Fig 2: SIRPa overexpression reduces PSD95 engulfment within host microglia but leads to synapse loss. (A) Representative Western blots of CD47, SIRPa, and PSD95 on POD3. (B–D) Quantitative analysis of CD47, SIRPa, and PSD95 levels compared with the vehicle group. (E) Representative 3D reconstruction and surface rendering of PSD95 inside Iba1+microglia from SIRPa overexpression mice versus vehicle mice. Microglia in CA1 region were chosen. (F) Quantification of PSD95 engulfment within microglia. n = 5 mice per group, 8–10 cells per mouse were quantified. (G) Representative images of the Golgi-stained dendrites in CA1 and DG neurons. Scale bar = 5 µm. (H–J) Quantitation of dendritic spine density. n = 4 mice per group, 13–15 spines per mice for each region. Data are shown as mean ± SEM. **p < 0.01; ***p < 0.001; and ****p < 0.0001.

Fig 3: Synapse markers in the hippocampus. The figure shows the results from the Western blotting of markers of synapse formation. Synaptophysin is down-regulated in the DEF group (p = 0.0160), while N-methyl-d-aspartate receptor 1 (NMDAR1) displays a tendency for down-regulation (p = 0.0525). Data is displayed as mean ± SD and analyzed by Student’s or Welch’s t-test. *: p < 0.05; PSD-95: Post-synaptic-density-protein-95; CTRL: Control animals (n = 13); DEF: Deficient animals (n = 12); GluR1: a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit 1.

Fig 4: (+)-Borneol is a positive allosteric modulator of a2- and a3-containing GABAARs without BZDs-associated behavioral effects. (A) The hypothesis: chronic use of PSD-95-nNOS inhibitor causes analgesic tolerance through the disinhibition of pain neural circuit at spinal level, and a2- and a3-containing GABAARs agonist reverses this process. (B) Left, chemical structure of (+)-borneol. Right, locomotor activities of the mice treated by (+)-borneol at supramaximal doses (45 mg/kg, i.v.) or diazepam (0.5 mg/kg, i.v.) in the open field test. Locomotor activity was expressed as distance travelled during 5 min after drug injection (F (3,36) = 37.33, ***p < 0.001, vs vehicle, ANOVA, n = 10). (C) Representative image showing patch-clamp from HEK293 cells transiently expressing GABAARs (images under 40 × magnification). (D) Dose/response plots of GABA-evoked currents in the HEK293 cells transiently expressing a1ß2?2, a2ß3?2 or a3ß3?2 GABAARs. (E-F) Representative recordings of GABA-evoked currents in the HEK293 cells transiently expressing a1ß2?2, a2ß3?2 or a3ß3?2 GABAARs (left) and dose/response plots (right) of potentiation of GABA-evoked currents by diazepam (E) or (+)-borneol (F), n =8. (G-H) Representative recordings of GABA-evoked currents in putative excitatory neurons (left) of brain cortex (G) and spinal dorsal horn (H) and dose/response plots (right) of potentiation of GABA-evoked currents by diazepam or (+)-borneol, n =12. All data were shown as mean ± SEM.

Fig 5: SIRPa deficiency enhanced cognitive impairment and synaptic loss without modifying Aß plaque depositions.a Schematics of the experimental procedures, Cx3cr1CreERT2:SIRPafl/fl (-TAM) mice are used as normal control. TAM tamoxifen. b Histograms depict that total distance mice traveled in open filed experiment has no significant difference. 5 M: n = 13, 14, 15, 15 mice/group; 8M: n = 10, 12, 10, 12 mice/group, one-way ANOVA, by Dunnett’s multiple comparisons test. c Histograms depict escape latency of four different groups of mice in visible platform test (time to find the visible platform) before plaque deposition (5 months old) and after plaque deposition (8 months old). 5M: n = 13, 14, 15, 15 mice/group; 8 M: n = 10, 12, 10,12 mice/group, one-way ANOVA, by Dunnett’s multiple comparisons test. d Line charts show Morris Water Maze escape latency (time to find the hidden platform) in five consecutive days of four different genotypic mice at the age of 5 months old and 8 months old respectively. 5M: n = 13, 14, 15, 15 mice/group; 8M: n = 10, 12, 10, 12 mice/group, two-way RM ANOVA, via Tukey’s multiple comparisons test. e Histograms depict the time spent in target quadrant in Morris Water Maze probe trial of four different genotypic mice at the age of 5 months old or 8 months old. 5M: n = 13, 14, 15, 15 mice/group, Kruskal–Wallis test via Dunn’s multiple comparisons test; 8M: n = 10, 12, 10, 12 mice/group, one-way ANOVA via Dunnett’s multiple comparisons test. f, g Representative immunostaining images exhibit 6E10 positive plaques in cortex and hippocampus of 8-months-old AD and AD/SIRPa-cKO mice. Scale bar, 200 µm. Quantification analyses show that 6E10 positive plaques in AD and AD/SIRPa-cKO mice were equivalent. n = 5, 7 mice/group; average of 5–6 fields from each mouse, two-tailed unpaired t-test. h, i ELISA analyses of both soluble and insoluble Aß42 in 5-months-old and 8-months-old AD and AD/SIRPa-cKO mice brain. n = 8 mice/group, two-tailed unpaired t-test. j, k Representative images of 6E10 immunoreactive plaques (diameter 20–50 µm as small groups; 50–80 µm as big group) surrounded by microglia in 8-months-old AD and AD/SIRPa KO mice. Scale bar, 25 µm. Histograms show the area ratio of Iba-1/6E10 are comparable in AD and AD/SIRPa-cKO mice. n = 5, 7 mice/group. Average of 3–4 plaques from each mouse, two-tailed unpaired t-test. l, m Representative confocal images depict synaptic staining for presynaptic marker Synapsin I (green) and postsynaptic marker PSD95 (red) in cortex of 5-months-old and 8-months-old mice. Synaptic number was determined as colocalized pre- and postsynaptic puncta. Scale bars, 10 µm. n = 5, 5, 7, 7 mice/group, average of 10–12 fields from each mouse, one-way ANOVA via Dunnett’s multiple comparisons test. n, o Golgi staining images of apical dendritic spine in cortex of 5-months-old and 8-months-old mice. Scale bars, 20 µm. n = 5, 5, 7, 7 mice/group, average of 10 dendrites from each mouse; one-way ANOVA via Dunnett’s multiple comparisons test. Data are mean ± s.e.m. *P < 0.05, **P < 0.01, ***P < 0.001, NS not significant. Detailed statistical information was listed in Supplementary Statistical Data. Source data are provided as a Source Data file.