This invention provides a method for treating a condition of a subject, comprising identifying the subject as suffering from heart failure; treating the heart failure by applying a stimulating current to parasympathetic nervous tissue of the subject, and configuring the stimulating current to change a level of protein expression of at least one NO synthase of the subject selected from the group consisting of: NOS-1, NOS-2, and NOS-3; and thereafter, measuring the level of the protein expression of at least one NO synthase, and evaluating an effectiveness of the current application by assessing at least one change in the level of the protein expression of at least one NO synthase.