title: Sodium depletion induces adrenergic potentiation at prejunctional site.
abstract: The objective of this study was to examine the effect of sodium depletion on basal sympathetic adrenergic vascular tone and vasoconstrictor responses to adrenergic nerve stimulation and norepinephrine in pentobarbital-anesthetized dogs. Mean arterial pressure, tibial blood flow, and tibial vascular resistance were not significantly different between sodium-replete and sodium-deplete dogs. However, plasma renin activity (PRA) was 11-fold higher in sodium-deplete dogs (P less than 0.01). Sympathetic denervation in sodium-replete and -deplete dogs resulted in a similar decrease in tibial vascular resistance. Nerve stimulation at 0.25 and 0.5 Hz caused 40 +/- 5 and 48 +/- 5% decreases, respectively, in tibial blood flow in sodium-replete dogs and 71 +/- 3 and 77 +/- 3% decreases, respectively, in sodium-deplete dogs (P less than 0.01). Responses to norepinephrine administered intra-arterially were similar in both groups. Neither captopril nor saralasin reduced the potentiated responses to nerve stimulation in sodium-deplete dogs. Bilateral nephrectomy 24 h prior to the experiment reduced PRA to an undetectable level in both sodium-replete and -deplete dogs and equalized the responses to nerve stimulation and norepinephrine in both groups. Because bilateral nephrectomy, but neither captopril nor saralasin, abolished the potentiated responses in sodium depletion, a renal hormone other than renin or vascular angiotensin II may be responsible for this prejunctional adrenergic potentiation.
mesh_terms: D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology; D004039:Diet, Sodium-Restricted; D004285:Dogs; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D007668:Kidney / Q000502:physiology*; D008297:Male; D009392:Nephrectomy; D009638:Norepinephrine / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D012083:Renin / Q000097:blood; D012504:Saralasin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013977:Tibia / Q000098:blood supply; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D005665:Furosemide; D002216:Captopril; D012964:Sodium; D012083:Renin; D012504:Saralasin; D009638:Norepinephrine