High Current Optogenetic Channels For Stimulation And Inhibition Of Primary Rat Cortical Neurons

ChR2-XXL and GtACR1 are currently the cation and anion ends of the optogenetic single channel current range. These were used in primary rat cortical neurons in vitro to manipulate neuronal firing patterns. ChR2-XXL provides high cation currents via elevated light sensitivity and a prolonged open state. Stimulating ChR2-XXL expressing putative presynaptic neurons induced neurotransmission. Moreover, stable depolarisation block could be generated in single neurons using ChR2-XXL, proving that ChR2-XXL is a promising candidate for in vivo applications of optogenetics, for example to treat peripheral neuropathic pain. We also addressed an anion channelrhodopsin (GtACR1) for the next generation of optogenetic neuronal inhibition in primary rat cortical neurons. GtACR1 s light-gated chloride conduction was verified in primary neurons and the efficient photoinhibition of action potentials, including spontaneous activity, was shown. Our data also implies that the chloride concentration in neurons decreases during neural development. In both cases, we find surprising applications of these high current channels. For ChR2-XXL inhibition and stimulation are possible, while for GtACR1 the role of Cl-during neural development becomes a new optogenetic target.