Carotid baroreflex resetting during drug-induced arterial pressure changes in humans.
We studied human baroreflex resetting during 25 min of drug-induced arterial pressure changes in 10 healthy volunteers. Average (+/- SE) base-line systolic pressure of 113 +/- 4 fell to 102 +/- 3 during nitroprusside infusions and rose to 135 +/- 6 mmHg during phenylephrine infusions. Average base-line R-R intervals of 932 +/- 37 shortened to 820 +/- 39 during nitroprusside infusions and lengthened to 1,251 +/- 61 ms during phenylephrine infusions. Carotid baroreceptor-cardiac reflex responses were evaluated with a complex series of neck chamber pressure changes, and R-R intervals were plotted as functions of carotid distending pressure. Baroreceptor-cardiac reflex relations shifted on both R-R interval and arterial pressure axes during drug infusions, but there was no significant change of the maximum slope or range of R-R interval responses. The position of baseline R-R intervals on the reflex relation (operational point) changed significantly. Resting R-R intervals were closer to threshold during pressure reductions and closer to saturation for baroreceptor-cardiac responses during pressure elevations. These results document short-term partial resetting of human baroreceptor-cardiac reflex responses as early as 25 min after the onset of arterial pressure changes.
Fritsch
J M
JM
Department of Medicine, Veterans Administration Medical Center, Richmond, Virginia 23249.
Rea
R F
RF
Eckberg
D L
DL
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D002346:Carotid Sinus / Q000187:drug effects / Q000502:physiology*; D005292:Ferricyanides / Q000494:pharmacology*; D006321:Heart / Q000502:physiology; D006801:Humans; D009599:Nitroprusside / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology*; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D012016:Reference Values
D005292:Ferricyanides; D009599:Nitroprusside; D010656:Phenylephrine