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At least 145 records · Page 8Linked to original sources
PubMed1985

Freeze-fracture studies on the perilymph-endolymph barrier in experimentally induced hydrops.

A double-blind study was performed on nine pigmented guinea pigs which were unilaterally operated on in order to create an endolymphatic hydrops. After 12-18 months, both inner ears of the animals were removed and investigated by the freeze-fracture technique. The ultrastructure of the epithelial cells lining the endolymphatic compartment of the cochlea and the vestibular apparatus was analyzed. Special attention was directed to possible changes of the tight junctions (zonulae occludentes) in these sites. The number and depth of strands between the cells of sensory and non-sensory epithelia of both operated and unoperated sides were compared by an examiner unaware of the operated side. After the code of double-blind study was broken, it was found that there were no significant differences between the operated and the unoperated ears. These results are discussed in relation to the late DC-potential decrease in experimentally induced hydrops.

Animals↗
PubMed1995

Role of ATP-sensitive K+ channels in anoxia-sensitive negative potential of endolymph.

To investigate the possible role of the ATP-sensitive K+ channels (KATP channels) in the generation of the anoxia-sensitive negative potential (ASNP), the effects of the treatment with glybenclamide and diazoxide on the endocochlear potential (EP) and K+ activity (AK) in the scala media were examined with double-barrelled K(+)-selective microelectrodes. The experiments were carried out in guinea pig cochleae, using glybenclamide as a KATP channel blocker and diazoxide as a KATP channel opener. Perilymphatic perfusion of glybenclamide decreased the amplitude of the ASNP and shortened its duration, whereas perfusion of diazoxide increased ASNP amplitude and prolonged its duration. Glybenclamide enhanced the decrease of endolymphatic AK by anoxia, whereas diazoxide suppressed this AK decrease. The results suggest that KATP channels may be involved in the generation of the ASNP.

Adenosine Triphosphate↗
PubMed1988

A mathematical approach enabling the calculation of the total endolymph flow in the semicircular ducts.

1. A mathematical treatment of the flow inside the vertebrate labyrinth is given. The main difference to former theories (e.g. the "torsion pendulum" theory) is that the entire system formed by the three semicircular ducts, interconnected by the crus commune and the utriculus, is considered, instead of a single duct circuit. 2. The theory consists of a geometrical description of a labyrinth rotating in space, the solution of the continuity equation, determination of the initial velocities in all the ducts in a "cupulometry" experiment and derivation of the equation of motion (e.o.m.). 3. Equations for a system consisting of two ducts and for the classical single-duct system are special cases of the three-duct system. 4. Three different methods for the solution of the e.o.m. are described: an analytical one, a Runge-Kutta simulation and an "asymptotic" method. The last method includes approximations of the solution of the e.o.m. on a long and a short time scale. Its advantage is that it gives an insight based on rather manageable formulae. 5. The physiological basis of the presented theory, biological applications and verification are given in a separate paper (Muller & Verhagen, 1988).

Animals↗
PubMed1998

ATP in endolymph enhances electrically-evoked oto-acoustic emissions from the guinea pig cochlea.

ATP was iontophoresed into the scala media of the guinea pig cochlea. A reversible increase in the amplitude of electrically-evoked oto-acoustic emissions (EEOAEs), and reductions in the endocochlear potential (EP) and the cochlear microphonic (CM) were observed. These effects were consistent with an action of ATP on P2X receptors on outer hair cells (OHC). The results confirm that endogenous endolymphatic ATP, acting via P2X receptors on OHCs, may serve a regulatory function in the cochlea.

Adenosine Triphosphate↗
PubMed2005

Effects of lithium on endolymph homeostasis and experimentally induced endolymphatic hydrops.

There is evidence to suggest that water homeostasis in the inner ear is regulated via the vasopressin (VP)-aquaporin 2 (AQP2) system in the same fashion as in the kidney. The VP-AQP2 system in the kidney is well known to be inhibited by lithium, resulting in polyuria due to a decrease in reabsorption of water in the collecting duct of the kidney. Therefore, lithium is also likely to inhibit the VP-AQP2 system in the inner ear, and consequently exert some influence on inner ear fluid homeostasis. In this study, we investigated the effects of lithium on AQP2 expression in the rat inner ear, and on the cochlear fluid volume in hydropic ears of guinea pigs. A quantitative PCR study revealed that lithium reduced AQP2 mRNA expression in the cochlea and endolymphatic sac. Lithium application also decreased the immunoreactivity of AQP2 in the cochlea and endolymphatic sac. In a morphological study, lithium intake significantly reduced endolymphatic hydrops dose-dependently. These results indicate that lithium acts on the VP-AQP2 system in the inner ear, consequently producing a dehydratic effect on the endolymphatic compartment.

Animals↗