Effects of salicylate and indomethacin in nonfebrile rats at different ambient temperatures

Dietary fatty acid composition influences tissue lipid profiles and regulation of body temperature in Japanese quail

Many avian species reduce their body temperature (T(b)) to conserve energy during periods of inactivity, and we recently characterized how ambient temperature (T(a)) and nutritional stress interact with one another to influence physiologically controlled hypothermic responses in Japanese quail (Coturnix japonica). In the present study, we examined how the fatty acid (FA) composition of the diet influences the FA composition of phospholipids in major organs and how these affect controlled hypothermic responses and metabolic rates in fasted birds. For 5 weeks prior to fasting, quail were fed a standard diet and gavaged each morning with 0.7 ml of water (control), or a vegetable oil comprising saturated fatty acids (SFA; coconut oil), or unsaturated fatty acids (UFA; canola oil). Birds were then fasted for 4 days at a T(a) of 15°C. We found that, while fasting, both photophase and scotophase T(b) decreased significantly more in the SFA treatment group than in the control group; apparently the former down-regulated their T(b) set point. This deeper hypothermic response was correlated with changes in the phospholipid composition of the skeletal muscle and liver, which contained significantly more oleic acid (18:1) and less arachidonic acid (20:4), respectively. Our data imply that these two FAs may be associated with thermoregulation.

Eicosanoids in non-febrile thermoregulation

Eicosanoids are a large group of oxygenated fatty acids [viz., omega-3 (n-3) and omega-6 (n-6) C(20) polyunsaturated fatty acids], the most important source being the omega-6 cell membrane-derived arachidonic acid (AA). Eicosanoids are produced by many different cell types; through their ligation and activation of specific membrane-bound and intracellular receptors, they regulate myriad physiological and pathological functions, including body temperature (T(b)). However, the thermoregulatory role of eicosanoids has mainly been associated with fever, i.e., with T(b) changes induced during illness; their importance in maintaining T(b) during health remains unclear. In this review, we address the question of whether AA-derived mediators (viz., prostaglandins, leukotrienes and other lipoxygenase metabolites, and the endocannabinoids/endovanilloids) are involved in normal (non-febrile) thermoregulation. We conclude that although prostaglandin E(2) is a principal mediator of fever, it is unlikely to be involved in the maintenance of normal T(b). Other eicosanoids reviewed also seem to have no major role in non-febrile thermoregulation. Newly discovered signaling pathways for eicosanoids, such as the endovanilloid system, may participate in thermoregulation, but further studies are required before definitive conclusions can be made.

Evaluation in rats of the somnogenic, pyrogenic, and central nervous system depressant effects of muramyl dipeptide

Muramyl dipeptide increased sleep during the dark-phase, but not the light-phase of the rats' sleep-awake cycle. This circadian variation may be due to the inability of MDP to increase sleep over the high baseline levels of sleep that occur during the light-phase. However, MDP was pyrogenic during the light-phase, indicating it was pharmacologically active. In the dark-phase, MDP was not pyrogenic, but when compared to concurrent vehicle-treated rats, rats treated with MDP did not demonstrate as great a fall in body temperature. At approximately equisomnogenic doses, MDP produced less potentiation of ethanol-induced loss of righting reflex than triazolam, indicating it produces less non-specific central nervous system depressant effects. These data indicate the possibility of a new generation of hypnotic agents derived from muramyl peptides.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC and related agents: II

Antipyretics, in particular acetaminophen, aspirin and ibuprofen, constitute the single most important class of drugs used therapeutically for an effect on body temperature. Hallucinogens exert prominent actions on the central nervous system, and it is not surprising that, like so many other centrally-acting agents, they too often affect temperature. This compilation primarily covers the considerable amount of data published from 1981 through 1985 on the interactions of these drugs and thermoregulation, but data from many earlier papers not included in a previous compilation are also tabulated. The effects of agents not classically considered as antipyretics on temperatures of febrile subjects are also covered. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent.

Indomethacin pretreatment inhibits fever after anodal, but not cathodal, medial preoptic lesions in rats

Pretreatment with indomethacin (15 mg/kg) prevented the fever occurring in unanesthetized rats immediately after unilateral anodal electrolytic lesions of the medial preoptic area. The drug had no effect on the fever if given before cathodal lesions. If given after the lesions, when the fever had begun to develop, indomethacin lowered anodal body temperature back to baseline for varied lengths of time and attenuated cathodal fever.