Effect of ketamine on thermoregulation in rats

1978 ◽  
Vol 56 (6) ◽  
pp. 963-967 ◽  
Author(s):  
M. T. Lin ◽  
C. F. Chen ◽  
I. H. Pang
Keyword(s):  
Drug Treatment ◽  
Skin Temperature ◽  
Rectal Temperature ◽  
Heat Production ◽  
Intraperitoneal Administration ◽  
Metabolic Heat Production ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Dose Dependent ◽  
Skin Temperatures

Intraperitoneal administration of ketamine produced dose-dependent hypothermia at the ambient temperatures (Ta) of both 8 and 23 °C in unanesthetized rats. At a Ta of 8 °C, the hypothermia was brought about solely by a decrease in metabolic heat production. There were no changes in either the tail skin temperature (Ttail) or the sole skin temperature (Tsole). At a Ta of 23 °C, the hypothermia was due to an increase in Ttail, an increase in Tsole, and a decrease in metabolic heat production. However, at a Ta of 31 °C, there were no changes in rectal temperature in response to ketamine application, since neither heat production nor skin temperatures (e.g., Ttail and Tsole) was affected by ketamine at this Ta. The data indicate that the effect of the drug treatment may be to decrease heat production and (or) increase heat loss.

Effects of phentolamine on thermoregulatory functions of rats to different ambient temperatures

1979 ◽  
Vol 57 (12) ◽  
pp. 1401-1406 ◽  
Author(s):  
M. T. Lin ◽  
Andi Chandra ◽  
T. C. Fung
Keyword(s):  
Heat Loss ◽  
Rectal Temperature ◽  
Heat Production ◽  
Room Temperature ◽  
Metabolic Heat Production ◽  
Central Component ◽  
Evaporative Heat Loss ◽  
Central Administration ◽  
Ambient Temperatures ◽  
Metabolic Heat

The effects of both systemic and central administration of phentolamine on the thermoregulatory functions of conscious rats to various ambient temperatures were assessed. Injection of phentolamine intraperitoneally or into a lateral cerebral ventricle both produced a dose-dependent fall in rectal temperature at room temperature and below it. At a cold environmental temperature (8 °C) the hypothermia in response to phentolamine was due to a decrease in metabolic heat production, but at room temperature (22 °C) the hypothermia was due to cutaneous vasodilatation (as indicated by an increase in foot and tail skin temperatures) and decreased metabolic heat production. There were no changes in respiratory evaporative heat loss. However, in the hot environment (30 °C), phentolamine administration produced no changes in rectal temperature or other thermoregulatory responses. A central component of action is indicated by the fact that a much smaller intraventricular dose of phentolamine was required to exert the same effect as intraperitoneal injection. The data indicate that phentolamine decreases heat production and (or) increases heat loss which leads to hypothermia, probably via central nervous system actions.

scholarly journals Human thermoregulatory responses during serial cold-water immersions

1998 ◽  
Vol 85 (1) ◽  
pp. 204-209 ◽  
Author(s):  
John W. Castellani ◽  
Andrew J. Young ◽  
Michael N. Sawka ◽  
Kent B. Pandolf
Keyword(s):  
Body Temperature ◽  
Rectal Temperature ◽  
Heat Production ◽  
Alternative Explanation ◽  
Cold Water ◽  
Metabolic Heat Production ◽  
Normal Body Temperature ◽  
Repeat Trial ◽  
Metabolic Heat ◽  
Made In

This study examined whether serial cold-water immersions over a 10-h period would lead to fatigue of shivering and vasoconstriction. Eight men were immersed (2 h) in 20°C water three times (0700, 1100, and 1500) in 1 day (Repeat). This trial was compared with single immersions (Control) conducted at the same times of day. Before Repeat exposures at 1100 and 1500, rewarming was employed to standardize initial rectal temperature. The following observations were made in the Repeat relative to the Control trial: 1) rectal temperature was lower and heat debt was higher ( P < 0.05) at 1100; 2) metabolic heat production was lower ( P < 0.05) at 1100 and 1500; 3) subjects perceived the Repeat trial as warmer at 1100. These data suggest that repeated cold exposures may impair the ability to maintain normal body temperature because of a blunting of metabolic heat production, perhaps reflecting a fatigue mechanism. An alternative explanation is that shivering habituation develops rapidly during serially repeated cold exposures.

