Differential pattern of splanchnic and lumbar sympathetic nerve activity to stimulation of rostral ventrolateral medulla in sedentary versus physically active rats

Abstract

The rostral ventrolateral medulla (RVLM) is involved in normal and pathological increases in sympathetic nerve activity (SNA). For example, enhanced responses to stimulation of the RVLM occur in sedentary compared to physically active rats. RVLM neurons can also drive SNA differentially and may in turn contribute to the “sympathetic signature” in hypertension. However, the impact of physical (in)activity on differential regulation of SNA by the RVLM is unknown. In Inactin anesthetized sedentary or active rats (running wheels, 10–14 wks), mean arterial pressure (MAP), splanchnic (sSNA) and lumbar sympathetic nerve activity (LSNA) were recorded simultaneously. Microinjections of glutamate (30 nl, 10 mM) were performed in a three dimensional grid pattern in the pressor region of the RVLM. Glutamate increased sSNA and LSNA differentially depending on the location of injection and whether animals were sedentary or active. These data suggest that differential regulation of sympathetic outflow by the RVLM is altered by sedentary or physically active conditions and may play a role in modifying the sympathetic signature of certain disease states. (R01HL096787)