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Contini D, Holstein GR, Art JJ. Synaptic cleft microenvironment influences potassium permeation and synaptic transmission in hair cells surrounded by calyx afferents in the turtle. J Physiol 2019; 598:853-889. [PMID: 31623011 DOI: 10.1113/jp278680] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/13/2019] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS In central regions of vestibular semicircular canal epithelia, the [K+ ] in the synaptic cleft ([K+ ]c ) contributes to setting the hair cell and afferent membrane potentials; the potassium efflux from type I hair cells results from the interdependent gating of three conductances. Elevation of [K+ ]c occurs through a calcium-activated potassium conductance, GBK , and a low-voltage-activating delayed rectifier, GK(LV) , that activates upon elevation of [K+ ]c . Calcium influx that enables quantal transmission also activates IBK , an effect that can be blocked internally by BAPTA, and externally by a CaV 1.3 antagonist or iberiotoxin. Elevation of [K+ ]c or chelation of [Ca2+ ]c linearizes the GK(LV) steady-state I-V curve, suggesting that the outward rectification observed for GK(LV) may result largely from a potassium-sensitive relief of Ca2+ inactivation of the channel pore selectivity filter. Potassium sensitivity of hair cell and afferent conductances allows three modes of transmission: quantal, ion accumulation and resistive coupling to be multiplexed across the synapse. ABSTRACT In the vertebrate nervous system, ions accumulate in diffusion-limited synaptic clefts during ongoing activity. Such accumulation can be demonstrated at large appositions such as the hair cell-calyx afferent synapses present in central regions of the turtle vestibular semicircular canal epithelia. Type I hair cells influence discharge rates in their calyx afferents by modulating the potassium concentration in the synaptic cleft, [K+ ]c , which regulates potassium-sensitive conductances in both hair cell and afferent. Dual recordings from synaptic pairs have demonstrated that, despite a decreased driving force due to potassium accumulation, hair cell depolarization elicits sustained outward currents in the hair cell, and a maintained inward current in the afferent. We used kinetic and pharmacological dissection of the hair cell conductances to understand the interdependence of channel gating and permeation in the context of such restricted extracellular spaces. Hair cell depolarization leads to calcium influx and activation of a large calcium-activated potassium conductance, GBK , that can be blocked by agents that disrupt calcium influx or buffer the elevation of [Ca2+ ]i , as well as by the specific KCa 1.1 blocker iberiotoxin. Efflux of K+ through GBK can rapidly elevate [K+ ]c , which speeds the activation and slows the inactivation and deactivation of a second potassium conductance, GK(LV) . Elevation of [K+ ]c or chelation of [Ca2+ ]c linearizes the GK(LV) steady-state I-V curve, consistent with a K+ -dependent relief of Ca2+ inactivation of GK(LV) . As a result, this potassium-sensitive hair cell conductance pairs with the potassium-sensitive hyperpolarization-activated cyclic nucleotide-gated channel (HCN) conductance in the afferent and creates resistive coupling at the synaptic cleft.
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Affiliation(s)
- Donatella Contini
- Department of Anatomy & Cell Biology, University of Illinois College of Medicine, 808 S. Wood St, Chicago, IL, 60612, USA
| | - Gay R Holstein
- Neurology, Icahn School of Medicine at Mount Sinai, 1468 Madison Ave, New York, NY, 10029, USA
| | - Jonathan J Art
- Department of Anatomy & Cell Biology, University of Illinois College of Medicine, 808 S. Wood St, Chicago, IL, 60612, USA
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Seasonal plasticity of auditory saccular sensitivity in “sneaker” type II male plainfin midshipman fish, Porichthys notatus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 203:211-222. [DOI: 10.1007/s00359-017-1157-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 02/16/2017] [Accepted: 02/17/2017] [Indexed: 10/20/2022]
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3
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Channeling your inner ear potassium: K+ channels in vestibular hair cells. Hear Res 2016; 338:40-51. [DOI: 10.1016/j.heares.2016.01.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 01/22/2016] [Accepted: 01/25/2016] [Indexed: 01/05/2023]
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Forlano PM, Sisneros JA, Rohmann KN, Bass AH. Neuroendocrine control of seasonal plasticity in the auditory and vocal systems of fish. Front Neuroendocrinol 2015; 37:129-45. [PMID: 25168757 PMCID: PMC4342331 DOI: 10.1016/j.yfrne.2014.08.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 08/09/2014] [Accepted: 08/14/2014] [Indexed: 11/27/2022]
Abstract
Seasonal changes in reproductive-related vocal behavior are widespread among fishes. This review highlights recent studies of the vocal plainfin midshipman fish, Porichthys notatus, a neuroethological model system used for the past two decades to explore neural and endocrine mechanisms of vocal-acoustic social behaviors shared with tetrapods. Integrative approaches combining behavior, neurophysiology, neuropharmacology, neuroanatomy, and gene expression methodologies have taken advantage of simple, stereotyped and easily quantifiable behaviors controlled by discrete neural networks in this model system to enable discoveries such as the first demonstration of adaptive seasonal plasticity in the auditory periphery of a vertebrate as well as rapid steroid and neuropeptide effects on vocal physiology and behavior. This simple model system has now revealed cellular and molecular mechanisms underlying seasonal and steroid-driven auditory and vocal plasticity in the vertebrate brain.