Acclimatization of calves to a hot dry environment

1959 ◽  
Vol 52 (3) ◽  
pp. 296-304 ◽  
Author(s):  
W. Bianca
Keyword(s):  
Heart Rate ◽  
Respiratory Rate ◽  
Rectal Temperature ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Metabolic Heat ◽  
Physiological Reactions

1. Three calves were individually exposed in a climatic room to an environment of 45° C. dry-bulb and 28° C. wet-bulb temperature for 21 successive days up to 5 hr. each day.2. In the 21-day period, mostly during the first half of it, the following changes in the physiological reactions of the animals were observed: progressive reductions in rectal temperature, in heart rate and in respiratory rate with a change of breathing from a laboured to a less laboured type.3. It was suggested that a decrease in metabolic heat production might play a part in the observed acclimatization.

Heat tolerance in dehydrated steers

1966 ◽  
Vol 66 (1) ◽  
pp. 57-60 ◽  
Author(s):  
W. Bianca
Keyword(s):  
Body Weight ◽  
Respiratory Rate ◽  
Skin Temperature ◽  
Heat Tolerance ◽  
Normal Level ◽  
Heat Production ◽  
Feed Intake ◽  
Metabolic Heat Production ◽  
Metabolic Heat ◽  
Initial Rise

Six steers kept in an environment of 15°C. were deprived of water for four consecutive days. This treatment, by depressing appetite, caused a reduction in voluntary hay intake to one-quarter of its normal level and a decrease in body weight by 10%.In spite of this reduction in feed intake, which must have been accompanied by a fall in metabolic heat production, the animals were less able to tolerate heat than when they were normally watered: during 4 hr. exposures to temperatures of 40.0°C. dry bulb and 32.5°C. wet bulb the waterdepleted animals showed higher values of rectal and skin temperature. This was associated with a slower initial rise and lower final values of respiratory rate (130 versus 155 respirations/min.).

Observations on the effect of salicylate in fever and the regulation of body temperature against cold

1976 ◽  
Vol 54 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Q. J. Pittman ◽  
W. L. Veale ◽  
K. E. Cooper
Keyword(s):  
Body Temperature ◽  
Skin Temperature ◽  
Rectal Temperature ◽  
Heat Production ◽  
Intravenous Infusion ◽  
Sodium Salicylate ◽  
Single Injection ◽  
Continuous Intravenous Infusion ◽  
Skin Temperatures

Prostaglandins appear to be mediators, within the hypothalamus, of heat production and conservation during fever. We have investigated a possible role of prostaglandins in the nonfebrile rabbit during thermoregulation in the cold. Shorn rabbits were placed in an environment of 20 °C, and rectal and ear skin temperatures, shivering and respiratory rates were measured. A continuous intravenous infusion of leucocyte pyrogen was given to establish a constant fever of approximately 1 °C, and after observation of a stable febrile temperature for 90 min, a single injection of 300 mg of sodium salicylate, followed by a 1.5 mg/min infusion was then given. After the salicylate infusion was begun, rectal temperature began to fall, and reached nonfebrile levels within 90 min. Shivering activity ceased, respiratory rates increased, and in two animals, ear skin temperature increased. When these same rabbits were placed in an environment of 10 °C, at a time they were not febrile, and an identical amount of salicylate was given, rectal and ear skin temperatures, shivering and respiratory rates did not change. These results indicate that prostaglandins do not appear to be involved in heat production and conservation in the nonfebrile rabbit.

