Thermogenetics has emerged recently as an evolving extension of optical methods for neuronal stimulation that employing focused light to activate photosensitive cationic channels in neuronal membrane. Light-activation to open photosensitive channels that can be expressed genetically in all types of neurons is aimed to induce depolarization of neuronal membrane to evoke a neuronal discharge. Unlike conventional optogenetics that employs visible spectrum, thermogenetics uses channels gated by heating. It provides the possibility to activate the channels not only with IR-radiation, but also with any other way to heat nervous tissue such as ultrasound or microwave radiation. The permeability of living tissue to IR-radiation is orders higher than that to visible light spectra, which allows use of thermogenetic stimulation in the experiments in vivo without invasive surgery to make access for optogenetic stimulation. On the other hand, the thermal nature of stimulation imposes additional limitations to application of thermogenetics as heating should be quite reasonable to avoid heat shock response at cellular level, while the threshold of activation of channels should be high enough to rule out their activation at normal physiological temperatures. We employed TRPA and TRPV channels for activation of neurons in cultures and acute brain slices in our experiments. In addition, we combined thermogenetics with the genetically encoded fluorescent marked tdTomato and calcium reporter GCaMP6s that required excitation by visible light that did not activate thermochannels.
Никитин Е. С.