FIGURE 4.

Expression of biosensors in vivo. (A) Delivery of biosensors to the animal brain using AAV particles. A typical structure of the AAV vector is shown (top). AAV transduction in adult animals can be performed by either stereotactic injection in the brain or tail injection (middle). Brain injection requires the stereotactic surgery, and the biosensor expression is restricted to the injection point. Via tail injection AAV are delivered to the whole body. The neuronal-specific promoters, such as for CaMKII kinase and Synapsin, provide biosensor expression in CNS (Stoica et al., 2013). Use of cell-specific Cre recombinase expression and AAV in which gene of biosensor is inverted and flanked with loxP and lox511 sequences allows to achieve cell-specific biosensor expression (bottom) (B) Generation of transgenic animals allows to achieve either even or cell-specific expression of biosensor in the animal brain (Xie et al., 2016).