Central effects of prostaglandins E2, A1 and F2alpha in adult fowls

Effect of central and peripheral injection of prostaglandin E2 and F2α on feeding and the crop-emptying rate in chicks

Prostaglandins (PGs) have been shown to cause several physiological changes in mammals including anorexia, awakening and sleeping, change in digestive function, and activation of the hypothalamus-pituitary-adrenal gland (HPA) axis. However, there is a paucity of information about the effect of PGs on physiological parameters in birds. The purpose of the present study was to clarify whether intracerebroventricular (ICV) and intraperitoneal (IP) injections of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) affect feeding, voluntary movement, crop-emptying rate, and corticosterone release in chicks (Gallus gallus). ICV injection of either PGE2 or PGF2α (2 and 4μg) significantly decreased food intake in chicks. The anorexigenic effect was also observed after IP injection of the PGs. Voluntary movement was significantly suppressed by ICV injection of PGE2 or PGF2α, although the time-course change was different between the two. In contrast, IP injection of the PGs had no or less effect on voluntary movement. Both ICV and IP injection of PGE2 significantly retarded the crop-emptying rate, whereas PGF2α significantly lowered the crop-emptying rate only after IP injection. The plasma corticosterone concentration significantly increased after ICV and IP injection of PGE2, whereas PGF2α had no effect. These results suggest that central and peripheral PGs are involved in the regulation of appetite, voluntary movement, food passage in the digestive tract, and activation of the HPA axis in chicks, although the effects depend on the site of action and type of PGs.

Brain IL-6- and PG-dependent actions of IL-1β and lipopolysaccharide in avian fever

There is no persuasive evidence of a correlation between proinflammatory cytokines and avian fever. In this study, for the first time, we use avian cytokines to investigate a role for proinflammatory cytokines in the central component of avian fever. IL-1β and IL-6 injected intracerebroventricularly into Pekin ducks ( n = 8) initiated robust fevers of equal magnitude and duration, although there was a significant difference in the latency to a febrile response. In addition, the IL-1β-induced fever could be abolished with an intracerebroventricular injection of antibodies to avian IL-6 or an oral administration of a PG synthesis inhibitor. Our findings indicate the following sequence of events within the central component of the avian febrile mechanism: IL-1β gives rise to bioactive IL-6, which stimulates an accelerated synthesis of PGs, and these PGs then adjust the sensitivity of warm-sensitive neurons in the avian brain stem to mediate fever. Yet PGE2 was not upregulated in the cerebrospinal fluid of ducks made febrile with LPS. We conclude that IL-1β and IL-6 may well mediate fever by instigating an accelerated synthesis of brain-derived PG, of a class other than PGE2, or that IL-6 serves as one of the terminal mediators of the avian febrile response.

Physiology of temperature regulation: comparative aspects

Few environmental factors have a larger influence on animal energetics than temperature, a fact that makes thermoregulation a very important process for survival. In general, endothermic species, i.e., mammals and birds, maintain a constant body temperature (Tb) in fluctuating environmental temperatures using autonomic and behavioural mechanisms. Most of the knowledge on thermoregulatory physiology has emerged from studies using mammalian species, particularly rats. However, studies with all vertebrate groups are essential for a more complete understanding of the mechanisms involved in the regulation of Tb. Ectothermic vertebrates-fish, amphibians and reptiles-thermoregulate essentially by behavioural mechanisms. With few exceptions, both endotherms and ectotherms develop fever (a regulated increase in Tb) in response to exogenous pyrogens, and regulated hypothermia (anapyrexia) in response to hypoxia. This review focuses on the mechanisms, particularly neuromediators and regions in the central nervous system, involved in thermoregulation in vertebrates, in conditions of euthermia, fever and anapyrexia.

Role of Prostaglandin E2 and Indomethacin in the Febrile Response of Pigeons

Intravenous (i.v.) injection of 10 microg/kg Escherichia coli lipopolysaccharide (LPS), applied at 13:00, evoked in pigeons a biphasic rise of core temperature (T(core)), so that LPS induced with a latency of 30 min first a decrease of T(core), and 90 min after LPS, T(core) increased, obtaining maximum values from 18:00 to 20:00. Prostaglandins have been considered to be importantly involved in fevers in mammals. To investigate an involvement of prostaglandins in the cyclic variations of T(core) in birds, pigeons were injected i.v. with either 10 mg/kg indomethacin (INDO) or 100 mg/kg aspirin, or they were treated with intracerebroventricular (i.c.v.) injections of 100 microg/kg INDO at various times before or after LPS. When INDO or aspirin was i.v. injected 30 or 15 min before LPS, it diminished the initial decrease of T(core) by more than 50%, whereas the i.v. injection of these drugs 2 and 4 h after LPS did not affect the febrile rise of T(core). i.c.v. injections of INDO given either before or after LPS neither influenced the initial drop of T(core) nor the following febrile hyperthermia. Both the i.v. injection of 1 mg/kg prostaglandin E(2) (PGE(2)) and the i.c.v. injection of 1 microg/kg PGE(2) lowered T(core). Our observations suggest that prostaglandins are not involved in the febrile elevation of T(core) in pigeons, but appear to participate in the decrease of T(core), which shortly follows the i.v. injection of LPS. This initial drop of T(core) following LPS may be caused by a peripheral action of prostaglandins because it was not influenced by the i.c.v. injection of indomethacin.

