Further observations on the suppression of fever in rabbits by intracerebral action of anisomycin

Antibodies to macrophage inflammatory protein-1beta in preoptic area of rats fail to suppress PGE2 hyperthermia

This study determined whether macrophage inflammatory protein-1beta (MIP-1beta) plays a role in the hyperthermia caused by prostaglandin E2 (PGE2) given intracerebroventricularly (i.c.v.) in the rat. In these experiments, anti-murine MIP-1beta antibody (anti-MIP-1beta) was micro-injected in the anterior hypothalamic, preoptic area (AH/POA) just before i.c.v. PGE2. The results showed that anti-MIP-1beta failed to alter the PGE2 hyperthermia. However, immunocytochemical studies revealed MIP-1beta immunoreactivity detectable in both the organum vasculosum laminae terminalis (OVLT) and AH/POA in the febrile rat. These data thus demonstrate that MIP-1beta is sequestered in diencephalic structures underlying thermoregulation even though it is not involved in PGE2 hyperthermia. This dissociation supports the viewpoint that at least two distinct systems exist in the brain which underlie a febrile response: MIP-1beta underlies one component whereas PGE2 comprises the other.

Role of interleukin-1 beta, interleukin-6 and macrophage inflammatory protein-1 beta in prostaglandin-E2-induced hyperthermia in rats

The purpose of this study was to investigate the role of pyrogenic cytokines, such as IL-1 beta, IL-6 and MIP-1 beta, in the mechanisms underlying the hyperthermic response of rats to central injection of PGE2. Thus, specific murine neutralizing antibodies against these cytokines were micro-injected directly into the anterior hypothalamic, preoptic area (AH/POA) of unrestrained rats just before intracerebroventricular injection of PGE2. The significant hyperthermia induced by PGE2 was markedly suppressed by micro-injection of anti-IL-6 and partially attenuated by anti-IL-1 beta. However, the micro-injection of anti-MIP-1 beta failed to alter the hyperthermic response. The results indicate that PGE2-induced hyperthermia is presumably mediated through actions of IL-6 on the thermosensitive cells of the AH/POA and confirm that distinct and alternate pathways exist in the rat brain for the induction of fever.

Fever induced in rats by intrahypothalamic macrophage inflammatory protein (MIP)-1 beta: role of protein synthesis

The effect of macrophage inflammatory protein-1 beta (MIP-1 beta) on body temperature, following its injection into the anterior hypothalamic pre-optic area (AH/POA), was examined by a radiotelemetry system in the freely moving rat. The purpose of this study was to examine the action of an inhibitor of protein synthesis, anisomycin, on the pyrexia which follows intrahypothalamic injection of MIP-1 beta. The micro-injection of 10 to 20 pg MIP-1 beta into the AH/POA induced a dose-dependent monophasic increase in body temperature, whereas a higher dose of 25 pg of the cytokine caused a biphasic febrile response. When MIP-1 beta was heated at 70 degrees C for 30 min prior to its administration, the pyrogenic response was abolished. Pretreatment of the micro-injection site in the AH/POA with 10 micrograms anisomycin did not alter the febrile response to 25 pg MIP-1 beta given at the same site in the AH/POA. When 10 mg/kg anisomycin was administered subcutaneously, the febrile response to 25 pg MIP-1 beta injected in the AH/POA was significantly suppressed. The present results suggest that fever caused by MIP-1 beta within the cells of the AH/POA may not require the synthesis of a new protein factor; however, the de novo synthesis of a protein outside of the AH/POA presumably plays a functional role, at least in part, in the intense fever produced by this cytokine in the hypothalamus.

Suppression of antipyretic response in rabbits by intraventricular protein synthesis inhibitor, anisomycin

Fevers induced by intravenous injection of endogenous pyrogen (EP) and intraventricular prostaglandin E2 (PGE2) were significantly prolonged when protein synthesis inhibitor, anisomycin was administrated intraventricularly 30 min before or 1 hr after injection of EP or PGE2. The present results show that protein synthesis in the central nervous system is involved in the development of antipyresis.

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.

Prostaglandin E as the neural mediator of the febrile response

The evidence favoring a role for prostaglandin E (PGE) as the neural mediator of the febrile response is reviewed and considered under five different essential criteria which would need to be satisfied, if such a role is to be accepted. These criteria are: the ability of intracerebrally microinjected exogenous PGE to cause fever; the detection of increased levels of endogenous PGE in the brain during the normal production of fever; the ability of substances that inhibit the production and release of PGE to block normal fevers; the ability of substances that are specific PGE antagonists to inhibit normal fevers; and the identification of a specific site and cell type for the release of PGE in response to the action of pyrogens. Evidence from the literature that supports these criteria is reviewed and presented in this format, and the conclusion is drawn that the evidence available is more than sufficient to support the initial hypothesis.

Inhibition of brain protein synthesis suppresses the release of prostaglandin E2 in febrile rabbits

In rabbits the third cerebral ventricle was perfused using a push-pull cannula. Prostaglandin E2 concentration in the perfusate was measured by radioimmunoassay. Prostaglandin concentration rose during fever induced by an intraventricular injection of endogenous pyrogen. Both fever and the increased prostaglandin concentration were suppressed by the intraventricular injection of 100 micrograms of the protein synthesis inhibitor, anisomycin. A possible interpretation of the findings is that anisomycin inhibits the formation of phospholipase A2. If this is true, the implication is that phospholipase A2 has a rapid turnover in brain.

Intraventricular injections of drugs which inhibit phospholipase A2 suppress fever in rabbits

Injection of two chemically dissimilar inhibitors of phospholipase A2 (mepacrine and parabromophenacylbromide) into the cerebral ventricles of rabbits inhibited the febrile response to endogenous pyrogen given by the same route. 2. The same doses of the inhibitors given intravenously did not affect the febrile response to endogenous pyrogen given into the ventricles, indicating that their action was central. 3. When given intraventricularly the inhibitors did not affect the maintenance of core temperature in a cold environment, indicating that they did not impair thermoregulatory ability. 4. The inhibitors had no effect on the temperature rise following intraventricular injection of arachidonic acid. 5. These observations are compatible with the proposition that one or more metabolic products of arachidonic acid other than prostaglandin are involved in pyrogenesis.

Inhibition, by trichothecene antibiotics, of brain protein synthesis and fever in rabbits

1. To test further the hypothesis that brain protein synthesis is necessary for fever, three structurally similar trichothecene antibiotics were injected into the cerebral ventricles of rabbits. They were 3,15-diacetoxy-12-hydroxytrichothec-9-ene (DAHT), 3,15-didesacetyl-calonectrin (DDAC) and T-2 toxin. Their actions on hypothalamic incorporation of [14C]leucine and fever were compared. 2. DDAC (60 micrograms) and T-2 toxin (10 micrograms) strongly inhibited leucine incorporation and fever. DAHT (60 micrograms) did not diminish fever and had a smaller effect upon leucine incorporation. 3. The findings strengthen considerably earlier suggestions that brain protein synthesis is an essential step in pyrogenesis.