The effect of isoflurane (Iso) exposure and rapamycin treatment on the numbers of excitatory axon–oligodendrocyte progenitor cell (OPC) synapses in fimbria. The vesicular glutamate transporter 1–positive axon–oligodendrocyte progenitor cell synapses were identified with terminals apposing on neural/glial antigen 2–positive oligodendrocyte progenitor cells (arrows indicate these synapses). The number in isoflurane exposure mice was lower than control and rapamycin treatment rescued these axon–oligodendrocyte progenitor cell synapses. Scale bar = 5 μm. (A) Control. (B) Isoflurane exposure plus vehicle group. (C) Isoflurane exposure with rapamycin treatment. (D) Graph showing quantitative data. n = 8 for each group; one-way ANOVA; **P < 0.01. Error bars: SD.