Mechanism of low-frequency, low-intensity ultrasound modulation of the mouse retina.

Ultrasound has been shown to modulate the activity of retinal ganglion cells (RGCs) in mice, but the mechanism remains poorly understood. This study aims to address this question.Multi-electrode recordings together with pharmacological methods were used to investigate the possible cellular/circuitry mechanism(s) underlying the neuronal modulation induced by low-frequency (1 MHz), low-intensity (0.5 W cm) ultrasound stimulation.We found that ultrasound activated mechanosensitive channels (transient receptor potential vanilloid 4 (TRPV4) channels are involved) in Müller cells, causing the release of glutamate, which acts on the extrasynaptic-methyl-D-aspartate receptors of RGCs, thus leading to the modulation of neuronal activity.Our results reveal a novel mechanism of low-frequency, low-intensity ultrasound modulation, involving TRPV4 as a mechanosensitive target for ultrasound and glutamate as an essential mediator of neuron-glia communication. These findings also demonstrate that the mechanical-force-mediated pathway is important for retinal signal modulation during visual processes, such as visual accommodation.