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Affiliation(s)
- Paul M Forlano
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY 11210, United States; Programs in Neuroscience, Ecology, Evolutionary Biology and Behavior, and Behavioral and Cognitive Neuroscience, The Graduate Center, City University of New York, New York, NY 10016, United States; Aquatic Research and Environmental Assessment Center, Brooklyn College, Brooklyn, NY 11210, United States.
| | - Joseph A Sisneros
- Department of Psychology, University of Washington, Seattle, WA 98195, United States; Department of Biology, University of Washington, Seattle, WA 98195, United States; Virginia Merrill Bloedel Hearing Research Center, Seattle, WA 98195, United States
| | - Kevin N Rohmann
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States
| | - Andrew H Bass
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, United States; Bodega Marine Laboratory, University of California, Bodega Bay, CA, 94923, United States
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5
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Plasticity in ion channel expression underlies variation in hearing during reproductive cycles. Curr Biol 2013; 23:678-83. [PMID: 23562266 DOI: 10.1016/j.cub.2013.03.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Revised: 02/19/2013] [Accepted: 03/04/2013] [Indexed: 01/19/2023]
Abstract
Sensory plasticity related to reproductive state, hormonal profiles, and experience is widespread among vertebrates, including humans. Improvements in audio-vocal coupling that heighten the detection of conspecifics are part of the reproductive strategy of many nonmammalian vertebrates. Although seasonal changes in hearing are known, molecular mechanisms determining this form of adult sensory plasticity remain elusive. Among both nonmammals and mammals, large-conductance, calcium-activated potassium (BK) channels underlie a primary outward current having a predominant influence on frequency tuning in auditory hair cells. We now report an example from fish showing that increased BK channel abundance can improve an individual's ability to hear vocalizations during the breeding season. Pharmacological manipulations targeting BK channels, together with measures of BK transcript abundance, can explain the seasonal enhancement of auditory hair cell sensitivity to the frequency content of calls. Plasticity in ion channel expression is a simple, evolutionarily labile solution for sculpting sensory bandwidth to maximize the detection of conspecific signals during reproductive cycles.
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6
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Sisneros JA. Adaptive hearing in the vocal plainfin midshipman fish: getting in tune for the breeding season and implications for acoustic communication. Integr Zool 2011; 4:33-42. [PMID: 21392275 DOI: 10.1111/j.1749-4877.2008.00133.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The plainfin midshipman fish (Porichthys notatus Girard, 1854) is a vocal species of batrachoidid fish that generates acoustic signals for intraspecific communication during social and reproductive activity and has become a good model for investigating the neural and endocrine mechanisms of vocal-acoustic communication. Reproductively active female plainfin midshipman fish use their auditory sense to detect and locate "singing" males, which produce a multiharmonic advertisement call to attract females for spawning. The seasonal onset of male advertisement calling in the midshipman fish coincides with an increase in the range of frequency sensitivity of the female's inner ear saccule, the main organ of hearing, thus leading to enhanced encoding of the dominant frequency components of male advertisement calls. Non-reproductive females treated with either testosterone or 17β-estradiol exhibit a dramatic increase in the inner ear's frequency sensitivity that mimics the reproductive female's auditory phenotype and leads to an increased detection of the male's advertisement call. This novel form of auditory plasticity provides an adaptable mechanism that enhances coupling between sender and receiver in vocal communication. This review focuses on recent evidence for seasonal reproductive-state and steroid-dependent plasticity of auditory frequency sensitivity in the peripheral auditory system of the midshipman fish. The potential steroid-dependent mechanism(s) that lead to this novel form of auditory and behavioral plasticity are also discussed.
