title: Posthearing Ca(2+) currents and their roles in shaping the different modes of firing of spiral ganglion neurons.
abstract: Whereas prehearing spiral ganglion neurons (SGNs) rely faithfully on outputs from spontaneously active developing hair cells, the electrical phenotypes of posthearing neurons are shaped by distinct rapid and graded receptor potentials from hair cells. To date, technical difficulties in isolation of fragile posthearing neurons from the rigid bony labyrinth of the inner ear have hindered analyses of the electrical phenotype of SGNs. Therefore, we have recently developed new strategies to isolate posthearing mouse SGNs for functional analyses. Here, we describe the coarse and fine properties of Ca(2+) currents, which sculpt the firing properties of posthearing SGNs. Murine SGNs express multiple Ca(2+) channel currents to enable diverse functions. We have demonstrated that suppression of Ca(2+) currents results in significant hyperpolarization of the resting membrane potential (rmp) of basal SGNs, suggesting that Ca(2+) influx primes rmp for excitation. In contrast, removal of external Ca(2+) has modest effects on rmp of apical SGNs. The blockade of Ca(2+) currents with a mixture of specific blockers attenuates spontaneously active SGNs. Paradoxically, different subtypes of Ca(2+) currents, such as R-type currents, may activate resting outward conductances since blockage of the current results in depolarization of rmp. In keeping with whole-cell current data, single-channel records revealed multiple diverse Ca(2+) channels in SGNs. Additionally, there were differential expressions of distinct Ca(2+) current densities in the apicobasal contour of the adult cochlea. This report provides invaluable insights into Ca(2+)-dependent processes in adult SGNs.
authors.affiliation: The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China 050017.
authors.forename: Ping
authors.initials: P
authors.lastname: Lv
authors.forename: Choong-Ryoul
authors.initials: CR
authors.lastname: Sihn
authors.forename: Wenying
authors.initials: W
authors.lastname: Wang
authors.forename: Haitao
authors.initials: H
authors.lastname: Shen
authors.forename: Hyo Jeong
authors.initials: HJ
authors.lastname: Kim
authors.forename: Sonia M
authors.initials: SM
authors.lastname: Rocha-Sanchez
authors.forename: Ebenezer N
authors.initials: EN
authors.lastname: Yamoah
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006309:Hearing / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D013136:Spiral Ganglion / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002118:Calcium