Ionic currents in cochlear hair cells

Fuchs, Paul

doi:10.1016/0301-0082(92)90003-w

Cited by 59 publications

(29 citation statements)

References 45 publications

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“…Among the list of genes found to be differentially expressed are many that would be predicted to show this pattern, as well as many with a previously uncharacterized pattern of expression or functional activity in the BP. Our data revealed that two inward-rectifying potassium channels (KCNJ2, KCNJ15) are transcribed at higher levels at the apical end, an interesting observation given that previous work has shown preferential expression of inward-rectifying potassium channels at the LF end of the BP (Fuchs et al 1990;Fuchs 1992;Navaratnam et al 1995;Wu et al 1996). Also suggested by our microarray data is relative upregulation of a number of voltage-gated potassium channels in the LF end (Table 4), confirming physiological data on the presence of voltage-gated potassium currents preferentially found in LF hair cells of the turtle BP (Fuchs et al 1990;Goodman and Art 1996).…”

Section: Discussionsupporting

confidence: 67%

Gene Expression Gradients along the Tonotopic Axis of the Chicken Auditory Epithelium

Frucht

Uduman

Kleinstein

et al. 2011

JARO

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There are known differences in the properties of hair cells along the tonotopic axis of the avian auditory epithelium, the basilar papilla (BP). To determine the genetic basis of these differences, we compared gene expression between the high-(HF), middle-, and lowfrequency (LF) thirds of 0-day-old chick auditory epithelia. RNA amplified from each sample was hybridized to whole-genome chicken arrays and GeneSpring software was used to identify differentially expressed genes. Two thousand six hundred sixty-three genes were found to be differentially expressed between the HF and LF segments, using a fold-change cutoff of 2 and a p value of 0.05. Many ion channel genes were differentially expressed between the HF and LF regions of the BP, an expression pattern that was previously established for some but not all of these genes. Quantitative PCR was used to verify tonotopic expression of 15 genes, including KCNMA1 (Slo) and its alternatively spliced STREX exon. Gene set enrichment analyses (GSEA) were performed on the microarray data and revealed many microRNA gene sets significantly enriched in the HF relative to the LF end, suggesting a tonotopic activity gradient. GSEA also suggested differential activity of the kinases protein kinase C and protein kinase A at the HF and LF ends, an interesting corollary to the observation that there is tonotopic expression of the STREX exon that confers on Slo sensitivity to the activity of kinases. Taken together, these results suggest mechanisms of induction and maintenance of tonotopicity and enhance our understanding of the complex nature of proximal-distal gene expression gradients in the chicken BP.

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Section: Discussionsupporting

confidence: 67%

Gene Expression Gradients along the Tonotopic Axis of the Chicken Auditory Epithelium

Frucht

Uduman

Kleinstein

et al. 2011

JARO

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“…Similarly, the significance of I A and I K gradients we evidenced is also difficult to interpret. It has been suggested that I A could compensate for the adaptation of the transduction current [4]. If this were true such a compensation would be more efficient in cells located at the beginning of the peripheral region which exhibit large I A .…”

Section: Discussionmentioning

confidence: 98%

Gradients of expression of calcium and potassium currents in frog crista ampullaris

Russo

Lelli

Marcotti

et al. 2001

Pfl�gers Archiv European Journal of Physiology

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In the present work we studied the intraregional expression of voltage-dependent Ca2+ and K+ currents in hair cells of frog crista ampullaris. The currents were recorded in situ from sensory cells of the peripheral region, the most populated region of the crista, by using the whole-cell variant of the patch-clamp technique. Voltage-clamp recordings revealed that the calcium current (I(Ca)) and the outward potassium currents of I(A), I(K) I(KCa) types and the inward rectifier potassium current of I(K1) type exhibited a significant gradient of density (pA/pF) along the region. I(A) density was maximal in cells located at the beginning of the peripheral region and decreased gradually becoming very small at the opposite end. All the other currents showed an opposite gradient of expression. Current-clamp experiments showed that the voltage behaviour of hair cells changed in relation to cell position. Cells located at the beginning of the peripheral region showed large depolarizations from the resting potential (close to -45 mV) which are consistent with the presence of small I(K) and I(KCa), and an I(A) largely inactivated at rest. These cells also exhibited slowly developing and large hyperpolarizations that approached passive ones, due to the lack of I(K1). In contrast, cells located at the opposite side of the region showed smaller depolarizations and hyperpolarizations from the resting potential (close to -65 mV), due to the presence of large I(K) and I(KCa), and I(K1), respectively. The possible role of the intraregional variation of Ca2+ and K+ currents in both hair cell function and afferent discharge properties is discussed.

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“…The action of ACh on OHCs is summarized below, but the many known details are outside the scope of this review (Blanchet, Eròstegui, Sugasawa, et al, 1996;Fuchs, 1992Fuchs, , 1996Housley & Ashmore, 1991). Figure 3 is a cartoon of an MOC terminal on an OHC.…”

Section: Olivocochlear Neurotransmittersmentioning

confidence: 98%

Olivocochlear Efferents: Anatomy, Physiology, Function, and the Measurement of Efferent Effects in Humans

Guinan¹

2006

Ear and Hearing

552

558

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This review covers the basic anatomy and physiology of the olivocochlear reflexes and the use of otoacoustic emissions (OAEs) in humans to monitor the effects of one group, the medial olivocochlear (MOC) efferents. MOC fibers synapse on outer hair cells (OHCs), and activation of these fibers inhibits basilar membrane responses to low-level sounds. This MOC-induced decrease in the gain of the cochlear amplifier is reflected in changes in OAEs. Any OAE can be used to monitor MOC effects on the cochlear amplifier. Each OAE type has its own advantages and disadvantages. The most straightforward technique for monitoring MOC effects is to elicit MOC activity with an elicitor sound contralateral to the OAE test ear. MOC effects can also be monitored using an ipsilateral elicitor of MOC activity, but the ipsilateral elicitor brings additional problems caused by suppression and cochlear slow intrinsic effects. To measure MOC effects accurately, one must ensure that there are no middle-ear-muscle contractions. Although standard clinical middle-ear-muscle tests are not adequate for this, adequate tests can usually be done with OAE-measuring instruments. An additional complication is that most probe sounds also elicit MOC activity, although this does not prevent the probe from showing MOC effects elicited by contralateral sound. A variety of data indicate that MOC efferents help to reduce acoustic trauma and lessen the masking of transients by background noise; for instance, they aid in speech comprehension in noise. However, much remains to be learned about the role of efferents in auditory function. Monitoring MOC effects in humans using OAEs should continue to provide valuable insights into the role of MOC efferents and may also provide clinical benefits.

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Ionic currents in cochlear hair cells

Cited by 59 publications

References 45 publications

Gene Expression Gradients along the Tonotopic Axis of the Chicken Auditory Epithelium

Gene Expression Gradients along the Tonotopic Axis of the Chicken Auditory Epithelium

Gradients of expression of calcium and potassium currents in frog crista ampullaris

Olivocochlear Efferents: Anatomy, Physiology, Function, and the Measurement of Efferent Effects in Humans

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