Fig. 3 |. CGRP and RAMP1 signalling contribute to bacterial meningitis.

a,b, Role of the CGRP receptor RAMP1 in bacterial meningitis. a, Bacterial load in samples collected from Ramp1 knockout (Ramp1^−/−) and control littermate (Ramp1^+/−, Ramp1^+/+) mice 24 h after injection with S. pneumoniae (3 × 10⁷ c.f.u.). n = 5 (Ramp1^+/+) or n = 4 (Ramp1^−/−, Ramp1^+/−). b, Flow cytometry quantification of meningeal macrophages (Cd11b⁺MRC1⁺ gates) and neutrophils (Cd11b⁺Ly6G⁺ gates) in Ramp1 knockout (Ramp1^−/−) and control (Ramp1^+/+) mice 24 h after injection with S. pneumoniae (3 × 10⁷ c.f.u.). n = 4 per group. c,d, Impact of CGRP (2 μg, intraperitoneally (i.p.)) treatment on bacterial meningitis. c, Bacterial load in samples collected 24 h after injection with S. pneumoniae (3 × 10⁷ c.f.u.) in mice treated with CGRP or vehicle. n = 6 per group. d, Flow cytometry quantification of meningeal macrophages (Cd11b⁺MRC1⁺ gates) and neutrophils (Cd11b⁺Ly6G⁺ gates) 24 h after injection with S. pneumoniae (3 × 10⁷ c.f.u.) in mice treated with CGRP or vehicle. n = 10 per group. e, Left, scheme of the experiment to examine the protective effects of the RAMP1 antagonist BIBN4096 (BIBN) on bacterial meningitis. Right, bacterial load in samples collected 24 h after injection with S. pneumoniae (3 × 10⁷ c.f.u.; n = 5 per group) or S. agalactiae (1 × 10⁸ c.f.u.; n = 6 per group) from mice treated with BIBN4096 (300 μg kg⁻¹, i.p.) or vehicle. Statistical analysis: one-way ANOVA with Tukey post-tests (a) or unpaired two-sided t-tests (b–e). *P < 0.05, **P < 0.01, ***P < 0.001. n = biologically independent samples from mouse tissues. Error bars indicate the mean ± s.e.m. Box plots show the median, IQR, and minimum and maximum values. Each experiment was performed at least twice, and results presented are representative of 2 or more replicates. Exact P values are provided in Supplementary Table 1.