Mechanisms of hypoxic effects on the cat DC electroretinogram.
نویسندگان
چکیده
Mild hypoxia elevates the standing potential and alters three slow components of the DC electroretinogram in the cat: the c-wave, the fast-oscillation trough, and the light peak. This paper considers the cellular mechanisms of these effects. Elevation of the standing potential results from a depolarization of the basal membrane of retinal pigment epithelial (RPE) cells. The depolarization is indirectly initiated by an elevation of [K+]0 in the subretinal space during hypoxia, and is accompanied by a decrease in basal membrane resistance that leads to an increase in the c-wave. There is also some evidence that hypoxia may alter the standing potential by directly affecting the basal membrane of the RPE. The fast-oscillation trough, which follows the c-wave when illumination is maintained, deepens during hypoxia. This is caused primarily by an increase in the amplitude of the delayed hyperpolarization of the RPE basal membrane that results from a slowing of the rate of recovery of light-evoked [K+]0 during hypoxia. The changes in [K+]0 probably result, in turn, from a decrease in the rate of the photoreceptors' Na+/K+ pump. The light peak's amplitude is reduced during hypoxia and its time-to-peak is lengthened, and this may be related to a change in photoreceptor metabolism that is distinct from the effect on the Na+/K+ pump. Knowledge of these mechanisms may eventually enhance the clinical usefulness of the standing potential and the c-wave, fast-oscillation, and light peak.
منابع مشابه
EFFECTS OF HYPOXIC HYPOXIA AND CARBON MONOXIDE-INDUCED HYPOXIA ON THE CARDIOVASCULAR SYSTEM AND REGIONAL BLOOD FLOW OF THE ANESTHETIZED CAT
The purpose of this study was to investigate the potential responses of the cardiovascular system and regional blood flow to hypoxic hypoxia (BB) and to carbon monoxide (CO)-induced hypoxia (COH). Ten anesthetized cats were studied under two nonnoxic (control: CONT) and two hypoxic conditions. Four types of radioactive micro spheres were used to measure regional blood flow during CONT an...
متن کاملHypoxic-ischemic encephalopathy in a young man due to tramadol overdose
Objective: Tramadol is a synthetic analgesic with two mechanisms. The opioid and non-opioid mechanisms are responsible for tramadol side effects. Non-opioid side effects of tramadol are due to the reuptake inhibitions of serotonin and norepinephrine. Some of the side effects include anaphylactoid reactions, CNS depression, hypoglycemia, hypotension, respiratory depression, seizures, and seroton...
متن کاملRadiosensitizing effects of gemcitabine on aerobic and chronically hypoxic HeLa and MRC5 cells in-vitro
Background: Gemcitabine (2′, 2′-difluoro-2′- deoxycytidine, an analogue of deoxycytidine) is a relatively new drug with wide range of anti-cancer activity. In this study, radiosensitizing effects of gemcitabine was investigated on HeLa and MRC5 human originated cell lines under both chronically hypoxic and normoxic conditions using the micronucleus (MN) assay. Materials and Methods: F...
متن کاملThe Role of Anion Exchanger on Pulmonary Vascular Response to Sustained Alveolar Hypoxia in the Isolated Perfused Rabbit Lung
Background: Some respiratory diseases may induce alveolar hypoxia thereby hypoxic pulmonary vasoconstriction (HPV). However, the mechanisms of this physiologic phenomenon are not fully understood. This study was the first to investigate the role of anion exchanger in sustained HPV.Methods: Experiments were performed in the isolated perfused rabbit lung. After preparation, the lungs were divided...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Investigative ophthalmology & visual science
دوره 27 9 شماره
صفحات -
تاریخ انتشار 1986