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PubMed1991

[The relationship between the deep body temperature and hemodynamics after open-heart surgery in children].

The relationships of the forehead-sole deep body temperature difference with the cardiac index (CI), and with the systemic vascular resistance index (SVRI) were studied in 10 pediatric patients (TOF 5, ASD 3, VSD 2) for 24 hours after open-heart surgery. A correlation between the deep body temperature difference (X) and CI (Y) was expressed as, Y = -0.49X + 4.51 (r = 0.72), and that between the deep body temperature difference (X) and SVRI (Z) as Z = 152X + 1039 (r = 0.62). The deep body temperature difference was 1.0 degrees C on the average in patients whose CI was more than 3.0 l.min-1.m-2, and was 3.3 degrees C in patients whose CI was less than 3.0 l.min-1.m-2. Conversely CI was less than 3.0 l.min-1.m-2 in patients whose deep body temperature difference was more than 3.0 degrees C. We conclude that the measurement of deep body temperature difference is useful as a circulatory monitor, and that a critical level of deep body temperature difference is 3 degrees C in children.

Body Temperature↗
PubMed1975

Central inhibitory effect of alpha-methyldopa on blood pressure, heart rate and body temperature of renal hypertensive rats.

The central inhibitory effect of alpha-methyldopa on blood pressure, heart rate and body temperature was studied in conscious renal hypertensive rats. Systemic administration of alpha-methyldopa decreased mean arterial blood pressure and body temperature and caused a short lasting increase in heart rate followed by a long lasting decrease. Inhibition of central decarboxylase activity prevented the decrease in blood pressure, heart rate and body temperature but not the initial increase in heart rate. Inhibition of peripheral decarboxylase activity blocked the increase in heart rate and partially reduced the decrease in heart rate and body temperature but did not affect the decrease in blood pressure. Alpha-Methyldopa also decreased blood pressure at an ambient temperature of 30 degrees C, but the decrease of body temperature was absent and the heart rate remained elevated for 7 hr. Similar results were obtained in normotensive rats. The decrease in heart rate was correlated with the decrease in body temperature in normotensive and renal hypertensive rats. These findings suggest that in the renal hypertensive rat the decrease in blood pressure and in body temperature depends on a central action of alpha-methyldopa metabolites.

Animals↗
PubMed1991

Medial preoptic area affects sleep-wakefulness independent of associated body temperature change in free moving rats.

Sleep-wakefulness and body temperature may modulate each other. Though both the functions are influenced by the medial preoptic area, the mechanism of action was not clear. This study was aimed at finding out whether the tonic influence of the medial preoptic area on sleep-wakefulness was independent of or secondary to simultaneous change in body temperature. The effects of inactivation of the area by a long acting local anaesthetic, marcain, on those physiological functions were investigated during the night and the day in freely moving rats. Though medial preoptic area influenced sleep-wakefulness and body temperature simultaneously, the effect on the latter was prolonged. The results suggest that the influence on sleep-wakefulness is unlikely to be associated with simultaneously changing body temperature. However, this study fails to differentiate whether the observed effects were due to inactivation of the cell body or the fibers passing through the area.

Animals↗
PubMed1998

Small changes in ambient temperature cause large changes in 3,4-methylenedioxymethamphetamine (MDMA)-induced serotonin neurotoxicity and core body temperature in the rat.

The amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA) is a drug of abuse and has been shown to be neurotoxic to 5-HT terminals in many species. MDMA-engendered neurotoxicity has been shown to be affected by both ambient temperature and core body temperature. We now report that small (2 degreesC) changes in ambient temperature produce changes in core temperature in MDMA-treated rats, but the same changes in ambient temperature do not affect core temperature of saline-treated animals. Furthermore, increases in core temperature of MDMA-treated animals increase neurotoxicity. Rats were given MDMA (20 or 40 mg/kg) or saline and placed in an ambient temperature of 20, 22, 24, 26, 28, or 30 degreesC using a novel temperature measurement apparatus that controls ambient temperature +/-0.5 degrees C. Two weeks after MDMA treatment, the rats were killed, and regional 5-HT and 5-hydroxyindole acetic acid levels were analyzed as a measure of neurotoxicity. Rats treated with MDMA at 20 and 22 degrees C showed a hypothermic core temperature response. Treatment with MDMA at 28 and 30 degreesC produced a hyperthermic response. At ambient temperatures of 20-24 degrees C, neurotoxicity was not observed in the frontal cortex, somatosensory cortex, hippocampus, or striatum. At ambient temperatures of 26-30 degrees C, neurotoxicity was seen and correlated with core temperature in all regions examined. These data indicate that ambient temperature has a significant affect on MDMA neurotoxicity, core temperature, and thermoregulation in rats. This finding has implications on both the temperature dependence of the mechanism of MDMA neurotoxicity and human use because fatal hyperthermia is associated with MDMA use in humans.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Daytime melatonin and temazepam in young adult humans: equivalent effects on sleep latency and body temperatures.

