Figure 5.

ACh hyperpolarization and relaxation in PE-stimulated mesenteric arteries are depressed by prior U46619 exposures or by apamin. Simultaneous measurement of smooth muscle membrane potential change (upper panel) and relaxation (lower panel) in mesenteric arteries during stimulation with 1 μM PE. ACh hyperpolarization during the first stimulation with PE (n=9) was reduced to a similar extent by the presence of apamin (n=4), as it was in arteries following three previous exposures (and washout) to U46619 (n=6). The loss of membrane potential overshoot was associated with reduced relaxation, which was more extensive in the arteries previously exposed to U46619 (^*P<0.05, ANOVA with Bonferroni multiple comparisons test). Resting membrane potential (rmp) for each group is shown in the left segment of the graph.