[The electrophysiological properties of voltage-gated potassium channels on cultivated porcine retinal ganglion cells irradiated with continuous near-infrared laser].
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To investigate the influence of continuous near-infrared (CNI) laser to potassium ion channels on retinal ganglion cell (RGC).Experiment study. Porcine RGC was cultured with enzymatic digestion method in vitro by taking off the retina from the piglets. Whole-cell patch clamp mode recordings were obtained from primary cultured porcine RGC. Whole-cell currents of porcine RGC irradiated with a single-mode CNI laser of 845 nm wavelength and 30 mW power were also recorded. The primary cultured porcine RGC were divided into laser irradiation group and control group according to whether they accepted CNI laser of 845 nm wavelength. t test was used to analyze the average peak amplitude between the two groups.The cells had the morphological characteristics of typical neurons after one week cultured observed by inverted phase contrast microscope. The body and bumps with yellow-green fluorescence was positive cell which observed by immune cell fluorescence chemical testing. CNI laser had a regulation on outward potassium current of porcine RGC in a voltage-dependent manner. There was significant difference on the average peak amplitude of potassium current between the laser irradiation group [(634.4 ± 86.8) Pa] and the control group [(580.5 ± 116.4) Pa], respectively (n = 30, t = 7.923, P = 0.000).CNI laser can change the properties of outward K(+) channel. Therefore, formation and releasing of action potential is affected. Further, physiological functions of RGC are regulated, which might contribute to the protection and restoration of injured RGC. It can be provided a new scholar direction for the protection of the RGC, which are injured by glaucoma.Cite
To investigate the influence of continuous near-infrared (CNI) laser to potassium ion channels on retinal ganglion cell (RGC).Experiment study. Porcine RGC was cultured with enzymatic digestion method in vitro by taking off the retina from the piglets. Whole-cell patch clamp mode recordings were obtained from primary cultured porcine RGC. Whole-cell currents of porcine RGC irradiated with a single-mode CNI laser of 845 nm wavelength and 30 mW power were also recorded. The primary cultured porcine RGC were divided into laser irradiation group and control group according to whether they accepted CNI laser of 845 nm wavelength. t test was used to analyze the average peak amplitude between the two groups.The cells had the morphological characteristics of typical neurons after one week cultured observed by inverted phase contrast microscope. The body and bumps with yellow-green fluorescence was positive cell which observed by immune cell fluorescence chemical testing. CNI laser had a regulation on outward potassium current of porcine RGC in a voltage-dependent manner. There was significant difference on the average peak amplitude of potassium current between the laser irradiation group [(634.4 ± 86.8) Pa] and the control group [(580.5 ± 116.4) Pa], respectively (n = 30, t = 7.923, P = 0.000).CNI laser can change the properties of outward K(+) channel. Therefore, formation and releasing of action potential is affected. Further, physiological functions of RGC are regulated, which might contribute to the protection and restoration of injured RGC. It can be provided a new scholar direction for the protection of the RGC, which are injured by glaucoma.
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Ion channels are important for the functions of excitable and non-excitable cells. Using the whole-cell patch clamp technique, we analyzed the electrophysiological and pharmacological properties of voltage-gated potassium channels in primary rat peritoneal macrophages. With intracellular solution contained K(+) as the main charge carrier, all cells showed outward currents in response to membrane depolarization. The currents can be inhibited by TEA (10 mM), a non-selective blocker for voltage-gated K(+) channels, and attenuated when intracellular K(+) was substituted with Cs(+). Changing holding potential from -80 to -30 mV or -10 mV also inhibited the outward currents. In contrast, increasing the concentration of ATP in the intracellular solution decreased the amplitude of the outward currents. Thus, rat peritoneal macrophages express several types of functional voltage-gated K(+) channels.
Voltage-gated potassium channel
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To observe damage effect of 578.2 nm laser on rabbit retina,ten eyes of five New Zealand albino rabbits were exposed to a copper vapour laser(578.2 nm)coupled to a slit lamp biomicroscope using a spot size of 2 mm.The irradiation dose included 60 J/cm2,80 J/cm2,100 J/cm2,120 J/cm2,160 J/cm2 and 200 J/cm2 with exposure time of 100 seconds.The fundus photograph and light microscopic examination were performed at 1 hour and 24 hour after laser irradiation.Retinal damage induced by laser was strongly influenced by laser power density.With increasing of the power density,retinal damage aggravated.The retinal damage showed more severity at 24 h after irradiation than 1 h.When the laser power dose was 80 J/cm2 or 60 J/cm2,there were no obvious changes in retina.The main histopathological change located in rabbit choroid.In conclusion,the laser irradiation dose should be controlled less than 80 J/cm2 when 578.2 nm laser is used as light source of photodynamic therapy on fundus diseases.
