Effect of Homeopathic Medicines and a Nosode on Larvae of Cochliomyia hominivorax (Diptera: Calliphoridae).

BACKGROUND: Cochliomyia hominivorax is the major fly causing primary myiasis in livestock animals in Brazil; its larvae develop in the host's living tissues, causing mutilations, which can even lead to death. In conventional treatments of myiasis, chemo-synthetic insecticides have been employed directly on larvae present in the wounds. Homeopathy may represent a healthy and sustainable alternative both to prevent and to treat myiasis in animals and humans. The current study evaluated how the emergence of adult insects is affected by the use of the homeopathic medicines Sulfur 12cH and Pyrogenium 12cH, and the nosode produced from C. hominivorax larvae at potencies 8cH and 12cH, on third-stage larvae of a C. hominivorax colony. MATERIALS AND METHODS: The homeopathic medicines and the nosodes were produced according to the Brazilian Homeopathic Pharmacopoeia. Control groups were distilled water, alcohol, no substance, and the organophosphate insecticide trichlorfon. For each group, 10 replicates were performed. Emergence rate of adult insects was evaluated by descriptive statistics followed by analysis of variance. Homogeneity of variances was verified by F-test and group means were compared with Tukey's test. RESULTS: Mortality rates in control groups were 2.7% for 30% (v/v) alcohol, 4.3% for distilled water, 3.2% for no substance (p > 0.05). In the trichlorfon group, the mortality rate of larvae was 90.8%. For Sulfur 12cH, the mortality of larvae was 94.6%, and for Pyrogenium 12cH it was 98.6%. The latter three means were not statistically different from each other or from the mean found for the trichlorfon group. The mortality rates of larvae were 61.3% and 66.6% for nosode C. hominivorax 8cH and 12cH, respectively (p > 0.05). CONCLUSIONS: Results suggest that homeopathy could be used therapeutically to prevent and treat animals and humans with myiasis caused by C. hominivorax.

The antipyretic effect of dipyrone is unrelated to inhibition of PGE(2) synthesis in the hypothalamus.

BACKGROUND AND PURPOSE: Bacterial lipopolysaccharide (LPS) induces fever through two parallel pathways; one, prostaglandin (PG)-dependent and the other, PG-independent and involving endothelin-1 (ET-1). For a better understanding of the mechanisms by which dipyrone exerts antipyresis, we have investigated its effects on fever and changes in PGE(2) content in plasma, CSF and hypothalamus induced by either LPS or ET-1. EXPERIMENTAL APPROACH: Rats were given (i.p.) dipyrone (120 mg·kg(-1)) or indomethacin (2 mg·kg(-1)) 30 min before injection of LPS (5 µg·kg(-1), i.v.) or ET-1 (1 pmol, i.c.v.). Rectal temperature was measured by tele-thermometry. PGE(2) levels were determined in the plasma, CSF and hypothalamus by elisa. KEY RESULTS: LPS or ET-1 induced fever and increased CSF and hypothalamic PGE(2) levels. Two hours after LPS, indomethacin reduced CSF and hypothalamic PGE(2) but did not inhibit fever, while at 3 h it reduced all three parameters. Three hours after ET-1, indomethacin inhibited the increase in CSF and hypothalamic PGE(2) levels but did not affect fever. Dipyrone abolished both the fever and the increased CSF PGE(2) levels induced by LPS or ET-1 but did not affect the increased hypothalamic PGE(2) levels. Dipyrone also reduced the increase in the venous plasma PGE(2) concentration induced by LPS. CONCLUSIONS AND IMPLICATIONS: These findings confirm that PGE(2) does not play a relevant role in ET-1-induced fever. They also demonstrate for the first time that the antipyretic effect of dipyrone was not mechanistically linked to the inhibition of hypothalamic PGE(2) synthesis.

Neurons and glial cells of the rat organum vasculosum laminae terminalis directly respond to lipopolysaccharide and pyrogenic cytokines.

