Lw. Dickerson et al., STIMULATION OF DOG RVLM AND A5 AREA CHANGES SYMPATHETIC OUTFLOW TO VASCULAR BEDS WITHOUT EFFECT ON THE HEART, American journal of physiology. Regulatory, integrative and comparative physiology, 41(3), 1997, pp. 821-839
Studies were conducted in anesthetized, vagotomized dogs while blood p
ressure; blood flows in femoral, renal, mesenteric, and left circumfle
x coronary arteries; electrocardiogram; and regional cardiac contracti
le force were monitored. The ventral surface of the medulla was expose
d, and presser sites in the rostral ventrolateral medulla (RVLM) were
mapped by microinjections of L-glutamate. L-Glutamate activation of th
e RVLM. evoked selective effects on different components of the cardio
vascular system. Increases of 20-130 mmHg in blood pressure were accom
panied by vascular conductance decreases in the femoral (-48 +/- 4%),
renal (-30 +/- 4%), and mesenteric (-38 +/- 3%) arterial beds. These e
ffects were without any obvious topography within the RVLM. There were
only small or negligible changes in heart rate (HR), cardiac contract
ile force, and coronary vascular conductance. Thus stimulation of the
canine RVLM increased sympathetic tone selectively to structures other
than the heart. Stimulation of the ventral medulla in a region that l
ay rostral to the RVLM and ventromedial to the facial nucleus selectiv
ely increased femoral vascular conductance by 103 +/- 33% and decrease
d vascular conductance in the renal (-20 +/- 5%) and mesenteric (-15 /- 4%) arterial beds. There was no increase in HR, and the increases i
n blood pressure were relatively small. Immunohistochemical data led u
s, tentatively, to identify this rostral area as overlapping part of t
he A5 area.