Influence of ventilation of the face on thermoregulation in man during hyper- and hypothermia.
Explore the source record for details and available documents.
Body Temperature↗
Biomedical subjects
M Cabanac
Publications and source records attributed to M Cabanac.
Ingestive/aversive response of rats to sweet stimuli. Influence of glucose, oil, and casein hydrolyzate gastric loads.
Facial consummatory responses reflecting ingestive and aversive perceptions were studied and quantified in rats chronically implanted with gastric and oral catheters. A gustatory stimulus of 50 microliters of 0.6 mol.l-1 sucrose was injected into the mouth every 5 min during 90 min. At time zero, one of seven loads was injected into the stomach. These consisted of, 5 ml of water, or 5 ml solution containing 1 g glucose, 3 g glucose, 1 g casein hydrolyzate, 3 g casein hydrolyzate, or of oil 0.6 ml, or 1.4 ml. The typical ingestive facial consummatory responses in response to sweet stimuli were observed prior to all gastric loads, and also after the water load. On the other hand, the consummatory responses to sweet stimuli turned aversive after all three high-calorie gastric loads. The magnitude of this decrease in palatability (negative alliesthesia) was similar after glucose, casein hydrolyzate, and oil. The reversal of the consummatory responses from ingestive to aversive did not reach the threshold of statistical significance after the three low-calorie gastric loads. These results would tend to show that the intestinal signal for alimentary alliesthesia is nonspecific.
Animals↗
Acute, but not chronic, exercise lowers the body weight set-point in male rats.
The influence of muscular training on overall energy balance and body weight is not clear. A group of male rats was trained to feed every day from 1000 to 1200. Then the intersect of regression line of food hoarded during meal time vs. body weight with the X-axis was measured. Finally, the rats were trained to run 1 h every day on a motor-driven treadmill. When the training took place in the morning, just before the hoarding session, the mean intersect was significantly lowered from control (497 +/- 18 g to 433 +/- 9 g). When the training took place in the afternoon, after the hoarding session, the mean intersect was not significantly different (504 +/- 21 g) from control. Food intake during the hoarding sessions was affected neither by body weight changes nor by muscular exercise. These results suggest that the set-point for body weight regulation is acutely lowered just after muscular exercise, but is not influenced by chronic training.
Animals↗
Duodenal preabsorptive origin of gustatory alliesthesia in rats.
Facial consummatory responses reflecting ingestive and aversive perceptions were studied and quantified in rats chronically implanted with gastric, duodenal, and oral catheters. A gustatory stimulus of 50 microliters of 1.75 mol/l sucrose was injected into the mouth every 5 min for 65 min. At time 0, 0.5 ml containing 0.3 g glucose was injected into the stomach or into the duodenum. Typical ingestive facial consummatory responses were observed in response to sweet stimuli prior to the load. Aversive consummatory responses were observed in response to sweet stimuli after the glucose duodenal load (negative alliesthesia). The gastric load of glucose was not followed by negative alliesthesia in response to sweet oral stimuli. In the last part of the experiment the rats were vagotomized. When the rats were subjected again to the same gustatory sessions, the duodenal load was followed by weak and delayed negative alliesthesia in response to sweet stimuli. These results in rats parallel results obtained in human subjects and reinforce the hypothesis of the existence of a duodenal preabsorptive signal for alimentary alliesthesia. They also suggest that the vagus nerve plays a part in the perception of satiety.
Absorption↗
Stress hyperthermia: physiological arguments that it is a fever.
The theory that stress (or emotional) rise in central temperature (Tc) in rats is a fever with an upward shift of the set-point temperature was tested with three experiments: 1) Measurement of tail skin temperature and Tc during the emotional Tc rise; 2) Investigation of the effect of ambient temperature on the emotional Tc rise; and 3) The assessment of emotional Tc rise during daytime and nighttime. Skin vasomotor responses helped the increase of Tc toward a higher level and contributed to the regulation of central temperature at this new higher level. The cold environment did not diminish the emotional rise of central temperature as it would be expected in the case of a hyperthermia. However, at night emotional fever reached a higher level than during the daytime, suggesting that prostaglandin rise in Tc is distinct from emotional or stress-induced hyperthermia. In conclusion, the experiments reported here confirm the hypothesis that the rise of Tc induced by handling or disturbance of the rats is regulated, and is due to a shift of the set-point as occurs in fever.
