Effects of EFS on membrane responses of longitudinal smooth muscle of the chicken mesenteric artery. EFS-evoked hyperpolarization and depolarization in 5-week-old (A) and in 12-week-old (B) chickens, respectively. Resting membrane potentials for A and B were −38 and −36 mV, respectively. Similar results were obtained in six independent experiments. The EFS-evoked hyperpolarization at 5 weeks of age was blocked by TTX (0.3 µM, n= 4) (C) or guanethidine (5 µM, n= 4) (D). EFS, electrical field stimulation; TTX, tetrodotoxin.