During systemic immune challenge, the organum vasculosum laminae terminalis (OVLT) with its dense vascularization by fenestrated capillaries lacking blood-brain barrier function allows direct access of circulating pyrogens to brain tissue located in close vicinity to the preoptic area. We aimed to analyze direct responses of OVLT cells to exposure to lipopolysaccharide (LPS) and fibroblast-stimulating lipopeptide-1 (FSL-1) or the cytokines tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and IL-6. A primary microculture of the OVLT was established from topographically excised rat pup brain tissue, with cellular identification by marker protein-specific immunocytochemistry. Employing the ratio calcium imaging technique, pyrogen-induced calcium signaling in single OVLT cells could be characterized. LPS--as opposed to FSL-1--stimulation caused fast, transient rises in intracellular calcium concentration in 17% of neurons, 9% of astrocytes, and <5% of microglial cells investigated. LPS additionally led to enhanced expression of TNF-α and IL-1ß exclusively in microglial cells, as well as a time-dependent release of TNF-α and IL-6 from OVLT microcultures. TNF-α evoked calcium signals in 11% of neurons, 22% of astrocytes, and 5% of microglial cells tested. A considerable population of neurons (11%) but only few astrocytes and microglial cells responded to IL-6, whereas 8% of microglial cells and 3% of astrocytes or neurons were activated by IL-1ß. The demonstration of direct cellular responses of OVLT-intrinsic cells to stimulations with LPS or cytokines reinforces the suggested role of this brain structure as a responsive brain site to circulating pyrogens.

Interleukin-1 receptor antagonist inhibits the release of glutamate, hydroxyl radicals, and prostaglandin E(2) in the hypothalamus during pyrogen-induced fever in rabbits.

The present study was attempted to determine whether interleukin-1 receptor antagonist (IL-1ra) pretreatment exerts its antipyresis by reducing organum vasculosum laminae terminalis (OVLT) release of glutamate, hydroxyl radicals and prostaglandin E(2) in rabbits. It was found that systemic administration of lipopolysaccharide induced increased levels of both core temperature and OVLT levels of glutamate, hydroxyl radicals, and prostaglandin E(2). The rise in both the core temperature and OVLT glutamate, hydroxyl radicals and prostaglandin E(2) could also be induced by intracerebroventricular injection of interleukin-1beta. Pretreatment with an intracerebroventricular dose of IL-1ra significantly prevented the lipopolysaccharide or IL-1beta-induced overproduction of glutamate, hydroxyl radicals, and prostaglandin E(2) in OVLT of rabbit's brain. The febrile response caused by systemic administration of lipopolysaccharide or central injection of interleukin-1beta could also be IL-1ra pretreatment-ameliorated. These results indicate that IL-1ra pretreatment may exert its antipyresis by inhibiting the glutamate-hydroxyl radicals-prostaglandin E(2) pathways in the OVLT of rabbit's brain during lipopolysaccharide fever.

Pyrogens enhance beta-endorphin release in hypothalamus and trigger fever that can be attenuated by buprenorphine.

At first, we investigated whether both beta-endorphin release level in the hypothalamus and body temperature can be altered after intracerebroventricular (i.c.v.) injection of either lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), or prostaglandin E(2) (PGE(2)) in rats. It was found that in the rat, i.c.v. administration of either LPS (0.5 microg in 10 microl), IL-1beta (10 ng in 10 microl), or PGE(2) (200 ng in 10 microl), in addition to producing fever, upregulated the immunoreactivity of beta-endorphin in the preoptic anterior hypothalamus of rat brain. Secondarily, we assessed whether the fever induced by either LPS, IL-1beta, or PGE(2) can be altered by pretreatment with buprenorphine (an opioid receptor antagonist). The results revealed that i.c.v. administration of buprenorphine (1 - 10 microg in 10 microl) alone had an insignificant effect on the body temperature. However, the fever induced by i.c.v. injection of either LPS, IL-1beta, or PGE(2) was significantly attenuated by pretreatment with i.c.v. injection of buprenorphine 1 h before the pyrogen injection in rats. The results suggest that pyrogens enhance beta-endorphin release in the hypothalamus and trigger fever which can be attenuated by buprenorphine, an opioid receptor antagonist.

Neuroimmune response to endogenous and exogenous pyrogens is differently modulated by sex steroids.

