Low-does atropine might affect alpha ganglion cell signaling in the mouse retina

Purpose: Atropine was used to retard myopia progression in clinic, while its effect on retina is unclear. Therefore, we explored the impact of atropine from concentrations 0.05 µM to 500 µM on retinal ganglion cells (RGCs) in the mouse retina.

Methods: Adult C57BL/6J mice, Kcng4-YFP mice, Cx36-knockout mice were used in this study. Retinas (n=5) were removed and immersed in 800 µM (0.05%) atropine sulfate for 30 minutes and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to detect atropine concentration in retina. Alpha RGCs (n=10) were injected with Neurobiotin to show morphology. In electrophysiological recording, retinas were directly applied in atropine and stimulated with 525nm full-field light. ON (n=5) and OFF αRGCs (n=5) were applied with 0 µM, 100 µM, 300 µM, 500 µM atropine subsequently for does-dependent test. For time and concentration-dependent test, alpha RGCs were recorded before and after application of 0.05 µM (n=8), 0.5 µM (n=8), 10 µM (n=8), 100 µM (n=9) atropine respectively.

Results: Around 400-fold reduction was detected in retina after 800 µM atropine applied in cornea and choroid side (1960.0 ± 524.2nmol/L). No morphological changes were observed after superfusion in 1µM atropine for 30 minutes. Atropine over 100µM had a does-dependent inhibition effect on light-evoked response in ON αRGCs (300 µM p=0.048, 500 µM p=0.001) and OFF αRGCs (300 µM p=0.048, 500µM p=0.003). Application of 100 µM, 10 µM, 0.5 µM, 0.05 µM atropine had no effect on spike frequency and time latency of original ON or OFF light-evoked responses. Synchronized firing pattern between OFF RGCs was not changed in 0.5 µM atropine. However, ON responses were induced in certain OFF αRGCs (20% in 0.05µM, 37% in 0.5µM, 40% in 10µM, 33% in 100µM). Atropine of 50µM extended the threshold of joint inter-spike interval (ISI) distribution of αRGCs.

Conclusions: Atropine of high concentration had inhibition effect on αRGCs firing response, while low-dose atropine did not interfere with spike frequency, synchronized pattern, and threshold of joint ISI distribution of ON and OFF αRGCs. However, atropine induced ON responses from certain OFF RGCs, which suggested unintended consequences on retinal information processing.