1. As changes in core body temperature are generally associated with concomitant changes in sleep propensity, it is possible that the effects of hypnotic/soporific agents may be related to changes in thermoregulation. Therefore, to increase our knowledge of the mechanisms by which these agents exert their soporific effects, we compared the thermoregulatory and soporific effects of temazepam (20 mg per os (p.o.)) with those of melatonin (5 mg p.o.) when administered at 14.00 h to 20 young healthy adults (13 male, 7 female; age, 23.5 +/- 0.4 years). 2. From 08.00 to 20.30 h, subjects lay in bed, and foot and rectal (Tc) temperatures were recorded. Sleep onset latency (SOL) was measured using 20 min multiple sleep latency tests, performed hourly from 11.00 to 20.00 h, during which time heart rate was recorded. 3. Compared with placebo, both melatonin and temazepam significantly reduced Tc (-0.17 +/- 0.02 and -0.15 +/- 0.03 C, respectively) and SOL (by 4.8 +/- 1.49 and 6.5 +/- 1.62 min, respectively). Although both treatments significantly increased heat loss, only melatonin demonstrated cardiac effects. Importantly, there was a temporal relationship between minimum SOL and the maximum rate of decline in Tc for both melatonin (r = 0.48) and temazepam (r = 0.44). 4. A possible role of thermoregulation in sleep initiation is suggested by the similar temporal relationship between Tc and SOL for two different classes of soporific agents.

Adolescent↗
PubMed1988

Bladder temperature as an estimate of body temperature during cardiopulmonary bypass.

Bladder temperature measured by a thermistor-tipped urinary catheter, was compared to oesophageal, nasopharyngeal, rectal and cutaneous temperatures in 33 patients during cardiopulmonary bypass. The bladder site was warmer than all other monitored sites in the pre-bypass period and showed least variation in temperature. The rate of change of bladder temperature during cooling and rewarming on bypass was significantly (p less than 0.01) lower than for oesophageal and nasopharyngeal temperatures, but was greater than or similar to the rate of change of rectal and cutaneous temperatures. This method of temperature measurement was found to be satisfactory during major surgery and also during the postoperative period in the intensive care unit.

Body Temperature↗
PubMed1996

Core body temperature during menopausal hot flushes.

OBJECTIVE: To measure core body temperature by ingested radiotelemetry pill and rectal temperature during menopausal hot flushes under controlled laboratory conditions. DESIGN: Patients were recorded during sleep using both methods in a sound-proofed, temperature and humidity-controlled laboratory room. SETTING: University medical center. PATIENTS: Eight postmenopausal women who were amenorrheic for > or = 1 year and reported frequent hot flushes. RESULTS: Thirty-seven hot flushes were detected by criterion increases in sternal skin conductance level. Significant increases in telemetered but not rectal temperature occurred before 24 of the hot flushes. CONCLUSIONS: Core body temperature elevations precede a majority of menopausal hot flushes and serve as one trigger of this heat-loss phenomenon.

Body Temperature↗
PubMed1998

Homeostatic and circadian control of body temperature in the fat-tailed gerbil.

The interplay of homeostasis and circadian rhythmicity in the control of body temperature was studied in the fat-tailed gerbil (Pachyuromys duprasi). In a first study, the body temperature rhythm of 8 gerbils maintained at 24 degrees C under a 14L:10D light-dark cycle was studied by telemetry. Data from 9 other species of small mammals were also obtained for comparison. The gerbils were found to exhibit a robust rhythm of body temperature (the most robust of the 10 species) with a high plateau during the dark phase of the light-dark cycle and a low plateau during the light phase. In a second experiment, 5 gerbils were allowed to select the temperature of their environment by moving along a thermal gradient. The animals consistently selected higher ambient temperatures during the light phase of the light-dark cycle (when their body temperature was at the low plateau). In a third experiment, the metabolic response of 8 gerbils to an acute cold exposure was determined by indirect calorimetry. Greater cold-induced thermogenesis was observed during the light phase. The fact that the animals selected higher ambient temperatures and displayed greater cold-induced thermogenesis when their body temperature was lower contradicts the hypothesis that the body temperature rhythm is caused by a rhythmic oscillation of the thermoregulatory set point.

