Agmatine attenuated the naloxone-induced elevation of hippocampal extracellular glutamate in chronic morphine-treated rats. A Effect of acute administration of morphine, agmatine, or naloxone on dialysate glutamate levels in the hippocampal CA1 region (n = 9; *P < 0.05; ***P < 0.001 vs baseline; two-way ANOVA for repeat measures followed by Bonferroni test). Nal naloxone, Mor morphine, Agm agmatine. B Effect of agmatine on the elevation of hippocampal glutamate levels after naloxone injection in chronic morphine-treated rats (n = 5; *P < 0.05 vs Con group, #
P < 0.05 vs Mor group; two-way ANOVA for repeat measures followed by Bonferroni test). Con control, Mor morphine, Agm + Mor agmatine concurrent with morphine for 5 days.