Circadian Systems and Neural Control of Blood Pressure

Abstract Purpose of Review Blood pressure (BP) follows a robust circadian rhythm and disruption of this rhythm is associated with hypertension and increased cardiovascular disease risk. This review discusses the current understanding of how circadian mechanisms regulate the neural control of BP, with a focus on autonomic brain circuits, local molecular clocks, and emerging neuroimmune mechanisms contributing to the regulation of BP. Recent Findings Numerous studies show that autonomic control areas of the brainstem are important for circadian BP regulation. Regions such as the rostral ventrolateral medulla (RVLM), the nucleus tractus solitarius (NTS), and paraventricular nucleus of the hypothalamus (PVN) all contain intrinsic molecular clocks that play a role in sympathetic activity and baroreflex function. Emerging evidence also indicates that disruption of clock function in microglia within the RVLM acts as a potential mechanism that contributes to neuroinflammation, sympathetic overactivity, and non-dipping hypertension. The growing interest in chronotherapy, renal denervation, and ambulatory BP monitoring emphasizes the clinical importance of circadian BP regulation. Summary Circadian regulation of BP is comprised of coordinated interactions between the SCN, autonomic neural circuits, and local molecular clocks. Disruptions in any of these mechanisms lead to abnormalities in BP rhythms increasing the risk of hypertension. Despite recent advances, many questions remain regarding the relative contributions of central and peripheral clocks, the causal role of circadian disruption in hypertension, and the mechanisms underlying sex differences. Addressing these gaps may identify new approaches for preventing and treating hypertension by targeting circadian regulation of cardiovascular function.