Effects of endotoxin, interleukin-1 beta and prostaglandin injections on fever response in broilers

1. The effect of endotoxin, interleukin-1 beta and prostaglandin on fever response was studied in 80 broilers (Hubbard strain). Endotoxin (E. coli, LPS) was injected i.v. (1.5 micrograms/kg) and icv (1.5 micrograms/bird); interleukin-1 (human recombinant IL-1 beta, 80 pg/bird) and prostaglandin E2 (5 micrograms/bird) were injected icv. Indomethacin (10 mg/kg, i.v.) pretreatment was also used before i.v. endotoxin injection. 2. The results showed that indomethacin was able to block the fever response induced by i.v. endotoxin injection, and IL-1 beta and PGE2 were both effective in producing fever when injected icv. These data suggest a prostaglandin-mediated fever response by broilers, and also a strong evidence of the involvement of endogenous pyrogen (interleukin-1) in fever response in birds.

Central and peripheral prostaglandins are involved in sickness behavior in birds

Many of the behavioral manifestations of mammals and birds following infection are now recognized as important mechanisms for maintaining homeostasis and promoting recovery. To investigate the role of prostaglandins (PGs) in the behavioral and physiological effects of lipopolysaccharide (LPS) in birds, chickens were injected with indomethacin (Ind) peripherally (IP, 5 mg) or centrally (ICV, 100 micrograms) and their behavior and body temperature following a challenge IP injection of LPS (2.5 mg) were assessed at 1 and 2 h, respectively. Pretreatment with Ind IP or ICV completely inhibited the hyperthermia caused by LPS. Ind injected IP but not ICV significantly attenuated the LPS-induced anorexia. The drowsiness caused by LPS was completely inhibited by Ind injected IP and partially inhibited by Ind administered ICV. These results are interpreted to indicate that LPS induces hyperthermia in the chicken by activating a PG system in the brain. Peripheral PGs appear to be involved in the anorectic response to LPS, whereas drowsiness caused by LPS may involve both peripheral and central PGs. These data are consistent with the hypothesis that multiple PG systems are activated during the acute-phase response, which may explain the dissociation between mechanisms controlling the behavioral and physiological responses to infection.

Prostaglandins E2 and D2 have little effect on rabbit sleep

Prostaglandins (PGs) are hypothesized to be involved in sleep regulation; PGE2 and PGD2 are major PGs in the hypothalamus of many species and are proposed to reciprocally promote wakefulness and sleep respectively. PGD2 and PGE2 are also major PGs in rabbit cerebrospinal fluid, yet their effects on rabbit sleep have not heretofore been systematically investigated. We report here that a bolus injection of PGE2 into a lateral cerebral ventricle induces dose-dependent fevers and transient sleep responses in rabbits. PGE2 induces a suppression of sleep of 24 min duration. In contrast, PGD2, across a wide range of doses (0.25-500 nmol) failed to alter sleep; however, at the highest dose it induced fever. We conclude that if PGs are involved in sleep regulation, a chronic stimulation of their production by other sleep factors is necessary.

Awaking effect of prostaglandin E2 in freely moving rats

The awaking effect of prostaglandin (PG) E2 was further examined in a long-term bioassay system. PGE2 in saline solution was infused between 11.00 and 17.00 h at 0.1, 1, 10, and 100 pmol/min (infusion volume 10 microliters/h) into the third cerebral ventricle of freely moving rats. These rats were otherwise infused with saline continuously and exhibited a circadian cycle, spending 70% of the daytime and 37% of the night in sleep. In the rats that received PGE2 infusion at 1, 10, and 100 pmol/min, slow wave sleep (SWS) decreased to 84%, 69% and 71% and paradoxical sleep (PS) to 85%, 37% and 40% of the paired controls. Thus, the effect of PGE2 was not specific to either SWS or PS. No effects were observed in the rats that received PGE2 at 0.1 pmol/min. After PGE2 infusion at 10 and 100 pmol/min, marked rebounds of both SWS and PS occurred during the night. SWS reduction by PGE2 was due to the shortened duration of SWS episodes, while SWS increase in the rebound phase was due to the increased number of episodes. PS reduction was due to both the shortened duration and decreased number of PS episodes and PS rebound was due to both the prolonged duration and increased number of episodes. The circadian sleep-wake cycle returned to the baseline on the first or second recovery day after PGE2 infusion. Sleep reduction by PGE2 was accompanied by elevation of the brain temperature and rebound increase of sleep occurred with the fall of the brain temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Awaking effect of PGE2 microinjected into the preoptic area of rats

