RESUMEN
It has been speculated that the control of core temperature is modulated by physiological demands. We could not prove the modulation because we did not have a good method to evaluate the control. In the present study, the control of core temperature in mice was assessed by exposing them to various ambient temperatures (Ta), and the influence of circadian rhythm and feeding condition was evaluated. Male ICR mice (n=20) were placed in a box where Ta was increased or decreased from 27°C to 40°C or to -4°C (0.15°C/min) at 0800 and 2000 (daytime and nighttime, respectively). Intra-abdominal temperature (Tcore) was monitored by telemetry. The relationship between Tcore and Ta was assessed. The range of Ta where Tcore was relatively stable (range of normothermia, RNT) and Tcore corresponding to the RNT median (regulated Tcore) were estimated by model analysis. In fed mice, the regression slope within the RNT was smaller in the nighttime than in the daytime (0.02 and 0.06, respectively), and the regulated Tcore was higher in the nighttime than in the daytime (37.5°C and 36.0°C, respectively). In the fasted mice, the slope remained unchanged, and the regulated Tcore decreased in the nighttime (0.05 and 35.9°C, respectively), while the slopes in the daytime became greater (0.13). Without the estimating individual thermoregulatory response such as metabolic heat production and skin vasodilation, the analysis of the Ta-Tcore relationship could describe the character of the core temperature control. The present results show that the character of the system changes depending on time of day and feeding conditions.
Asunto(s)
Regulación de la Temperatura Corporal , Ritmo Circadiano , Animales , Ayuno/metabolismo , Masculino , Ratones , Ratones Endogámicos ICR , Actividad Motora , Consumo de Oxígeno , TemperaturaRESUMEN
In a previous study, we investigated the contribution of the surface of the face, chest, abdomen, and thigh to thermal comfort by applying local temperature stimulation during whole-body exposure to mild heat or cold. In hot conditions, humans prefer a cool face, and in cold they prefer a warm abdomen. In this study, we extended investigation of regional differences in thermal comfort to the neck, hand, soles, abdomen (Experiment 1), the upper and lower back, upper arm, and abdomen (Experiment 2). The methodology was similar to that used in the previous study. To compare the results of each experiment, we utilized the abdomen as the reference area in these experiments. Thermal comfort feelings were not particularly strong for the limbs and extremities, in spite of the fact that changes in skin temperature induced by local temperature stimulation of the limbs and extremities were always larger than changes that were induced in the more proximal body parts. For the trunk areas, a significant difference in thermal comfort was not observed among the abdomen, and upper and lower back. An exception involved local cooling during whole-body mild cold exposure, wherein the most dominant preference was for a warmer temperature of the abdomen. As for the neck and abdomen, clear differences were observed during local cooling, while no significant difference was observed during local warming. We combined the results for the current and the previous study, and characterized regional differences in thermal comfort and thermal preference for the whole-body surface.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Estimulación Física/métodos , Temperatura Cutánea/fisiología , Sensación Térmica/fisiología , Abdomen , Dorso , Frío , Extremidades , Pie , Mano , Calor , Humanos , Tórax , Adulto JovenRESUMEN
We would like to emphasize about the system involved with homeostatic maintenance of body temperature. First, the primary mission of the thermoregulatory system is to defend core temperature (T (core)) against changes in ambient temperature (T (a)), the most frequently encountered disturbance for the system. T (a) should be treated as a feedforward input to the system, which has not been adequately recognized by thermal physiologists. Second, homeostatic demands from outside the thermoregulatory system may require or produce an altered T (core), such as fever (demand from the immune system). There are also conditions where some thermoregulatory effectors might be better not recruited due to demands from other homeostatic systems, such as during dehydration or fasting. Third, many experiments have supported the original assertion of Satinoff that multiple thermoregulatory effectors are controlled by different and relatively independent neuronal circuits. However, it would also be of