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Figure 4 (A) Recordings of electrocardiogram (EKG), blood pressure (BP), muscle sympathetic nerve activity (MSNA), and respiration at baseline and after spit tobacco. Despite increased BP with tobacco use, heart rate (HR) increases, and MSNA is not suppressed. Contrast this with panel B showing the same measurements at baseline and after raising blood pressure using phenylephrine. With phenylephrine, there is a slowing of HR and a complete elimination of MSNA because of baroreflex activation.