Comparison in Conscious Rabbits of the Baroreceptor-Heart Rate Reflex Effects of Chronic Treatment with Rilmenidine, Moxonidine, and Clonidine

Figures

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  Figure 1. Average sigmoid curves indicating the relationship between mean arterial pressure (MAP, mmHg) and heart rate (HR, beats/min) for the intact baroreflex curves (left panel) and the sympathetic and calculated vagal baroreflex curves (right panel) in six conscious rabbits before (weeks 0, black line, black circles on all panels) and at weeks 1 (blue line, blue square on all panels) and 3 (red line, red triangle on all panels) of moxonidine treatment. Symbols on curves represent resting values. Error bars are average SEM indicating variation between animals calculated from the ANOVA.

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  Figure 2. Average sigmoid curves indicating the relationship between mean arterial pressure (MAP, mmHg) and heart rate (HR, beats/min) for the intact baroreflex curves (left panel) and the sympathetic and calculated vagal baroreflex curves (right panel) in eight conscious rabbits before (weeks 0, black line, black circles on all panels) and at weeks 1 (blue line, blue square on all panels) and 3 (red line, red triangle on all panels) of rilmenidine treatment. Symbols on curves represent resting values. Error bars are average SEM indicating variation between animals calculated from the ANOVA.

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  Figure 3. Average sigmoid curves indicating the relationship between mean arterial pressure (MAP, mmHg) and heart rate (HR, beats/min) for the intact baroreflex curves (left panel) and the sympathetic and calculated vagal baroreflex curves (right panel) in seven conscious rabbits before (weeks 0, black line, black circles on all panels) and at weeks 1 (blue line, blue square on all panels) and 3 (red line, red triangle on all panels) of clonidine treatment. Symbols on curves represent resting values. Error bars are average SEM indicating variation between animals calculated from the ANOVA.

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  Figure 4. Average sigmoid curves indicating the relationship between mean arterial pressure (MAP, mmHg) and heart rate (HR, beats/min) for the intact baroreflex curves (left panel) and the sympathetic and calculated vagal baroreflex curves (right panel) in seven conscious rabbits before (weeks 0, black line, black circles on all panels) and at weeks 1 (blue line, blue square on all panels) and 3 (red line, red triangle on all panels) of vehicle treatment. Symbols on curves represent resting values Error bars are average SEM indicating variation between animals calculated from the ANOVA.

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  Figure 5. Average contribution of the sympathetic and vagal influences on resting heart rate at 1 and 3 weeks of treatment in vehicle (Veh), moxonidine (Mox), Rilmenidine (Ril) and clonidine (Clo). Vagal contribution calculated as the change in heart rate induced by the administration of methscopolamine. Sympathetic component calculated as the heart rate under methscopolamine minus the intrinsic heart rate. The latter was estimated as 200 b/min according to the literature for rabbits at that body weight (Opthof, 2000). **P < 0.01 and ***P < 0.001 for the effect of treatment compared to vehicle.