Figure 15.

Immunostaining against VAChT (red) revealed the expression of ChAT–ChR2–EYFP+ cells, with an affinity towards cholinergic transgenic mouse neurons. (A) Images taken from the horizontal diagonal band of Broca (HDB). EYFP expression was weak in somata, because ChR2 protein tends to localize to neuronal membranes. (B) Retrograde tracing confirmed that HDB neurons feed into the main olfactory bulb (MOB). Some neurons lacked EYFP expression, since the MOB is only partially innervated by cholinergic neurons. (C-D) Blue light stimulation up to 50 Hz led to activation and firing of ChR2– EYFP+ neurons in the HDB. (E) Light pulses produced vigorous subsequent firing of HDB neurons. Reproduced with permission from [204].