Behavioral self warming and cooling of spinal canal by rats

Rats with a chronic thermode implanted in their spinal canal could bar-press to warm or cool their spinal cord. With a “cold” lever, they cooled their spinal canal less in a cold environment than in a warm environment. With a “warm” lever they behaved in the same way, i.e., warmed their spinal canal more in a warm than in a cold environment. In a two-lever situation they pressed the cold and the warm levers alternately in warm environment, but did not press either in cold environment. These results suggest that cold and warm spinal cord provided the rats with rewards of a different nature.     

Cytotoxic lesions of the pontine tegmentum alter the sleep of cats in a cold environment.

The pontine tegmentum of the cat was lesioned by microinjection of a cytotoxin (ibotenic acid) into the brainstem. The sleep-waking cycle of intact cats and cats with the cytotoxic lesions of the pontine tegmentum was studied as a function of ambient temperature. In a cold environment lesioned cats showed a reduction in sleep that was significantly greater than the reduction shown by the intact animals. In a warm environment cats with the tegmental lesions show changes in the sleep-waking cycle similar to intact animals. It is shown that in wakefulness the cytotoxically pontine lesioned cats are more sensitive to cold, but not to heat, than intact animals. The results of these experiments are consistent with the hypothesis that the decreased sleep shown by lesioned animals is due to an alteration in thermoregulation such that the damaged brain interprets ambient temperature to be colder than it is.     

The effects of changes in the environmental temperature on the growth of tail bones in the mouse

The tails of baby mice grow rapidly and independently of environmental temperature because they are kept warm by their mothers. After weaning, at approximately 3 weeks of age, tail growth is strictly related to environmental temperatures. During the first 2 weeks after weaning growth rates of 1.2-1.4 mm/day/tail were seen at 33 degrees and a maximum of 2.43 mm/day/tail was observed in one group kept at 36 degrees. Animals kept at 8 degrees or 4 degrees showed tail growth rates of 0.4 mm/day or less. However, the tails of animals transferred from either hot to cold or cold to hot during their first 2 weeks after weaning immediately grew at the same rate as those of animals kept in these conditions continuously, thus indicating that heat was acting directly on bone growth. The tails of animals kept continuously in the hot environment at 33 degrees completed their growth early so that their growth rate fell below that of controls after about 3 weeks of treatment (when they were 6-7 weeks old) and below that of "cold" animals after about 4 weeks (7-8 weeks old). The tails of the "control" and "cold" animals grew slowly for a very long time, 150-195 days. Even so, because of the very rapid early growth of tails in the hot environment, their final length was always greater than either the "control" or "cold" tails.     

The effects of changes in the environmental temperature on the growth of tail bones in the mouse.

The tails of baby mice grow rapidly and independently of environmental temperature because they are kept warm by their mothers. After weaning, at approximately 3 weeks of age, tail growth is strictly related to environmental temperatures. During the first 2 weeks after weaning growth rates of 1.2-1.4 mm/day/tail were seen at 33 degrees and a maximum of 2.43 mm/day/tail was observed in one group kept at 36 degrees. Animals kept at 8 degrees or 4 degrees showed tail growth rates of 0.4 mm/day or less. However, the tails of animals transferred from either hot to cold or cold to hot during their first 2 weeks after weaning immediately grew at the same rate as those of animals kept in these conditions continuously, thus indicating that heat was acting directly on bone growth. The tails of animals kept continuously in the hot environment at 33 degrees completed their growth early so that their growth rate fell below that of controls after about 3 weeks of treatment (when they were 6-7 weeks old) and below that of "cold" animals after about 4 weeks (7-8 weeks old). The tails of the "control" and "cold" animals grew slowly for a very long time, 150-195 days. Even so, because of the very rapid early growth of tails in the hot environment, their final length was always greater than either the "control" or "cold" tails.     

