title: Sex differences in blood pressure control during 6° head-down tilt bed rest.
abstract: Spaceflight-induced orthostatic intolerance has been studied for decades. Although ∼22% of the astronaut corps are women, most mechanistic studies use mostly male subjects, despite known sex differences in autonomic control and postflight orthostatic intolerance. We studied adrenergic, baroreflex, and autonomic indexes during continuous infusions of vasoactive drugs in men and women during a 60-day head-down bed rest. Volunteers were tested before bed rest (20 men and 10 women) and around day 30 (20 men and 10 women) and day 60 (16 men and 8 women) of bed rest. Three increasing doses of phenylephrine (PE) and sodium nitroprusside were infused for 10 min after an infusion of normal saline. A 20-min rest period separated the phenylephrine and sodium nitroprusside infusions. Autonomic activity was approximated by spectral indexes of heart rate and blood pressure variability, and baroreflex sensitivity was measured by the spontaneous baroreflex slope. Parasympathetic modulation and baroreflex sensitivity decreased with bed rest, with women experiencing a larger decrease in baroreflex sensitivity by day 30 than men. The sympathetic activation of men and parasympathetic responsiveness of women in blood pressure control during physiological stress were preserved throughout bed rest. During PE infusions, women experienced saturation of the R-R interval at high frequency, whereas men did not, revealing a sex difference in the parabolic relationship between high-frequency R-R interval, a measurement of respiratory sinus arrhythmia, and R-R interval. These sex differences in blood pressure control during simulated microgravity reveal the need to study sex differences in long-duration spaceflight to ensure the health and safety of the entire astronaut corps.
authors: Wyle Science, Technology and Engineering Group, Houston, Texas, USA.
authors: Natalia M
authors: NM
authors: Arzeno
authors: Michael B
authors: MB
authors: Stenger
authors: Stuart M C
authors: SM
authors: Lee
authors: Robert
authors: R
authors: Ploutz-Snyder
authors: Steven H
authors: SH
authors: Platts
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology; D000328:Adult; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001510:Bed Rest; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D054971:Orthostatic Intolerance / Q000503:physiopathology*; D010656:Phenylephrine / Q000494:pharmacology; D010953:Plasma Volume / Q000187:drug effects / Q000502:physiology; D012737:Sex Factors; D013026:Space Flight; D014665:Vasodilator Agents / Q000494:pharmacology; D018474:Weightlessness Simulation
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine
references: Am J Physiol Heart Circ Physiol. 2005 Feb;288(2):H839-47
references: 15486040
references: Circulation. 1991 Aug;84(2):482-92
references: 1860193
references: J Appl Physiol (1985). 2002 Feb;92(2):586-94
references: 11796668
references: Am J Physiol. 1998 Dec;275(6):R1909-20
references: 9843880
references: Clin Auton Res. 2000 Oct;10(5):269-77
references: 11198482
references: Am J Physiol. 1985 Jan;248(1 Pt 2):H151-3
references: 3970172
references: Psychophysiology. 1997 Nov;34(6):623-48
references: 9401419
references: J Appl Physiol (1985). 1996 Jul;81(1):7-18
references: 8828642
references: Clin Chim Acta. 1970 Aug;29(2):303-9
references: 5493187
references: Aviat Space Environ Med. 2009 May;80(5 Suppl):A29-36
references: 19476167
references: Hypertension. 2005 Jun;45(6):1159-64
references: 15867130
references: Clin Exp Pharmacol Physiol. 1999 Feb;26(2):122-6
references: 10065332
references: Aviat Space Environ Med. 2009 May;80(5 Suppl):A1-8
references: 19476163
references: J Appl Physiol (1985). 2001 Nov;91(5):2374-83
references: 11641383
