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IP3 receptor in the hair cells of frog semicircular canal and its possible functional role
Author(s) -
Rossi Maria Lisa,
Prigioni Ivo,
Gioglio Luciana,
Rubbini Gemma,
Russo Giancarlo,
Martini Marta,
Farinelli Federica,
Rispoli Giorgio,
Fesce Riccardo
Publication year - 2006
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2006.04708.x
Subject(s) - serca , receptor , semicircular canal , inositol trisphosphate receptor , cyclopiazonic acid , endoplasmic reticulum , chemistry , hair cell , inositol , biophysics , anatomy , medicine , biology , endocrinology , microbiology and biotechnology , inner ear , neuroscience , vestibular system , biochemistry , atpase , enzyme
The presence and functional role of inositol trisphosphate receptors (IP3R) was investigated by electrophysiology and immunohistochemistry in hair cells from the frog semicircular canal. Intracellular recordings were performed from single fibres of the posterior canal in the isolated, intact frog labyrinth, at rest and during rotation, in the presence of IP3 receptor inhibitors and drugs known to produce Ca 2+ release from the internal stores or to increase IP3 production. Hair cell immunolabelling for IP3 receptor was performed by standard procedures. The drug 2‐aminoethoxydiphenyl borate (2APB), an IP3 receptor inhibitor, produced a marked decrease of mEPSP and spike frequency at low concentration (0.1 m m ), without affecting mEPSP size or time course. At high concentration (1 m m ), 2APB is reported to block the sarcoplasmic‐endoplasmic reticulum Ca 2+ ‐ATPase (SERCA pump) and increase [Ca 2+ ]i; at the labyrinthine cytoneural junction, it greatly enhanced the resting and mechanically evoked sensory discharge frequency. The selective agonist of group I metabotropic glutamate receptors (RS)‐3,5‐dihydroxyphenylglycine (DHPG, 0.6 m m ), produced a transient increase in resting mEPSP and spike frequency at the cytoneural junction, with no effects on mEPSP shape or amplitude. Pretreatment with cyclopiazonic acid (CPA, 0.1 m m ), a SERCA pump inhibitor, prevented the facilitatory effect of both 2APB and DHPG, suggesting a link between Ca 2+ release from intracellular stores and quantal emission. Consistently, diffuse immunoreactivity for IP3 receptors was observed in posterior canal hair cells. Our results indicate the presence and a possibly relevant functional role of IP3‐sensitive stores in controlling [Ca 2+ ]i and modulating the vestibular discharge.