Effects of altering rostral brain stem temperature on temperature regulation in the Adelie penguin,Pygoscelis adeliae

Summary In 4 Adelie penguins, thermodes were implanted in the rostral brain stem. Two animals were additionally equipped with spinal canal thermodes. At thermoneutral (+ 8 to + 16°C) and cold (–18 to –22° C) ambient conditions, the effects of hypothalamic heating and cooling on the surface temperature of one flipper (skin blood flow), oxygen consumption (metabolic heat production) and esophageal (core) temperature were observed in the conscious animals.—Heating the rostral brain stem induced heat defence responses: Heat production was reduced in the cold and skin vasodilatation was evoked at thermoneutral ambient conditions. As a rule, core temperature fell during rostral brain stem heating.—Cooling the rostral brain stem did not induce clear-cut cold defence responses. On the contrary, strong cooling at thermoneutral ambient conditions induced vasodilatation in the skin. In the cold, even slight degrees of rostral brain stem cooling decreased metabolic heat production. As a rule, core temperature fell when the rostral brain stem was cooled.—It is concluded from the results that thermosensitive structures in the stimulated section of the rostral brain stem of the Adelie penguin contribute to the central temperature signal input in the range of normal to elevated core temperatures. These hypothalamic warm signals appear to be at least as effective as spinal warm signals in controlling skin blood flow and metabolic heat production. The inhibition of ongoing thermoregulatory effector activity by rostral brain stem cooling suggests positive temperature coefficients of the integrative and/or efferent neurons in the hypothalamic temperature regulation center of the Adelie penguin.A preliminary report was given at the 45th meeting (autumn meeting) of the Deutsche Physiologische Gesellschaft, Wien, Sept. 23–26, 1975. Pflügers Arch.359, R57 (1975).     

Effect of localized changes in scrotal and trunk skin temperature on the demand for radiant heat by pigs

Localized warming of the scrotal skin to 42 degrees C decreased the number of operant responses for reinforcements of radiant heat when young pigs were exposed to cold (15 degrees C); warming a similar area of the skin on the trunk had no effect on behaviour. The decrease in responding for heat was more pronounced immediately after a meal than when animals were observed 22 hr after their last meal. Cooling the scrotal or trunk skin to 20 degrees C did not modify operant behaviour. It is concluded that the thermal signal from the scrotum is in disproportion to the surface area of the scrotum indicating either increased concentration of thermal receptors per surface unit of the skin, or processing and amplifying the thermal information along the scrotal-brain neural pathway. The significance of the elicited changes in the demand for radiant heat is discussed in relation to the control of testes temperature.     

The effect of intraventricular injections of noradrenaline, 5-hydroxytryptamine, acetylcholine and tranylcypromine on the ox (Bos taurus) at different environmental temperatures

1. Noradrenaline, 5-hydroxytryptamine (5-HT), acetylcholine and tranylcypromine were injected or infused into the lateral ventricle of the ox. The effects of these drugs on heart and respiration rates, heat production, rectal, skin and hypothalamic temperatures and skin evaporative loss were measured when the animal was exposed to environmental temperatures ranging from -1 degrees C to +30 degrees C.2. Acetylcholine (0.001-2 mg) had no detectable effect on temperature regulation at 20 degrees C.3. In small doses (0.005-0.05 mg) 5-HT had no detectable effect. Larger doses (2-5 mg) given in a cold environment (-1 degrees C) also had no effect but the same doses given in warm environments (15-30 degrees C) caused increases in skin temperatures, skin evaporative loss and respiratory rate, and decreases in rectal and hypothalamic temperatures.4. Infusion of tranylcypromine (0.107 ml./min of a 1 in 50 solution) in a warm environment (20 degrees C) also caused a decrease in rectal temperature after a delay of 1-1(1/2) hr during which no effects were apparent.5. Noradrenaline (2 mg) had no effect on temperature regulation when injected into animals in a warm environment (30 degrees C). When injected (1 mg) into animals in a cold environment (-1 degrees C) shivering stopped and heat production and rectal and hypothalamic temperatures were decreased.6. It is concluded that intraventricular 5-HT and noradrenaline both cause a decrease in body temperature, and it is unlikely that central temperature regulation in the ox is mediated only by these two substances.     

