Fig. 3
From: Artificial association of memory events by optogenetic stimulation of hippocampal CA3 cell ensembles
Optogenetic stimulation of CA3 induces LTP within CA3-CA3 recurrent synapses. a KA1::Cre or CA3-NR1 KO mice received injections of AAV into the CA3 regions of their right hemispheres. Gray and white triangles represent loxP and lox2272 sequences, respectively. b After AAV infection, field excitatory postsynaptic potentials (fEPSPs) were recorded while the mice were under urethane anesthesia. Rec, recording electrode. c Representative images of ChR2-mCherry expression in the CA3 regions of KA1::Cre and CA3-NR1 KO mice. Arrows indicate the tips of the recording electrodes. Scale bar, 500 μm. The loci of the recording electrodes were confirmed by histology (see Additional file 2). d Representative traces showing LTP in the CA3 in the KA1::Cre mice but not in the CA3-NR1 KO mice after the 20-Hz optical stimulation. Black and red traces represent baseline and 160 min after 20-Hz stimulation periods, respectively. Blue columns indicate the time point of the optical test pulse (473 nm, 500 μs). e Plot showing the time course of fEPSP slopes after 20-Hz optical stimulation (n = 4 mice/group, Two-way RM ANOVA; interaction, F42,129 = 1.418, p = 0.0709; time, F42,129 = 0.6796, p = 0.9248, genotype; F1,129 = 160.7, p < 0.0001; Bonferroni’s multiple comparisons test, KA1::Cre vs. CA3-NR1 KO, p < 0.05, 155–175 min after the 20-Hz laser stimulation). f Mean values of fEPSP slopes between − 20 and − 1 min, 40 and 59 min, 100 and 119 min, and 160 and 179 min (n = 4 mice/group; KA1::Cre: − 20 to − 1 min vs. 40–59 min, paired Student’s t test; t3 = 3.440, p = 0.0412; KA1::Cre: − 20 to − 1 min vs. 160–179 min, paired Student’s t test; t3 = 4.327, p = 0.0228; CA3-NR1 KO: − 20 to − 1 min vs. 40–59 min, paired Student’s t test; t3 = 0.3868, p = 0.7247; CA3-NR1 KO: − 20 to − 1 min vs. 160–179 min, paired Student’s t test; t3 = 0.4318, p = 0.6951; 160–179 min: KA1::Cre vs. CA3-NR1 KO, unpaired Student’s t test; t6 = 2.690, p = 0.036). Significant difference between genotype and baseline at */#p < 0.05, error bars are the means ± SEMs