Evidence supporting a role for endogenous vasopressin in natural suppression of fever in the sheep

1. The antipyretic effect of arginine vasopressin (AVP) introduced into the brain by push-pull perfusion was investigated in the sheep. 2. Control perfusions with sucrose solutions had no effect on fevers induced by a bacterial endotoxin. Sucrose solutions containing AVP (4.0 microgram/ml.) perfused at 40 microliter./min had significant antipyretic activity, reducing the two peaks of the fever but had no effect on resting body temperature. 3. Loci in which AVP induced antipyresis were limited to the septal region about 2-3 mm anterior to the anterior commissure. 4. The amounts of AVP in perfusates from the septal region correlated negatively with changes in body temperature. 5. AVP administered I.V. did not lower fever. 6. AVP plasma levels correlated negatively with fever magnitude following premature birth induced by dexamethasone.

Observations on the site & mode of action of pyrogens in the rabbit brain

1. Leucocyte pyrogen has been injected bilaterally into various parts of the rabbit brain. It caused fever when injected into the pre-optic area and the anterior hypothalamus, but not when injected into the posterior hypothalamus, the mid-brain, the pons, the cerebellum or the cerebral cortex.2. The mean time which elapsed between a leucocyte pyrogen injection into the anterior hypothalamus and the onset of fever was 7.8 min. For similar injections of bacterial pyrogen the time lag was 24.8 min. The mean time lag between bilateral injections of noradrenaline into the anterior hypothalamus and the onset of fever was 7.4 min.3. The amount of leucocyte pyrogen required to cause fever when injected into the anterior hypothalamus was less than 1/100 of that required to cause a similar fever on intravenous injection. The quantity of bacterial pyrogen injected into the hypothalamus was of the same order as that which would cause a similar fever on intravenous injection.4. Control injections of saline, plasma, cerebrospinal fluid, heated leucocyte pyrogen and red cells into the anterior hypothalamus did not cause fever.5. After attempts to deplete the hypothalamus of its monoamine stores by intraventricular injections of reserpine, the rabbit had fever as a result of an intravenous injection of bacterial pyrogen.6. We conclude that the anterior hypothalamus and the pre-optic area are sites at which leucocyte pyrogen acts to cause fever in the rabbit. The mechanism of this febrile response is not clear, but it appears that part, at least, of the response could be mediated by a mechanism other than release of noradrenaline or failure to release 5-HT.

Convulsive and hypothermic effects of vasopressin in the brain of the rat

Arginine vasopressin (AVP) was administered into the lateral cerebral ventricles of rats to assess its effects when given directly into the brain. AVP (1.0 microgram) caused an immediate sharp decrease in body temperature. Behaviorally, AVP caused short pauses of immobility and staring upon the first injection but the same dose caused myoclonic-myotonic convulsions upon the second injection 2 days later. Thereafter, as little as 10 ng of AVP caused seizures.

A cation channel in frog lens epithelia responsive to pressure and calcium

Patch-clamp recording from the apical surface of the epithelium of frog lens reveals a cation-selective channel after pressure (about +/- 30 mm Hg) is applied to the pipette. The open state of this channel has a conductance of some 50 pS near the resting potential (-56.1 +/- 2.3 mV) when 107 mM NaCl and 10 HEPES (pH 7.3) is outside the channel. The probability of the channel being open depends strongly on pressure but the current-voltage relation of the open state does not. With minimal Ca2+ (55 +/- 2 microM) outside the channel, the current-voltage relation is nonlinear even in symmetrical salt solutions, allowing more current to flow into the cell than out. The channel, in minimal Ca2+ solution, is selective among the monovalent cations in the following sequence K+ greater than Rb+ greater than Cs+ greater than Na+ greater than Li+. The conductance depends monotonically on the mole fraction of K+ when the other ion present is Li+ or Na+. The single-channel current is a saturating function of [K+] when K+ is the permeant ion, for [K+] less than or equal to 214 mM. When [Ca2+] = 2 mM, the current-voltage relation is linearized and the channel cannot distinguish Na+ and K+.

