Prostaglandins and Body Temperature

Temperature and hemodynamic changes associated with increased neural damage to global hemispheric hypoxic ischemia by prior prostaglandin E2, D2 and F2alpha administration

Experiments compared the hemispheric neural damage resulting from global hemispheric hypoxic ischemia (GHHI, ligation of right common carotid artery plus 35 min of 12% O2) in groups of anesthetized, male Long Evans rats, 9-10 weeks of age, kept at 37 degrees C, and previously given an intracerebroventricular (i.c.v., 2.5 microl) injection of 28 or 70 pmoles of PGE2, PGF2alpha or PGD2 or sterile saline (SS) 30 min beforehand. Mean arterial pressure (MAP), ipsilateral cortical capillary blood flow (CBF), colonic (Tc), ipsilateral (Tipsi) and contralateral (Tcontra), temporalis muscle temperatures were measured before, during and for 15 min after GHHI. Necrotic neural damage was assessed 7 days post-GHHI. All groups given GHHI + PGs showed increased ipsilateral hemispheric damage to GHHI especially due to enhanced neocortical damage, compared to the saline control group given the same insult. PGD2 was the most potent PG to cause further damage to the global insult. Tc, Tipsi, Tcontra and MAP increased following the i.c.v. injection of PGE2. I.c.v. PGF2alpha transiently decreased MAP, PGD2 tended to decrease cerebral blood flow and neither evoked changes in temperature compared to respective pre-injection control values. Results demonstrate increased neural damage to GHHI with prior i.c.v. PGE2, PGF2alpha or PGD2 administration.

Acetaminophen fails to inhibit ethanol-induced subjective effects in human volunteers

In animals, ethanol causes some of its CNS effects by releasing prostaglandins (PG); this is demonstrated by reports that prostaglandin synthetase inhibitors (PGSIs) diminish ethanol-induced effects. However, use of animals in these studies has precluded testing for subjective effects. We studied the interaction of ethanol and acetaminophen, a PGSI, in a double-blind crossover experiment. Six adult males were given no drug or acetaminophen (0, 325, 650, 1300 or 1950 mg) 75 min before ethanol (total dose = 0.625 g/kg; five divided doses). Physiologic, subjective and performance measures were collected. Compared to the no drug condition, ethanol significantly increased ratings of drug "liking," "drunk," "sluggish" and "drug strength" and decreased ratings of "sober." Ethanol increased heart rate and acetaminophen did not diminish or enhance this effect. The failure to antagonize ethanol-induced subjective and physiologic effects by acetaminophen in humans may be due to species differences or inadequate dosage of the PGSI. It is also possible that subjective and certain physiologic effects of ethanol in humans are not mediated by prostaglandin-dependent neural processes. Nevertheless, the finding that at greater than typical analgesic doses, acetaminophen failed to prevent subjective effects of ethanol is of clinical significance.

Estimation of the in vivo effect of cyclooxygenase inhibitors on prostaglandin E2 levels in mouse brain

The purpose of the present study was to develop a biochemical marker of inhibition of cyclooxygenase in the central nervous system following oral administration of cyclooxygenase inhibitors. An ex vivo method was developed wherein the brain was removed, incubated at room temperature for 2 min permitting prostaglandins to be synthesized from spontaneously released arachidonic acid. Indomethacin, zomepirac Na, naproxen Na, ibuprofen, aspirin and acetaminophen inhibited the ex vivo production of prostaglandin E2 in a dose-related manner at doses that correlated well with both their potency to inhibit mouse brain cyclooxygenase in vitro, and their antinociceptive potency in a mouse abdominal constriction test. When the brains were frozen immediately after the mice were killed, the above drugs did not reduce the endogenous prostaglandin E2 level. Thus while cyclooxygenase inhibitors did not reduce normal prostaglandin E2 levels in brain, they did attenuate post-mortem increases in prostaglandin E2. This novel assay permits an estimate of cyclooxygenase inhibitory effects in vivo. The data further support the suggestion that many of these drugs may have a central as well as a peripheral effect.

Hyperthermia induced by open-field stress is blocked by salicylate

Psychological stress results in a rise in body temperature. Here we report that in rats, hyperthermia induced by open-field stress can be blocked by administration of the antipyretic drug sodium salicylate. These data suggest that this rise in body temperature is a true fever, perhaps mediated by prostaglandins.

Central versus peripheral sites of antipyretic action of a non-steroidal anti-inflammatory agent, AD-1590, in rabbits

The site of antipyretic action of AD-1590 in the sequential process involved in the development of fever caused by bacterial pyrogen (LPS) was investigated in rabbits. AD-1590 (1 microgram/ml) did not inactivate both LPS and leucocytic pyrogen (LP) and did not affect the generation of LP in the in vitro test. AD-1590 (0.1 mg/kg i.v.) prevented the fever caused by LP as well as LPS, but did not prevent the fever by PGE2 (100 ng/rabbit) injected into the preoptic anterior hypothalamic (PO/AH) regions. A significant antipyretic effect of AD-1590 on LPS-fever was found when AD-1590 (4 micrograms/rabbit) was injected into the PO/AH regions. AD-1590 (0.4 mg/kg i.v.) did not produce anti-pyretic activity against 2,4-dinitrophenol-hyperthermia; the monoamine levels in the brain were not affected with AD-1590 (10 mg/kg p.o.). These results suggest that AD-1590, like acidic non-steroidal anti-inflammatory drugs, produces its antipyretic action through the central mechanisms.

AD-1590, a potent antagonist of lipopolysaccharide-induced fever in rabbits

The antipyretic activity of AD-1590 (2-[8-methyl-10,11-0xodibenz[b,f]oxepin-2-yl]propionic acid), a non-steroidal anti-inflammatory drug with a novel chemical structure, was investigated in rabbits with lipopolysaccharide (LPS)-induced fever and monkeys with leucocytic pyrogen-induced fever. AD-1590 produced a dose-related inhibition of the LPS-fever at oral doses of 0.1 mg kg-1 or more (ED50 = 0.089 mgg kg-1). Its potency was 10-12, 20-35, 100-170, 400-540, greater than 1500 and greater than 2000 times that of ketoprofen, diclofenac sodium, indomethacin, ibuprofen, mefenamic acid and aspirin, respectively. The fever caused by leucocytic pyrogen was significantly inhibited by intravenous administration of 0.1-0.2 mg kg-1 of AD-1590 (10 mg kg-1 oral or i.v.) did not affect body temperature in afebrile rabbits or monkeys. These results suggest that AD-1590 shows a potent antipyretic activity in the rabbit and monkey and is a potent antagonist of LPS-fever.

Absence of endotoxin-fever but not hyperthermia in Brattleboro rats

I.c.v. administration of bacterial endotoxin produced a fever in the Long-Evans rat but not in the Brattleboro rat. Similar administration of arachidonic acid, prostaglandin E2, prostacyclin, dibutyryl cAMP, norepinephrine, morphine and beta-endorphin caused hyperthermia in both Long-Evans and Brattleboro rats. Variable doses of exogenous arginine vasopressin (AVP) when centrally administered with endotoxin caused fever in the Brattleboro rat. It is suggested that AVP may play an important role in the production and release of endogenous pyrogen.