Fig. 1.
Experimental design. (A) GRABACh3.0 (ACh3.0) virus was injected in hippocampal CA1 area (ACh fiberphotometry) in ChAT-Cre transgenic and C57/B6 mice, and AAV-DIO-ChR2-GFP was injected in medial septum of ChAT-Cre transgenic mice (optogenetics). After 21 d of virus injection, optical fiber was implanted in the medial septum for optogenetic activation of cholinergic neurons. Optical fiber for photometric measurement and silicon probe for electrophysiological recording were implanted in the hippocampal CA1 region. (B) Mice were trained to learn a hippocampus-dependent figure-eight–maze task. They were rewarded each time they reached the end of side maze arms in the correct task sequence (center-left-center-right-center, and so on). Between choices, they were confined in the start (delay) area for 10 s. Optogenetic stimulation was administered in the delay area or center arm.