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Affiliation(s)
- Joseph A Sisneros
- Department of Psychology, the Department of Biology and the Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, USA
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7
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Rohmann KN, Bass AH. Seasonal plasticity of auditory hair cell frequency sensitivity correlates with plasma steroid levels in vocal fish. J Exp Biol 2011; 214:1931-42. [PMID: 21562181 PMCID: PMC3092729 DOI: 10.1242/jeb.054114] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/18/2011] [Indexed: 01/14/2023]
Abstract
Vertebrates displaying seasonal shifts in reproductive behavior provide the opportunity to investigate bidirectional plasticity in sensory function. The midshipman teleost fish exhibits steroid-dependent plasticity in frequency encoding by eighth nerve auditory afferents. In this study, evoked potentials were recorded in vivo from the saccule, the main auditory division of the inner ear of most teleosts, to test the hypothesis that males and females exhibit seasonal changes in hair cell physiology in relation to seasonal changes in plasma levels of steroids. Thresholds across the predominant frequency range of natural vocalizations were significantly less in both sexes in reproductive compared with non-reproductive conditions, with differences greatest at frequencies corresponding to call upper harmonics. A subset of non-reproductive males exhibiting an intermediate saccular phenotype had elevated testosterone levels, supporting the hypothesis that rising steroid levels induce non-reproductive to reproductive transitions in saccular physiology. We propose that elevated levels of steroids act via long-term (days to weeks) signaling pathways to upregulate ion channel expression generating higher resonant frequencies characteristic of non-mammalian auditory hair cells, thereby lowering acoustic thresholds.
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Affiliation(s)
- Kevin N Rohmann
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14854, USA.
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8
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Sisneros JA. Seasonal plasticity of auditory saccular sensitivity in the vocal plainfin midshipman fish, Porichthys notatus. J Neurophysiol 2009; 102:1121-31. [PMID: 19553489 DOI: 10.1152/jn.00236.2009] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The plainfin midshipman fish, Porichthys notatus, is a seasonally breeding species of marine teleost fish that generates acoustic signals for intraspecific social and reproductive-related communication. Female midshipman use the inner ear saccule as the main acoustic endorgan for hearing to detect and locate vocalizing males that produce multiharmonic advertisement calls during the breeding season. Previous work showed that the frequency sensitivity of midshipman auditory saccular afferents changed seasonally with female reproductive state such that summer reproductive females became better suited than winter nonreproductive females to encode the dominant higher harmonics of the male advertisement calls. The focus of this study was to test the hypothesis that seasonal reproductive-dependent changes in saccular afferent tuning is paralleled by similar changes in saccular sensitivity at the level of the hair-cell receptor. Here, I examined the evoked response properties of midshipman saccular hair cells from winter nonreproductive and summer reproductive females to determine if reproductive state affects the frequency response and threshold of the saccule to behaviorally relevant single tone stimuli. Saccular potentials were recorded from populations of hair cells in vivo while sound was presented by an underwater speaker. Results indicate that saccular hair cells from reproductive females had thresholds that were approximately 8 to 13 dB lower than nonreproductive females across a broad range of frequencies that included the dominant higher harmonic components and the fundamental frequency of the male's advertisement call. These seasonal-reproductive-dependent changes in thresholds varied differentially across the three (rostral, middle, and caudal) regions of the saccule. Such reproductive-dependent changes in saccule sensitivity may represent an adaptive plasticity of the midshipman auditory sense to enhance mate detection, recognition, and localization during the breeding season.
