Ultrasonic Regulation Of Neuron Activity By Mediating Mechanosensitive Ion Channel

To activate or inhibit the target neuron accurately is an important approach for the studying the function of nervous system.Currently,the widely used method-optogenetics,is to insert the fiber into a specific brain area,and deliver specific wavelengths of light to activate or silence target neurons.However,it is need for invasive intracranial surgery,which will cause damage to animals.Therefore,we look forward to finding a new method to overcome these shortcomings.Compared to the optical signal,non-invasive ultrasound have been shown that can easily focus on the deep brain area,and will not affect the adjacent tissue.Moreover,as a kind of mechanical stimulation,ultrasound can stretch cellular membrane to alter the state of mechanosensitive ion channels embedded within and mediate transmembrane currents,which change the excitability of the cell.In the study,we used E.Coli MscL(Mechanosensitive Channel Large conductance)as a trigger responding for ultrasound to regulate the excitability of cells to testify the feasibility of this scheme.E.Coli MscL is a homopentamerie channel,which including 136 amino acids,with each subunit mainly consist of TM1,TM2 and loop domain.As the tractable nature,MscL serves as good candidate for the propose.Utilizing electrophysiological recording and Ca2+ imaging methods,We observed that primary cultured rat hippocampal neurons showed evoked action potential and increased intracellular Ca2+ signal in response to ultrasound,but limited to high-intensitive stimulation.However,when MscL was transfected into neurons,the ultrasound evoked action potential could be recorded in much lower intensity of stimulation.Especially the GOF mutant of I92L-MscL,which conferred the neuron to be sensitive to the ultrasound stimuli as low as 0.17 MPa.By expressing of MscL-I92L,we can record neuron activity in low Ultrasound intensity.In control of the stimuli strength and stimuli time,we could repeatedly generate neuronal spiking as high as 5 Hz in response to ultrasound stimulation.These data reveal at the single cell level that Ultrasound modulates the activity of specific ion channels to mediate transmembrane currents,and then alter neural processing at the level of single spikes.These findings open doors to investigations of the effects of Ultrasound on ion channels expressed in neurons,which may lead to important medical applications.It may also pave the way to the development of sonogenetics:a non-invasive,ultrasound-based analogue of optogenetics.