Fig. 2: 5-HT_1A receptor-mediated age-dependent LFS-LTD.

a Q-PCR measurements of 5-HT receptor profiles in the hippocampal CA1 region from two age groups of mice (n = 7 mice/group; two-tailed Student’s t test; 5-HT_1B, t₍₁₂₎ = 1.214, P = 0.186; 5-HT_1D, t₍₁₂₎ = -0.826, P = 0.523; 5-HT_1F, t₍₁₂₎ = -1.093, P = 0.274; 5-HT_2A, t₍₁₂₎ = 1.245, P = 0.385; 5-HT_2B, t₍₁₂₎ = 0.835, P = 0.538; 5-HT_2C, t₍₁₂₎ = 1.374, P = 0.674; 5-HT₃, t₍₁₂₎ = 0.937, P = 0.183; 5-HT₄, t₍₁₂₎ = 1.468, P = 0.109; 5-HT_5A, t₍₁₂₎ = 1.235, P = 0.201; 5-HT_5B, t₍₁₂₎ = 0.246, P = 0.483; 5-HT₆, t₍₁₂₎ = 1.104, P = 0.386; 5-HT₇, t₍₁₂₎ = 0.274, P = 0.208). b Q-PCR measurements of 5-HT transporters in CA1 from 21 and 60 day old mice (n = 7 mice/group; two-tailed Student’s t test; SERT, t₍₁₂₎ = 0.209, P = 0.863; TPH-1, t₍₁₂₎ = -0.283, P = 0.736; TPH-2, t₍₁₂₎ = -1.832, P = 0.735). c Hippocampal 5-HT_1AR levels at different time points (n = 8–10/group; one-way ANOVA; F_{(4, 37)} = 32.138, P = 0.012). d Correlation plot of the mRNA level of 5-HT_1AR against the magnitude of LTD at the developmental age point (r² = 0.4177, P < 0.0001). e, f Western blots showing differences in 5-HT_1AR protein levels between the two age groups (n = 4 experiments/group; two-tailed Student’s t test, P = 0.006). g, h The 5-HT_1AR and GABA_AR agonists impaired LFS-LTD, while their antagonists facilitated LFS-LTD in P21 mice (n = 6 slices/group; one-way ANOVA, F_{(4, 25)} = 47.147, P = 0.043). i, j The 5-HT_1AR antagonist reversed the impaired LFS-LTD in P60 mice (n = 6-8 slices/group; two-tailed Student’s t test, P < 0.001). k, l Western blots of 5-HT_1AR in the hippocampus of 5-HT_1A R KO mice and their WT littermates (n = 4 experiments/group; two-tailed Student’s t test; P < 0.0001). m, n LFS-LTD was greater in P21 5-HT_1AR KO mice (n = 7 slices/group; two-tailed Student’s t test; P = 0.036). o, p LFS-LTD was successfully induced in P60 5-HT_1AR KO mice (n = 7-10 slices/group; two-tailed Student’s t test; P < 0.0001). The data are presented as the means ± s.e.m.s; *p < 0.05; **p < 0.01; ***p < 0.001.