Effect Of The Expression Of TH On Retina After Optic Nerve Transection In Dark Rearing In Rat

Objective: Observed the expression of tyrosine hydroxylase in dopaminergic amacrine cells within the inner plexiform layer of the rat retina after optic nerve transection, and then to further explore the impact of visual deprivation on this change.Methods: 144 SD rat were randomly divided into normal groups (n=12), Sham groups (n=12), and experimental groups (n=120). We transected the optic nerve in the optic nerve sheath at the place where 0.5cm after the posterior pole of the right eye at the experimental animals. And then divided into normal diurnal cycle feeding group and dark rearing group randomly, then survived for l d, 3d, 5d, 7d, 14d respectively(n=24). Immunohistochemistry, immunofluorescence staining and western blot were used for detecting the effect of the dark rearing on the expression of TH and the change of the number of TH-positive particles in the model after optic nerve transection.Results: In normal rats, TH immunoreactivity was found in the IPL, and some TH-positive particles can be found in the INL. The TH immunohistochemisry staining showed that the expression of TH in sham groups was similar to the normal groups. Compared with the normal groups, the expression of TH sustained decrease at the 1st day, the 3rd day and the 5th day in diurnal cycle rearing groups after optic nerve transection, and reached the lowest value at the 5th day. TH-positive area increased to normal level at the 7th day, and then reduced at the 14th day; and compared with the normal groups, the expression of TH decreased to the lowest value at the 1st day in dark rearing groups after optic nerve transection, and then increasing at the 3rd day, the 5th day and the 7th day gradually. The TH-positive area reached the normal level at the 5th day and 7th day. It was reduced that the TH-positive area expressed at the 14th day than 7th day. The number of TH-positive synaptic particles was counted within elemental area in the IPL of retina in immunofluorescence staining. The tendency of change of TH-positive synaptic particles was similar to the result of the immunohistochemisry staining. Unlike diurnal cycle rearing groups, The TH-positive area expression was not reduced at the 14th day than 7th day.The result of the TH protein expression detected by western blot was similar to the result of immunohistochemistry staining. Compared with the normal groups, the expression of TH sustained decrease at the 1st day, the 3rd day and the 5th day in diurnal cycle rearing groups after optic nerve transection, and reached the lowest value at the 5th day. The expression of TH was increased at the 7th day and the 14th day obviously, but the level was below the normal. The expression of TH protein decreased to the lowest value at the 1st day in dark rearing groups after optic nerve transection, and then increasing at the 3rd day, the 5th day and the 7th day gradually. The TH-positive area reached the normal level at the 5th day, 7th day and the 14th day.Conclusions: Our data showed that the expression of TH reduced at early stage, and then up-regulation in the retina of rat after optic nerve transaction, and dark rearing condition can maintain the strength of the expression of TH to a certain extent in the critical period of synaptic degeneration.