Improved electrode assemblies for treating a tissue region at or near a sphincter comprise a support structure and an electrode carried by the support structure for advancement in a path to penetrate the tissue region. In one arrangement, the electrode has a non-cylindrical cross section selected to resist deflection when advanced to penetrate the tissue region. In another arrangement, the electrode includes a tissue stop to resist tissue penetration beyond a selected depth. In another arrangement, the electrode includes a proximal portion formed from a first material and a distal tissue penetrating portion formed of a second material different than the first material. The first material can comprise, e.g., stainless steel, and the second material can comprise, e.g., nickel titanium.