mutant `motor endplate disease', Nature Genetics 10 (1995) 461–465; K.L. Schaller, D.M. Krzemien, P.J. Yarowsky, B.K. Krueger, J.H. Caldwell, A novel, abundant sodium channel expressed in neurons and glia, J. Neurosci. 15 (1995) 3231–3242]. Sodium channels in Purkinje cells produce an unusual, “resurgent” current when the cells are repolarized to intermediate potentials (−60 to −20 mV) following a strong depolarization that completely inactivates transient sodium current [I.M. Raman, L.K. Sprunger, M.H. Meisler, B.P. Bean, Altered subthreshold sodium currents and disrupted firing patterns in Purkinje neurons of Scn8a mutant mice, Neuron 19 (1997) 881–891; I.M. Raman, B.P. Bean, Resurgent sodium current and action potential formation in dissociated cerebellar Purkinje neurons, J. Neurosci. 17 (1997) 4517–4526]. Here, we have examined whether large spinal neurons (predominantly motoneurons), isolated from P6–P8 mice and cultured overnight, produce sodium currents resembling those either of Purkinje cells or of Xenopus oocytes after heterologous expression of Scn8a. We found that P10–P14 Purkinje cells exhibited resurgent current (ranging from −3.6 to −15.4 pA/pF in 16 cells at −40 mV), but cultured spinal neurons had little or no such current (