Animals↗
PubMed1991

Modulation of body temperature through taste aversion conditioning.

Injection of rats with bacterial lipopolysaccharide (LPS) results in an initial fall in body temperature followed by a fever. Lithium chloride (LiCl) injection induces a fall in body temperature without subsequent fever production. When these substances were incorporated as unconditioned stimuli in a taste aversion conditioning paradigm, using saccharin flavour as the conditioning stimulus, these differential effects on body temperature were reenlisted on reexposure to saccharin alone 7 days after conditioning. The changes in body temperature on reexposure were similar in direction and kinetics as on the conditioning day although reduced in magnitude. The finding of a true conditioned effect in these studies is in contrast to the paradoxical or compensatory conditioned body temperature responses described elsewhere using different conditioning models. This apparent conflict may be explained on the basis of different unconditioned stimuli acting on efferent versus afferent arms of a negative feedback system. Since body temperature changes often occur in association with immune responses, these findings may have implications to behavioural conditioning of immunity, the outcome of which may reflect the indirect effects on immunity of inadvertent conditioning of thermoregulatory changes.

Animals↗
PubMed1998

Different nocturnal body temperatures and sleep with forced-air warming in men and in women taking hormonal contraceptives.

We studied how forced-air warming, conventionally used to control body temperature during and after anaesthesia, affected the nocturnal rectal temperatures and sleep composition of young men and women. Seven healthy women who were taking oral or injection contraceptives, and six healthy men spent 3 nights in a controlled environment: an adaptation night followed by 2 nights when they slept under either a down duvet (baseline) or a quilt perfused with warm air (hot). Repeated analysis of variance (ANOVA) revealed significant gender differences in the body temperature responses. On the baseline night, despite sleeping under the same conditions, the women did not show a nocturnal drop in body temperature as shown by the men. Forced-air warming increased body temperature to a similar extent in the men and the women, and resulted in enhanced hyperthermia in the women, and blunted the drop in body temperature in the men, compared to their baseline nights. The significant increases in body temperature had no consequences, however, for the subjective sleep quality of either the men or women, and only minor consequences for objective sleep composition. Both men and women had increased amounts of Stage 2 sleep on the hot night (P < 0.04). In addition, the women had reduced rapid eye movement (REM) sleep when compared to their baseline night (P < 0.04). Our results confirm that in a passive thermal environment, women who are taking oral or injection contraceptives have higher nocturnal body temperatures than men. Also, as sleep architecture was minimally affected by the increases in body temperature of between 0.2 and 0.3 degree C on the hot night in the men and women, and subjective sleep quality was unaffected, our results question the existence of a tight association between sleep and body temperature.

Adult↗
PubMed1978

Body temperature and 5-hydroxytryptamine during early postnatal maturation in mice.

A relationship between the maturational increases in body temperature and brain indoleamines has been explored through altering brain 5-hydroxytryptamine (5-HT) content. Effects on body temperature at approximately constant ambient temperature (about 24 degrees C) have been studied following pharmacological manipulations in mice up to 16 days postpartum. Administration of 5-hydroxytryptophan (5-HTP) to increase 5-HT levels was associated with decreased body temperature throughout the maturational period. Depletion of 5-HT with p-chlorophenylalanine (p-CPA) was associated with increased body temperature at all ages studied, although 5-HT depletion was less effective in young animals than in older animals. The drug NSD-1034 acts at a different enzymatic step, and is effective in both central and peripheral tissues to reduce 5-HT and norepinephrine (NE) levels. NSD-1034 decreased body temperature up to 10 days of age; however, the effect was reversed at about 14 days, and the drug increased body temperature significantly in 16-day-old animals. These results suggest a role for 5-HT in the mechanisms of heat production in early postnatal life.

Animals↗
PubMed1981

Alcohol's effect on body temperature: hypothermia, hyperthermia or poikilothermia?

