Brainstem sites regulating muscle sympathetic nerve activity in healthy and disease states

      It is well-established that the brainstem contains the neural circuitry responsible for maintaining muscle sympathetic nerve activity (MSNA). Additionally, behavioral state changes which can be generated from high-order processing sites such as the cingulate and prefrontal cortices, send projections either directly or indirectly to the brainstem to alter blood pressure, heart rate and MSNA. Over the past half century, experimental animal investigations have delineated the brainstem circuitry responsible for generating sympathetic nerve activity which has recently been confirmed in awake healthy humans using concurrent microneurography and functional magnetic resonance imaging. The aim of this presentation is to describe the brainstem circuitry responsible for generating resting MSNA in humans and altered MSNA in disease states such as obstructive sleep apnea. In addition, brainstem sites responsible for generating behaviorally-coupled changes in MSNA, such as those evoked by acute noxious stimuli will be discussed. Finally, changes in brainstem structure associated with changes MSNA will be discussed as well as the possible underlying neural mechanisms.
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