Circadian rhythm in sweating and cutaneous blood flow

1984 ◽  
Vol 246 (3) ◽  
pp. R321-R324 ◽  
Author(s):  
L. A. Stephenson ◽  
C. B. Wenger ◽  
B. H. O'Donovan ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Circadian Rhythm ◽  
Body Temperature ◽  
Forearm Blood Flow ◽  
Sweat Rate ◽  
Circadian Variation ◽  
Esophageal Temperature ◽  
Cutaneous Blood Flow ◽  
Cutaneous Vasodilation ◽  
Cutaneous Blood

To characterize the changes in the control of the heat loss responses associated with the circadian variation in body temperature, we studied five men during 20 min of exercise in 25 degrees C on 6 separate days. Experiments were conducted at six times, equally spaced over the 24-h day. Esophageal temperature (Tes) and chest sweat rate (msw) were measured continuously, and forearm blood flow (FBF) was measured one to two times per minute. The thresholds for sweating and forearm vasodilation were significantly higher at 1600 and 2000 than at 2400 and 0400, averaging 0.57 and 0.65 degrees C higher, respectively, at 1600 than at 0400. Resting Tes and the Tes thresholds for cutaneous vasodilation and sweating during exercise all showed a similar circadian rhythm. The level at which core temperature is regulated therefore varies over the 24-h day with the zenith occurring around 1600 and the nadir at 0400. However, whereas the slope of the msw-to-Tes relation did not change over the 24-h day, the slope of the FBF-to-Tes relation tended to increase between 0400 and 2400, implying that the circadian rhythm may be more complex than just a shift in the central reference temperature.

Cutaneous blood flow during exercise is higher in endurance-trained humans

2000 ◽  
Vol 88 (2) ◽  
pp. 738-744 ◽  
Author(s):  
Ricardo G. Fritzsche ◽  
Edward F. Coyle
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Forearm Blood Flow ◽  
Peak Oxygen Uptake ◽  
Metabolic Rates ◽  
Esophageal Temperature ◽  
Cutaneous Blood Flow ◽  
Cycling Exercise ◽  
C 50 ◽  
Cutaneous Blood

This study determined whether cutaneous blood flow during exercise is different in endurance-trained (Tr) compared with untrained (Untr) subjects. Ten Tr and ten Untr men (62.4 ± 1.7 and 44.2 ± 1.8 ml ⋅ kg− 1 ⋅ min− 1, respectively; P < 0.05) underwent three 20-min cycling-exercise bouts at 50, 70, and 90% peak oxygen uptake in this order, with 30 min rest in between. The environmental conditions were neutral (∼23–24°C, 50% relative humidity, front and back fans at 2.5 m/s). Because of technical difficulties, only seven Tr and seven Untr subjects completed all forearm blood flow and laser-Doppler cutaneous blood flow (CBF) measurements. Albeit similar at rest, at the end of all three exercise bouts, forearm blood flow was ∼40% higher in Tr compared with Untr subjects (50%: 4.64 ± 0.50 vs. 3.17 ± 0.20, 70%: 6.17 ± 0.61 vs. 4.41 ± 0.37, 90%: 6.77 ± 0.62 vs. 5.01 ± 0.37 ml ⋅ 100 ml− 1 ⋅ min− 1, respectively; n = 7; all P < 0.05). CBF was also higher in Tr compared with Untr subjects at all relative intensities ( n = 7; all P < 0.05). However, esophageal temperature was not different in Tr compared with Untr subjects at the end of any of the aforementioned exercise bouts (50%: 37.8 ± 0.1 vs. 37.9 ± 0.1°C, 70%: 38.1 ± 0.1 vs. 38.1 ± 0.1°C, and 90%: 38.8 ± 0.1 vs. 38.6 ± 0.1°C, respectively). We conclude that a higher CBF may allow Tr subjects to achieve an esophageal temperature similar to that of Untr, despite their higher metabolic rates and thus higher heat production rates, during exercise at 50–90% peak oxygen uptake.

Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise

1992 ◽  
Vol 73 (4) ◽  
pp. 1340-1350 ◽  
Author(s):  
S. J. Montain ◽  
E. F. Coyle
Keyword(s):  
Blood Flow ◽  
Prolonged Exercise ◽  
Forearm Blood Flow ◽  
Sweat Rate ◽  
Sodium Concentration ◽  
O2 Consumption ◽  
Esophageal Temperature ◽  
Warm Environment ◽  
Cardiovascular Drift ◽  
Highly Correlated

This investigation determined the effect of different rates of dehydration, induced by ingesting different volumes of fluid during prolonged exercise, on hyperthermia, heart rate (HR), and stroke volume (SV). On four different occasions, eight endurance-trained cyclists [age 23 +/- 3 (SD) yr, body wt 71.9 +/- 11.6 kg, maximal O2 consumption 4.72 +/- 0.33 l/min] cycled at a power output equal to 62-67% maximal O2 consumption for 2 h in a warm environment (33 degrees C dry bulb, 50% relative humidity, wind speed 2.5 m/s). During exercise, they randomly received no fluid (NF) or ingested a small (SF), moderate (MF), or large (LF) volume of fluid that replaced 20 +/- 1, 48 +/- 1, and 81 +/- 2%, respectively, of the fluid lost in sweat during exercise. The protocol resulted in graded magnitudes of dehydration as body weight declined 4.2 +/- 0.1, 3.4 +/- 0.1, 2.3 +/- 0.1, and 1.1 +/- 0.1%, respectively, during NF, SF, MF, and LF. After 2 h of exercise, esophageal temperature (Tes), HR, and SV were significantly different among the four trials (P < 0.05), with the exception of NF and SF. The magnitude of dehydration accrued after 2 h of exercise in the four trials was linearly related with the increase in Tes (r = 0.98, P < 0.02), the increase in HR (r = 0.99, P < 0.01), and the decline in SV (r = 0.99, P < 0.01). LF attenuated hyperthermia, apparently because of higher skin blood flow, inasmuch as forearm blood flow was 20–22% higher than during SF and NF at 105 min (P < 0.05). There were no differences in sweat rate among the four trials. In each subject, the increase in Tes from 20 to 120 min of exercise was highly correlated to the increase in serum osmolality (r = 0.81-0.98, P < 0.02-0.19) and the increase in serum sodium concentration (r = 0.87-0.99, P < 0.01-0.13) from 5 to 120 min of exercise. In summary, the magnitude of increase in core temperature and HR and the decline in SV are graded in proportion to the amount of dehydration accrued during exercise.

Cutaneous blood flow during heating and cooling in the American alligator

1978 ◽  
Vol 235 (3) ◽  
pp. R160-R167 ◽  
Author(s):  
E. N. Smith ◽  
S. Robertson ◽  
D. G. Davies
Keyword(s):  
Blood Flow ◽  
Body Mass ◽  
Local Heating ◽  
Alligator Mississippiensis ◽  
Skin Thickness ◽  
Cutaneous Blood Flow ◽  
Heating And Cooling ◽  
Cutaneous Vasodilation ◽  
Cooling Conditions ◽  
Cutaneous Blood

Nine alligators, Alligator mississippiensis, were injected with 133Xe and the clearance half times measured in response to heating and cooling. Mean half times for thermostable, heating, and cooling conditions were 12.2, 8.6, and 28.3 min, respectively, indicating cutaneous vasodilation in response to local heating and reduced blood flow during cooling. Alterations of cutaneous blood flow occurred before changes in body temperature or heart rate. Warming portions of the animal while shading the injection site resulted in reduced blood flow when heat loss occurred. Skin thickness (S in cm) was related to body mass (M in kg) as S = 0.08 M0.38. Cutaneous blood flow per unit area was found to increase with increasing body mass from approximately 0.0025 to 0.025 ml blood-cm-2 of skin-min-1 during warming and from 0.0018 to 0.0045 during cooling for the 0.18--8.6 kg animals, respectively.

