Impact of simulated microgravity on flash electroretinogram and retinal microcirculation in adult mice / 国际眼科杂志(Guoji Yanke Zazhi)

ABSTRACT

@#AIM: To observe changes in the flash electroretinogram(ERG)and retinal microcirculation in mice suspended by their tails, an animal model that simulates cephalad movement of bodily fluids under conditions of microgravity.<p>METHODS: Thirty-six adult male C57BL/6J mice(36 eyes)were randomly divided into three experimental groups and three control groups. Mice in the experimental groups were tail-suspended for 15d(Group one), tail-suspended for 30d(Group two), or tail-suspended followed by returning to normal position for 30d(Group three). Three control groups were similarly fixed with a harness but kept in the normal position for corresponding periods of 15, 30, and 60d. The mice were immediately examined using scotopic ERG(including oscillatory potentials \〖OPs\〗)and fundus fluorescein angiography(FFA)<i>in vivo</i>, and subsequently sacrificed to analyze the retinal histology(methods including immunohistochemistry and TUNEL staining)<i>in vitro</i>. Independent sample <i>t</i>-test was used for data comparison between the same time-point groups.<p>RESULTS: Following 15-days' tail-suspension, scotopic ERG showed a decline in OPs, but not in the b-wave; the second OP(O2)showed an amplitude of 197±33μV, which was about 60% of the control level(<i>t</i>=-5.938, <i>P</i><0.001). Following 30-days' tail-suspension, ERG recovered, with O2 showing an average value of 264±39μV; when compared to the corresponding control group(308±41μV), no significant difference was observed(<i>t</i>=-1.887, <i>P</i>>0.05). Morphologically, only the 15-days' tail-suspended mice showed FFA with microvascular dilation and tortuosity. Rhodopsin and cone-opsin were almost normal and no apoptotic-positive signals were detected in the retinas of the three tail-suspended groups.<p>CONCLUSION: Simulating cephalad shifting of bodily fluids as under microgravity, using short-term tail-suspension can affect rodent ERG and retinal microcirculation; however, the change is reversible with no obvious permanent injury observed in the retinas.