Diurnal variations in the electroretinographic c-wave and retinal melatonin content in rats with inherited retinal dystrophy

Abstract

The inability of retinal pigment epithelium to phagocytose shed photoreceptor disks is a cause of retinal degeneration in the Royal College of Surgeons rat; retinal pigment epithelial phagocytosis and disk shedding are regulated by the diurnal rhythm of retinal melatonin level. The diurnal rhythms of the electroretinogram (particularly that of the retinal pigment epithelial potential, the electroretinographic c-wave) and retinal melatonin content were thus investigated in Royal College of Surgeons rats from postnatal day 17 to 24, the period preceding retinal degeneration. The amplitudes of both the b- and c-waves of the electroretinogram fell significantly during the peak time of rod disk shedding and rose after the time of expected light off in the control and dystrophic rats. While the b-wave rhythms did not differ between the two strains, diurnal changes in the c-wave were significantly less distinct in the dystrophic rats than in controls. This difference may reflect lack of phagocytosis in dystrophic rats. Furthermore, the ERG c-wave was significantly larger and prolonged, and the retinal melatonin content higher, in dystrophic rats of this age group than in controls. It appears that retinal melatonin metabolism may play an important role in the maintenance of retinal pigment epithelial and photoreceptor function.

The c-wave of the direct-current electroretinogram and the standing potential of the albino rabbit eye in response to repeated series of light stimuli with different interstimulus intervals

“…After a minimum occurring about 1-1.5 hours after the expected onset of room illumination in the morning, an increase in the b-and c-wave amplitudes was seen [25]. In the present study, the amplitudes of the a-, b-and c-waves recorded in response to the initial light stimulus of each series increased between the first (8-minute interstimulus interval) and the last (70-second interstimulus interval) series of experiments performed during the day (Fig.…”

“…Sandberg et al [24] and Hawlina et al [25] observed diurnal changes in ERG amplitudes recorded from normal rats. After a minimum occurring about 1-1.5 hours after the expected onset of room illumination in the morning, an increase in the b-and c-wave amplitudes was seen [25].…”

Light-emitting diodes and half-cell electrodes in experimental recording of electroretinogram c-wave

“…Interestingly, measurements of corneofundal potential (electro-oculogram) were carried out as early as in 1966 to measure retinal pigment epithelial function of dystrophic Royal College of Surgeons (RCS) rats with defective retinal pigment epithelial phagocytosis [11]. The method described here enables recording of the c-wave simultaneously with other components of the ERG, which may be helpful in a combined study of retinal and RPE dysfunctions, such as in RCS rats [3,5,9].…”

“…Preparatory procedures are described in detail elsewhere [9]. Briefly, anesthetized pigmented rats (1.5 g/kg of urethane intraperitoneally; pupils dilated by 1% atropine) were placed in a stereotaxic frame with earbars and a mouthbar (Fig.…”

The Effect of Intravitreal N-Methyl-dl-Aspartic Acid on the Electroretinogram in Royal College of Surgeons Rats

“…[45][46][47] Although the dopamine receptor is distributed throughout the retina in rodents, 48 intravitreal administration of dopamine suppresses the third-order neuronal response more than the second-order neuronal response. 49 Therefore, depletion of intraretinal dopamine could result in augmentation of the third-order neuronal response.…”