Effect of rapid slight cooling of the skin in various phases of immunogenesis on the immune response

Slight cooling had no effect on heat emission and heat production, but modulated the immune response to antigen in animals. Changes in the immune response upon rapid slight cooling of the skin (by 1.5°C) depended on the phase of immunogenesis corresponding to cold exposure. When cooling was performed immediately after immunization, antibody production increased in the spleen and blood, while antigen binding in the spleen remained unchanged. Cold exposure on day 5 after antigen treatment as well as immunization at the peak of cooling did not modulate antibody production, but increased antigen binding in the spleen. Our findings attest to an important role of the temperature factor in the formation of the immune response, which should be taken into account during vaccination. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 10, pp. 389–392, October, 2006     

Relationships between skin temperature and temporal summation of heat and cold pain

Temporal summation of heat pain during repetitive stimulation is dependent on C nociceptor activation of central N-methyl-d-aspartate (NMDA) receptor mechanisms. Moderate temporal summation is produced by sequential triangular ramps of stimulation that control skin temperature between heat pulses but do not elicit distinct first and second pain sensations. Dramatic summation of second pain is produced by repeated contact of the skin with a preheated thermode, but skin temperature between taps is not controlled by this procedure. Therefore relationships between recordings of skin temperature and psychophysical ratings of heat pain were evaluated during series of repeated skin contacts. Surface and subcutaneous recordings of skin temperatures revealed efficient thermoregulatory compensation for heat stimulation at interstimulus intervals (ISIs) ranging from 2 to 8 s. Temporal summation of heat pain was strongly influenced by the ISIs and cannot be explained by small increases in skin temperature between taps or by heat storage throughout a stimulus series. Repetitive brief contact with a precooled thermode was utilized to evaluate whether temporal summation of cold pain occurs, and if so, whether it is influenced by skin temperature. Surface and subcutaneous recordings of skin temperature revealed a sluggish thermoregulatory compensation for repetitive cold stimulation. In contrast to heat stimulation, skin temperature did not recover between cold stimuli throughout ISIs of 3-8 s. Psychophysically, repetitive cold stimulation produced an aching pain sensation that progressed gradually and radiated beyond the site of stimulation. The magnitude of aching pain was well related to skin temperature and thus appeared to be established primarily by peripheral factors.     

Gabapentin relieves mechanical, warm and cold allodynia in a rat model of peripheral neuropathy

Although recent studies demonstrated the relieving effect of gabapentin on neuropathic pain, the effect has not been sufficiently examined. In the present study, we investigated the effect of gabapentin on mechanical, warm and cold allodynia in a rat model of peripheral neuropathy. Under enflurane anesthesia, animals were subjected to the partial injury of the nerves innervating the tail. Behavioral tests for mechanical, cold and warm allodynia on the tail were performed by von Frey hair (2.0 g) stimulation, 4 and 40 degrees C water immersion, respectively. Intraperitoneal injection of gabapentin (30, 100, 300 mg/kg) significantly alleviated mechanical, warm and cold allodynia in a dose-dependent manner. Our results suggest that gabapentin is an effective agent against mechanical, warm and cold allodynia in a rat model of peripheral neuropathy.     

60例正常人不同部位皮肤的温度觉差异

目的：探讨正常人不同部位皮肤的温度觉阈值的差异性。方法：对60例正常人进行大鱼际肌、食指、脚背皮肤的冷觉、热觉、冷痛觉、热痛觉神经定量感觉测试（QST）并进行比较分析。结果：在冷觉、热觉、热痛觉方面大鱼际肌的感觉比脚更加敏感，而冷痛觉则无明显差异；大鱼际肌皮肤温度觉比食指皮肤更敏感。结论：人体不同部位皮肤的温度觉存在差异性，但同一部位左右两侧相比则差异不明显。     

Comparative cerebral responses to non-painful warm vs. cold stimuli in man: EEG power spectra and coherence.

