Baroreflex Control of Heart Rate in Mice Overexpressing Human SOD1: Functional Changes in Central and Vagal Efferent Components

Figures

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  Fig. 1. Recordings of phasic arterial pressure (PAP), aortic depressor nerve activity (Raw ADNA), integrated ADNA (Int ADNA), and ECG. Uppermost trace, PAP. Upper middle trace, ADNA occurred as rhythmic bursts that were synchronized with the PAP. Note that ADNA increased before the PAP increases because the PAP catheter was inserted into the femoral artery while ADNA was recorded from the ADN that innervates the aortic arch. Lower middle trace, integrated ADNA using a 10-ms time constant; small boxes enclose silent intervals (noise level) between the ADNA bursts that were used as basal activity. Lowest trace, ECG. The QRS waves were used to automatically separate ADNA firing intervals (arrows).

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  Fig. 2. Original recordings of heart rate (HR) depression following stimulation of the aortic depressor nerve at 3 µA, 1-ms pulses in a 20-s train in C57 and SOD1 mice. Representative figures encompass the mid-range frequencies between 5 and 60 Hz.

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  Fig. 3. Central mediation of baroreflex bradycardia and mean arterial pressure. Electrical stimulation of the left aortic depressor nerve (ADN) evoked frequency-dependent decreases in HR (A) and MAP (B) in both C57 and SOD1 mice. They were not significantly different (P > 0.05).

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  Fig. 4. Time courses of HR depression in response to electrical stimulation at 30 (A) and 60 Hz (B) did not differ between SOD1 and C57 control mice (P > 0.05).

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  Fig. 5. Original recordings of heart rate (HR) depression following stimulation of the right cervical vagus nerve at 30 µA, 1-ms bursts of 20-s trains in C57 and SOD1 mice. Representative figures encompass the mid-range frequencies between 5 and 30 Hz.

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  Fig. 6. Electrical stimulation of the right cervical vagus nerve evoked frequency-dependent decreases in HR (A) and MAP (B) in both SOD1 and C57 mice. The differences were significant (†P < 0.05 between groups, *P < 0.05 at the given frequency).

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  Fig. 7. Time courses of HR depression in response to electrical stimulation at 10 (A) and 30 Hz (B) were significantly different between SOD1 and C57 control mice (†P < 0.05 between groups, *P < 0.05 at a given time).