Effects of memantine on isoproterenol (ISO)- and sodium nitroprusside (SNP)-induced vasorelaxation.
All experiments were carried out in endothelium-denuded porcine basilar arteries in the presence of active muscle tone induced by U46619 (0.2 µM). Panel A, a representative tracing showing that ISO (10−8 M–10−5 M) induced a concentration-dependent vasodilation which was not affected by memantine (10 µM). In panels B and C, concentration-response curves showing effects of memantine on ISO- and SNP-induced relaxation in porcine basilar arteries. The EC50 values of ISO in inducing relaxation in the presence and absence of memantine were 0.06 (0.02–0.18) µM and 0.03 (0.01–0.09) µM, respectively. The EC50 values of SNP in inducing relaxation in the presence and absence of memantine were 0.61 (0.2–2) µM and 0.71 (0.29–1.76) µM, respectively. The EC50 values for isoproterenol and sodium nitroprusside-induced relaxation were not significantly different between the control and that in the presence of memantine (p>0.05). The values are mean ± SEM. n, number of experiments. Relaxation is estimated as percent of PPV (100 µM)-induced maximum relaxation.