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Affiliation(s)
- Joseph A Sisneros
- Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
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9
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Rohmann KN, Deitcher DL, Bass AH. Calcium-activated potassium (BK) channels are encoded by duplicate slo1 genes in teleost fishes. Mol Biol Evol 2009; 26:1509-21. [PMID: 19321796 DOI: 10.1093/molbev/msp060] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Calcium-activated, large conductance potassium (BK) channels in tetrapods are encoded by a single slo1 gene, which undergoes extensive alternative splicing. Alternative splicing generates a high level of functional diversity in BK channels that contributes to the wide range of frequencies electrically tuned by the inner ear hair cells of many tetrapods. To date, the role of BK channels in hearing among teleost fishes has not been investigated at the molecular level, although teleosts account for approximately half of all extant vertebrate species. We identified slo1 genes in teleost and nonteleost fishes using polymerase chain reaction and genetic sequence databases. In contrast to tetrapods, all teleosts examined were found to express duplicate slo1 genes in the central nervous system, whereas nonteleosts that diverged prior to the teleost whole-genome duplication event express a single slo1 gene. Phylogenetic analyses further revealed that whereas other slo1 duplicates were the result of a single duplication event, an independent duplication occurred in a basal teleost (Anguilla rostrata) following the slo1 duplication in teleosts. A third, independent slo1 duplication (autotetraploidization) occurred in salmonids. Comparison of teleost slo1 genomic sequences to their tetrapod orthologue revealed a reduced number of alternative splice sites in both slo1 co-orthologues. For the teleost Porichthys notatus, a focal study species that vocalizes with maximal spectral energy in the range electrically tuned by BK channels in the inner ear, peripheral tissues show the expression of either one (e.g., vocal muscle) or both (e.g., inner ear) slo1 paralogues with important implications for both auditory and vocal physiology. Additional loss of expression of one slo1 paralogue in nonneural tissues in P. notatus suggests that slo1 duplicates were retained via subfunctionalization. Together, the results predict that teleost fish achieve a diversity of BK channel subfunction via gene duplication, rather than increased alternative splicing as witnessed for the tetrapod and invertebrate orthologue.
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Affiliation(s)
- Kevin N Rohmann
- Department of Neurobiology and Behavior, Cornell University.
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10
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Sisneros JA. Steroid-dependent auditory plasticity for the enhancement of acoustic communication: recent insights from a vocal teleost fish. Hear Res 2009; 252:9-14. [PMID: 19168118 DOI: 10.1016/j.heares.2008.12.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Revised: 12/02/2008] [Accepted: 12/29/2008] [Indexed: 10/21/2022]
Abstract
The vocal plainfin midshipman fish (Porichthys notatus) has become an excellent model for identifying neural mechanisms of auditory perception that may be shared by all vertebrates. Recent neuroethological studies of the midshipman fish have yielded strong evidence for the steroid-dependent modulation of hearing sensitivity that leads to enhanced coupling of sender and receiver in this vocal-acoustic communication system. Previous work shows that non-reproductive females treated with either testosterone or 17beta-estradiol exhibit an increase in the degree of temporal encoding by the auditory saccular afferents to the dominant frequency content of male vocalizations produced during social-reproductive behaviors. The expanded frequency sensitivity of steroid treated females mimics the reproductive female's auditory phenotype and is proposed to improve the detection and localization of calling conspecific mates during the summer breeding season. This review focuses on the novel form of steroid-dependent auditory plasticity that is found in the adult midshipman fish and its association with the reproductive biology and behavior of this species. Evidence for midshipman reproductive-state and steroid-dependent auditory plasticity is reviewed and the potential mechanisms that lead to this novel form of adaptive plasticity are discussed.
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Affiliation(s)
- Joseph A Sisneros
- Department of Psychology, University of Washington, 337 Guthrie Hall, Box 351525, Seattle, WA 98195-1525, USA.
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11
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Alshuaib WB, Mathew MV. Resistance of delayed-rectifier K+ current to cadmium in Drosophila neurons. Int J Neurosci 2004; 114:481-91. [PMID: 15195353 DOI: 10.1080/00207450490422795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The delayed-rectifier potassium current (IKDR) is important in repolarizing the membrane potential and determining the level of neuronal excitability. We investigated the effect of cadmium on this potassium current. The whole-cell patch-clamp technique was used to measure IKDR from cultured Drosophila neurons derived from embryonic neuroblasts. The current was measured from neurons before and after the application of 0.1 mM cadmium to the external saline. IKDR was similar in the cadmium-containing saline (383 +/- 47 pA) and the control saline (401 +/- 60 pA). These results indicate that cadmium neurotoxicity does not specifically affect IKDR in Drosophila neurons.
