| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
1) The effect of nilvadipine on the voltage-gated Ca channel of retinal ganglion cells (GC).
GC were enzymatically dissociated from isolated retina. Cells were recorded by perforated-patch clamp technique in whole cell configuration The current-voltage relation for the nilvadipine-sensitive current was bell-shaped and the peak current reached a maximum at -8 mV in the presence and absence of nilvadipine. Nilvadipine block of voltage-gated Ca current was dose-dependent between 1 and 100 μM. The inhibitory actions of nilvadipine on Ca channels could relieve the intracellular Ca increase in GCs and rescue the GCs from death in glaucoma.
2) Elevation of intracellular Ca^<2+> concentration ([Ca^<2+>]_i) induced by hypoxia in ganglion cells
Application of fluo-3 to the cut edge of the optic nerve of 6-week-old rats. The Ca images of sliced retina were captured. A hypoxic condition was created by superfusing the retinal slice with a solution with an oxygen/glucose deprived solution.
Results : The retrograde staining method stained GC selectively. Fifteen minutes of hypoxic conditions induced [Ca^<2+>]_i increases in GC (Δ0.13±0.03, n=23). Application of 60 μM
DL-2-amino-5-phosphonovaleric acid counteracted the hypoxia-induced [Ca^<2+>]_i increase in dendrites partially (Δ0.03±0.02, n=4, p<0.005), but not in somata (Δ0.12±0.02, n=9). GC dendrites showed a further increase in [Ca^<2+>]_i after switching back to oxygenated solution (Δ0.14±0.04, n=4). Neither 6-cyano-7-nitroquinoxaline-2,3-dione disodium, DL-threo-β-benzyloxyaspartate, nifedipine nor bepridil inhibited the hypoxia-induced [Ca^<2+>]_i increase. Ca^<2+>-free superfusion prevented the anoxia-induced [Ca^<2+>]_i increase in somata (Δ0.07±0.02, n=5, p<0.005), not in dendrites (Δ0.16±0.005, n=4).
Conclusions : The mechanisms of hypoxia-induced increase in [Ca^<2+>]_i differ between somata and dendrites. The NMDA channel of dendrites seems to be the main route of Ca^<2+> influx.
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