Fig. 1
From: Artificial association of memory events by optogenetic stimulation of hippocampal CA3 cell ensembles
System for activity-dependent labeling of CA3 neurons. a Diagram showing the activity-dependent labeling of neurons in c-fos:: tTA/KA1::Cre double transgenic mice with an AAV system. Gray and white triangles represent loxP and lox2272 sequences, respectively. b Scheme of the experiment. Neural activity was elicited during context A pre-exposure and CFC in context B (i.e., the two events) in animals off of doxycycline treatment (OFF Dox). c Representative image of ChR2-mCherry expression in the CA3 region of the hippocampus of an AAV-injected c-fos::tTA/KA1::Cre double transgenic mouse exposed to the two events in the OFF Dox condition. Scale bar, 500 μm. d Representative images of ChR2-mCherry expression in the CA3 regions of AAV-injected c-fos::tTA/KA1::Cre double transgenic mice exposed to the two events in an ON Dox condition (left) or an OFF Dox condition (middle) and in mice in the home cage in the OFF Dox condition (right). The ChR2-mCherry signal is in red and DAPI nuclear staining is in blue. Arrowheads indicate ChR2-mCherry-positive cells. Scale bar, 300 μm. e Graph showing the average numbers of ChR2-mCherry-positive cells per section in the CA3 region from one hemisphere (counted from both hemisphere, two sections from 4 mice/group, one-way ANOVA; F2, 9 = 13.4, p = 0.0020; Tukey’s post hoc multiple-comparisons test, *p < 0.05, **p < 0.01)