ABSTRACT
Ultrasound can modulate the electrical activity of the brain and other excitable tissues but the mechanisms underlying this effect are not understood, either at the molecular level or in terms of the physical modality through which ultrasound exerts its effects. An obvious approach to address this question would be to measure ultrasound’s effects on specific candidate ion channels using patch-clamp recording, but ultrasound at the most commonly used frequencies permanently damages the gigaOhm seals required for patch-clamp recording. Here we report an experimental system that allows for stable patch-clamp recording in the presence of ultrasound at 43 MHz, a frequency known to stimulate neural activity in tissue in vitro. We describe the effects of ultrasound on two ion channels proposed to be involved in the response of excitable cells to ultrasound: the mechanosensitive Piezo1 channel and the voltage-gated sodium channel NaV1.2. Our patch-clamp recordings, together with finite-element simulations of acoustic field parameters indicate that Piezo1 channels can be activated by ultrasound through cell membrane stress and that acoustic streaming is required for this effect. Despite the reported sensitivity of voltage-gated sodium channels to membrane stress, NaV1.2 channels were not affected through this mechanism, but their activation and inactivation rates could be accelerated by ultrasound-induced heating. The approach described here will be useful in exploring the effects of different ultrasound modalities on ion channels, to better understand the endogenous response of excitable tissues to ultrasound and to help design ultrasound-sensitive channels for “sonogenetic” manipulation of cell activity.