value to be able to characterize strictly regulatory properties of the entire system by providing a clear definition for the level of regulation. Based on the assumption that T (core) is the regulated variable of the thermoregulatory system, regulated T (core) is defined as the T (core) that pertains within the range of normothermic T (a) (Gordon in temperature and toxicology: an integrative, comparative, and environmental approach, CRC Press, Boca Raton, 2005), i.e., the T (a) range in which an animal maintains a stable T (core). The proposed approach would facilitate the categorization and evaluation of how normal biological alterations, physiological stressors, and pathological conditions modify temperature regulation. In any case, of overriding importance is to recognize the means by which an alteration in T (core) (and modification of associated effector activities) increases the overall viability of the organism.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Neuronas/fisiología , Animales , Gatos , Humanos , Ratas , Gorriones/fisiología , Tachyglossidae/fisiologíaRESUMEN
Sensations evoked by thermal stimulation (temperature-related sensations) can be divided into two categories, "temperature sensation" and "thermal comfort." Although several studies have investigated regional differences in temperature sensation, less is known about the sensitivity differences in thermal comfort for the various body regions. In the present study, we examined regional differences in temperature-related sensations with special attention to thermal comfort. Healthy male subjects sitting in an environment of mild heat or cold were locally cooled or warmed with water-perfused stimulators. Areas stimulated were the face, chest, abdomen, and thigh. Temperature sensation and thermal comfort of the stimulated areas were reported by the subjects, as was whole body thermal comfort. During mild heat exposure, facial cooling was most comfortable and facial warming was most uncomfortable. On the other hand, during mild cold exposure, neither warming nor cooling of the face had a major effect. The chest and abdomen had characteristics opposite to those of the face. Local warming of the chest and abdomen did produce a strong comfort sensation during whole body cold exposure. The thermal comfort seen in this study suggests that if given the chance, humans would preferentially cool the head in the heat, and they would maintain the warmth of the trunk areas in the cold. The qualitative differences seen in thermal comfort for the various areas cannot be explained solely by the density or properties of the peripheral thermal receptors and thus must reflect processing mechanisms in the central nervous system.
Asunto(s)
Temperatura , Sensación Térmica/fisiología , Abdomen/inervación , Abdomen/fisiología , Sistema Nervioso Autónomo/fisiología , Regulación de la Temperatura Corporal/fisiología , Frío , Cara/inervación , Cara/fisiología , Calor , Humanos , Masculino , Estimulación Física , Temperatura Cutánea/fisiología , Adulto JovenRESUMEN
We investigated the effects of alcohol on thermoregulatory responses and thermal sensations during cold exposure in humans. Eight healthy men (mean age 22.3+/-0.7 year) participated in this study. Experiments were conducted twice for each subject at a room temperature of 18 degrees C. After a 30-min resting period, the subject drank either 15% alcohol at a dose of 0.36 g/kg body weight (alcohol session) or an equal volume of distilled water (control session), and remained in a sitting position for another 60 min. Mean skin temperature continued to decrease and was similar in control and alcohol sessions. Metabolic rate was lower in the alcohol session, but the difference did not affect core temperature, which decreased in a similar manner in both alcohol and control sessions (from 36.9+/-0.1 degrees C to 36.6+/-0.1 degrees C). Whole body sensations of cold and thermal discomfort became successively stronger in the control session, whereas these sensations were both greatly diminished after drinking alcohol. In a previous study we performed in the heat, using a similar protocol, alcohol produced a definite, coordinated effect on all autonomic and sentient heat loss effectors. In the current study in the cold, as compared to responses in the heat, alcohol intake was followed by lesser alterations in autonomic effector responses, but increased changes in sensations of temperature and thermal discomfort. Overall, our results indicate that although alcohol influences thermoregulation in the cold as well as in the heat, detailed aspects of the influence are quite different.