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Affiliation(s)
- Waleed B Alshuaib
- Department of Physiology, Faculty of Medicine, Kuwait University, P.O. Box 24923, Safat 13110, Kuwait.
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12
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Abstract
Female midshipman fish (Porichthys notatus) use the auditory sense to detect and locate vocalizing males during the breeding season. Detection of conspecific vocal signals is essential to their reproductive success and can evoke strong phonotactic responses in gravid females but not in spent females that have released all of their eggs. Here, we test the hypothesis that seasonal variation in reproductive state affects the neurophysiological response properties of the peripheral auditory system in female midshipman fish. Iso-intensity responses of eighth nerve afferents from the sacculus, the main auditory end organ of the inner ear, to individual tones were measured for spike rate and vector strength (VS) of synchronization. Most auditory saccular units in reproductive, summer females showed robust temporal encoding up to 340 Hz, whereas nonreproductive winter females showed comparable encoding only up to 100 Hz. The dramatic upward shift in temporal encoding among summer fish was paralleled by increases in best frequency (BF), maximum evoked spike rate at BF, VS values at BF, and the percentage of units that showed significant VS to iso-intensity tones >140 Hz. Reproductive summer females were best suited to encode the higher harmonic components of male advertisement calls. This first demonstration of a natural cyclicity in peripheral auditory frequency sensitivity among vertebrates may represent, in this case, an adaptive plasticity of the female midshipman's auditory system to enhance the acquisition of auditory information needed for mate identification and localization during the breeding season.
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13
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Affiliation(s)
- Ruth Anne Eatock
- The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, Houston, Texas 77030, USA
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14
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Marcotti W, Russo G, Prigioni I. Inactivating and non-activating delayed rectifier K+ currents in hair cells of frog crista ampullaris. Hear Res 1999; 135:113-23. [PMID: 10491960 DOI: 10.1016/s0378-5955(99)00097-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The possible presence of different types of delayed rectifier K+ current (I(K)) was studied in vestibular hair cells of frog semicircular canals. Experiments were performed in thin slice preparations of the whole crista ampullaris and recordings were made using the whole-cell patch-clamp technique. We found that an apparent homogeneous I(K), isolated from the other K+ currents, could be pharmacologically separated into two complementary components: a capsaicin-sensitive current (I(Kc)) and a barium-sensitive current (I(K,b)). I(K,c) was recruited at potentials more positive than -60 mV and showed a slow activation having a time constant (tau(a)) ranging on average from 12 ms at 40 mV to 32 ms at -20 mV. This current inactivated slowly with two voltage-independent time constants (ta(d1) and tau(d2) were 300 ms and 4 s respectively) and more than 80% of the channels were in an inactivated state at the cell resting potential. I(K,b) was also recruited at potentials more positive than -60 mV, but in contrast to I(K,c), it activated more rapidly (tau(a) ranged on average from 1 ms at 40 mV to 4.5 ms at -20 mV) and it did not exhibit any inactivation process. Current clamp experiments revealed that I(K,b), at variance with I(K,c), contributes to the cell resting potential and represents the main repolarizing current when sensory cells are depolarized from rest. I(K,c) could have a role in hair cells when they are depolarized after hyperpolarizing stimuli, a condition that removes channel inactivation.
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Affiliation(s)
- W Marcotti
- Institute of General Physiology, University of Pavia, Italy
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15
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Abstract
Although it is widely accepted that the electrical resonance seen in many types of auditory and vestibular hair cells contributes to frequency selectivity in these sensory systems, unexplained discrepancies in the frequency (f) and sharpness (Q) of tuning have raised serious questions. For example, enzymatically dissociated hair cells from bullfrog (Rana catesbeiana) sacculus resonate at frequencies well above the range of auditory and seismic stimuli to which the sacculus is most responsive. Such disparities, in addition to others, have led to the proposal that electrical resonance alone cannot account for frequency tuning. Using grassfrog (Rana pipiens) saccular hair cells, we show that the reported discrepancies in f and Q in this organ can be explained by the deleterious effects of enzyme (papain) exposure during cell dissociation. In patch-clamp studies of hair cells in a semi-intact epithelial preparation, we observed a variety of voltage behaviors with frequencies of 35-75 Hz. This range is well below the range of resonant frequencies observed in enzymatically dissociated hair cells and more in tune with the frequency range of natural stimuli to which the sacculus is maximally responsive. The sharpness of tuning also agreed with previous studies using natural stimuli. In contrast to results from enzymatically dissociated hair cells, both a calcium-activated K+ (KCa) current and a voltage-dependent K+ (KV) current contributed to the oscillatory responses of hair cells in the semi-intact preparation. The properties of the KCa and the Ca2+ current were altered by enzymatic dissociation. KV and a small-conductance calcium-activated K+ current were apparently eliminated.
