The effect of low-dose atropine on alpha ganglion cell signaling in the mouse retina

Abstract

Low-dose atropine helps to control myopia progression with few side effects. However, the impact of atropine, a non-selective muscarinic Acetylcholine (ACh) receptor antagonist, on retinal ganglion cells (RGCs) remains unclear. After immersing the cornea and adjacent conjunctiva of enucleated eyes in 0.05% (approximately 800 mM) atropine solution for 30 min, the atropine concentration reached in the retina was below 2 mM. After direct superfusion of the retina with 1 mM atropine (considering that the clinical application of 0.05% atropine eye drops will be diluted over time due to tear flow for 30 min), no noticeable changes in the morphology of ON and OFF alpha RGCs (aRGCs) were observed. Atropine affected the light-evoked responses of ON and OFF aRGCs in a dose- and time-dependent fashion. Direct application of less than 100 mM atropine on the retina did not affect light-evoked responses. The time latency of light-induced responses of ON or OFF aRGCs did not change after the application of 0.05–100 mM atropine for 5 min. However, 50 mM atropine extended the threshold of joint inter-spike interval (ISI) distribution of the RGCs. These results indicated that low-dose atropine (<0.5 mM; equal to 1% atropine topical application) did not interfere with spike frequency, the pattern of synchronized firing between OFF aRGCs, or the threshold of joint ISI distribution of aRGCs. The application of atropine unmasked inhibition to induce ON responses from certain OFF RGCs, possibly via the GABAergic pathway, potentially affecting visual information processing.