A series of five experiments was undertaken in order to characterize the pharmacological effects of alcohol on the body temperature of the unrestrained rat. After a thermistor probe was fixed within the colon of each animal and its body temperature had stabilized, physiological saline. 2.0 g/kg or 4.0 g/kg of ethyl alcohol was given by intragastric gavage. A constant concentration of 20% was utilized with doses determined volumetrically according to the individual weight of the animal. The following observations were made: (1) At a laboratory room temperature of 22 degrees C, alcohol produced a dose-dependent decline in colonic temperature. This fall was enhanced when the rat was placed in a chamber with an ambient temperature of 8 degrees C, but reversed into a hyperthermic response when the ambient temperature of the rat was elevated to 36 degrees C. (2) If the rat was exposed for one hour to either a warm (36 degrees C) or cold (8 degrees C) ambient temperature beginning at the time of the intragastric gavage with alcohol, the body temperature of the animal correspondingly decreased or increased, respectively. The magnitude of the shift in the animal's colonic temperature depended solely on the dose of alcohol given, i.e., thermolability was enhanced to a greater extent by the r.0 g/kg dose than the 2.0 g/kg dose. Exposure of the rat to a high or low ambient temperature prior to intragastric gavage with alcohol also affected the body temperature displacement as well as the direction of change. (3) Following the 4.0 g/kg alcohol dose, the animal's colonic temperature could be controlled precisely by varying the ambient temperatures in the 26 degrees C--32 degrees C range of thermoneutrality; in fact, within limits, the rat's temperature could be held constant at any predetermined level. (4) Pretreatment of the animal with 6.0 ml of a 50% solution of glucose given subcutaneously failed to attenuate the poikilothermic effect of intragastric alcohol administered in a dose of 4.0 g/kg. (5) Comparisons of the effect on body temperature of equipotent doses of sodium pentobarbital (25 mg/kg), administered intraperitoneally, and alcohol (4.0 g/kg) given by gavage showed that either a high or low ambient temperature elevated or lowered the colonic temperature of the rat at an identical rate and magnitude. It is concluded that alcohol acts acutely as any other anesthetic agent to abolish all thermoregulatory control functions. Thus, the physiological mechanisms for the dissipation of body heat as well as those for heat production are incapacitated by the drug. Clearly, alcohol is a poikilothermic agent, and thus, the decline in body temperature observed in the animal typically kept at a laboratory room temperature of 20 degrees C--24 degrees C represents the result of a cold challenge and is not due to a postulated "hypothermic" effect of alcohol.

Animals↗
PubMed1985

Neurotransmitter effects on body temperature are modified with increasing age.

This study reports effects on body temperature, in two different age groups of Sprague Dawley rats, of intracerebroventricular (ICV) administration of prostaglandin E2, noradrenaline, serotonin, dopamine, and carbachol. Young animals (3-5 months) developed fevers in response to administration of prostaglandin E2 (+ 1.02 +/- 0.26 degrees C), while no significant changes in colonic temperature were observed in the older (15-18 months) group of rats. Noradrenaline (10.0 micrograms), caused a decrease in colonic temperature in the younger group of animals (-2.02 +/- 0.70 degrees C), but had no significant effects on the body temperature of the older group. Similarly, differences between the temperature responses of the young as compared with the older group of animals were observed following ICV administration of carbachol, dopamine and serotonin. These data suggest that the roles of these substances in the hypothalamic control of body temperature may be modified with increasing age.

Aging↗
PubMed2000

The preoptic area in the hypothalamus is the source of the additional respiratory drive at raised body temperature in anaesthetised rats.

In mammals that use the ventilatory system as the principal means of increasing heat loss, raising body temperature causes the adoption of a specialised breathing pattern known as panting and this is mediated by the thermoregulatory system in the preoptic area of the hypothalamus. In these species an additional respiratory drive is also present at raised body temperature, since breathing can reappear at low Pa,CO2 levels, when stimulation of chemoreceptors is minimal. It is not known whether the preoptic area is also the source of this additional drive. Rats do not pant but do possess this additional respiratory drive at raised body temperatures. We have therefore tested whether the preoptic area of the hypothalamus is the source of this additional respiratory drive in rats. Urethane anaesthesia and hyperoxia were used in eleven rats to minimise behavioural and chemical drives to breathe. The presence of the additional respiratory drive was indicated if rhythmic diaphragmatic EMG activity reappeared during hypocapnia (a mean Pa,CO2 level of 21+/-2 mm Hg, n = 11), induced by mechanical ventilation. The additional respiratory drive was absent at normal body temperature (37¿C). When the temperature of the whole body was raised using an external source of radiant heat, the additional respiratory drive appeared at 40.6+/-0.5 degrees C (n = 3). In two further rats this drive was induced at normal body temperature by localised warming in the preoptic area of the intact hypothalamus. The additional respiratory drive appeared at similar temperatures to those in control rats in three rats following isolation of the hypothalamus from more rostral areas of the brain. In contrast, the additional respiratory drive failed to appear at these temperatures in three rats after isolating the hypothalamus from the caudal brainstem, by sectioning pathways medial to the medial forebrain bundle. Since the preoptic area is known to contain thermoreceptors and to receive afferents from peripheral thermoreceptors, the results show that this area is also the source of the additional respiratory drive at raised body temperature in anaesthetised rats.

