Spectral Analysis of Barosensitive Neurons in the Rat Rostral Ventrolateral Medulla

Abstract

Regulation of blood pressure occurs primarily via the activity of bulbospinal rostral ventrolateral medulla (RVLM) neurons that drive sympathetic nerve activity (SNA). Central and peripheral stimuli influence the activity of RVLM neurons and are reflected in their cardiac and respiratory modulation. Dysregulation of RVLM neurons can lead to increased SNA and the development and maintenance of cardiovascular disease. In this study we used spectral (frequency‐domain) analysis to identify cardiac‐ and/or respiratory‐related (CR, RR) activity in barosensitive RVLM neurons (n=22) and splanchnic SNA of 16 Inactin‐anesthetized rats in which we also recorded arterial pressure (AP) and an index of respiration. SNA had RR activity (0.40±0.05; mean ± SE) and/or CR activity (0.63±0.05) as evidenced by a coherence value > 0.1 at the frequency of respiration and the heart rate, respectively, in the corresponding coherence functions. RVLM unit activity was also shown to be RR (0.40±0.14; n=4) or CR (0.41±0.07; n=4). Moreover, RVLM unit activity cohered to SNA at the frequency of the heart rate (0.39±0.08; n=4) or respiration (0.21; n=1). AP‐triggered analysis (time‐domain analysis) revealed CR activity in 4 other RVLM neurons. These data demonstrate our ability to study the relationships among rat RVLM unit activity, SNA, AP, and respiration, which will allow us to explore whether differences in the strengths of these relationships contribute to changes in SNA and AP under different physiological conditions.HL096787