title: Putative role of border cells in generating spontaneous morphological activity within Kölliker's organ.
abstract: Kölliker's organ is a transient epithelial structure, comprising a major part of the organ of Corti during pre-hearing stages of development. The auditory system is spontaneously active during development, which serves to retain and refine neural connections. Kölliker's organ is considered a key candidate for generating such spontaneous activity, most likely through purinergic (P2 receptor) signalling and inner hair cell (IHC) activation. Associated with the spontaneous neural activity, ATP released locally by epithelial cells induces rhythmic morphological changes within Kölliker's organ, the purpose of which is not understood. These changes are accompanied by a shift in cellular refractive index, allowing optical detection of this activity in real-time. Using this principle, we investigated the origin of spontaneous morphological activity within Kölliker's organ. Apical turns of Wistar rat cochleae (P9-11) were dissected, and the purinergic involvement was studied following acute tissue exposure to a P2 receptor agonist (ATPγS) and antagonist (suramin). ATPγS induced a sustained darkening throughout Kölliker's organ, reversed by suramin. This effect was most pronounced in the region closest to the inner hair cells, which also displayed the highest frequency of intrinsic morphological events. Additionally, suramin alone induced swelling of this region, suggesting a tight regulation of cell volume by ATP-mediated mechanisms. Histological analysis of cochlear tissues demonstrates the most profound volume changes in the border cell region immediately adjacent to the IHCs. Together, these results underline the role of purinergic signalling in initiating morphological events within Kölliker's organ, and suggest a key involvement of border cells surrounding IHCs in regulating this spontaneous activity.
authors.affiliation: Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand. Electronic address: n.dayaratne@auckland.ac.nz.
authors.forename: M W Nishani
authors.initials: MW
authors.lastname: Dayaratne
authors.affiliation: Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Srdjan M
authors.initials: SM
authors.lastname: Vlajkovic
authors.affiliation: Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Janusz
authors.initials: J
authors.lastname: Lipski
authors.affiliation: Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Section of Audiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Thorne
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D003051:Cochlea / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000378:metabolism*; D006198:Hair Cells, Auditory / Q000166:cytology; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects; D006309:Hearing / Q000502:physiology; D006868:Hydrolysis; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008297:Male; D009925:Organ of Corti / Q000166:cytology / Q000254:growth & development* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011983:Receptors, Purinergic / Q000378:metabolism; D015398:Signal Transduction; D013498:Suramin / Q000627:therapeutic use
chemical_list: D011983:Receptors, Purinergic; C022571:adenosine 5'-O-(3-thiotriphosphate); D013498:Suramin; D000255:Adenosine Triphosphate
keywords: Cochlea; Development; Kölliker's organ; Purinergic signalling; Spontaneous activity