Vasopressin generates a persistent voltage-dependent sodium current in a mammalian motoneuron

Raggenbass, Mario; Goumaz, M.; Sermasi, E.; Tribollet, Eliane; Dreifuss, Jean-Jacques

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Title		Vasopressin generates a persistent voltage-dependent sodium current in a mammalian motoneuron
Authors		Raggenbass, Mario Goumaz, M. Sermasi, E. Tribollet, Eliane Dreifuss, Jean-Jacques
Published in		Journal of Neuroscience. 1991, vol. 11, no. 6, p. 1609-1616
Abstract		During the period of life that precedes weaning, the facial nucleus of the newborn rat is rich in 3H-vasopressin binding sites, and exogenous arginine vasopressin (AVP) can excite facial motoneurons by interacting with V1 (vasopressor-type) receptors. We have investigated the mode of action of this peptide by carrying out single-electrode voltage-clamp recordings in coronal brainstem slices from the neonate. Facial motoneurons were identified by antidromic invasion following electrical stimulation of the genu of the facial nerve. When the membrane potential was held at or near its resting level, vasopressin generated an inward current whose magnitude was concentration related; the lowest peptide concentration still effective in eliciting this effect was 10 nM. The vasopressin-induced current, IAVP, was resistant to tetrodotoxin (TTX) and was insensitive to a reduction in extracellular calcium concentration. It was sustained, was inward at all potentials tested (-120 to -25 mV), and increased in magnitude during depolarization. IAVP was not generated by the blockade of a potassium current, because it did not reverse at hyperpolarized potentials, was not affected by a two-fold increase in the transmembrane potassium gradient, and was not modified by the potassium channel blockers tetraethylammonium bromide (TEA), 4-aminopyridin (4-AP), barium, cesium, quinine, glibenclamide, and apamin. Also, IAVP was not affected by changes in the transmembrane chloride gradient. In contrast, it could be reduced by partially substituting extracellular sodium with equimolar N-methyl-D-glucamine or Tris. Our results suggest that vasopressin increases the excitability of facial motoneurons by generating a persistent sodium-dependent membrane current that is voltage gated and TTX resistant.
Keywords		Animals — Animals, Newborn — Arginine Vasopressin/metabolism/ pharmacology — Brain Stem/ physiology — Electric Conductivity/drug effects — Electric Stimulation — Facial Nerve/drug effects/ physiology — Kinetics — Male — Membrane Potentials/drug effects — Motor Neurons/drug effects/ physiology — Rats — Rats, Inbred Strains — Receptors, Angiotensin/metabolism/physiology — Receptors, Vasopressin — Sodium Channels/drug effects/ physiology — Tetrodotoxin/pharmacology
Identifiers		PMID: 1646297
Full text		Article - Limited access to UNIGE Other version: http://www.jneurosci.org/cgi/reprint/11/6/1609.pdf
Structures		Faculté de médecine / Section de médecine fondamentale / Département de neurosciences fondamentales
Citation (ISO format)		RAGGENBASS, Mario et al. Vasopressin generates a persistent voltage-dependent sodium current in a mammalian motoneuron. In: Journal of Neuroscience, 1991, vol. 11, n° 6, p. 1609-1616. https://archive-ouverte.unige.ch/unige:10414