Progressive Increase in Renal Sympathetic Nerve Activity Induced by Cold Exposure.

Background: Exposure to cold environments is linked to cold-induced hypertension due to activated sympathetic nerve activity (SNA) and arterial baroreceptor reflex dysfunction. However, direct measurement of SNA during cold-induced hypertension and changes in baroreflex control of SNA remain unexplored.

Methods: Chronically instrumented rats were exposed to cold temperatures (10 °C) over 4 days after a control period (24 °C), and renal and lumbar sympathetic nerve activities were simultaneously measured during cold-induced hypertension.

Method for measuring cervical vagal nerve activity in conscious rats.

The current study aimed to propose a method to directly measure right cervical vagal nerve activity (cVNA) alongside renal sympathetic nerve activity (RSNA) in conscious rats. The right cervical vagus nerve was surgically exposed and fitted with a bipolar electrode to record cVNA. A microcatheter was used to administer levobupivacaine to selectively block afferent cVNA.

Simultaneous measurement of central amygdala neuronal activity and sympathetic nerve activity during daily activities in rats.

New Findings: What is the central question of this study? The functional relationships between central amygdala neuronal activity (CeANA) and sympathetic nerve activity in daily activities remain unclear. We aimed to measure CeANA, renal and lumbar sympathetic nerve activity (RSNA and LSNA, respectively), heart rate (HR) and arterial pressure simultaneously in freely moving rats. What is the main finding and its importance? The CeANA was significantly related to RSNA and LSNA and HR in a behavioural state-dependent and regionally different manner; meanwhile, CeANA was tightly associated with RSNA and HR across all behavioural states.

Regional Differences in Sympathetic Nerve Activity Are Generated by Multiple Arterial Baroreflex Loops Arranged in Parallel.

In this review, by evaluating the responses during freezing, rapid eye movement (REM) sleep, and treadmill exercise, we discuss how multiple baroreflex loops arranged in parallel act on different organs to modulate sympathetic nerve activity (SNA) in a region-specific and coordinated manner throughout the body. During freezing behaviors, arterial pressure (AP) remains unchanged, heart rate (HR) persistently decreases, renal SNA (RSNA) increases, and lumbar SNA (LSNA) remains unchanged. The baroreflex curve for RSNA shifts upward; that for LSNA remains unchanged; and that for HR shifts to the left.

Differential shifts in baroreflex control of renal and lumbar sympathetic nerve activity induced by freezing behaviour in rats.

New Findings: What is the central question of this study? Is the arterial baroreflex involved in causing patterned, region-specific changes in sympathetic nerve activity during freezing behaviour in conscious rats? What is the main finding and its importance? Freezing behaviour is accompanied by differential shifts in the baroreflex control of renal and lumbar sympathetic nerve activity and heart rate. It is noteworthy that baroreflex pathways may be discretely separated, allowing differential modification of baroreflex curves that may generate differential changes in sympathetic nerve activity during freezing behaviour.

Abstract: The present study was designed to test whether the baroreflex stimulus-response curves for renal sympathetic nerve activity (RSNA), lumbar sympathetic nerve activity (LSNA) and heart rate (HR) were shifted in a regionally specific manner during freezing behaviour in conscious rats.

Renal and Lumbar Sympathetic Nerve Activity During Development of Hypertension in Dahl Salt-Sensitive Rats.

To study the contribution of sympathetic nerve activity (SNA) to the development of hypertension, experiments were designed to continuously and simultaneously measure renal (RSNA) and lumbar SNA (LSNA) during the development of hypertension induced by 8% salt loading in Dahl salt-sensitive (DS) rats. Male DS and salt-resistant rats were instrumented with bipolar electrodes to record RSNA and LSNA and a telemeter to record arterial pressure (AP). AP increased during the first 3 days after the onset of salt loading by ≈10 mm Hg in both DS and Dahl salt-resistant rats.