2001 Fiscal Year Final Research Report Summary
Electrophysiological and molecular biological study for cell-membranous ionic transport in the cochlea
| Project/Area Number |
11671690
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Otorhinolaryngology
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| Research Institution | Miyazaki Medical College |
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Principal Investigator |
KAWANO Hirokazu Miyazaki Medical College, Assistant, 医学部, 助手 (20204745)
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| Co-Investigator(Kenkyū-buntansha) |
HARUTA Atsushi Miyazaki Medical College, Assistant Prof., 医学部, 講師 (90201722)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Endocochlear potential / Endolymph / Cochlea / Basigin / Immunohistochemistry / RT-PCR / In situ hybridization / Pituitary adenylate cyclase-activating polypeptide |
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| Research Abstract |
To clarify the developmental process of monovalent ions (Na^+, K^+, Cl^-) in the endolymph of the mouse in relation to the development of the endocochlear potential (EP), the EP and ionic concentrations were measured with the ion-sensitive double-barreled microelectrodes. The EP increased abruptly 7 days after birth (DAB) and reached adult level 14DAB. These date suggest the presence of a different mechanism between the production of K^+ in the endolymph and that of EP.
The blood-labyrinth barrier (BLB) is important in that it maintains the characteristic environment of the inner ear. The morphological characteristics of BLB are very similar to those of blood-brain barrier (BBB). Basign, a highly glycosyiated transmembrane protein belonging to the immunoglobulin superfamily, has been implicated in the function of BBB. Its expression was investigated immunohistochemically. Positive Bsg immunoreactivity was found in the capillaries of the auditory nerve and in the basal cells of the stria vascularis. These findings suggest that Bsg may play an important role in maintenance of homeostasis in the cochlea.
It has been suggested that neuropeptides play an important role for modulating the cochlear circumstance. We are investigating pituitary adenylate cyclase-activating polypeptide (PACAP) in the cochlea. In situ hybridization study demonstrated that the spiral ganglion cells and the marginal cells in the stria expressed PACAP mRNA. Additionally, RT-PCR study showed the expression of mRNAs for PACAP receptors in the cochlea. These data suggest that PACAP functions in an autocrine or paracrine manner. PACAP interacts synergistically with glutamate to increase the strength of glutamate-mediated neural signaling, whereas PACAP suppressed glutamate-induced neuronal cell death. Taken together, it is likely that PACAP plays an important role for controlling action for neural cells mediated by glutamate in the cochlea.
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