Animals↗
Facial consummatory responses in rats support the ponderostat hypothesis.
Facial consummatory responses reflecting ingestive and aversive perceptions were studied and quantified in rats chronically implanted with gastric and oral catheters. A gustatory stimulus of 50 microliters of 1.75 mol.1-1 sucrose was injected into the mouth every 5 min during 60 min. At time zero, 1.7 ml of 3.3 mol.1-1 glucose was injected into the stomach. Typical ingestive facial consummatory responses were observed in response to sweet stimuli prior to the gastric load. Aversive consummatory responses were observed in response to sweet stimuli after the glucose gastric load (negative alliesthesia). The rats were then fasted until they had lost about 14% of their body weight (from 411 +/- 34 g to 353 +/- 28 g). When lean, the rats were subjected to the same gustatory session as in the control period described above. In lean rats the gastric load of glucose was not followed by negative alliesthesia in response to sweet oral stimuli. In the last part of the experiment the rats were fed ad lib and they recovered their initial body weight. When the rats were subjected again to the same gustatory sessions, the gastric load was followed by negative alliesthesia in response to sweet stimuli. Thus, after recovering their initial body weight, the rats displayed the same response as in the control sessions prior to losing weight. These results in rats parallel results obtained in human subjects, and reinforce the hypothesis of the existence of a ponderostat regulating body mass.
Animals↗
Role of set-point theory in body weight.
Explore the source record for details and available documents.
Body Weight↗
Heat loss from the human head during exercise.
Evaporative and convective heat loss from head skin and expired air were measured in four male subjects at rest and during incremental exercise at 5, 15, and 25 degrees C ambient temperature (Ta) to verify whether the head can function as a heat sink for selective brain cooling. The heat losses were measured with an open-circuit method. At rest the heat loss from head skin and expired air decreased with increasing Ta from 69 +/- 5 and 37 +/- 18 (SE) W (5 degrees C) to 44 +/- 25 and 26 +/- 7 W (25 degrees C). At a work load of 150 W the heat loss tended to increase with increasing Ta: 119 +/- 21 (head skin) and 82 +/- 5 W (respiratory tract) at 5 degrees C Ta to 132 +/- 27 and 103 +/- 12 W at 25 degrees C Ta. Heat loss was always higher from the head surface than from the respiratory tract. The heat losses, separately and together (total), were highly correlated to the increasing esophageal temperature at 15 and 25 degrees C Ta. At 5 degrees C Ta on correlation occurred. The results showed that the heat loss from the head was larger than the heat brought to the brain by the arterial blood during hyperthermia, estimated to be 45 W per 1 degree C increase above normal temperature, plus the heat produced by the brain, estimated to be up to 20 W. The total heat to be lost is therefore approximately 65 W during a mild hyperthermia (+1 degrees C) if brain temperature is to remain constant.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Postingestive alliesthesia: the rat tells the same story.
Facial consummatory responses reflecting ingestive and aversive perceptions were studied and quantified in rats chronically implanted with gastric and oral catheters. A gustatory stimulus of 50 microliters of 0.6 mol.l-1 sucrose was injected into the mouth every 5 min during 60 min. At time zero, 5 ml of either 1.1 mol.l-1 glucose or water were injected into the stomach. The typical ingestive facial consummatory responses were observed in response to sweet stimuli prior to all gastric loads, and after the water loads. On the other hand, the aversive consummatory responses were observed in response to sweet stimuli after glucose gastric loads. The reversal of the consummatory responses from ingestive to aversive was stronger with higher concentration of the gastric load, and relatively independent from the volume of the load or the amount of glucose injected intragastrically. These results in rats parallel human postingestive alliesthesia.
Animals↗
Effect of environmental temperature on pleasure ratings of odors and tastes.
Explore the source record for details and available documents.
Adult↗
Sensory pleasure.