references: J Appl Physiol (1985). 2001 Nov;91(5):2088-92
references: 11641348
references: Am J Physiol Heart Circ Physiol. 2001 May;280(5):H2230-9
references: 11299226
references: Psychophysiology. 1971 Jan;8(1):1-6
references: 5578378
references: J Hypertens Suppl. 1985 Dec;3(3):S79-81
references: 2856787
references: Am J Physiol. 1998 Jun;274(6):H1875-84
references: 9841515
references: Hypertension. 1982 Jul-Aug;4(4):566-71
references: 7152632
references: J Appl Physiol (1985). 1994 Oct;77(4):1776-83
references: 7836199
references: J Appl Physiol (1985). 2010 Mar;108(3):646-54
references: 20075261
references: J Appl Physiol (1985). 2005 Oct;99(4):1552-7
references: 15961614
references: J Physiol. 2010 Apr 1;588(Pt 7):1129-38
references: 20156846
references: Eur Heart J. 1996 Mar;17(3):354-81
references: 8737210
references: Acta Physiol Scand. 1988 Jun;133(2):221-31
references: 3227916
references: Auton Neurosci. 2002 Sep 30;100(1-2):66-76
references: 12422962
references: J Clin Endocrinol Metab. 2002 Apr;87(4):1569-75
references: 11932284
references: Aviat Space Environ Med. 1994 Apr;65(4):293-300
references: 8002908
references: J Appl Physiol (1985). 2000 Sep;89(3):1039-45
references: 10956348
references: J Clin Pharmacol. 1991 Oct;31(10):951-5
references: 1761726
references: Aviat Space Environ Med. 1994 Dec;65(12):1105-9
references: 7872911
references: Am J Physiol. 1994 May;266(5 Pt 2):H2152-7
references: 8203614
references: J Physiol. 2002 Jan 1;538(Pt 1):321-9
references: 11773339
references: J Appl Physiol (1985). 2001 Dec;91(6):2611-8
references: 11717226
references: J Appl Physiol (1985). 1998 Feb;84(2):576-83
references: 9475868
references: Am J Physiol Heart Circ Physiol. 2012 Jan 1;302(1):H368-74
references: 22021328
references: Clin Exp Pharmacol Physiol. 1974 Jan-Feb;1(1):65-76
references: 4218140
references: Am J Physiol Regul Integr Comp Physiol. 2004 Nov;287(5):R1256-62
references: 15242830
references: Am J Physiol Regul Integr Comp Physiol. 2000 Dec;279(6):R2189-99
references: 11080085
references: BMC Physiol. 2004 Apr 27;4:6
references: 15113425
references: Am J Physiol Heart Circ Physiol. 2001 Nov;281(5):H2028-35
references: 11668064
references: J Appl Physiol (1985). 1990 Apr;68(4):1458-64
references: 2347788
references: Hypertension. 2009 Mar;53(3):571-6
references: 19171792
references: J Hypertens. 2009 Mar;27(3):551-61
references: 19262409
references: Circulation. 2001 Apr 17;103(15):1977-83
references: 11306527
references: Hypertension. 1999 May;33(5):1195-200
references: 10334811
references: J Appl Physiol (1985). 2005 May;98(5):1682-90
references: 15649869
references: Acta Astronaut. 1991;23:9-17
references: 11537153
references: J Appl Physiol (1985). 1992 Aug;73(2):664-71
references: 1399995
references: J Cardiovasc Electrophysiol. 2008 Dec;19(12):1296-303
references: 18662181
references: Am J Physiol. 1974 Mar;226(3):724-30
references: 4817426
references: Am J Cardiol. 1993 Oct 1;72(11):821-2
references: 8093124
references: J Physiol. 2002 Jan 1;538(Pt 1):331-40
references: 11773340
references: Circulation. 2000 Feb 29;101(8):862-8
references: 10694525
references: Circulation. 2005 Feb 1;111(4):494-8
references: 15687139
references: J Appl Physiol (1985). 2007 Jul;103(1):156-61
references: 17446414
references: Stroke. 2011 Jul;42(7):1844-50
references: 21617145
references: J Appl Physiol (1985). 2008 Nov;105(5):1569-75
references: 18756008
references: Am J Physiol. 1990 Oct;259(4 Pt 2):R792-8
references: 2221146
references: Circ Res. 1986 Aug;59(2):178-93
references: 2874900
references: J Appl Physiol (1985). 1994 Jul;77(1):69-77
references: 7961277
references: Circ Res. 1969 Jan;24(1):109-21
references: 4303309
references: J Appl Physiol (1985). 1994 Aug;77(2):606-13
references: 8002506
references: J Clin Invest. 1986 Aug;78(2):366-74
references: 3734097