title: Excitation and desensitization of mouse rod photoreceptors in vivo following bright adapting light.
abstract: Electroretinographic (ERG) methods were used to determine response properties of mouse rod photoreceptors in vivo following adapting illumination that produced a significant extent of rhodopsin bleaching. Bleaching levels prevailing at approximately 10 min and approximately 20 min after the adapting exposure were on average 14 % and 9 %, respectively, based on the analysis of visual cycle retinoids in the eye tissues. Recovery of the rod response to the adapting light was monitored by analysing the ERG a-wave response to a bright probe flash presented at varying times during dark adaptation. A paired-flash procedure, in which the probe flash was presented at defined times after a weak test flash of fixed strength, was used to determine sensitivity of the rod response to the test flash. Recovery of the response to the adapting light was 80 % complete at 13.5 +/- 3.0 min (mean +/- S.D.; n = 7) after adapting light offset. The adapting light caused prolonged desensitization of the weak-flash response derived from paired-flash data. By comparison with results obtained in the absence of the adapting exposure, desensitization determined with a test-probe interval of 80 ms was ~fourfold after 5 min of dark adaptation and approximately twofold after 20 min. The results indicate, for mouse rods in vivo, that the time scale for recovery of weak-flash sensitivity substantially exceeds that for the recovery of circulating current following significant rhodopsin bleaching. The lingering desensitization may reflect a reduced efficiency of signal transmission in the phototransduction cascade distinct from that due to residual excitation.
authors.affiliation: Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Kang Derwent
authors.forename: Nasser M
authors.initials: NM
authors.lastname: Qtaishat
authors.forename: David R
authors.initials: DR
authors.lastname: Pepperberg
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D003624:Darkness; D004594:Electrophysiology; D004596:Electroretinography; D005260:Female; D008027:Light; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010775:Photic Stimulation; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012176:Retinoids / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D012176:Retinoids; D012243:Rhodopsin