Study on retinal dopamine transporter in form deprivation myopia using the radiopharmaceutical tracer 99mTc-TRODAT-1
Purpose: To investigate the distributions and changes in dopamine transporters (DATs) using 99mTc-TRODAT-1 ([99mTc-(2((2-(((3-(4-chlorophenyl)-8-methyl-8-azabicyclo(3,2,1)-oct-2-yl)-methyl)(2-mercaptoethyl)amino)ethyl)amino)ethane-thiolato(3-)-N2,N2',S2,S2)oxo-(1R-(exo-exo)))]) in form deprivation myopia retina. Methods: Pigmented guinea pigs aged 3 weeks were randomly assigned into two groups: form-deprivation myopia and normal control group. The test group wore a translucent goggle covering randomly for 4 weeks, and both groups underwent biometric measurement before and after the experiment. Both Micro-single-photon emission computed tomography (SPECT) imaging and ex-vivo autoradiography were performed with the injection of 99mTc-TRODAT-1 on the 4th week for all the guinea pigs. Results: The retinas were clearly resolved with 99mTc-TRODAT-1 in both Micro-SPECT imaging and ex-vivo autoradiography. In Micro-SPECT imaging, the ratio of 99mTc-TRODAT-1 uptake in the myopic retinas (11.55±2.80) was 3.64±1.40 lower than that in the normal control eyes (15.20±1.98, P=0.026, F=2.94, t=2.605), and 2.35±1.05 lower than that in the fellow eyes (13.90±2.04, P=0.003, t=5.476). In ex-vivo autoradiography, the ratio of 99mTc-TRODAT-1 uptake in the myopic retina (95.52±12.04) was 18.54±5.86 lower than in the normal control eyes (114.06±7.81, P=0.01, F=0.331, t=3.164), and was 16.95±5.78 lower than in the fellow eyes (112.47±15.67, P=0.001, t=7.179). Conclusion: 99mTc-TRODAT-1 can be used to trace the distributions and changes in DAT in the retina. DATs in the myopic retinas were lower than that in the fellow and normal control eyes. Radionuclide tracing may provide a new approach in vivo for further studies on the dopamine system in myopia.