AIMS: The cerebral processing of painful thermal (heat/cold) stimulation have been extensively studied, but little is known about cerebral activation to non-painful warm and cold stimuli. This study aimed to investigate the comparative EEG effects of warm vs. cold stimulus in man. MATERIALS AND METHODS: The left nondominant hands of 13 healthy male subjects were stimulated by non-painful warm (40-43 degrees C) and cold (12-15 degrees C) water. The somatic sensations were continuously assessed with an analogue visual scale device. EEG data (32 channels) recorded before, during and after the warm and cold stimulations were analysed quantitatively. RESULTS: No significant difference in intensity of sensation was found during warm and cold stimulations. Different patterns of EEG activity were superimposed on the similar background of EEG activation during and after warm and cold stimulations. Significant decrease of theta activity in contra-stimulus frontal region was observed during cold stimulation rather than warm stimulation. EEG power spectra in theta, alpha-1 and alpha-2 bands significantly increased after cold stimulation compared to baseline. EEG coherence in delta, alpha-1 and alpha-2 bands significantly increased in the contra-stimulus hemisphere during stimulations. CONCLUSION: This suggests that similar neural networks may process somatic warm and cold sensory inputs differently and the differential EEG patterns may be encoded by the qualities of thermal stimuli.     

Changes in fasting-induced adrenocortical secretion of cold-acclimated rats

Effect of cold acclimation on fasting-induced adrenocortical and metabolic responses was studied in rats. The animals were acclimated to cold by exposure to 5 degrees C for 4 weeks. The warm control animals were kept at 25 degrees C for the same period. Fasting for 48 h decreased the body weight to the same extent in warm controls (WC) and cold-acclimated rats (CA). Plasma free fatty acids concentration increased by fasting, but the degree of increase did not differ between WC and CA. Plasma glucose level decreased in WC, while it increased in CA by fasting. Plasma corticosterone level was significantly higher in CA than in WC. Fasting increased the level in both groups, and the extent of increase as assessed by 95% confidence interval was significantly greater in CA as compared with that in WC. The present results indicate that fasting-induced glucocorticoid secretion is potentiated by cold acclimation, suggesting a possible role of this hormone in some metabolic changes in fasting.     

Rates of energy substrates utilization during human cold exposure

Summary Although it is well established in animals that acute cold exposure markedly increases the oxidation of energy substrates, the absolute quality and quantity of substrate oxidation is poorly understood in humans. This study compared the rates of substrate utilization in seven healthy young men exposed to both the warm (control exposure at 29° C; semi-nude, 14 h fasted) and to the cold for 2 h (10° C, 1 m·s⁻¹ wind velocity). Substrate utilization was calculated using indirect calorimetry and the nonprotein respiratory exchange ratio, which was derived from the urinary urea nitrogen output. Cold exposure induced a 3.1±0.2° C drop in mean body temperature and a body heat debt of 825.9±63.3 kJ (p<0.01). These parameters remained essentially unchanged in the warm. Cold exposure elevated the 2 h energy expenditure 2.46-fold in comparison to the warm (p<0.01). This cold-induced thermogenesis was accompanied by increases of 588% in carbohydrate oxidation (p<0.01) and 63% in fat oxidation (p<0.05), whereas protein oxidation remained unchanged. Although the greatest proportion of the energy expenditure in the warm was derived from lipid (59%), carbohydrate oxidation represented the major fuel for thermogenesis in the cold, since it accounted for 51% of the corresponding total energy expenditure. The results demonstrate that cold exposure causes a much greater increase in the utilization of carbohydrate than lipid. It is suggested that these substrates are directly utilized for thermogenesis in the shivering skeletal muscles. This is DCIEM paper no. 89-P-/6     