In response to a stimulus, a sensation is tridimensional: qualitative, quantitative, and affective. The affective part of sensation, pleasure or displeasure, depends on the qualities of the stimulus. Within a narrow range of intensity, chemical, thermal, and mechanical stimuli are able to arouse pleasure. In addition, pleasure depends on the internal state of the subject. This is easily observed in the case of temperature: pleasure is aroused by a warm stimulus in a hypothermic subject and by a cold stimulus in a hyperthermic subject. This property of a given stimulus to arouse pleasure or displeasure according to the internal state of the subject is termed alliethesia. Alliesthesia is also produced by chemical and mechanical stimuli. Acquired preferences or aversions for alimentary stimuli represent a case of alliesthesia. In the same way, the capacity of any indifferent stimulus to become rewarding, or punishing, by association with some reward or punishment, is also a case of alliethesia. In all cases, pleasure is a sign of a stimulus useful to the subject; displeasure a sign of danger. Usefulness and danger are judged by the central nervous system with reference to homeostasis and the set point of the implied regulation. Pleasure and displeasure thus appear to motivate useful behaviors.
Animals↗
Natural selective cooling of the human brain: evidence of its occurrence and magnitude.
1. The technique of perceptual rating of thermal stimuli was used, in eight human subjects immersed in warm water, in order to appreciate whether they were hypo-, normo- or hyperthermic. Oesophageal, tympanic and forehead skin temperatures were recorded, as also was the temperature of the skin above the angularis oculi vein. Once the subjects gave clearly hyperthermic ratings, one arm was exposed to a 6 m/s wind. After 5--10 min the arm was re-immersed and the face was fanned. 2. Fanning of the arm resulted in lowering of body core temperature. However ratings of thermal stimuli remained hyperthermic. 3. Face fanning decreased forehead skin, angularis oculi vein and tympanic temperatures. Hyperthermic ratings were replaced by normothermic ratings, although oesophageal temperature continued to rise. 4. The upper limit of oesophageal temperature for normothermic ratings was 37.o6 +/- 0.09 degrees C during the control period without fanning. This temperature rose to 37.91 +/- 0.09 degrees C during facial ventilation. 5. These results suggest a selective cerebral cooling due to venous blood returning from facial skin via the ophthalmic vein to the cavernous sinus, where a cooling of arterial blood ascending to the brain can take place.
Body Temperature Regulation↗
Open loop increase in trunk temperature produced by face cooling in working humans.
1. Five human subjects pedalled on a bicyle ergometer for at least two 74 min periods at 10 degrees C ambient temperature. During the first period the subjects cycled for 42 min with face fanning, followed by 32 min with the head thermally insulated. In the second period, this procedure was reversed. Oesophageal (tes), tympanic (Tty), forehead and hand skin temperatures were recorded. In addition, heart rate (H.R.) was counted throughout the experiments, and the technique of perceptual rating of cool and warm stimuli was used in order to appreciate whether the subjects were hypo-, normo-, or hyperthermic. 2. Face fanning resulted in decreased Tty, decreased H.R., mild skin vasoconstriction but increased Tes. 3. Head covering resulted in increased Tty and H.R., while Tes decreased slightly, due to peripheral vasodilatation. 4. When their faces were being fanned so that Tty was low and Tes was high, the subjects gave slightly hypothermic ratings. Ratings were clearly hyperthermic when their heads were covered and Tty was high and Tes was low. 5. The close correlation between vasomotor response and H.R. on the one hand and Tty on the other confirms that this variable is a better approximation of regulated core temperature than Tes. 6. Increase in Tes during face fanning and decrease in Tes during face insulation is new evidence for the possibility of the human brian being cooled during exercise by cool blood returning from the face. 7. We suggest that this selective brain cooling determines the apparent upper resetting of core temperature during exercise while brain temperature remains precisely regulated and constant.
Body Temperature Regulation↗
Bradycardia during face cooling in man may be produced by selective brain cooling.
In human subjects, bradycardia was produced by immersing the subjects' faces in water at 15 degrees C when they were hyperthermic. When they were hypothermic, the same face cooling produced tachycardia. It is suggested that the difference in cardiac response originates in selective brain cooling during hyperthermia, by venous return from the face to the brain, via ophthalmic veins.
Adult↗
[Thermoregulatory behavior].
Explore the source record for details and available documents.
Acclimatization↗
[Reversal of human ophthalmic vein blood flow : selective cooling of the brain].
Direction of blood flow in angularis oculi veins was recorded in humans. In mild hypothermia, blood flow was weak and directed from brain to face. In hyperthermia, however, blood flowed rapidly in the opposite direction, angularis oculi vein collecting cool facial blood and supplying cavernous sinus. Therefore selective cooling of human brain is possible.
Adult↗