The objective of this study was to explore whether and how ovarian hormones interact with the febrile response to pyrogens. Estrogen and progesterone treatment of ovariectomized rats was associated with a reduction in lipopolysaccharide (LPS)-induced fever, compared with ovariectomized controls. LPS-fever reduction was accompanied by reduced levels of the inducible cyclooxygenase-2 (COX-2) protein expression in the hypothalamus as well as reduced plasma levels of IL-1beta. The amount of LPS-induced IL-6 in the plasma was not affected by ovarian hormone replacement. In contrast, hypothalamic COX-2 expression in response to intraperitoneal injection of IL-1beta was potentiated by the ovarian hormone replacement. IL-1beta induced a moderate increase in plasma levels of IL-6 that was suppressed by ovarian hormone replacement. These data suggest that ovarian hormone replacement attenuated the proinflammatory response to LPS by suppressing the LPS-induced IL-1beta production and COX-2 expression in the hypothalamus. The markedly different action of ovarian hormones on IL-1beta and LPS effects suggests that this sex hormone modulation of the immune response is a function of the nature of infection and provides further evidence that LPS actions are different from those of IL-1beta.

Peri-OVLT E-series prostaglandins and core temperature do not increase after intravenous IL-1beta in pregnant rats.

Rats have an attenuated febrile response to endogenous pyrogen near the term of pregnancy. Given the fundamental role of E-series prostaglandins (PGEs) in mediating the febrile response to blood-borne endogenous pyrogen, the present experiments were carried out to determine whether PGEs increase in the area surrounding the organum vasculosum laminae terminalis (peri-OVLT) of near-term pregnant (P) rats as in nonpregnant (NP) rats after intravenous (iv) administration of recombinant rat interleukin-1beta (rrIL-1beta). Core temperature was measured by telemetry and peri-OVLT interstitial fluid was sampled in 12 NP and 12 P chronically instrumented, Sprague-Dawley rats by microdialysis for determination of total PGEs by radioimmunoassay. Basal core temperatures were higher in NP compared with P rats (NP 37.9 degrees C +/- 0.5, P 36.9 degrees C +/- 0.4; P < 0.05), but basal peri-OVLT PGEs were similar in both groups (NP 260 +/- 153 pg/ml, P 278 +/- 177 pg/ml; P =not significant). Intravenous administration of rrIL-1beta to NP rats produced a significant increase in core temperature with a latency, magnitude, and duration of 10 min, 0.87 degrees C, and at least 170 min, respectively; peri-OVLT PGEs were increased significantly by 30 min and averaged 270% above basal levels throughout the experiment. In P rats, however, neither core temperature nor peri-OVLT PGEs increased significantly after iv administration of rrIL-1beta. Intravenous administration of vehicle did not significantly alter core temperature or peri-OVLT PGEs in either group of rats. Thus peri-OVLT PGEs do not increase in P rats as they do in NP rats after iv administration of rrIL-1beta. The mechanism of this interesting component of the maternal adaptation to pregnancy, which likely plays a major role in mediating the attenuated febrile response to endogenous pyrogen near the term of pregnancy, warrants further investigation.

Detection of bacterial pyrogens on the basis of their effects on gamma interferon-mediated formation of neopterin or nitrite in cultured monocyte cell lines.

In a number of mammalian cell types, pteridine biosynthesis from guanosine 5'-triphosphate and formation of nitric oxide from L-arginine are induced by gamma interferon (IFN-gamma) and bacterial lipopolysaccharide (LPS). We assessed the possibility of using such metabolic alterations for the in vitro detection of pyrogens. Products from gram-negative and gram-positive bacteria and related synthetic compounds were tested for their potential to induce either of these pathways. Stimulation of pteridine biosynthesis was monitored as the formation of neopterin in the human myelomonocytic cell line THP-1. The formation of nitric oxide was determined as nitrite in murine J774A.1 macrophage cultures. The substances tested included toxic and detoxified parts of LPS and lipid A from Escherichia coli, Salmonella typhimurium, Salmonella minnesota, and Klebsiella pneumoniae as well as lipoteichoic acid and toxic shock syndrome toxin 1 from Staphylococcus aureus. Furthermore, two cell wall compounds from Mycobacterium tuberculosis, trehalose 6,6'-dimycolate and N-acetylmuramyl-L-alanyl-D-isoglutamine, which are active components of Freund's adjuvant, were used. When applied as a single stimulus, only the whole LPS molecule potently stimulated neopterin or nitrite formation. Lipid A and products from gram-positive bacteria were weakly active. For neopterin formation, lipid A required the presence of fetal calf serum. Besides detoxified LPS and independently from the presence of serum, all bacterial compounds tested strongly increased the effects mediated by IFN-gamma. Our results show that bacterial pyrogens can be detected by monitoring the formation of neopterin or nitrite. This may provide a basis for the development of an in vitro assay for the detection of pyrogenic contamination with the aim of replacing the currently used animal test.