Asunto(s)
Sistema Nervioso Autónomo/efectos de los fármacos , Depresores del Sistema Nervioso Central/farmacología , Frío , Etanol/farmacología , Sensación Térmica/efectos de los fármacos , Adulto , Regulación de la Temperatura Corporal/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Masculino , Metabolismo/efectos de los fármacos , Temperatura Cutánea/efectos de los fármacos , TelemetríaRESUMEN
We report a new system for monitoring sensations of many body parts as well as comprehensively showing the distribution of overall skin temperature (T(sk)) and temperature-related sensations. The system consists of a console with 52 levers to report temperature-related sensations and software that facilitates the visualization of the distribution of T(sk) and temperature-related sensations by displaying them on a model of the human body. The system's utility was demonstrated with a physiological experiment involving three males and three females. They were exposed to step changes of ambient temperature from 23 degrees C to 33 degrees C. We measured T(sk) at 50 points, and the subjects concurrently provided estimates of local temperature sensation and thermal comfort/discomfort at 25 loci. This system greatly facilitates the perception and analysis of spatial relationships and differences in temperature and sensation in various areas of the body.
Asunto(s)
Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Articulaciones/fisiología , Temperatura Cutánea/fisiología , Sensación Térmica/fisiología , Adulto , Temperatura Corporal/fisiología , Simulación por Computador , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador/instrumentación , Imagenología Tridimensional/instrumentación , Masculino , Programas InformáticosRESUMEN
Acute ethanol exposure decreases regulated body temperature. Tolerance and dependence develop with continued exposure. Removal of ethanol following chronic exposure produces withdrawal. There is little information on the time course for the development of tolerance and disagreement about the presence of a rebound effect on body temperature during withdrawal. For tolerance, we monitored the selected temperature [T(sel)] of goldfish [Carassius auratus] for 8 h while they were exposed to one of three doses of ethanol. During the period from 90 to 150 min post-exposure, T(sel) was: control: 24.1+/-0.07 degrees C; 0.4% ethanol: 21.9+/-0.09 degrees C; 0.8% ethanol: 21.3+/-0.05 degrees C; 1.1% ethanol: 18.4+/-0.10 degrees C. The difference between control and experimental T(sel) decreased by the following amounts for the final 1.5 h in the gradient: 0.4% ethanol: 2.60+/-0.12 degrees C; 0.8% ethanol: 1.58+/-0.09 degrees C; 1.1% ethanol: 4.08+/-0.12 degrees C. At all 3 doses, tolerance proceeded in a stepwise manner rather than continuously. Temperature regulation during withdrawal was evaluated by maintaining the goldfish in 0.8% ethanol for three days and subsequently monitoring T(sel) in an ethanol-free temperature gradient for 36 h. During withdrawal there was no evidence for an effect on T(sel); experimental and control values were nearly identical.
Asunto(s)
Depresores del Sistema Nervioso Central/farmacología , Etanol/farmacología , Carpa Dorada/fisiología , Síndrome de Abstinencia a Sustancias/psicología , Animales , Conducta Animal/efectos de los fármacos , Temperatura Corporal/efectos de los fármacos , Depresores del Sistema Nervioso Central/sangre , Tolerancia a Medicamentos , Etanol/sangre , Actividad Motora/efectos de los fármacos , TemperaturaRESUMEN
We investigated the effects of alcohol on thermoregulatory responses and thermal sensations during mild heat exposure in humans. Eight healthy men participated in this study. Experiments were conducted twice for each subject at a room temperature of 33 degrees C. After a 30-min resting period, the subject drank either 15% alcohol (alcohol session) at a dose of 0.36 g/kg body weight or equal volume of water (control session). Skin blood flow and chest sweat rate in the alcohol session significantly increased over those in controls 10 min after drinking. Deep body temperature in the alcohol session started to decrease 20 min after the onset of sweating and eventually fell 0.3 degrees C lower than in the controls. Whole body hot sensation transiently increased after alcohol drinking, whereas it changed little after water drinking. The increased "hot" sensation would presumably cause cool-seeking behavior, if permitted. Thus, alcohol influences thermoregulation so that body core temperature is lowered not only by automatic mechanisms (sweating and skin vasodilation) but also behaviorally. These results suggest that decreases in body temperature after alcohol drinking are not secondary to skin vasodilation, a well-known effect of alcohol, but rather result from a decrease in the regulated body temperature evidenced by the coordinated modulation of various effectors of thermoregulation and sensation.