Gene effect in carriers of anhidrotic ectodermal dysplasia

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Antipyresis: its effect on mortality rate of bacterially infected rabbits

The effect of an antipyretic drug administered directly into the preoptic-anterior hypothalamus was measured in order to investigate the role of fever on mortality of bacterially infected mammals. New Zealand white rabbits (Oryctolagus cuniculus) were injected intravenously with Pasteurella multocida and either sodium salicylate or a control solution was infused directly into the preoptic-anterior hypothalamus. Both groups developed fevers, but the fever of the rabbits infused with the antipyretic was reduced by 50% during the initial stage of infection. Hypothalamic sodium salicylate infusions produced a lower average fever than control infusions over an initial 5 hour period of infection, reducing average 5 hour fevers from 1.56 degrees C to 0.72 degrees C. All of the infected rabbits infused with sodium salicylate died whereas only 29% of the infected control rabbits died. Rabbits receiving sodium salicylate alone did not die. The increased mortality could possibly be the result of a fulminating infection caused by rapidly multiplying bacteria during the initial, attenuated phase of the febrile course in the salicylate-treated rabbits.

Evidence supporting a role for endogenous vasopressin in fever suppression in the rat

1. Infusion of human purified interleukin-1 into a lateral cerebral ventricle of the rat evoked a rise in core temperature which was abolished by heating the interleukin-1. 2. When the intracerebroventricular infusion of interleukin-1 was preceded by a bilateral injection of saline into the ventral septal area, the resulting febrile response was not different from that induced by interleukin-1 alone. However, when the vasopressin V1 antagonist, d(CH2)5Tyr(Me)AVP, was injected into the ventral septal area prior to interleukin-1, a fever was evoked which was significantly greater in magnitude and duration. This enhancement of fever by the V1 antagonist was dose related. 3. Injection of either saline or the V1 antagonist into the ventral septal area, in the absence of interleukin-1, did not evoke any consistent alteration in the core temperature of the rats. 4. The vasopressin V2 antagonist, d(CH2)5-D-ValVAVP, was injected into the ventral septal area to determine the effect of another vasopressin analogue on the fever evoked by interleukin-1. The V2 antagonist did not alter the time course of interleukin-1-induced fever or alter core temperature in the afebrile rat. 5. These data are consistent with the hypothesis that endogenous vasopressin, released in the ventral septal area, may be involved in limiting fever. In addition, these results indicate that the central receptor mediating the antipyretic action of vasopressin may resemble the V1 subtype of peripheral vasopressin receptor.

Vasopressin may mediate febrile convulsions

The possibility that arginine vasopressin (AVP) is involved in the etiology of febrile convulsions was investigated by experiments on hyperthermia-induced convulsions in rats. Homozygous Brattleboro rats, which genetically lack AVP, and Long Evans rats, which were passively immunized by intracerebroventricular anti-AVP antiserum, either convulsed at higher body temperatures than untreated Long Evans rats or did not convulse at all. This indicates that a lack of AVP increases the threshold for the convulsions. High blood levels of AVP in hyperthermic convulsing rats compared to hyperthermic non-convulsive rats support the hypothesis that AVP may mediate febrile convulsions.

Surmounting barriers in ionic channels

Biological cells are defined by the membrane that shields their vital molecules from the environment. The lipid bilayer of the membrane is an effective dielectric shield (Parsegian, 1969; Andersen, 1978; Honiget al.1986), preventing penetration by charged molecules: the lipid presents a large electrostatic energy barrier because it cannot neutralize the charge of solute molecules nearly as well as water. This energy barrier inhibits the permeation of solutes with local charge, even metabolites. Of course, metabolites do enter cells, and so physiologists have suspected (for a very long time, Hille, 1984, ch. 8) that the membrane shield is pierced by aqueous channels, through which solutes diffuse (with their local charge substantially neutralized) as they cross the membrane. These aqueous pores now have molecular reality (e.g. Nodaet al.1984; Miller, 1986). Each is formed by a specialized protein, integral to membranes, perhaps shaped like a thick-walled pipe, called ionic channels. Channels control the movement of many important molecules in and out of cells by the ‘gating’ mechanism that controls their opening and closing and by the selective properties of their open channel.

