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

Abstract

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. Thus, it is likely that the amygdala is a component of neural networks generating regional differences in RSNA and LSNA.

Abstract: The central amygdala (CeA) is involved in generating diverse changes in sympathetic nerve activity (SNA) in response to changes in daily behavioural states. However, the functional relationships between CeA neuronal activity (CeANA) and SNA in daily activities are still unclear. In the present study, we developed a method for simultaneous and continuous measurement of CeANA and SNA in freely moving rats. Wistar rats were chronically instrumented with multiple electrodes (100-μm-thick stainless-steel wire) for the measurement of CeANA, renal SNA (RSNA) and lumbar SNA (LSNA), and electroencephalogram, EMG and ECG electrodes, in addition to catheters for measurement of arterial pressure (AP). During the transition from non-rapid eye movement sleep to quiet wakefulness, moving and grooming states, a significant linear relationship was observed between CeANA and RSNA (P < 0.0001), between CeANA and LSNA (P = 0.0309), between CeANA and heart rate (HR) (P = 0.0123) and between CeANA and EMG (P = 0.0089), but no significant correlation was observed between CeANA and AP (P = 0.5139). During rapid eye movement sleep, the relationships between CeANA and RSNA, LSNA, HR, AP and EMG deviated from the previously observed linear relationships, but the time course of RSNA and HR changes was the mirror image of that of CeANA, whereas the time course of changes in LSNA and AP was not related to that of CeANA. In conclusion, CeANA was related to RSNA, LSNA and HR in a behavioural state-dependent and regionally different manner, and CeANA was tightly associated with RSNA and HR across all behavioural states.

Keywords: central amygdala; lumbar sympathetic nerve activity; renal sympathetic nerve activity.