Acclimatization of calves to a hot humid environment

1959 ◽  
Vol 52 (3) ◽  
pp. 305-312 ◽  
Author(s):  
W. Bianca
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Respiratory Rate ◽  
Skin Temperature ◽  
Rectal Temperature ◽  
Heat Production ◽  
Metabolic Heat ◽  
Hot Environment ◽  
Humid Environment ◽  
Physiological Reactions

1. Three calves were exposed in a climatic room to an environment of 40° C. dry-bulb and 38° C. wet-bulb temperature for up to 110 min. each day for 1-2 weeks.2. These exposures produced progressive changes in the physiological reactions of the animals to heat:(a) Rectal temperature and skin temperature (for a given time of exposure) declined. In consequence there was a marked increase in the tolerance time, i.e. in the time for which the animals could withstand the hot environment before reaching a rectal temperature of 42° C.(b) Respiratory rate rose earlier and assumed higher levels (for given levels of body temperature).(c) Heart rate decreased markedly.3. These changes are discussed in relation to heat loss and heat production and have been interpreted as reflecting chiefly a reduction in the metabolic heat production of the animals.

Influence of Respiratory Heat Transfer on Thermogenesis and Heat Storage after Cold Immersion

1982 ◽  
Vol 63 (2) ◽  
pp. 127-135 ◽  
Author(s):  
J. B. Morrison ◽  
M. L. Conn ◽  
P. A. Hayes
Keyword(s):  
Heat Production ◽  
Heat Input ◽  
Heat Storage ◽  
Metabolic Heat Production ◽  
Central Temperature ◽  
The Core ◽  
Metabolic Heat ◽  
Male Subjects ◽  
Skin Temperatures ◽  
Cold Immersion

1. Ten male subjects were cooled on three occasions to a rectal temperature of 35°C by immersion to the neck in water at 11·3°C. The subjects were rewarmed for 60 min, once by metabolic heat production alone (shivering), once by inhalation rewarming with spontaneous breathing of saturated air at 47°C (control) and once by inhalation rewarming with ventilation regulated at 40 litres/min by respiring a controlled fraction of CO2 (hyperventilation). 2. Metabolic heat production was substantially reduced by inhalation rewarming (P < 0·05), from 913 kJ when shivering to 766 kJ (control) and 613 kJ when hyperventilating. The fall in metabolic heat production was greater than the corresponding respiratory heat gain, which increased from a loss of 41 kJ when shivering to gains of 85 kJ (control) and 169 kJ (hyperventilation). 3. As differences in mean skin temperatures were small (<1·0°C), it is concluded that the lower metabolic heat production in response to increased respiratory heat input must result from more rapid central temperature gains. This conclusion is supported by the relative values of rectal and tympanic temperatures. It was calculated that the percentage of the total heat supply which was donated to the core increased from 13% during shivering to 16% for the control and 23% in hyperventilation. Results imply that respiratory heat input is more efficient than metabolic heat production in elevating central temperature.

The effects of temperature and relative humidity on the thermoregulatory responses of grouped and isolated neonate chicks

1976 ◽  
Vol 86 (1) ◽  
pp. 35-43 ◽  
Author(s):  
B. H. Misson
Keyword(s):  
Body Size ◽  
Relative Humidity ◽  
Rectal Temperature ◽  
Heat Production ◽  
Water Loss ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Effects Of Temperature

SUMMARYMeasurements of O2 consumption (Vo2), CO2 production (VCO2) evaporative water loss and rectal temperature (Tr) have been made and metabolic heat production (H), evaporative heat loss (—E) and respiratory quotient (RQ) calculated with individual and groups of 1-day-old chicks at constant ambient temperatures (To) in the range 20—43 °C and 80 or 20% relative humidity (R.H.).Minimal metabolism (10·7 kJ/kgJ/h) occurred at 35 °C.One-day-old chicks act as heterotherms outside the zone of minimal metabolism since neither H nor —E are sufficiently developed mechanisms to maintain homeothermy.Huddling allows chicks to maintain a higher TT at a lower H per unit metabolic body size.Reducing E.H. from 80 to 20% raised the upper temperature survival limit (UTSL) from 41·5 to 43 °C.Panting was initiated when Ta = 38 °C and Tr was between 39·5 and 39·9 °C.