Vasopressin: a homeostatic effector in the febrile process

This review compares the physiological changes which accompany infection and fever with the effects of the peptide, arginine vasopressin (AVP). AVP may act as a neuromodulator, a releasing factor, or a hormone to induce responses which are opposite to those homeostatic changes accompanying fever. Since AVP is released into blood and brain during fever, it is hypothesized that AVP contributes to the maintenance of homeostasis in the infected organism.

Changes in body temperature produced by prostaglandins and pyrogens in the chicken

Bacterial pyrogen from S. abortus equi (SAE) was injected into the wing veins of chickens. Following injection of 0.05-0.5 mug SAE, body temperatures did not change significantly, whereas 2.0 or 10 mug of pyrogen caused falls in body temperature of 0.56 +/- 0.10degrees C and 1.1 +/- 0.21degrees C (mean +/- SE, n=5). The temperature falls were accompanied by a flushing of the comb and an increase in respiratory rate and were not antagonized by 1.0 g of acetylsalicylic acid (ASA) given orally. The injection of SAE (0.1 mug in 1 mul) into the anterior hypothalamus produced fevers averaging 1.24 +/- 0.07 degrees C (n=9) which were antagonized by oral ASA. Injections of SAE at other brainstem loci produced no temperatur changes. Seven chickens were also injected with 0.1 mug PGE in 1.0 mul into the anterior hypothalamus, and they developed fevers averaging 0.90 +/- 0.16 degrees C. The results support the concept that prostaglandins may be involved in fever in chickens but suggest that the action of pyrogen injected intravenously may be different from that following its injection directly into the hypothalamus.

Peripheral blood flow during rewarming from mild hypothermia in humans

During the initial stages of rewarming from hypothermia, there is a continued cooling of the core, or after-drop in temperature, that has been attributed to the return of cold blood due to peripheral vasodilatation, thus causing a further decrease of deep body temperature. To examine this possibility more carefully, subjects were immersed in cold water (17 degrees C), and then rewarmed from a mildly hypothermic state in a warm bath (40 degrees C). Measurements of hand blood flow were made by calorimetry and of forearm, calf, and foot blood flows by straingauge venous occlusion plethysmography at rest (Ta = 22 degrees C) and during rewarming. There was a small increase in skin blood flow during the falling phase of core temperature upon rewarming in the warm bath, but none in foot blood flow upon rewarming at room air, suggesting that skin blood flow seems to contribute to the after-drop, but only minimally. Limb blood flow changes during this phase suggest that a small muscle blood flow could also have contributed to the after-drop. It was concluded that the after-drop of core temperature during rewarming from mild hypothermia does not result from a large vasodilatation in the superficial parts of the periphery, as postulated. The possible contribution of mechanisms of heat conduction, heat convection, and cessation of shivering thermogenesis were discussed.

Changes in body temperature and vasopressin content of brain neurons, in pregnant and non-pregnant guinea pigs, during fevers produced by Poly I:Poly C

The synthetic polyribonucleotide pyrogen Poly I:Poly C (800 micrograms.kg-1) was injected intramuscularly on alternate days into pregnant and non-pregnant female guinea pigs. Pregnant animals, close to term, had smaller fevers in response to the pyrogen than did non-pregnant animals. Repeated injections of the pyrogen caused sequentially smaller fevers for the first 3-4 injections, particularly in non-pregnant animals, and this appeared to be like the tolerance usually developed to repeated injections of endotoxin. Continued pyrogen injections then caused, in non-pregnant animals, fevers of increasing magnitude until the original fever levels were reached, whereas in pregnant guinea pigs the fever responses remained reduced until parturition. The development of tolerance was associated with an increase in immunoreactivity for arginine vasopressin (AVP) in some neurons in the medial part of the paraventricular nucleus, and in terminals in the lateral septum and amygdala similar to changes found in these areas at term of pregnancy. These observations raise the possibility that AVP in these regions may have a role in the development of tolerance to pyrogens, and further quantitative studies of the AVP content of, and release from, nerve terminals projecting to the limbic system seem warranted.

