Functional studies of rostral ventrolateral medulla neurons using manganese‐enhanced magnetic resonance imaging in sedentary versus physically active rats (686.36)

A sedentary lifestyle, a key risk factor in cardiovascular disease (CVD), is linked to increased sympathetic nerve activity (SNA). Control of SNA occurs via bulbospinal catecholaminergic (C1) and non‐C1 neurons primarily in the RVLM. We recently reported that sedentary, but not physically active rats, exhibit increased dendritic branching in bulbospinal C1 RVLM neurons in a specific caudal to rostral pattern. However, regionally specific increases in RVLM neuronal activation have not yet been associated with increased dendritic branching. In many brain regions, manganese (Mn 2+ ), a paramagnetic ion, has been used as a contrast agent to detect neuronal activity via calcium channel uptake. The purpose of this study was to develop MeMRI for in vivo studies of the RVLM, with the hypothesis that sedentary rats would have increased RVLM neuronal activity and greater Mn 2+ uptake. One sedentary and one active rat (12 wks wheel running) were administered Mn 2+ chloride (66mg/kg, IP), and a control rat was given saline. After 24 hours, rats were imaged (7T, Bruker Avance) and saline values were subtracted from Mn 2+ injected animals. Uptake of Mn 2+ in the RVLM was greater in the sedentary versus active rat (e.g. 808 vs. 327 avg voxel intensity, respectively). Notably, only the sedentary rat had a pattern of increased uptake in the caudal to rostral RVLM, very similar to our structural studies. These preliminary studies suggest that increased dendritic branching in more rostral RVLM neurons may account for enhanced RVLM neuronal activity and the growing prevalence of CVD in sedentary individuals. Grant Funding Source : Supported by HL096787‐PJM; VA 1l01RX001095‐01‐AGH