title: BK channels mediate pathway-specific modulation of visual signals in the in vivo mouse retina.
abstract: The modulatory role of large-conductance Ca(2+)-activated K(+) (BK) channels in the nervous system has been extensively studied. In the retina, it has been shown that BK channels play a pivotal role in modulating feedback from A17 amacrine cells to rod bipolar cells (RBCs). Here, we used electroretinography to examine the functional role of BK channels for rod and cone vision in the retina in vivo using a genetically engineered mouse lacking functional BK channels (Bk(-/-)). Under dark-adapted and light-adapted conditions, the lack of BK channels had no effect on photoreceptor activity, suggesting that these ion channels do not modulate photoreceptor responses. At the bipolar cell level, the ERG signals attributed to RBCs in Bk(-/-) mice were not different from those in wild-type mice at low scotopic stimulus intensities. However, at high scotopic and low mesopic stimulus intensities, close to RBC saturation, a significant reduction of ERG signals reflecting RBC activity was present in the Bk(-/-) retina. At higher mesopic stimulus intensities activating both RBCs and cone bipolar cells (CBCs), no difference in ERG signals between Bk(-/-) and wild-type mice was found. In photopic stimulus paradigms, activity of ON- and OFF-CBCs in Bk(-/-) and wild-type retinae was indistinguishable. These findings demonstrate that BK channels modulate visual responses in vivo at the bipolar cell level at intermediate stimulus conditions.
authors.affiliation: Division of Ocular Neurodegeneration, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany. naoyuki.tanimoto@med.uni-tuebingen.de
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Tanimoto
authors.forename: Vithiyanjali
authors.initials: V
authors.lastname: Sothilingam
authors.forename: Thomas
authors.initials: T
authors.lastname: Euler
authors.forename: Peter
authors.initials: P
authors.lastname: Ruth
authors.forename: Mathias W
authors.initials: MW
authors.lastname: Seeliger
authors.forename: Timm
authors.initials: T
authors.lastname: Schubert
mesh_terms: D000818:Animals; D003624:Darkness; D004596:Electroretinography / Q000379:methods; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D008027:Light; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels