Fig. 2

Osmotherapy-induced brain water loss and electrolyte gain. Rats were treated with isosmolar NaCl (control), hyperosmolar NaCl (osmotherapy, denoted NaCl in legend), or mannitol. a The brain water content (in ml/g dry weight) in naïve (n = 3) and control (n = 9) rats, and in rats exposed to osmotherapy in the form of NaCl (n = 9) or mannitol (n = 6). The theoretical brain water loss assuming ideal osmotic behavior (to 3.24 ml/g dry weight, calculated by Eq. 1) is illustrated as a dashed red line. b, c The brain electrolyte content (in mmol/kg dry weight) shown for naïve rats (197 ± 4 Na⁺ and 141 ± 2 Cl⁻, n = 3), control rats (197 ± 1 Na⁺ and 132 ± 3 Cl⁻, n = 9), and rats exposed to NaCl-mediated osmotherapy (227 ± 2 Na⁺ and 173 ± 3 Cl⁻, n = 9) or mannitol-mediated osmotherapy (209 ± 1 Na⁺ and 182 ± 3 Cl⁻, n = 6). d, e Plasma electrolyte concentrations (in mM) for rats exposed to mannitol-mediated osmotherapy (117.9 ± 0.8 Na⁺ and 94.9 ± 5.7 Cl⁻, n = 6). Values from control rats and rats exposed to NaCl-mediated osmotherapy are from Fig. 1d, e and included for comparison. To determine whether means of naïve, control, and NaCl were statistically different from each other, a one-way ANOVA with Tukey’s multiple comparisons post hoc test was performed. This statistical analysis was further performed to determine differences between means of control, NaCl, and mannitol groups [note; comparison of mannitol (no vehicle treatment) with either of the experimental NaCl groups (i.v. or intraventricular vehicle) provided similar results]. Asterisk above the scatter plot indicates statistical significance compared to control rats and asterisk within the lines indicates statistical significance between the indicated groups. *p < 0.05, ***p < 0.001