Fat metabolism and heat production in young rabbits

1. The rates of oxygen consumption were measured in 6-8-day-old rabbits at 34 and 15 degrees C after varying periods of starvation and cold exposure. At the start of the experiment the rabbits had been fasted for 24 hr. Eight rabbits were studied immediately, six after 24 and six after 48 hr in a cold environment (20 degrees C), and twelve after a further 48 hr in a warm environment (34 degrees C). All the animals had a similar increase in oxygen consumption during the final hour of cold exposure (15 degrees C).2. The rabbits kept at 20 degrees C lost 83% of the fat stored in their brown adipose tissue within 24 hr and a further 11% in the next 24 hr. The fat content of white adipose tissue had fallen by 75% at 48 hr. In contrast rabbits kept unfed at 34 degrees C had lost 47% of the fat in brown adipose tissue and 44% of the fat in white adipose tissue after 48 hr.3. In six rabbits subcutaneous thermocouples demonstrated that local heat production continued in brown adipose tissue after 48 hr cold exposure.4. In the rabbits kept at 34 degrees C the final cold exposure caused a large increase in the serum free fatty acid and glycerol concentrations. Much lower concentrations were found in rabbits kept at 20 degrees C.5. The results show that the fat stored in the brown adipose tissue of young rabbits exposed to cold is preferentially used for heat production. When this store of fat is exhausted, brown adipose tissue still produces heat presumably by oxidizing fat and glucose taken from the circulation.     

Bilateral hand/wrist heat and cold hyperalgesia,but not hypoesthesia,in unilateral carpal tunnel syndrome

The aim of the current study was to evaluate bilaterally warm/cold detection and heat/cold pain thresholds over the hand/wrist in patients with carpal tunnel syndrome (CTS). A total of 25 women with strictly unilateral CTS (mean 42 ± 10 years), and 20 healthy matched women (mean 41 ± 8 years) were recruited. Warm/cold detection and heat/cold pain thresholds were assessed bilaterally over the carpal tunnel and the thenar eminence in a blinded design. Self-reported measures included both clinical pain history (intensity, location and area) and Boston Carpal Tunnel Questionnaire. No significant differences between groups for both warm and cold detection thresholds in either carpal tunnel or thenar eminence (P > 0.5) were found. Further, significant differences between groups, but not between sides, for both heat and cold pain thresholds in both the carpal tunnel and thenar eminence were found (all P < 0.001). Heat pain thresholds (P < 0.01) were negatively correlated, whereas cold pain thresholds (P < 0.001) were positively correlated with hand pain intensity and duration of symptoms. Our findings revealed bilateral thermal hyperalgesia (lower heat pain and reduced cold pain thresholds) but not hypoesthesia (normal warm/cold detection thresholds) in patients with strictly unilateral CTS when compared to controls. We suggest that bilateral heat and cold hyperalgesia may reflect impairments in central nociceptive processing in patients with unilateral CTS. The bilateral thermal hyperalgesia associated with pain intensity and duration of pain history supports a role of generalized sensitization mechanisms in the initiation, maintenance and spread of pain in CTS.     

Activity of warm receptors inBoa constrictor raised at various temperatures

Nine young specimens ofBoa constrictor were raised for 4 years in a climatic chamber at an ambient temperature of 30°C under artificial illumination. Seven boas were raised at 23°C under the same conditions. At the end of the adaptation period, mean body weight of the warm adapted boas was 9.6±0.8 kg and that of the cold adapted ones 5.9±0.3 kg.Static and dynamic activities of single specific trigeminal warm fibers were recorded when applying static temperatures of 20, 23, 26, 29, 32, 35 and 38°C and dynamic warming steps of 3°C, the initial temperatures being 20, 23, 26, 29, 32 and 35°C. Eighty-nine warm fibers were examined in the warm adapted and 62 fibers in the cold adapted group.The average static frequencies between 29 and 35°C were higher in the warm adapted animals, the respective values for both groups at 32°C being 16.5 and 12s^–1. The average peak frequencies for dynamic warming were 80s^–1 for both groups, but the temperature of the dynamic maximum was shifted from 32°C in the warm adapted to 26°C in the cold adapted boas. At 32 and 35°C the average peak frequencies were higher in the warm adapted animals.The whole fiber population contained various groups with static maxima between 23 and 35°C. Long-term adaptation modified mainly the static and dynamic discharge of the low-temperature fibers. The fiber group with a static maximum at 29°C showed a crossing of the static and dynamic frequency-temperature curves. In the higher temperature range the warm adapted animals had a higher and in the lower temperature range a lower static and dynamic frequency.     

