Dialysis of a double cocktail of antagonists (5 mM ATR, 267 μM SPA, n = 5) in the VRC significantly increased the effluent SP concentration (P < 0.001, C) relative to time-control studies (n = 7) but had no significant effect (P > 0.05) on serotonin (5-HT, A), glutamine (GLN, B), glycine (D), or GABA (E), although the effect on GABA was close to significant. The x-axes indicate hour of dialysis; y-axes indicate effluent neurochemical concentration. Filled bars indicate dialysis of cocktail; open bars indicate dialysis of mCSF. Bars on the left are data from time-control studies; bars on the right are data from cocktail studies. F and P indicate values for interaction term from two-way RM ANOVA. **P ≤ 0.001 vs. hour 1; ††P ≤ 0.001 vs. hour 2; ##P ≤ 0.001 vs. time-control value per post hoc analysis.