Anesthesia, Intravenous↗
PubMed2002

Extended lowered body temperature increases the effective CS-US interval in conditioned taste aversion for adult rats.

Assuming body temperature correlates with metabolic activities, rate of body temperature recovery was manipulated to assess effects on long-trace conditioning in a conditioned taste-aversion paradigm. Following 10 min. access to a .1% saccharin solution and then 10 min. immersion in 0-0.5 degrees C water, two groups of 16 Wistar-derived, 81-113 day-old, male albino rats received either saline or lithium chloride injections 3 hr. later. These two groups were subdivided on basis of warming rate during the 3-hr. interval. Half of the rats recovered at room temperature (20 degrees to 21 degrees C), and half recovered in an incubator maintained at 30 degrees C. Maintaining a lowered body temperature between the conditioned stimulus and unconditioned stimulus allowed an association to be made at 3 hr., an interval that normally does not support conditioning. In contrast, lowering body temperature and then inducing a fast warming rate did not produce evidence of an aversion. It is suggested that maintaining a low body temperature over the interval between the presentation of the conditioned stimulus and unconditioned stimulus slows a metabolic clock that extends the measured interval at which associations can be made using conditioned taste-aversion procedures.

Animals↗
PubMed1989

Feeding time and body temperature interactions in broiler breeders.

Four groups of 70-wk-old broiler breeder females were fed once daily at 0600, 1000, 1400, and 1800 h to determine the effect of feeding time and eating on body temperature. The photoperiod was from 0430 to 1930 h. Four floor pens of 30 hens each were assigned per feeding time. Following a 9-day adjustment period, body temperature was determined, in series, by rectal probe of 5 birds/pen at 7 and 3 h prefeeding and 1, 5, 9, and 13 h postfeeding. Body temperature was increased .5 C at 1 h postfeeding in all groups and at 5 h postfeeding in the 0600-h fed group. The rate of feed consumption was fastest with afternoon feeding. Four 1-yr-old broiler breeder males were implanted with an FM radio transmitter for monitoring body temperature and housed in an environmental control chamber. Body temperature was monitored when the birds were fed at 0600, 1000, 1400, and 1800 h. The chamber temperature cycled from 22.2 to 33.3 C (22.2 C: 2200 to 0800 h; 33.3 C: 1200 to 1600 h; 27.8 C: 0800 to 1200 h and 1600 to 2200 h). Lights were on from 0430 to 1930 h. Body temperature changes were also monitored under constant temperature (27.8 C) and light for birds fed ad libitum or at 1000 h. Body temperature increased as much as 1.5 C following feeding and reached a maximum at 5, 4, 3, and 2 h postfeeding at feeding times of 0600, 1000, 1400, and 1800 h, respectively. Males unable to feed displayed a significantly increased body temperature when they observed other birds eating. A specific body temperature response to feeding activity was observed only when males were fed once daily under constant environment.

Animal Feed↗
PubMed1997

Regulation of the 24-hour rhythm of body temperature in menstrual cycles with spontaneous and gonadotropin-induced ovulation.

OBJECTIVE: To investigate the relation between gonadal steroids and the 24-hour body temperature rhythm. PATIENT(S): Nineteen normally cycling women. DESIGN: Controlled clinical study in volunteer women. SETTING: Clinical hospital. INTERVENTION(S): Eleven women were studied in the early follicular and luteal menstrual phases of cycles with spontaneous ovulation, and 8 women were studied in the early follicular, preovulatory, and luteal phases of cycles with multiple follicular development. MAIN OUTCOME MEASURE(S): Starting at 5:00 P.M., intravaginal body temperature was monitored continuously for 24 hours and its values were related to E2 and P levels. RESULT(S): Twenty-four-hour body temperature rhythm parameters were related to the P:E2 ratio. Very low P:E2 ratios in the preovulatory phase were associated with a reduced 24-hour mean and an elevated body temperature rhythm amplitude. The progressive increase in the P:E2 ratio in the early follicular and luteal phases was associated with an increase in the 24-hour mean body temperature and a decrease in the rhythm amplitude. Body temperature differences between the luteal and early follicular phases were less pronounced in cycles with multiple follicular development. CONCLUSION(S): A woman's body temperature is related to her P:E2 ratio. Even in the presence of elevated P values, alterations of this ratio may influence negatively the postovulatory rise in body temperature.

Adult↗