We examined the effect of prostaglandin (PG)E2 on the sleep-wake activity and on body temperature by microinjecting PGE2 into the preoptic area of rats that had been chronically implanted with guide cannulae and electrodes for the recordings of electroencephalogram and electromyogram. PGE2 at doses of 2.5 X 10(-13), 2.5 X 10(-11), and 2.5 X 10(-9) mol reduced the time of slow wave sleep (SWS) to 75%, 61%, and 59% and that of paradoxical sleep (PS) to 73%, 50%, and 25% of the controls, respectively. The SWS and PS reductions were mainly due to the shortening of the SWS episode and the less frequent occurrence of PS episodes. The sleep reduction was accompanied by increased behavioral movement. The maximum increases of rectal temperature at doses of 2.5 X 10(-11) and 2.5 X 10(-9) mol of PGE2 were 1.3 degrees C and 2.7 degrees C, respectively. At a dose of 2.5 X 10(-13) mol of PGE2, the time of SWS and that of total sleep (sum of SWS and PS) decreased significantly, but the change in body temperature was negligible. This may imply that the effect of PGE2 on the sleep-wake activity is not caused by the hyperthermia produced by PGE2. Injections of PGE2 at a dose of 2.5 X 10(-15) mol and saline control induced alteration in neither sleep-wake activity nor body temperature. PGD2 at a dose of 2.5 X 10(-9) mol slightly elevated the rectal temperature (0.5 degree C), but did not produce any change in the sleep-wake activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Sedation produced by prostaglandins is not a nonspecific fatty acid effect

The fatty acid specificity of the depressant actions associated with prostaglandin (PG) administration was studied in mice. Administration of PG-E2 (0.4 and 1.0 mg/kg) or PG-D2 (0.4 and 4 mg/kg) significantly potentiated pentobarbital sleeping time. Arachidonic acid (3.3 mg/kg) administration also significantly potentiated pentobarbital sleeping time. Pretreatment with indomethacin (3 mg/kg) or ibuprofen (10 mg/kg) inhibited the potentiation of pentobarbital sleeping time produced by arachidonic acid. A nonspecific fatty acid (11, 14, 17-eicosatrienoic acid), which cannot be incorporated into the PG synthetic scheme, did not potentiate pentobarbital sleeping time. These results imply that the depressant activity associated with PG administration is a specific PG-induced action rather than a general effect of long-chain unsaturated fatty acids.

Prostaglandins A as possible endogenous ligands of benzodiazepine receptor

We carried out biochemical studies on several prostaglandins to determine if whey would displace [3H]diazepam binding to the membranes of bovine cerebral cortex. Prostaglandins A1 and A2 were the most potent inhibitors of this binding and all the others tested were either less potent or not effective. As prostaglandins A1 and A2 competitively inhibited [3H]diazepam binding with Ki values of 7.1 +/- 0.1 and 15 +/- 1 microM, respectively, their possible function as endogenous ligands of benzodiazepine receptors warrants further attention.

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents

This survey, the second in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of cholinergic agonists and antagonists, histamine and H1- and H2-receptor antagonists, narcotic analgesics and antagonists in both non-tolerant and tolerant subjects and of prostaglandins and related agents. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug.

PGD2 effects on rodent behavior and EEG patterns in cats

Prostaglandin (PG) D2 was studied to determine the pharmacological effects of this PG on the central nervous system. PGD2 (0.45-4.05 mg/kg) decreased spontaneous locomotor activity in rats by as much as 66% of control, however, the neuromuscular coordination of mice, treated at the same doses of PGD2, was not impaired. PGD2 (0.05-4.05 mg/kg) also increased pentobarbital sleeping time in mice from 42% to 238% of control, in a dose-related manner. PGD2 did not prevent convulsions induced in response to electroshock or pentylenetetrazol. Cats monitored for EEG responses to PGD2 infusion displayed variable sensitivity to different doses (16-3000 microgram) of drug, however, the characteristic response to PGD2 was the conversion from a uniform low voltage, fast wave pattern to high voltage, slow waves. Cats administered PGD2 were sedated and sometimes catatonic, and displayed brief periods of hypotension, bradycardia, diarrhea, analgesia and hyperthermia at higher doses of the drug. Thus, PGD2 possesses sedative properties in rodents and cats and may have a role in the central nervous system.

Influence of polyphloretin phosphate on the central effects of prostaglandin E2 and F2alpha in rats

The possibility that polyphloretin phosphate (PPP) antagonizes the central effects elicited by prostaglandin (PG) E2 and F2alpha was investigated. PPP was administered i.c.v. to male Wistar rats (10 or 25 microgram) 10 or 30 min before i.c.v. injection of PGF2 or PGF2alpha (1 or 10 microgram). The duration of several component of behavior, the degree of irritability, and the rectal temperature of rats were measured; the levels of noradrenaline, dopamine, 5-hydroxytryptamine, and 5-hydroxyindoleacetic acid were measured spectrophoto-fluorometrically in discrete brain areas. PPP antagonized temperature and behaviroal changes induced in rats by PGF2alpha, but not those induced by PGE2. The magnitude of antagonism depended on the dose of PPP and on the time of the pretreatment before PGF2alpha administration. Changes in the level of biogenic amines in discrete brain areas evoked by PGs were not affected by PPP. We found that PPP antagonizes the central effects of PGF2alpha but not those of PGE2, and that changes of biogenic amines in discrete brain areas elicited by PGs are not specific.