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Steinacker A, Monterrubio J, Perez R, Mensinger AF, Marin A. Electrophysiology and pharmacology of outward potassium currents in semicircular canal hair cells of toadfish, Opsanus tau. Hear Res 1997; 109:11-20. [PMID: 9259232 DOI: 10.1016/s0378-5955(97)00038-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Outward currents from hair cells from the horizontal semicircular canal (HSCC) of the toadfish were investigated using whole cell patch clamp methods. Two classes of hair cells are found. One class (approx. 10% of cells) showed only a non-inactivating current (IKCa) which was blocked by 2 mM TEA. A second class had both inactivating and non-inactivating currents. The former (IA) was blocked by 4-AP (1 mM) and the latter (IKCa) by TEA (2-20 mM) . While the majority of the cells expressed both these outward currents, due to IA inactivation both currents are functionally present in the same cell only between -60 and -40 mV. At more depolarized membrane potentials, IA was inactivated, suggesting that a single hair cell may have two distinct signalling modes, one dominated by IA at more hyperpolarized membrane potentials and the other by IKCa at depolarized values where ICa is beginning to grow, increasing both amplitude and activation rate of IKCa. The switch between modes will be determined by the amplitude and frequency characteristics of the stimulus and possibly also by actions of efferent transmitters. In current clamp mode, 10% of the HSCC hair cells showed high Q and high frequency resonance, from 44 to 360 Hz at 12 degrees C. These cells expressed only one outward calcium dependent, non-inactivating, TEA sensitive current, characteristic of IKCa. A suggested role for high frequency resonance is as positive feedback to produce a high frequency updating of the stereociliary compliance to most faithfully transduce angular acceleration.
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Affiliation(s)
- A Steinacker
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, USA.
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Nenov AP, Norris C, Bobbin RP. Acetylcholine response in guinea pig outer hair cells. II. Activation of a small conductance Ca(2+)-activated K+ channel. Hear Res 1996; 101:149-72. [PMID: 8951441 DOI: 10.1016/s0378-5955(96)00143-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The type of K+ channel involved in the acetylcholine (ACh) evoked response (Ksub; sub stands for suberyldicholine) in guinea pig outer hair cells (OHCs) is still uncertain. The present study tests the hypotheses that Ksub is one of the following: a big conductance Ca(2+)-dependent K+ channel (BK), a small conductance Ca(2+)-dependent K+ channel (SK), a KA type of K+ channel, or a Kn type of K+ channel. Patch-clamp technique in the whole-cell mode was used to record from single guinea pig OHCs. ACh (100 microM) was applied to voltage-clamped OHCs and the ACh-induced currents (IACh) were measured. Charybdotoxin (100 nM) had no effect on IACh, while apamin (1 microM) blocked more than 90% of IACh. Lowering the external Ca2+ concentration caused a hyperpolarizing shift of the IACh monitored as a function of the prepulse voltage. Increasing internal Mg2+ (Mgi2+) concentration caused a reduction in the outward IACh without affecting the inward IACh. The Ksub channel was found to be permeable to Cs+. In Cs+ solutions, IACh was 45% of the IACh in K+ solutions. The block of IACh by apamin, the dependence on extracellular Ca2+, the incomplete block of IACh by Cs+, and the ACh-induced Cs+ currents favor the hypothesis that Ksub belongs to the SK type of channels. An ionotropic/nicotinic nature of the ACh mechanism of action is favored. It is suggested that, in vivo, the amplitude of the ACh-induced hyperpolarization may depend on the Ca2+/Mg2+ ratio inside and outside the cell.
