title: Glutamate induced modulation of free Ca(2+) in isolated inner hair cells of the guinea pig cochlea.
abstract: To explore the possible involvement of glutamate (Glu) in modulation of inner hair cell (IHC) functions, the glutamate (Glu) induced changes in intracellular free Ca(2+) ([Ca(2+)]i) concentration in isolated IHCs and outer hair cells (OHCs) of the guinea pig cochlea were investigated with fluo-3, a fluorescent probe for intracellular Ca(2+). Their unique flask shape identified the IHCs with a distinct neck and spherical base with a large spherical nucleus. Normal cell shapes could be maintained for about 2 h. Fluorescence of fluo-3 was distributed in the whole isolated IHC with brighter staining nuclei. Static [Ca(2+)]i remained constant within the observation period in the absence of Glu. In the presence of a low concentration of Glu (3.85 microM), there was an increase of [Ca(2+)]i in IHCs, whereas no obvious [Ca(2+)]i change was found in OHCs. The increase of the fluorescence in IHCs reached peak level at 180 s and then gradually reduced at 400 s after the administration of Glu. The increases of [Ca(2+)]i were observed in nine of 10 IHCs, but one IHC did not show any change. For 10 of the observed OHCs, seven showed no [Ca(2+)]i change, and three showed minor reduction of [Ca(2+)]i. The increase of the Glu concentration resulted in a corresponding change of [Ca(2+)]i in the IHCs after three times administration of Glu. These results suggest that Glu acts on the IHCs presynaptic autoreceptor in a positive feedback manner.
authors.affiliation: The Institute of Otolaryngology, Chinese PLA General Hospital, 100853, Beijing, PR China. lixq1@plagh.com.cn
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Sun
authors.forename: N
authors.initials: N
authors.lastname: Yu
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
authors.forename: Z
authors.initials: Z
authors.lastname: Tan
authors.forename: S
authors.initials: S
authors.lastname: Jiang
authors.forename: N
authors.initials: N
authors.lastname: Li
authors.forename: C
authors.initials: C
authors.lastname: Zhou
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002469:Cell Separation; D003051:Cochlea / Q000166:cytology / Q000378:metabolism*; D018698:Glutamic Acid / Q000494:pharmacology*; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000166:cytology / Q000378:metabolism*; D018072:Hair Cells, Auditory, Outer / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D009994:Osmolar Concentration; D012016:Reference Values
chemical_list: D018698:Glutamic Acid; D002118:Calcium