What roles does the organum vasculosum laminae terminalis play in fever in rabbits?

Experiments were designed to clarify the role of the brain's organum vasculosum laminae terminalis (OVLT) in the development of fever in rabbits. Rectal and ear skin temperatures were recorded in conscious animals in which the OVLT had been electrolytically destroyed or in which the preoptic anterior hypothalamus (PO/AH) had been transected bilaterally. When the OVLT had been ablated the febrile responses to intravenous injection of interleukin-1 beta (IL-1 beta) or tumour necrosis factor alpha were significantly attenuated, while those to intracerebroventricular injection of IL-1 beta were not affected. Fever induced by intracerebroventricular injection of prostaglandin E2 (PGE2) was prolonged significantly. The febrile responses to intravenous injection of IL-1 beta and to intracerebroventricular injection of PGE2 were attenuated when the transection was located caudally to the anterior wall of the third ventricle and extended laterally more than about 3 mm in the ventricular wall. The results show that the OVLT region is a site through which signals to increase body temperature are transferred from the blood to the brain in rabbits.

Effects of pyrogenic immunomodulators on the release of corticotrophin-releasing factor-41 and prostaglandin E2 from the intact rat hypothalamus in vitro.

1. The actions of the following pyrogens: lipopolysaccharide (LPS), polyinosinic:polycytidylic acid (Poly-I:C), human interleukin (IL)-1 alpha and IL-1 beta, human IL-6 and rat interferon (INF) on corticotrophin-releasing factor-41 (CRF-41) and prostaglandin E2 (PGE2) release from the intact rat hypothalamus in vitro have been studied. 2. Rat hypothalami were incubated in vitro in an artificial cerebrospinal fluid. Immunoreactive (ir)-CFR-41 and PGE2 released into the medium were measured by two-site enzyme amplified immunometric assay (EAIA) and radioimmunoassay (RIA) respectively. 3. Human IL-6 (1 to 10,000 IU ml-1) caused a dose-dependent release of irCRF-41, rising to a maximal 3-4 fold increase over basal at the highest dose tested. Human IL-1 alpha (1 to 1000 IU ml-1), human IL-1 beta (1 to 1000 IU ml-1), poly-I:C (10 pg ml-1 to 100 micrograms ml-1) and rat INF (1 to 10,000 IRu ml-1) all failed to alter irCRF-41 release. 4. LPS (1 mg ml-1) caused a 35% decrease in irCRF-41 release; however, over the dose-range of 0.1 microgram ml-1 to 100 micrograms ml-1, LPS failed to alter irCRF-41 release. The decreased irCRF-41 release in response to LPS (1 mg ml-1) was accompanied by a decrease in the subsequent 56 mM KCl stimulation of irCRF-41. 5. Human IL-1 alpha and IL-1 beta (1000 IU ml-1) were able to stimulate the release of irPGE2 from intact hypothalami, causing a 2 fold increase over basal release. Poly-I:C (100 microg ml-1), LPS (0.1 microg ml-1 to 1 mg ml-1), rat INF (10,000 IRu ml-1) and human IL-6 (1 to 10,000 iu ml-1) all failed to alter irPGE2release.6. In conclusion, these results suggest that the in vitro release of CRF-41 and PGE2, in response to pyrogens, are mediated via different cytokines. In view of this it is possible that different cytokines may mediate the temperature, prostaglandin and hypothalamo-pituitary-adrenocortical axis activation seen during pyrogenic stimulation in vivo.

Pyrogenicity of polyadenylic.polyuridylic acid in rabbits.

Polyadenylic.polyuridylic acid injected intravenously into rabbits produced a rapid-onset, monophasic fever. Pyrogenic tolerance occurred in rabbits following daily injections of polyadenylic.polyuridylic acid. However, direct injection of the agent into the preoptic anterior hypothalamic region of rabbit's brain produced a markedly different fever. After an intrahypothalamic injection of polyadenylic.polyuridylic acid, fever was delayed in onset and persisted for a longer period. At room temperature, the fever was due to both increased metabolism and cutaneous vasoconstriction. In a colder atmosphere the fever was due solely to increased metabolism, whereas in the heat the fever was due to reduction in cutaneous blood flow and respiratory evaporative heat loss. In addition, the fever induced by intravenous polyadenylic.polyuridylic acid injection was reversed by a cyclooxygenase inhibitor, but not by a protein synthesis inhibitor. Polyadenylic.polyuridylic acid was shown to stimulate PGE2 production from rabbit's hypothalamus in vitro. The results reveal that this agent is a prostaglandin-dependent pyrogen.