Asunto(s)
Regulación de la Temperatura Corporal/efectos de los fármacos , Depresores del Sistema Nervioso Central/farmacología , Etanol/farmacología , Calor , Adulto , Humanos , Masculino , Flujo Sanguíneo Regional/efectos de los fármacos , Piel/irrigación sanguínea , Temperatura Cutánea/efectos de los fármacos , Sudoración/efectos de los fármacos , TemperaturaRESUMEN
Regional activation of the brain was studied in humans using functional magnetic resonance imaging during whole body cooling that produced thermal comfort/discomfort. Eight normal male subjects lay in a sleeping bag through which air was blown, exposing subjects to cold air (8 degrees C) for 22 min. Each subject scored their degree of thermal comfort and discomfort every min. As the subjects reported more discomfort the blood oxygen level dependent response in the bilateral amygdala increased. There was no activation in the thalamus, somatosensory, cingulate, or insula cortices. This result suggests that the amygdala plays a role in the genesis of thermal discomfort due to cold.
Asunto(s)
Encéfalo/metabolismo , Hipotermia Inducida , Imagen por Resonancia Magnética , Adulto , Amígdala del Cerebelo/metabolismo , Mapeo Encefálico/métodos , Humanos , Hipotermia Inducida/métodos , Hipotermia Inducida/estadística & datos numéricos , Modelos Lineales , Imagen por Resonancia Magnética/métodos , Imagen por Resonancia Magnética/estadística & datos numéricos , MasculinoRESUMEN
We examined body core and skin temperatures and thermal comfort in young Japanese women suffering from unusual coldness (C, n = 6). They were selected by interview asking whether they often felt severe coldness even in an air-conditioned environment (20-26 degrees C) and compared with women not suffering from coldness (N, n = 6). Experiments were conducted twice for each subject: 120-min exposure at 23.5 degrees C or 29.5 degrees C after a 40-min baseline at 29.5 degrees C. Mean skin temperature decreased (P < 0.05) from 33.6 +/- 0.1 degrees C (mean +/- SE) to 31.1 +/- 0.1 degrees C and from 33.5 +/- 0.1 degrees C to 31.1 +/- 0.1 degrees C in C and N during the 23.5 degrees C exposure. Fingertip temperature in C decreased more than in N (P < 0.05; from 35.2 +/- 0.1 degrees C to 23.6 +/- 0.2 degrees C and from 35.5 +/- 0.1 degrees C to 25.6 +/- 0.6 degrees C). Those temperatures during the 29.5 degrees C exposure remained at the baseline levels. Rectal temperature during the 23.5 degrees C exposure was maintained at the baseline level in both groups (from 36.9 +/- 0.2 degrees C to 36.8 +/- 0.1 degrees C and 37.1 +/- 0.1 degrees C to 37.0 +/- 0.1 degrees C in C and N). The rating scores of cold discomfort for both the body and extremities were greater (P < 0.05) in C than in N. Thus the augmented thermal sensitivity of the body to cold and activated vasoconstriction of the extremities during cold exposure could be the mechanism for the severe coldness felt in C.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Frío , Sensación Térmica/fisiología , Adulto , Temperatura Corporal , Femenino , Dedos , Frecuencia Cardíaca/fisiología , Hormonas/sangre , Humanos , Recto/fisiología , Temperatura CutáneaRESUMEN
Recently we found that food-deprived rats kept under a light-dark cycle showed a progressive reduction in body temperature during the light phase on each subsequent day while body temperature in the dark phase did not differ from baseline values. In this study, we investigated the effect of lesioning the hypothalamic suprachiasmatic nucleus (SCN) on body temperature modulation by food deprivation. In the SCN-lesioned rats in which daily rhythms of body temperature and activity were abolished, body temperature was unchanged by food deprivation. We also examined the effect of food deprivation on the daily changes in Fos expression in the SCN. Under normal fed conditions the number of SCN cells expressing Fos is high during the day and low at night. Food deprivation attenuated the amplitude of this daily change in Fos expression in the SCN. This tendency was prominent in the dorsal part of the SCN, while the ventral part showed no effect of food deprivation. These findings suggest that the SCN plays some role in body temperature modulation due to food deprivation.