FIGURE 2.

Quantitative features of a typical dose-response curve (β-curve) displaying hormesis (shaded region). (A) The maximum stimulatory response. (B) The width of the stimulatory response calculated from the lowest (P₁) to the highest (P₂) concentration showing a response that is 110% of the control response. (C) Distance from the concentration of the maximum stimulatory response to the highest concentration with a response equal to the control, the zero equivalent point (ZEP). In order for a concentration-response to be evaluated it must have a response in the low-concentration region ≥110% and a response at a higher concentration ≤80% of the control. (after Calabrese and Baldwin, 1997; Nascarella et al., 2009).