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Affiliation(s)
- A P Nenov
- Kresge Hearing Research Laboratory of the South, Department of Otorhinolaryngology and Biocommunication, Louisiana State University Medical Center, New Orleans 70112-2234, USA
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Steinacker A. Ionic current contribution to signal processing by toadfish semicircular canal hair cells. Ann N Y Acad Sci 1996; 781:150-63. [PMID: 8694412 DOI: 10.1111/j.1749-6632.1996.tb15699.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- A Steinacker
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan 00901.
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19
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Affiliation(s)
- J J Art
- Department of Anatomy and Cell Biology, University of Illinois, College of Medicine, Chicago 60612, USA.
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20
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Kros CJ. Physiology of Mammalian Cochlear Hair Cells. SPRINGER HANDBOOK OF AUDITORY RESEARCH 1996. [DOI: 10.1007/978-1-4612-0757-3_6] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Edds-Walton PL, Popper AN. Hair cell orientation patterns on the saccules of juvenile and adult toadfish, Opsanus tau. ACTA ZOOL-STOCKHOLM 1995; 76:257-65. [PMID: 11539851 DOI: 10.1111/j.1463-6395.1995.tb00998.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Saccules from 10 adult (five female, five male) toadfish (Opsanus tau) 13.5-26 cm standard length, were examined for individual/sexual variation in the hair cell orientation pattern. In addition, saccules from two juveniles (5 and 6 cm standard length) were compared with those of the adults to determine whether maturational differences exist in the hair cell orientations. The hair cell orientation pattern is unlike any reported previously for this species or its congener, O. beta. There are no major differences between the hair cell orientations of males and females, nor between the juveniles and the adults. A slight individual variation is present in the proportion of hair cells oriented in a particular direction in a specific area of the sensory epithelium. Potential ramifications of this hair cell orientation pattern are discussed with regard to development and auditory processing.
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Affiliation(s)
- P L Edds-Walton
- Department of Zoology, University of Maryland, College Park 20742, USA
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22
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Dulon D, Sugasawa M, Blanchet C, Erostegui C. Direct measurements of Ca(2+)-activated K+ currents in inner hair cells of the guinea-pig cochlea using photolabile Ca2+ chelators. Pflugers Arch 1995; 430:365-73. [PMID: 7491260 DOI: 10.1007/bf00373911] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Intracellular photorelease of Ca2+ from caged Ca2+ (DM-nitrophen or nitr5) and the patch-clamp technique in the whole-cell configuration were used to investigate Ca(2+)-activated currents in inner hair cells (IHCs) of the mammalian cochlea. Photoliberation of intracellular Ca2+ activated outward currents with a mean amplitude of 260 +/- 110 pA when IHCs were voltage-clamped, near the resting membrane potential, at -50 mV. The photoactivated currents were reversibly blocked by extracellular application of tetraethylammonium (TEA, 10 mM), neomycin (1 mM) and charybdotoxin (1 microM), but not by apamin. The voltage dependence of membrane currents activated by photolysis of DM-nitrophen demonstrated a reversal potential near the K+ equilibrium potential (Ek) and saturation near 0 mV. The presence of Ca(2+)-activated currents was further confirmed by the effects of extracellular adenosine 5'-triphosphate (ATP, 10 microM) and the Ca2+ ionophore ionomycin (10 microM). Both agents raised intracellular Ca2+ and simultaneously activated outward currents when IHCs were voltage-clamped near the resting membrane potential. In experiments where currents were activated by depolarizing voltage steps, nifedipine (50 microM) and Cd2+ (1 mM) reduced significantly (20-50%) the whole-cell outward currents, suggesting the presence of L-type Ca2+ currents activating K+ currents. These results are the first direct evidence for Ca(2+)-activated K+ currents in mammalian IHCs, these currents being potentially important for cell repolarization during sound-induced depolarization and synaptic transmission.
