THE EFFECTS OF CHOLERA TOXIN ON THE cAMP LEVEL OF THE RETINA AND THE SURVIVAL AS WELL AS THE APOPTOSIS OF THE RETINAL GANGLION CELLS AFTER DISTAL AXOTOMY OF THE OPTIC NERVE / 解剖学报

ABSTRACT

Objective To investigate the effects of Cholera Toxin(CTx)on the cAMP level and the survival as well as the apoptosis of retinal ganglion cells (RGCs) after distal axotomy of the optic nerve.Method After transecting the optic nerve intracranially, CTx was injected intravitreally. Fluorescent retrograde tracing method and TUNEL(TdT-mediated dUTP nick end labeling)technique were used to show the surviving RGCs and the apoptotic cells in the ganglion cell layer. The Brown's radioimmunoassay method was used to measure the cAMP level of the retina. Result The cAMP level of the normal retina was 6.22?2.02pmol/g/retina. The mean density of RGCs in the normal retina was 2 192?66/mm 2 and it decreased to 1 520?116/mm 2、736?39/mm 2 and 466?53/mm 2 at 1W、2W and 3W respectively after distal axotomy. The densities of RGCs in the distal axotomy groups treated with CTx and killed at 1W、2W and 3W were 1 642?122/mm 2、1 091?107/mm 2、 748?35/mm 2 respectively and were significantly higher than those of distal axotomy group without CTx treatment. Conclusions The results show that CTx can elevate cAMP level of the retina and promote the survival of RGCs and inhibit the apoptosis of RGCs after distal axotomy of the optic nerve in adult hamsters.