Differential heating of trunk and extremities

Summary Experiments in which the whole human body was heated or cooled are compared with others in which one extremtiy (arm or leg) was simultaneously cooled or heated. With a warm load on the rest of the body resulting in general sweating, a cold load on one extremity did not evoke local shivering; with general body cooling, heating one limb did not stop the shivering. Skin temperatures of the other parts of the body were not influenced by warming or cooling one extremity. Evaporative heat loss was influenced by local, mean skin and core temperature, whereas shivering did not depend on local temperature, and vasomotor control seemed to be controlled predominantly by central temperatures. A cold load on an extremity during whole body heating in most cases induced an oscillatory behaviour of core temperature and of the evaporative heat loss from the body and the extremity.It is assumed that local, mean skin and core temperatures influence the three autonomous effector systems to very different degree.Supported by the Deutsche Forschungsgemeinschaft, SFB 114     

Behavioral and autonomic temperature regulation in competition with food intake and water balance of pigeons

Four adult pigeons were conditioned to adjust to a preferred ambient temperature and to receive food or water by instrumental responses. The experiments were performed in a Skinner-box under heat load conditions. Each session lasted 1 h. The birds were deprived of food and water for several days before the actual experiments with the exception of the control tests.The exposure to different heat loads (50°, 55° and 60° C) effected both an increase in the responses for cold reward and a rise in respiratory evaporation (panting). The combined effort of behavioral and autonomous responses resulted in constant body temperature (42° C) under the three heat conditions (Fig. 1).The food deprivation effected a preference of instrumental response for feeding and a negligence of behavioral temperature regulation, whereby a slight hyperthermia resulted in the first part of heat exposure (55° C, Fig. 2).Water deprivation reduced the rate of respiration and simultaneously forced the response for cold reward, through which the deep body temperature was adjusted to the control level of 42° C (Fig. 3).Intragastric infusion of 20 ml NaCl (0.8 mol) half an hour before starting heat load (55° C) produced the same result as water deprivation. Whereas infusion of isoosmotic KCl solution did not produce any deviation from the control tests (Fig. 4).The results show competition between the conditioned thermal behaviour and the motivation of feeding or drinking in animals which may permit to compare the conditioned thermal behaviour with the natural kinds of behavioral temperature regulation. The non-appearance of hyperthermia under conditions of water deprivation and NaCl loading may indicate that the animals are able to use the autonomous and the behavioral types of heat defence responses to a greater or lesser extent as circumstances demand. This question seems to be of great interest and is fully discussed here.     

The short term effects of a supra-lethal dose of irradiation and changes in the environmental temperature on the growth of tail bones of the mouse

The growth and histological features of the tail vertebrae of young mice (31 day old) were observed for 48 h after transference from a cold (8 degrees) to a hot (33 degrees) environment. Some mice received a massive (5000 rad) dose of X-ray to the tail. Less than 2 h after housing the animals in the heat there was a period of very rapid growth lasting 12 h after which time growth slowed but was still much greater than the animals in the cold. Animals whose tails were irradiated (and also put in the heat) showed the same rapid growth for 12 h but after this growth ceased. Evidence is provided which shows that the initial rapid growth in the heat is due to an abnormal increase in the linear dimensions of the hypertrophic cells of the growth plate. This is most marked in the hot-irradiated animals.