Gender does not influence sympathetic neural reactivity to stress
in healthy humans.
Jones, Pamela Parker, Maximillian Spraul, Kathleen S. Matt, Douglas R.
Seals, James S. Skinner, and Eric Ravussin.
Clinical Nutrition and Diabetes Section, National Institute of
Diabetes and Digestive and Kidney Diseases, National Institutes of
Health, 4212 N. Sixteenth Street, Room 541, Phoenix, AZ 85016
APStracts 2:0330H, 1995.
Previous data on cardiovascular and catecholamine responses to acute
stress support the idea of heightened sympathetically-mediated
cardiovascular reactivity in males. However, definitive conclusions
of exaggerated sympatho-circulatory reactivity in males cannot be
made because of inconsistencies among previous reports, possibly
stemming from imprecise measurement of sympathetic activity and/or
failure to equate the stress stimuli between genders. The aim of the
present study was to test the hypothesis that, in response to three
stressors (isometric handgrip exercise, cold pressor test, and mental
arithmetic task), males would exhibit heightened sympathetic
reactivity which would be associated with heightened cardiovascular
and plasma catecholamine responses. In 37 healthy, normotensive
adults (20 males, 17 females: age = 20-42 yr), direct intraneural
recordings of skeletal muscle sympathetic nerve activity (MSNA),
plasma norepinephrine and epinephrine, heart rate, blood pressure,
and perceived stress were measured before and during the laboratory
stressors. Compared to females, males had significantly higher levels
of MSNA, norepinephrine, and systolic blood pressure at rest (15 +/-
2 vs. 27 +/- 2 bursts/min, P < 0.001; 134 +/- 14 vs. 184 +/- 24
pg/ml, P < 0.05; 112 +/- 3 vs. 122 +/- 2 mmHg, P < 0.01,
respectively, mean +/- SE). However, MSNA, catecholamine, and
cardiovascular reactivity (defined as change from rest to stress)
were not consistently different between genders. For the isometric
handgrip, when expressed as absolute unit changes, males had larger
MSNA responses (P < 0.01) which were partially explained by
greater contraction force; they did not differ in terms of percent
change from baseline or in perceived stress. The responses to the
cold pressor and mental arithmetic tasks were similar between
genders. These findings indicate that the tonic regulation of
sympathetic vasomotor activity operates at a higher level in males
than in females, but that stress-evoked vasoconstrictor neural
excitation and the associated increases in blood pressure are not
consistently influenced by gender.
Received 16 March 1995; accepted in final form 12 July 1995.
APS Manuscript Number H255-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 August 1995.