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Affiliation(s)
- D Dulon
- Laboratorie d'Audiologie Expérimentale, Inserm et Université de Bordeaux II, France
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23
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Griguer C, Kros CJ, Sans A, Lehouelleur J. Potassium currents in type II vestibular hair cells isolated from the guinea-pig's crista ampullaris. Pflugers Arch 1993; 425:344-52. [PMID: 8060388 DOI: 10.1007/bf00374185] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Type II vestibular hair cells were isolated from cristae ampullares of guinea-pig and maintained in vitro for 2-3 h. Outward membrane currents were studied under whole-cell voltage-clamp conditions. Type II hair cells had resting potentials of about -45 mV. Depolarizing voltage steps from a holding potential of -80 or -90 mV induced time- and voltage-dependent outward currents which slowly decayed to a sustained level. Tail currents reversed at about -70 mV, indicating that the outward currents were mainly carried by potassium ions. The currents had an activation threshold around -50 mV. The transient component was completely removed by a depolarizing pre-pulse positive to -10 mV. While bath application of 4-aminopyridine (5 mM) reduced both components, extracellular tetraethylammonium (10 mM) or zero calcium preferentially diminished the sustained current. We conclude that at least two potassium conductances are present, a delayed rectifier with a relatively fast inactivation and a calcium-dependent potassium current. Depolarizing current injections induced an electrical resonance in the voltage responses, with a frequency of 25-100 Hz, larger currents causing higher frequencies.
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Affiliation(s)
- C Griguer
- Laboratoires de Neurophysiologie Cellulaire et Sensorielle, INSERM U254, Université de Montpellier II, France
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24
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Griguer C, Sans A, Valmier J, Lehouelleur J. Inward potassium rectifier current in type I vestibular hair cells isolated from guinea pig. Neurosci Lett 1993; 149:51-5. [PMID: 8469379 DOI: 10.1016/0304-3940(93)90345-l] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Large inward current activated by hyperpolarization was studied using whole cell patch clamp technique in type I vestibular hair cells of guinea pig. Near the resting membrane potential, at an holding potential of -60 mV (HP -60), this current increased with hyperpolarizing steps and showed time-dependent decay for steps below -80 mV. This current was progressively inactivated at more negative holding potential and was totally abolished at HP -90 mV. The underlying conductance was a K+ conductance as indicated by: (i) its dependence on the external potassium concentration; (ii) its tail currents, which reversed at about -90 mV in solutions with a normal gradient for K+ ions. Pharmacological studies revealed that external application of 4-aminopyridine (5 mM) reversibly blocked (95%) the total inward current, while external application of tetraethylammonium (10 mM) or cesium (2 mM) did not significantly affect the amplitude of this current. This potassium inward rectifier current could contribute to restoration of the resting membrane potential during negative stimulations.
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Affiliation(s)
- C Griguer
- Laboratoires de Neurophysiologie cellulaire et sensorielle, INSERM U-254, Université Montpellier II, France
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25
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Affiliation(s)
- P A Fuchs
- Department of Physiology, University of Colorado School of Medicine, Denver 80262
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26
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Steinacker A, Romero A. Voltage-gated potassium current and resonance in the toadfish saccular hair cell. Brain Res 1992; 574:229-36. [PMID: 1353401 DOI: 10.1016/0006-8993(92)90821-p] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Resonance of the membrane potential in response to a perturbing current has been demonstrated in sensory hair cells of many acoustico-lateralis systems and modelled as the result of the interaction of passive membrane properties and the magnitude and kinetics of activation and deactivation of an outward calcium-activated potassium current (IKCa) and an inward calcium current (ICa). However, the majority of the hair cells of the toadfish saccule have, in addition to IKCa, a voltage-gated potassium current (IK) active in the same membrane potential range as IKCa but with considerably slower activation and deactivation kinetics. Additionally, some of these cells have an A current (IA). In the present work, the resonance of cells with these three outward potassium currents were compared with those from cells containing only IKCa. Hair cells with only IKCa produced a high-quality factor (Q) resonance with symmetrical ringing at current onset and termination. In many cells having the IK, resonance could be evoked as a high Q ringing only at the onset of the current pulse. The resonance at command onset was dependent on the presence of IKCa and could be converted into a spike by blocking the IKCa with TEA. Some hair cells with IKCa and IK produced spikes rather than resonance at all holding potentials tested. This spiking was seen in cells with low levels of IKCa or slowly activating IKCa and with cells with IA. The presence of cells with such different response modes implies a difference between hair cells in their role in sensory coding.
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Affiliation(s)
- A Steinacker
- Institute of Neurobiology, University of Puerto Rico, San Juan 00901
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