Lateralized changes in renal sympathetic activity evoked by unilateral stimulation of lateral/dorsolateral periaqueductal gray

Abstract

Periaqueductal gray (PAG) is considered an important synaptic relay for behavioral, thermal and cardiovascular responses to stress. Stimulation of lateral/dorsolateral PAG (l/dl PAG) causes fight/flight reaction and sympathetically mediated cardiovascular changes. In adult male anesthetized rats (n=5), we compared changes in heart rate (HR), mean arterial pressure (MAP) and renal sympathetic activity (RSNA) produced by chemical activation (NMDA 100pmol/100nl) of right (R) and left (L) sides of l/dl PAG. RSNA was recorded only on the L side. We observed greater increases in left RSNA following ipsilateral l/dl PAG stimulation (Δ: L 92±14 vs. R 17±4%; P=0.0012). These responses were accompanied by increases in MAP and HR (average Δ: 17mmHg and 35bpm, respectively), but no differences in the magnitude of these responses were found between left or right l/dl PAG stimulation. Maximal changes in MAP and RSNA occurred at the same time, about 30s after l/dl PAG stimulation. Intriguingly, however, the maximal response for HR was delayed (≈90s), following a different time course. We conclude that the functional descending pathways from l/dl PAG to renal sympathetic nerves are prominently lateralized. The mechanisms involved in the differential time course responses between MAP/RSNA and HR require further investigation. Support: FAPEMIG‐PPM and CNPq.