Fig. 3.

Effects of changes in vascular perfusion fluid pH_e, intracellular endothelial pH_i, and the presence of sodium on [³H]-nicotine transport at the Swiss mouse BBB. a Effects of perfusion with Krebs carbonate fluid pH_e at 5.40 or 7.40 on the brain transport (K _in; in microliters per second per gram) of [³H]-nicotine with (black column) or without (white column) co-perfusion of unlabelled nicotine (10 mM) measured by in situ mouse carotid perfusion for 60 s. Data are presented as the means ± SD of five to seven animals. **p < 0.01, ***p < 0.001 for the experimental groups compared to the control group at pH_e 5.4; ^‡ p < 0.05, ^‡‡ p < 0.01 for comparisons between data at the same pH with or without added unlabelled nicotine (10 mM). b Effect of altering pH_i (empty column) and removing sodium (grey column). The vascular perfusion fluids were Krebs carbonate buffer plus NH₄Cl (30 mM; “NH₄”), HEPES-buffered fluid without or with ACTZ (10 mM) and “mannitol” (sodium-free and chloride-free) Krebs carbonate buffer used to alter pH_i (empty column). The effect of a Na⁺-free carbonate perfusion fluid (pH_e 7.40) was studied by replacing sodium with lithium (Li⁺; grey column). Data represent the means ± SD of four to seven animals. *p < 0.05, **p < 0.01, ***p < 0.001 for comparisons between experimental and control groups; ^† p < 0.05 for comparisons between the presence and absence of ACTZ (10 mM)