title: FMRFamide-related peptide expression in the vestibular-afferent neurons.
abstract: Vestibular-afferent neurons innervate hair cells from the sensory epithelia of vestibular end-organs and their action-potential discharge dynamics are driven by linear and angular accelerations of the head. The electrical activity of the vestibular-afferent neurons depends on their intrinsic properties and on the synaptic input from hair cells and from the terminals of the efferent system. Here we report that vestibular-afferent neurons of the rat are immunoreactive to RFamide-related peptides, and that the stronger signal comes from calyx-shaped neuron dendrites, with no signal detected in hair cells or supporting cells. The whole-cell voltage clamp recording of isolated afferent neurons showed that they express robust acid-sensing ionic currents (ASICs). Extracellular multiunit recordings of the vestibular nerve in a preparation in vitro of the rat inner ear showed that the perfusion of FMRFamide (a snail ortholog of this family of neuropeptides) exerts an excitatory effect on the afferent-neurons spike-discharge rate. Because the FMRFamide cannot activate the ASIC but reduces its desensitization generating a more robust current, its effect indicates that the ASIC are tonically active in the vestibular-afferent neurons and modulated by RFamide-like peptides.
authors.affiliation: Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Apartado Postal 406, Puebla, Pue. CP 72000, Mexico.
authors.forename: Francisco
authors.initials: F
authors.lastname: Mercado
authors.forename: Iván
authors.initials: I
authors.lastname: López
authors.forename: Aida
authors.initials: A
authors.lastname: Ortega
authors.forename: Angélica
authors.initials: A
authors.lastname: Almanza
authors.forename: Enrique
authors.initials: E
authors.lastname: Soto
authors.forename: Rosario
authors.initials: R
authors.lastname: Vega
mesh_terms: D000818:Animals; D055724:Electrophysiological Phenomena; D019835:FMRFamide / Q000096:biosynthesis*; D005455:Fluorescent Antibody Technique; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D008297:Male; D009475:Neurons, Afferent / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D020318:Rats, Long-Evans; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000166:cytology* / Q000294:innervation
chemical_list: D019835:FMRFamide