Abstract Body (Do not enter title and authors here): Introduction: The sympathetic nervous system plays a crucial role in cardiovascular regulation and in the pathophysiology of cardiovascular diseases such as hypertension, arrhythmias, and heart failure. Therefore, assessment of sympathetic nerve activity is important for understanding the pathophysiology in patients with cardiovascular disease. In humans, the gold standard for indicators of sympathetic nerve activity is muscle sympathetic nerve activity recording, but this is invasive and not a versatile method because it requires special techniques and equipment. Recently, skin sympathetic nerve activity (SKNA) has been reported as a novel indicator of cardiac sympathetic nerve activity derived from non-invasive ECG recording in humans. However, the utility and validation of SKNA have not been fully established.
Research Question: Does SKNA truly reflect sympathetic nerve activity?
Aims: To evaluate whether SKNA correlates with renal sympathetic nerve activity (RSNA), an established measure of sympathetic activity, in experimental animals.
Methods and Results: Blood pressure, heart rate, RSNA, and SKNA were measured simultaneously in Sprague-Dawley rats under anesthesia. RSNA was recorded directly using bipolar electrodes, and SKNA was isolated from body surface ECG recordings by band-pass filtering to remove electrocardiograms and electromyograms. Changes in RSNA and SKNA were evaluated when blood pressure was altered by intravenous phenylephrine or nitroprusside and when the sympathetic nervous system was blocked by intravenous hexamethonium, a ganglion blocker. Baroreceptor reflexes functioned; RSNA decreased when blood pressure was raised with phenylephrine and increased when blood pressure was lowered with nitroprusside. SKNA was altered similarly to these RSNA responses (Figure A). In addition, administration of the ganglion blocker hexamethonium markedly attenuated RSNA, and SKNA was attenuated similarly to RSNA. Changes in SKNA in response to phenylephrine or nitroprusside were significantly correlated with changes in RSNA (r²=0.54, p <0.05; Figure B).
Conclusion: SKNA correlates with RSNA, an established measure of sympathetic activity, in rats. Our study confirms that SKNA can be an alternative, novel indicator of sympathetic activity. This non-invasive SKNA recording will allow for application to animal experiments under unanesthetized awake conditions.