Fig. 1

Effects of hNB001 on trace fear memory in aged mice. a Schematic diagram showing trace fear memory performed on aged mice. The CS of a white noise (80 dB, 15 s) was delivered 30 s (trace) before the US of a foot shock (0.75 mA, 0.5 s). Mice were conditioned by 10 CS-trace-US-ITI (210 s) trials for training, and received 10 CS–ITI trials in a novel chamber for test after 24 h of training. The mice were administered hNB001 (30 mg/kg) or saline orally for 7 days before training. hNB001 or saline was taken orally 45 min before test. b No effects of hNB001 on trace fear conditioning in aged mice (Saline, n = 9 mice; hNB001, n = 10 mice, Two-way ANOVA, F _(1,17) = 0.9233, p = 0.3501). c hNB001-treated mice showed no significant difference in freezing during ITI-1 to ITI-7, but significantly reduced freezing during ITI-8 to ITI-10, compared with saline-treated mice during trace fear test (Two-way ANOVA, F _(1,17) = 1.817, p = 0.1953; ITI-8, Student’s t-test, t ₍₁₇₎ = 3.271, p = 0.0045; ITI-9, Student’s t-test, t ₍₁₇₎ = 2.316, p = 0.0333; ITI-10, Student’s t-test, t ₍₁₇₎ = 2.896, p = 0.0100). d Statistical results of trace fear conditioning and test in aged mice with oral hNB001 or saline (Student’s t-test, Training, t ₍₁₇₎ = 0.9609, p = 0.3501; Test, t ₍₁₇₎ = 1.348, p = 0.1953). e hNB001-treated mice showed no significant difference in freezing during the first 7 ITI of trace fear test, compared with saline-treated mice (Student’s t-test, t ₍₁₇₎ = 0.2986, p = 0.7689). f hNB001-treated mice showed significantly reduced freezing during the last 3 ITI of trace fear test, compared with saline-treated mice (Student’s t-test, t ₍₁₇₎ = 3.055, p = 0.0072). *p < 0.05, **p < 0.01