Recording Methods, Conditions And Influencing Factors Of Pattern Electroretinography And Multifocal Electroretinography In Small Animals

With the development of visual electrophysiology, visual evoked potentials (VEP), electroretinogram (ERG) and multifocal electroretinogram (mfERG) have been able to reflect the function of the visual system, which can provide important evidence for the diagnoses, identification and evaluation of the prognosis in ophthalmology. As animal experiments are the basis of clinical application of visual electrophysiology, improvement of visual electrophysiology recording technologies in experimental animals can play an important role in establishing the animal models of ophthalmic diseases and analyzing different waves in different diseases. Our laboratory has established a standardized recording scheme of conventional VEP and ERG in small animals. As a very important part of visual electrophysiology, PERG can mainly reflect function of retinal ganglion cells and can help diagnose some diseases especially for glaucoma. MfERG can reflect function of retina more roundly. However, there has no relevant research about recording methods and influencing factors of PERG in small animals till now. There also have few relevant reports about recording methods and influencingfactors of mfERG in small animals.Based on the recording methods and influencing factors of PERG and mfERG in small animals and clinical application of PERG and mfERG, main objects of this research are as follow: 1. The recording methods and influencing factors of PERG in SD rat and Kunming mouse; 2. The recording methods and influencing factors of PERG in guinea pigs; 3. The recording methods and influencing factors of mfERG in guinea pigs.Methods and material:Sprague-Dawley albino male rats, mouse and guinea pigs, which were no opacity observed by ophthalmoscope, were used in present study and grouped according to the different experimental settings. Anesthesia drugs: Sumianxin was made by veterinary laboratory in Changchun university of agricultural and animal husbandry sciences, code: [1990]47 in Ji Mu Fang Bian Zi. Small animals were all treated with anesthesia drugs and vehicle by intraperitoneal injection (i.p.). When cornea reflection vanished (-), which was checked by cotton swab, the rats were considered getting in the anesthesia condition. The duration between cornea reflect vanish (-) and comeback (+) was deemed to the period of anesthesia condition. The relaxation of muscle was judged by counteractions of the limbs.Animals including SD rat, mouse, guinea pigs were kept on a special platform, which can be moved in three dimensions, and the distance between the tested eye and CRT were controlled by a self-made apparatus. After animals were anaesthetized, PERG and mfERG were recorded by RETIport system. In the experiments the characters of PERG and mfERG in three kinds of animals and the effect of every influencing factor have been observed. We also evaluated reliability of recording methods we established.Result1. The recording methods of PERG in small animals established by our laboratory have been verified reliable.A silver chloride loop electrode was contacted with comeal limbus as recording electrode. A stainless steel needle electrode was inserted in the temporal subcutaneous as reference. Also a stainless steel needle electrode was inserted in the tail (in the neck in guinea pigs) as groud. The disturbance in the recording was tiny.The amplitude of PERG in SD rat was small (about 2 MV) and varied in the testing. Steady wave cannot be recorded in this way.In mouse, amplitude of PERG was even smaller than rats and wave was not exact.In guinea pigs, waves of pattern electroretinograms were clear and similar to humans. Ni wave located on 25ms; Pi wave located on 50ms and N2 located on 95ms. The amplitude of Pi~N2was about from 2 to 6HV, which decreased with spatial frequencies and slightly decreased with temporal frequencies. Nevertheless, the amplitude increased with mean luminance and contrast. Waves and variety trends of PERG in normal guinea pigs are similar to humans. The recording condition is stable. So guinea pigs can be used in clinical elctrophysiology of vision as a good model for humans.2. The exact mfERG in guinea pigs can be recorded with the method established by our laboratoryWe have recorded mfERG in SD rats successfully in scotopic adaptation. Guinea pigs has more cones than Muridae, such as rats and mice and their retina contains at least two different types of cone photoreceptor pigments so that they have at least two classes of cones with peak sensitivities of 429 and 529 nm. On account of the retinal difference we attempt to record mfERG ofguinea pigs in photopic adaptation. Wave of mfERG in guinea pigs was exact and repeatly record had no significant effect on the testing outcome. Amplitudes of superior temporal quadrant were much higher than other quadrants. We could record exact mfERG wave from 3 to 10 frames. In the same time, we also have changed colors of stimulus. When in black and green or black and blue alteration, we could record the exact mfERG wave.On the contrast, when in black and red alteration, wave was not exact. The amplitude changes with eccentricity may be related to the distribution of photoreceptors in guinea pigs' retina while difference of amplitudes between superior and inferior part of testing field may be related to guinea pigs' habits. The result conformed to the retinal structure.Conclusion1. PERG of small animals including rats, mouse, guinea pigs can be recorded with the method established by our laboratory. When its amplitude is big enough, such as guinea pigs, waves of PERG are exact and the recording condition is stable. Variety trends of PERG in normal guinea pigs are similar to humans. So guinea pigs can be used in clinical elctrophysiology of vision as a good model for humans. In contrast with guinea pigs, as amplitudes of PERG in mouse and SD rat are a bit small, waves are uncertain. To recorde satisfied waves of mouse and SD rat, we can attempt to change the recording electrodes such as DTL or Burian-Allen electrode or take other measures to improve it.2. The simple recording methods of mfERG in SD rat have been established by our laboratory. On account of particularity of retinal structure, we change the adaptation and other factors to record exact scotopic mfERG...