EFFECT OF FEED TEMPERATURE ON COLD SUSCEPTIBILITY OF CATTLE AND SHEEP

1990 ◽  
Vol 70 (1) ◽  
pp. 191-197 ◽  
Author(s):  
A. M. NICOL ◽  
B. A. YOUNG
Keyword(s):  
Critical Temperature ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Lower Critical Temperature ◽  
Temperature Heat ◽  
Feed Temperature ◽  
Key Words Cold ◽  
Cattle And Sheep

The metabolic heat production of steers was measured at ambient temperatures of +10, −8 and −20 °C following their consumption of 15-kg turnip bulbs (Brassica napus) with a temperature of 27, 2 or −8 °C, or 10-kg turnips with a temperature of 2 °C followed by 1 kg hay. Metabolic heat production was elevated 13–80% after eating the cold and frozen turnips when steers were exposed to −8 °C and 35–80% when exposed to −20 °C. Sheep fed 20, 35, 55, 80 and 110 g pelleted ration per kg−0.75 d−1, accompanied by a ruminal infusion of water at 38 or 2 °C at a volume required to simulate a 10% dry matter feed had their metabolic heat production measured at +10 and −20 °C. Heat production was significantly increased at −20 °C for only the 2 °C infusion although with the 38 °C infusion at the lower feed intake levels, metabolic heat production was higher by up to 37% at an ambient temperature of −20 °C than at +10 °C. The lower critical temperature of the steers after ingestion of the turnips was estimated to be −4.5, −2.4, +3.2 and +13.9 °C forthe27, 2 + hay, 2 and −8 °C turnips, respectively. The lower critical temperature of sheep was raised by 1, 11, 31, 25 and > 22 °C by the ruminal infusion of water at 2 °C compared to water at 38 °C in sheep fed 20, 35, 55, 80 and 110 g feed kg−0.75 d−1, respectively. Key words: Cold, temperature, heat production, cattle, sheep

Regulation of body temperature in the Budherygah, Melopsittacus undulatus

1976 ◽  
Vol 24 (1) ◽  
pp. 39 ◽  
Author(s):  
WW Weathers ◽  
DC Schoenbaechler
Keyword(s):  
Body Temperature ◽  
Heat Production ◽  
Water Loss ◽  
Standard Metabolic Rate ◽  
Evaporative Water Loss ◽  
Metabolic Heat Production ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Metabolic Water

The standard metabolic rate of budgerygahs, determined during October and November, was 30% lower at night (1.96 ml O2 g-1 h-1) than during the day (2.55 ml O2 g-1h-1 ). The zone of thermal neutrality extended from 29 to 41�C. At ambient temperatures (Ta) below 29�C, oxygen consumption [V(02)] increased with decreasing Ta according to the relation V(02) (ml O2 g-1 h-1) = 5.65 - 0.127Ta. At Ta's between 0 and 16�C, body temperature (Tb) averaged 37.7�C (which is low by avian standards) and was independent of Ta. Above 20�C, Tb increased with increasing Ta, and within the zone of thermal neutrality Tb increased by approximately 4�C. The relation between V(O2) and Tb within the zone of thermal neutrality is described by the equation V(O2 = 6.29 - 0.105 Tb. This ability to decrease metabolic heat production while Tb rises could contribute to the water economy of budgerygahs. At moderate Ta's the rate of evaporative water loss of budgerygahs is only 60% that predicted for a 31 g bird. At Ta's below 14�C budgerygahs can balance evaporative water loss with metabolic water production. At 45�C Tb was between 1.0 and 5.0�C below Ta, and evaporative cooling accounted for up to 156% of metabolic heat production. At high Ta's budgerygahs appear to augment evaporation by lingual flutter.

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