Sudden failure of swimming in cold water

To investigate the effect of cold water on swimming four men who declared themselves good swimmers were immersed fully clothed on separate days in water at 23.7 degrees and 4.7 degrees C. The time that they were able to swim in the cold water was much shorter than in the warm. The two shortest swims ended after 1.5 and 7.6 minutes, before rectal temperature fell, when the men suddenly floundered after developing respiratory distress with breathing rates of 56-60/min. The other cold swims, by the two fattest men, ended less abruptly with signs of general and peripheral hypothermia.It is concluded that swimming in cold water was stopped partly by respiratory reflexes in the thin men and hypothermia in the fat, and partly by the cold water's high viscosity. The longer swimming times of the fat men are attributed largely to their greater buoyancy enabling them to keep their heads above water during the early hyperventilation.The findings explain some reports of sudden death in cold water. It is clearly highly dangerous to attempt to swim short distances to shore without a life-jacket in water near 0 degrees C.

Vasopressin and fever: evidence supporting the existence of an endogenous antipyretic system in the brain

Vasopressin administered into the ventral septum exerts a dose-related antipyresis. This site of action is similar in a number of species. The fever-reducing properties of vasopressin are both site and neuropeptide specific. Evidence supporting a role for endogenous vasopressin in fever suppression is the demonstration that the release of the peptide from the ventral septal area is altered during fever: the amount released correlates negatively with febrile changes in body temperature. In addition, changes in the concentration of vasopressin in the septum and amygdala have been demonstrated immunocytochemically during fever: an activation of vasopressinergic neurons occurs which is similar to that observed in pregnant animals at term when fever is absent. Specific antibodies directed against vasopressin or specific vasopressin antagonist analogues (e.g., d(CH2)5Tyr(Me)AVP) enhanced the febrile response to a pyrogen challenge when injected into the ventral septum. The same antagonist also can antagonize the antipyretic effect of exogenously administered vasopressin. The use of relatively specific antagonists and agonists of vasopressin, directed against the V1 and V2 subtypes of the peripheral vasopressin receptor, suggests that the central receptor responsible for the antipyretic effect of vasopressin may resemble the V1 subtype. Recent experiments using electrophysiological techniques have demonstrated the existence of thermoresponsive units in the ventral septal area whose activity may be altered by vasopressin which is possibly derived from the paraventricular nucleus and bed nucleus of the stria terminalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature responses of lambs after centrally injected prostaglandins and pyrogens

It has been proposed that pyrogens may produce their febrile response by the release of prostaglandins in the hypothalamus. To test this theory, prostaglandin E1 (PGE1) was injected into a lateral ventricle in dosages of 2-200 ug into conscious newborn lambs, ages 4-168 h. Fiifteen of 40 injections were followed by rises in rectal temperature but the remainder were followed either by no change or by falls. Temperature responses did not appear to be related to age and a variation in responses to the same dosage of PGE was often observed. Some lambs were able to develop fevers in response to intravenous bacterial pyrogen yet did not develop fever after intraventricular PGE 1. Intraventricular bacterial pyrogen (3 ng) produced no change in body temperature, whereas three of four injections of 300 ng pyrogen caused fever. The results suggest that the newborn lamb may be able to develop a fever independently of the central involvement of PGE1. Alternatively, the intraventricular approach may not be useful for the study of the central control of body temperature in the newborn lamb.

Effect of hemorrhage on fever: the putative role of vasopressin

The effects of hemorrhage on the febrile response of the sheep was examined because hemorrhage is a potent stimulant for arginine vasopressin (AVP) release into cerebrospinal fluid and blood. Removal of 20% of the estimated blood volume of the conscious sheep led to small physiologic changes and significantly decreased fevers in response to bacterial endotoxin. Mean arterial blood pressure decreased in hemorrhaged febrile sheep to a significantly greater extent than in nonhemorrhaged febrile sheep. AVP levels were considerably greater in the blood of hemorrhaged febrile sheep than in nonhemorrhaged febrile sheep and the concentrations correlated with the magnitude of the decrease in fever. Sheep hemorrhaged in the cold had changes in body temperature similar to control sheep. These experiments support the hypothesis that AVP may be an antipyretic neuromodulator.