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Abstract Retinal ganglion cell line (RGC-5) has been widely used as a valuable model for studying pathophysiology and physiology of retinal ganglion cells in vitro. However, the electrophysiological characteristics, especially a thorough classification of ionic currents in the cell line, remain to be elucidated in details. In the present study, we determined the resting membrane potential (RMP) in RGC-5 cell line and then identified different types of ionic currents by using the whole-cell patch-clamp technique. The RMP recorded in the cell line was between −30 and −6 mV (−17.6 ± 2.6 mV, n = 10). We observed the following voltage-gated ion channel currents: (1) inwardly rectifying Cl − current ( I Cl,ir ), which could be blocked by Zn 2+ ; (2) Ca 2+ -activated Cl − current ( I Cl,Ca ), which was sensitive to extracellular Ca 2+ and could be inhibited by disodium 4,4’-diisothiocyanatostilbene-2,2’-disulfonate; (3) inwardly rectifying K + currents ( I K1 ), which could be blocked by Ba 2+ ; (4) a small amount of delayed rectifier K + current ( I K ). On the other hand, the voltage-gated sodium channels current ( I Na ) and transient outward potassium channels current ( I A ) were not observed in this cell line. These results further characterize the ionic currents in the RGC-5 cell line and are beneficial for future studies especially on ion channel (patho)physiology and pharmacology in the RGC-5 cell line.
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Retinal topographies of some cell types and distribution of the tapetum lucidum in the sheep's eye were investigated in this study. The tapetum was observed macroscopically in the fundus. The topographical distributions of retinal ganglion cells (RGCs), cones, and rods were simultaneously analyzed in retinal whole mounts stained with cresyl violet. Short-wavelength-sensitive (S) cones were immunocytochemically identified in retinal whole mounts. The tapetum was located dorsal to the optic disc, with the nasal part elongated horizontally and the temporal part expanded dorsally. RGCs were distributed densely in the area centralis, horizontal visual streak, and anakatabatic area. The highest density in the area centralis was approximately 18,000 RGCs/mm(2). Cones showed high density in the horizontal area crossing the optic disc and dorsotemporal area, whereas rods showed high density in the horizontal area, which was greater in height than the horizontal area of high cone density. S cones showed high density in the dorsotemporal retina. The rod/cone ratios were high horizontally in the dorsal retina to the optic disc, with a mean value of 11:1. The cone/RGC and rod/RGC ratios were lower in the horizontal and dorsotemporal retina, and the rod/cone/RGC ratio was lowest in the area centralis (9:1:1). The retinal topographies and distribution of the tapetum were specialized in the horizontal and dorsotemporal fundus. This suggests that sheep have better visual acuity in horizontal and anteroinferior visual fields and that this specialization is related to the visual ecology of sheep.
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Optic disc
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Epibatidine (EPI), a potent cholinergic agonist, disrupts acetylcholine-dependent spontaneous retinal activity. Early patch-clamp recordings in juvenile ferrets suggested that EPI blocks all retinal ganglion cell (RGC) action potentials when applied to the retina. In contrast, recent experiments on the developing mouse that relied on multielectrode array (MEA) recordings reported that EPI application decorrelates the activity of neighboring RGCs and eliminates retinal waves while preserving the spiking activity of many neurons. The different techniques used in previous studies raise the question of whether EPI has different effects on RGC activity in mouse compared with that in ferret. A resolution of this issue is essential for interpreting the results of developmental studies that relied on EPI to manipulate retinal activity. Our goal was to compare the effects of EPI on the spontaneous discharges of RGCs in mouse and ferret using 60-electrode MEA as well as patch-clamp recordings during the developmental stage when retinal waves are driven by acetylcholine in both species. We found that in both mouse and ferret EPI decorrelates RGC activity and eliminates retinal waves. However, EPI does not block all spontaneous activity in either species. Instead, our whole cell recordings reveal that EPI silences more than half of all RGCs while significantly increasing the activity of the remainder. These results have important implications for interpreting the results of previous studies that relied on this cholinergic agonist to perturb retinal activity.
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Tetrodotoxin
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Abstract Voltage dependent potassium currents were recorded using the whole‐cell mode of the patch‐clamp technique for the first time from endfeet of Müller cells dissociated from the frog retina. Recordings from intact cells and isolated endfeet indicate that the inward rectifier potassium channel is the dominant ion channel in these cells and that the density of these channels is highest in the endfoot as has been previously reported for several other species. The present study uses rapid changes in [K + ] o to understand the behavior of these channels in buffering [K + ] o in the retina. With rapid changes in [K + ] o , it was found that, at a membrane potential of −90 mV, which is close to E K , increasing [K + ] o from 3 to 10 mM produced an inward K + current 5.48 ± 0.89 SD (n = 9) times larger than outward current induced by decreasing [K + ] o from 3 to 1 mM. The outward current was maximal at a holding potential of about −80 mV and exhibited inactivation at more positive potentials. At −40 mV both the inward and outward currents are markedly reduced. The current voltage curve for the inward current was linear at holding potentials from −50 mV to −140 mV. Using 20 mV voltage steps, it was found that the voltage dependent K + currents were unaffected by the addition of 2 mM Cd 2+ , a blocker of Ca 2+ ‐activated potassium currents, decreasing [Cl − ] o from 120 mM to 5 mM or the substitution of 30 mM Na + by TEA. The addition of 5 mM [Cs + ] o blocked only the inward current. Both the outward and inward currents disappeared in the absence of intracellular and extracellular K + ; 0.3 mM [Ba 2+ ] o blocked the inward current completely and strongly inhibited the outward current in a time and voltage dependent manner. We conclude that at physiological [K + ] o and membrane potential, the K + channels in the Müller cell endfoot are well suited to carry K + both inward and outward across the membrane as required for spatial buffering. © 1995 Wiley‐Liss, Inc.
GRENOUILLE
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