Hypohydration affects forearm vascular conductance independent of heart rate during exercise

1992 ◽  
Vol 73 (4) ◽  
pp. 1232-1237 ◽  
Author(s):  
C. G. Tankersley ◽  
D. H. Zappe ◽  
T. G. Meister ◽  
W. L. Kenney
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Mean Arterial Pressure ◽  
Forearm Blood Flow ◽  
Body Core Temperature ◽  
Esophageal Temperature ◽  
Vascular Conductance ◽  
Cutaneous Vasodilation ◽  
Forearm Vascular Conductance ◽  
Body Core

Elevated body core temperature stimulates cutaneous vasodilation, which can be modified by nonthermal factors. To test whether hypohydration affects forearm vascular conductance discretely from relative alterations in heart rate (HR), eight trained cyclists exercised progressively for 20 min each at 60, 120, and 180 W [approximately 22, 37, and 55% of maximal cycling O2 consumption (VO2peak), respectively] in a warm humid environment (dry bulb temperature 30 degrees C; wet bulb temperature 24 degrees C). Esophageal temperature and forearm blood flow were measured every 30 s, and mean arterial pressure and HR were measured at rest and during each exercise intensity (minutes 15, 35, and 55). In the hypovolemic (HP) compared with the euvolemic (EU) state, blood volume was contracted by 24-h fluid restriction an average of 510 ml, and this difference was sustained throughout exercise. The esophageal temperature and HR responses were similar between EU and HP states at 60 and 120 W but were significantly (P < 0.05) higher in HP by the end of 180 W. In contrast, the forearm blood flow response was significantly (P < 0.05) depressed during exercise at 120 and 180 W in HP, whereas mean arterial pressure remained similar between conditions. When body core temperature is elevated in a hypohydrated state, forearm vascular conductance is reduced at exercise intensities of approximately 37% VO2peak, which is independent of relative changes in HR. These findings are consistent with the notion that during exercise an attenuated cutaneous vasodilation is elicited by alterations in regionalized sympathetic outflow, which is unaccompanied by activation of cardiac pacemaker cells.

scholarly journals Effects of atropine and l-NAME on cutaneous blood flow during body heating in humans

2000 ◽  
Vol 88 (2) ◽  
pp. 467-472 ◽  
Author(s):  
Shubha Shastry ◽  
Christopher T. Minson ◽  
Shurea A. Wilson ◽  
Niki M. Dietz ◽  
Michael J. Joyner
Keyword(s):  
Blood Flow ◽  
Receptor Activation ◽  
No Synthase ◽  
Cutaneous Blood Flow ◽  
Cutaneous Vasodilation ◽  
Forearm Skin ◽  
Synthase Inhibitor ◽  
Cutaneous Vascular Conductance ◽  
Cutaneous Blood ◽  
Doppler Flowmeter

We sought to investigate further the roles of sweating, ACh spillover, and nitric oxide (NO) in the neurally mediated cutaneous vasodilation during body heating in humans. Six subjects were heated with a water-perfused suit while cutaneous blood flow was measured with a laser-Doppler flowmeter. After a rise in core temperature (1.0 ± 0.1°C) and the establishment of cutaneous vasodilation, atropine and subsequently the NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME) were given to the forearm via a brachial artery catheter. After atropine infusion, cutaneous vascular conductance (CVC) remained constant in five of six subjects, whereasl-NAME administration blunted the rise in CVC in three of six subjects. A subsequent set of studies using intradermal microdialysis probes to selectively deliver drugs into forearm skin confirmed that atropine did not affect CVC. However, perfusion ofl-NAME resulted in a significant decrease in CVC (37 ± 4%, P < 0.05). The results indicate that neither sweating nor NO release via muscarinic receptor activation is essential to sustain cutaneous dilation during heating in humans.

