Excitation and desensitization of mouse rod photoreceptors in vivo following bright adapting light

• Published in: The Journal of physiology 2002-05, Vol.541 (1), p.201-218
• Main Authors: Derwent, Jennifer J. Kang, Qtaishat, Nasser M., Pepperberg, David R.
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Animals; Darkness; Electrophysiology; Electroretinography; Female; Light; Male; Mice; Mice, Inbred C57BL; Original; Photic Stimulation; Retinal Rod Photoreceptor Cells - physiology; Retinoids - metabolism; Rhodopsin - metabolism; Signal Transduction - physiology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2001.013227

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 ∼10 min and ∼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 ∼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.