Effects of Zinc and Hypothermic Process during the Light and Dark Adaptation of Vertebrate Retina

PURPOSE: The purpose of this study was to clarify the effects of zinc treatment and hypothermia on visual adaptation and visual sensitivity in bullfrogs (Rana catesbeiana), which are poikilothermal animals capable of adjusting quickly to environmental temperature changes. METHODS: The effects of both zinc treatment and hypothermia on visual sensitivity were studied by using electroretinogram (ERG) recording and absorption spectra scanning before and after zinc and TSQ (N-[6-methoxy-8-quinolyl]-p-toluene sulfonamide) treatment, with or without temperature changes. RESULTS: In spite of malnutrition due to hibernation, the optimal zinc concentration effect was obtained at 10-4 M (10-2 M 200 microliter ZnCl2 in 20 microliter Ringer's solution) according to ERG recording. After zinc treatment and hypothermia induction, increments of all ERG components and thresholds were taken by ERG recording. These results showed that both zinc treatment and hypothermia may increase visual sensitivity during visual adaptation. In spectral scans, the absorbance increment due to zinc treatment and hypothermia was shown over the whole spectral range (400~750 nm), and it was especially prominent at alpha-peak (about 500 nm). In addition, there was a decrease in absorption differences between dark adaptation and light adaptation after zinc treatment. Furthermore, according to the visual sensitivity decrement using TSQ as a zinc specific chelator, this visual sensitivity increase was shown to be caused by zinc. CONCLUSIONS: As the results suggest, both zinc treatment and hypothermic effects may improve visual sensitivity by promoting rhodopsin regeneration and inhibiting rhodopsin bleaching induced by light illumination. Zinc may activate the enzyme activity of retinol dehydrogenase and phosphodiesterase, while hypothermic effects may improve precursor transport, which is required for rhodopsin regeneration, by tightening membrane adhesion between retinas and retinal pigment epithelia. In addition, we believe that zinc treatment and hypothermic effects may work synergistically to accelerate visual sensitivity during visual adaptation.

EXPERIMENTAL STUDIES ON THE RESISTANCE TO HYPO-XIA OF TOTAL GLUCOSIDES OF PAEONY ROOT / 中国药理学通报

Total Glucosides of Paeony Root ( TGPs, 5-40 mg/kg) had a dose-related increasing effect on the survival time of mice under normobaric hypoxia. TGPs (20 mg/kg) had a significant increasing effect on survival time of mice under hypobaric hypoxia & a decreasing effect in the oxygen consumption in mice. TGPs ( 40mg/kg ) decreased the mortality of mice from the acute hypoxia induced by KCN. Increasing effect on the survival time of mice under normobaric hypoxia of TGPs was significantly antagonised by chlortrimeton. The efficacy of TGPs (icv 2.5-5 mg/kg) approximated to that of TGPs (ip 5-40 mg/kg) respectively. It suggested that the effect of TGPs on resistance to hypoxia was produced by central nervous system. The efficacy of TGPs ( icv) was significantly antagonised by chlortrimeton. It was shown that the effect of TGPs was produced by H1-receptor. In the experiment of resistance to hypoxia of TGPs (ip or icv), we measured the change of rectal temperature of mice. The data indicated the positive corr- elation of both effects of TGPs (r=0.58, P