title: Firing properties of auditory primary afferents from the basilar papilla in the chick.
abstract: We performed intracellular and single-unit extracellular recordings of neurons from different regions of the basilar papilla in the isolated chicken inner ear. We compared the spontaneous activity and the response properties of these neurons in embryos at E15 versus posthatching animals at P1. The recordings were carried out from the apical (position 0) to the basal extension at three positions of the basilar papilla, at 5%, 10% and 40% of the entire length of the cochlea. We found that the neurons at E15 recorded from these three regions exhibited a significant higher coefficient of variation compared with those neurons at P1 recorded in the same positions. This shows that in the posthatching age P1 the neurons from the whole basilar papilla become less irregular. We found that the intracellular action potential waveforms generated at E15 had small amplitudes and small depolarization slopes in comparison to those recorded at P1, respectively (53 ± 1 mV vs. 62 ± 2 mV; 66 ± 12 mV/msec vs. 166 ± 23 mV/msec). Furthermore, we also found that the response patterns to injection of current steps were phasic, tonic, or in the form of a not yet reported "burst" pattern. Our study shows that the low irregular discharge, the immature action potential waveforms, and the differences in the response patterns to current injection, highlights the important differences between neurons at E15 and P1, consistent with the incapacity of auditory neurons at embryonic age E16, to respond at sound levels <100 decibels.
authors.affiliation: Escuela de Biología, Benemérita Universidad Autónoma de Puebla (BUAP), Blvd. Valsequillo y Av. San Claudio, Edif. 112-A C.U. Colonia Jardines de San Manuel CP 72570 Puebla, Pue., Mexico.
authors.forename: Salvador
authors.initials: S
authors.lastname: Galicia
authors.affiliation: Facultad de Medicina, BUAP, Av. 13 Sur 2702 Colonia Volcanes CP 72410 Puebla, Pue., Mexico.
authors.forename: Celso
authors.initials: C
authors.lastname: Cortes
authors.affiliation: Facultad de Medicina, BUAP, Av. 13 Sur 2702 Colonia Volcanes CP 72410 Puebla, Pue., Mexico; Hospital Universitario de Puebla, BUAP, Av. 25 poniente 1301Colonia Volcanes CP 72410 Puebla, Pue., Mexico.
authors.forename: Jorge
authors.initials: J
authors.lastname: Cebada
authors.affiliation: Facultad de Psicología, BUAP, Av. 3 oriente 403 Colonia Centro CP 72000 Puebla, Pue., Mexico.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Méndez-Balbuena
authors.affiliation: Instituto de Fisiología, BUAP, Av. 14 Sur 6301 Colonia Jardines de San Manuel CP 72570 Puebla, Pue., Mexico. Electronic address: amira.flores@correo.buap.mx.
authors.forename: Amira
authors.initials: A
authors.lastname: Flores
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000344:Afferent Pathways / Q000502:physiology*; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics; D002642:Chick Embryo; D004558:Electric Stimulation; D004594:Electrophysiology; D009474:Neurons / Q000502:physiology*; D009925:Organ of Corti / Q000166:cytology* / Q000254:growth & development*
keywords: Action potential; Basilar papilla; Chicken; Cochlea; Development; Inner ear