Influence of menstrual cycle on shivering, skin blood flow, and sweating responses measured at night

1985 ◽  
Vol 59 (6) ◽  
pp. 1902-1910 ◽  
Author(s):  
V. Hessemer ◽  
K. Bruck
Keyword(s):  
Blood Flow ◽  
Menstrual Cycle ◽  
Body Temperature ◽  
Sweat Rate ◽  
Serum Progesterone ◽  
Mean Body Temperature ◽  
Cutaneous Vasodilation ◽  
Threshold Temperatures ◽  
Early Follicular Phase ◽  
Heat Clearance

In 10 women, external cold and heat exposures were performed both in the middle of luteal phase (L) and in the early follicular phase (F) of the menstrual cycle. Serum progesterone concentrations in L and F averaged 46.0 and 0.9 nmol X l-1, respectively. The experiments took place between 3:00 and 4:30 A.M., when the L-F core temperature difference is maximal. At neutral ambient temperature, esophageal (Tes), tympanic (Tty), rectal (Tre), and mean skin (Tsk) temperatures averaged 0.59 degrees C higher in L than in F. The thresholds for shivering, chest sweating, and cutaneous vasodilation (heat clearance technique) at the thumb and forearm were increased in L by an average of 0.47 degrees C, related to mean body temperature [Tb(es) = 0.87Tes + 0.13 Tsk] and to Tes, Tty, Tre, or Tsk. The above-threshold chest sweat rate and cutaneous heat clearances at the thumb and forearm were also enhanced in L, when related to Tb(es) or time. The metabolic rate, arm blood flow, and heart rate at thermoneutral conditions were increased in L by 5.0%, 1.1 ml X 100 ml-1 X min-1, and 4.6 beats X min-1, respectively. The concomitant increase in threshold temperatures for all autonomic thermoregulatory responses in L supports the concept of a resetting of the set point underlying the basal body temperature elevation in L. The effects of the increased threshold temperatures are counteracted by enhanced heat loss responses.

scholarly journals Cutaneous blood flow and sweat rate responses to exogenous administration of acetylcholine and methacholine

2007 ◽  
Vol 102 (5) ◽  
pp. 1856-1861 ◽  
Author(s):  
Kenichi Kimura ◽  
David A. Low ◽  
David M. Keller ◽  
Scott L. Davis ◽  
Craig G. Crandall
Keyword(s):  
Blood Flow ◽  
Dose Response ◽  
Sweat Rate ◽  
Molar Concentration ◽  
Maximal Response ◽  
Cutaneous Blood Flow ◽  
Response Curves ◽  
Forearm Skin ◽  
Dose Response Curves ◽  
Cutaneous Blood

The aim of this study was to evaluate cutaneous vasodilation and sweating responses to exogenous administration of acetylcholine (ACh) and methacholine (MCh), which have different sensitivities to endogenous cholinesterase. Four intradermal microdialysis probes were placed in dorsal forearm skin: two sites were perfused with ACh (1 × 10−7–1 M) and the other two with the same molar concentrations of MCh. Sweat rate (SR) and cutaneous blood flow were simultaneously assessed directly over each microdialysis membrane. Dose-response curves were constructed, and the effective concentration of the drug resulting in 50% of the maximal response (EC50) was identified. For SR and cutaneous vascular conductance (CVC), there were no significant differences in EC50 between sites receiving the same drug: −1.52 ± 0.18 and −1.19 ± 0.09 log-molar concentration of ACh at distal and proximal sites, respectively, and −2.35 ± 0.24 and −2.42 ± 0.23 log-molar concentration of MCh at distal and proximal sites, respectively, for SR ( P > 0.05) and −3.87 ± 0.32 and −3.97 ± 0.27 log-molar concentration of ACh at distal and proximal sites, respectively, and −4.78 ± 0.17 and −4.46 ± 0.16 log-molar concentration of MCh at distal and proximal sites, respectively, for CVC ( P > 0.05). However, the EC50 for CVC and SR was significantly lower at the MCh than at the ACh sites. A second procedure was performed to confirm that differences in responses between ACh and MCh could be attributed to different cholinesterase sensitivities. Similarly, four microdialysis membranes were placed in dorsal forearm skin: two sites were perfused with ACh and other two with MCh. However, one of each of the ACh and MCh sites was also perfused with 10 μM neostigmine (an acetylcholinesterase inhibitor). Neostigmine at the ACh site induced a leftward shift (i.e., lower EC50) of the SR and CVC dose-response curves compared with the site treated with ACh alone, resulting in no difference in the EC50 for SR and CVC between the ACh + neostigmine and the MCh site. These results suggest that elevations in SR and CVC occur earlier with MCh than with ACh treatment because of differences in cholinesterase susceptibility between these drugs.

