title: The role of α-adrenergic receptors in mediating beat-by-beat sympathetic vascular transduction in the forearm of resting man.
abstract: Sympathetic vascular transduction is commonly understood to act as a basic relay mechanism, but under basal conditions, competing dilatory signals may interact with and alter the ability of sympathetic activity to decrease vascular conductance. Thus, we determined the extent to which spontaneous bursts of muscle sympathetic nerve activity (MSNA) mediate decreases in forearm vascular conductance (FVC) and the contribution of local α-adrenergic receptor-mediated pathways to the observed FVC responses. In 19 young men, MSNA (microneurography), arterial blood pressure and brachial artery blood flow (duplex Doppler ultrasound) were continuously measured during supine rest. These measures were also recorded in seven men during intra-arterial infusions of normal saline, phentolamine (PHEN) and PHEN with angiotensin II (PHEN+ANG). The latter was used to control for increases in resting blood flow with α-adrenergic blockade. Spike-triggered averaging was used to characterize beat-by-beat changes in FVC for 15 cardiac cycles following each MSNA burst and a peak response was calculated. Following MSNA bursts, FVC initially increased by +3.3 ± 0.3% (P = 0.016) and then robustly decreased to a nadir of -5.8 ± 1.6% (P < 0.001). The magnitude of vasoconstriction appeared graded with the number of consecutive MSNA bursts; while individual burst size only had a mild influence. Neither PHEN nor PHEN+ANG infusions affected the initial rise in FVC, but both infusions significantly attenuated the subsequent decrease in FVC (-2.1 ± 0.7% and -0.7 ± 0.8%, respectively; P < 0.001 vs. normal saline). These findings indicate that spontaneous MSNA bursts evoke robust beat-by-beat decreases in FVC that are exclusively mediated via α-adrenergic receptors.
authors: Biomedical Sciences, University of Missouri, Columbia, MO 65212, USA.
authors: Seth T
authors: ST
authors: Fairfax
authors: Seth W
authors: SW
authors: Holwerda
authors: Daniel P
authors: DP
authors: Credeur
authors: Mozow Y
authors: MY
authors: Zuidema
authors: John H
authors: JH
authors: Medley
authors: Peter C
authors: PC
authors: Dyke
authors: D Walter
authors: DW
authors: Wray
authors: Michael J
authors: MJ
authors: Davis
authors: Paul J
authors: PJ
authors: Fadel
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000328:Adult; D000804:Angiotensin II / Q000494:pharmacology; D005542:Forearm / Q000098:blood supply / Q000502:physiology*; D006801:Humans; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D012146:Rest / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D055815:Young Adult
chemical_list: D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D010646:Phentolamine
references: Hypertension. 2002 Jan;39(1):173-8
references: 11799098
references: Am J Physiol Heart Circ Physiol. 2012 Jun 1;302(11):H2419-27
references: 22427525
references: Hypertension. 2000 Mar;35(3):764-8
references: 10720592
references: Am J Physiol Heart Circ Physiol. 2010 Apr;298(4):H1128-35
references: 20154260
references: Circ Res. 1995 May;76(5):885-91
references: 7729006
references: Exp Physiol. 2011 Oct;96(10):1019-27
references: 21784788
references: J Hypertens. 1985 Apr;3(2):117-29
references: 2991369
references: Clin Sci (Lond). 2013 Mar;124(6):413-22
references: 22985469
references: Hypertension. 2010 Jul;56(1):10-6
references: 20497993
references: J Appl Physiol (1985). 1994 Jan;76(1):204-11
references: 8175506
references: J Physiol. 2004 May 1;556(Pt 3):1001-11
references: 14990681
references: J Appl Physiol (1985). 2009 Jan;106(1):302-10
references: 19008493
references: J Physiol. 2011 Nov 1;589(Pt 21):5285-97
references: 21859824
references: Circulation. 2001 Nov 13;104(20):2424-9
references: 11705819
references: Physiol Rev. 1979 Oct;59(4):919-57
references: 227005
references: Exp Physiol. 2011 Aug;96(8):718-35
references: 21602293
references: Clin Auton Res. 1993 Jun;3(3):201-5
references: 8400820
references: Med Sci Sports Exerc. 2008 Dec;40(12):2055-62
references: 18981944
references: J Appl Physiol (1985). 2013 Jan 15;114(2):203-10
references: 23195626
references: J Physiol. 1977 Nov;272(2):383-97
references: 592196
references: J Appl Physiol (1985). 1989 Jun;66(6):2778-81
references: 2745341
references: J Appl Physiol (1985). 2002 Feb;92(2):651-6
references: 11796677
references: Clin Exp Pharmacol Physiol. 2002 Jul;29(7):603-7
references: 12060104
references: Circulation. 2011 May 24;123(20):2244-53
references: 21555712
references: J Physiol. 1994 Jan 15;474(2):331-8
references: 8006818
references: Anesth Prog. 2008 Summer;55(2):40-8
references: 18547152
references: J Auton Nerv Syst. 1993 Nov;45(2):139-47
references: 8282946
references: Microcirculation. 2012 Feb;19(2):99-114
references: 21895845
references: Am J Physiol Heart Circ Physiol. 2013 Mar 1;304(5):H759-66
references: 23292718
references: Hypertension. 1998 Aug;32(2):298-304
references: 9719058
references: J Physiol. 2002 May 1;540(Pt 3):1103-10
references: 11986395
references: J Appl Physiol (1985). 2003 Dec;95(6):2370-4
references: 12923119
references: J Appl Physiol (1985). 2011 Feb;110(2):389-97
references: 21088203
references: Exp Physiol. 2010 Apr;95(4):561-8
references: 20080867
references: Hypertension. 1999 Feb;33(2):753-8
references: 10024340
references: Circulation. 2000 Feb 29;101(8):862-8
references: 10694525
references: J Appl Physiol (1985). 2002 May;92(5):2105-13
references: 11960963
references: Br J Pharmacol. 1988 Dec;95(4):1101-8
references: 2851357
references: Hypertension. 2012 Oct;60(4):1016-22
references: 22949528
references: Am J Physiol Heart Circ Physiol. 2011 Dec;301(6):H2454-65
references: 21963834
references: Physiol Rev. 1981 Jan;61(1):151-247
references: 6110212