Differences in regional grey matter volume of the brain are related to mean blood pressure and muscle sympathetic nerve activity in normotensive humans

Objectives: The brainstem plays a critically important role in the beat-to-beat control of blood pressure, as well as setting mean blood pressure (MBP). We recently showed that regional cerebral blood flow to specific brainstem nuclei is inversely related to resting MBP in healthy normotensive individuals. Here we tested the hypothesis that grey matter volume in these same nuclei, and areas above the brainstem to which they are connected, is also associated with resting MBP and muscle sympathetic nerve activity (MSNA). Methods: Structural MRI of the brain and recordings of MSNA and BP were collected in 54 healthy participants. Subjects were divided into a lower MBP group (mean ± SEM 78.8 ± 1.5mmHg, n=27) and higher MBP group (96.6 ± 1.2 mmHg, n=27), as well as into a lower MSNA (9.5 ± 0.8bursts/min, n=27) and higher MSNA (25.4 ± 1.2bursts/min, n=27) group. Results: Regional grey matter volume was higher in the region of the rostral ventrolateral medulla, nucleus tractus solitarius, and medullary raphe in the group with higher MBP and correlated significantly with mean MBP across all participants. Grey matter volume was significantly higher in the dorsomedial hypothalamus and anterior and posterior cingulate cortices in the group with lower MSNA and was inversely related to MSNA across all participants. Conclusion: We conclude that small differences in MBP and MSNA are associated with significant differences in grey matter volume in cortical and subcortical regions known to be involved in blood pressure regulation, suggesting that these structural differences contribute to resting MBP and MSNA and can predict the establishment of hypertension.