Figure 3. Anatomical and cell-type specific targeting strategy of optogenetics and chemogenetics.

A Schematic representation of the method for expressing opsins in neurons and activation of opsins or designer receptors. A DNA vector encoding an opsin is injected into the brain region of interest (e.g. locus coeruleus, LC), inducing opsin expression in target neurons. Cell type specificity of opsin expression can be achieved by injecting the recombinase dependent (e.g. cre-) opsin virus into a recombinase driver animal (e.g. injecting cre-dependent opsins into the LC of TH-cre transgenic mice will specifically express opsins in the TH positive LC cells). Light or drugs can be delivered to a specific target area either over the cell bodies that project to multiple target areas or in a specific projection region (e.g. prefrontal cortex, P; amygdala, A; hippocampus, H). E.g. to activate the LC projections targeting hippocampus (H), fiber optic can be implanted above hippocampus in the illustration.