Hypothalamic thermoregulatory pathways in the rat

1977 ◽  
Vol 43 (5) ◽  
pp. 770-777 ◽  
Author(s):  
T. M. Gilbert ◽  
C. M. Blatteis
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Medial Forebrain Bundle ◽  
Male Rats ◽  
Cutaneous Blood Flow ◽  
Cutaneous Vasodilation ◽  
Rate Of Oxygen Consumption ◽  
Cutaneous Vasoconstriction ◽  
Cutaneous Blood

The cutaneous blood flow (mbl), rate of oxygen consumption (Vo2), rectal (Tre) and cutaneous (Tsk) temperatures, and shivering activity were measured in unanthetized male rats during a 2-h exposure to 26, 33, or 5 degrees C 2 wk after selective bilateral hypothalamic microknife cuts. Animals with preoptic-anterior hypothalamic (PO/AH) junction cuts 1.5 or 3.0 mm lateral to the midline, as well as parasagittal cuts which separated connections between the PO/AH and medial forebrain bundle exhibited a higher mbl at 26 degrees C than did sham-operated rats. At 5 degrees C the extended (3.0 mm) PO/AH cuts as well as the parasagittal cuts prevented cutaneous vasoconstriction but had no effect on shivering activity; hence Tre was not maintained. None of the cuts demonstrably impaired thermoregulation in the 33 degrees C environment. These results suggest that different sites in the hypothalamus may separately control cold-induced skin vasoconstriction and shivering activity, as well as heat-induced skin vasodilation. It would seem therefore that the integrity of the PO/AH is indispensable in rats for cold-induced cutaneous vasoconstriction but not for cold thermogenesis, and also not for heat-induced cutaneous vasodilation.

Effect of upright exercise on threshold for cutaneous vasodilation and sweating

1981 ◽  
Vol 50 (4) ◽  
pp. 814-818 ◽  
Author(s):  
J. M. Johnson ◽  
M. K. Park
Keyword(s):  
Blood Flow ◽  
Sweat Rate ◽  
Temperature Threshold ◽  
Upright Posture ◽  
Esophageal Temperature ◽  
Internal Temperature ◽  
Cutaneous Vasodilation ◽  
The Difference ◽  
Relationship Of ◽  
The Relationship

To find whether exercise or upright posture affected the internal temperature threshold for cutaneous vasodilation or the relationship between skin blood flow (SkBF) and sweat rate (SR), the relationship of esophageal temperature (Tes) to forearm SkBF and SR was measured in four settings: supine rest, upright rest, supine exercise, and upright exercise. All studies were performed at an elevated skin temperature (38-38.5 degrees C). Compared with values from supine rest, upright exercise was associated with an increase in the internal temperature threshold for vasodilation of 0.39 +/- 0.07 degrees C (P less than 0.01), whereas there was no significant alteration in the threshold for the onset of sweating. Neither the ultimate slope of the SkBF-Tes relationship nor that of the SR-Tes relationship was altered by upright exercise. The upright posture and exercise each contributed to the elevation in the threshold for cutaneous vasodilation, with the average shifts being 0.11 +/- 0.05 degrees C (P less than 0.05) and 0.28 +/- 0.08 degrees C (P less than 0.01), respectively. The net effect of this shift in threshold was to reduce the level of SkBF at any level of Tes during exercise and to increase the difference in threshold between vasomotor and sudomotor responses.

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