Spontaneous pressure-flow patterns in the kidney of conscious rats.
We have developed a model that permits a quantitative analysis of the contribution of different mechanisms to the spontaneously occurring pressure-flow patterns of a vasculature. In this study we evaluated the spontaneous relationship between arterial pressure (P) and renal blood flow (F) in resting conscious rats during control conditions, autonomic ganglionic blockade (hexamethonium), and nonselective alpha-adrenoreceptor blockade (phentolamine). In a total of 250 trials in 29 rats, we measured the average P and F for each cardiac cycle over 13-min periods (approximately 4,000 cardiac cycles/trial). The P and F values for each cardiac cycle were expressed as percentage change from each 13-min average (beat-to-beat changes). The slope and angle of each consecutive beat-to-beat P-F change were calculated and collated into one of eight zones representing the physiological mechanisms responsible for the concurrent spontaneous changes in P and F. Our results reveal that, in the absence of any chemical or mechanical intervention (control), the renal circulation demonstrated a baroreflex-like P-F pattern approximately 38% of the time. An autoregulatory-like P-F pattern occurred, at the most, 35% of the time. Autonomic ganglionic blockade significantly (P < 0.05) decreased the baroreflex-like pattern and increased the presence of P-F patterns indicative of autoregulation. alpha-Adrenoreceptor blockade resulted in a P-F pattern that was qualitatively similar to that produced by hexamethonium, but with considerably more variability. These results indicate that, in the resting conscious undisturbed state, the autonomic nervous system exerts a tonic influence on the renal circulation that facilitates arterial pressure regulation via a baroreflex-like pattern.
Skarlatos
S
S
Department of Physiology and Biophysics, Medical College of Ohio, Toledo 43699-0008.
Metting
P J
PJ
Britton
S L
SL
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D005730:Ganglionic Blockers / Q000494:pharmacology; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D006706:Homeostasis; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D005730:Ganglionic Blockers; D006584:Hexamethonium Compounds; D018738:Hexamethonium; D010646:Phentolamine