Macrophage inflammatory protein-1: unique action on the hypothalamus to evoke fever.

Macrophage inflammatory protein (MIP-1) administered systemically causes a fever not blocked by a prostaglandin (PGE) synthesis inhibitor. The purpose of this study was to examine the central mechanism of pyrexic action of this cytokine in the unrestrained rat. After guide cannulae for microinjection were implanted stereotaxically just above the anterior hypothalamic preoptic area (AH/POA), the body temperature of each rat was monitored by a colonic thermistor probe. Saline control vehicle or MIP-1 was microinjected into the AH/POA in one of eight concentrations ranging from 0.0028-9.0 ng per 0.5 mu 1 volume. MIP-1 induced a biphasic or monophasic fever of short latency characterized by an inverse dose-response curve. The potency of MIP-1 was in the femtomolar (10(-15)) range with the lowest dose of 0.028 ng producing a fever of over 2.0 degrees C with a latency of 15 min or less. To determine whether a PGE mediates MIP-1 fever, indomethacin was administered either intraperitoneally in a dose of 5.0 mg/kg or directly into the MIP-1 injection site in a dose of 0.5 microgram/0.5 mu 1, both injected 15 min before MIP-1. Pretreatment of the injection site in the AH/POA with indomethacin failed to prevent the febrile response evoked by MIP-1 injected at the same locus. Further, the dose of systemic indomethacin, which blocks PGE-induced fever in the rat, attenuated only partially the MIP-1 fever. The results demonstrate that MIP-1 is the most potent endopyrogen discovered thus far, and that its action is directly in the region of the hypothalamus which contains both thermosensitive and pyrogen-sensitive neurons. The local action of MIP-1 on cells of the AH/POA in evoking fever is unaffected by the PGE inhibitor which indicates, therefore, that a cellular mechanism operates in the hypothalamus to evoke fever independently of the central synthesis of a PGE.

Prostaglandin formation in the hypothalamus in vivo: effect of pyrogens.

Conscious cats were used to study the local release of prostaglandin (PG) E2 and thromboxane (Tx) B2 (the stable TxA2 by-product) from the preoptic-anterior hypothalamus (AH-POA) and the tuberal-posterior hypothalamus (PH-Tu) using a modified "push-pull" perfusion procedure. In the absence of fever, PGE2 release was steady from the 2nd h of perfusion onward, its rate at either site ranging between 0.08 and 0.12 pg/min. Local treatment with probenecid (1 mM) increased PGE2 release about threefold. Compared with PGE2, basal release of TxB2 was greater (0.15-0.43 pg/min) and, occasionally, tended to fall with time. Both compounds were found in higher amounts (2- to 10-fold increase) after locally injecting endotoxin, and the effect was greater in AH-POA than PH-Tu. Conversely, intravenous endotoxin (bolus) or interleukin 1 (IL-1) (bolus plus infusion) at doses causing a sustained fever selectively stimulated the formation of PGE2, but the response itself did not differ between AH-POA and PH-Tu. In either region, the degree of enhancement in PGE2 release correlated with the magnitude of the fever. Intravenous indomethacin (2 mg/kg) reversed both the fever and PGE2 elevation. These findings support an intermediary role for PGE2 in the central action of pyrogens and the ensuing fever. Blood-borne pyrogens may act at multiple sites in brain, which are tentatively identified with the circumventricular organs.

[Changes in the bioelectrochemical activity of the neurosecretory hypothalamic nuclei in fever caused by endogenous pyrogen/interleukin-1]. / Izmenenie bioélektrokhimicheskoi aktivnosti neirosekretornykh iader gipotalamusa pri likhoradke, vyzvannoi éndogennym pirogenom/interleukinom-1.

Bioelectrochemical potentials of the rabbit hypothalamic supraoptic, paraventricular, suprachiasmatic nuclei, and medial preoptic area changed in a similar way in fever induced with i.v. administration of leucocytic pyrogen/interleukin I in all the structures due, probably, to their compact localization. The dynamics of bioelectrochemical activity coincided with that of rectal temperature derivative. The alterations of bioelectrochemical activity seem to reflect hypothalamic metabolic changes closely associated with effector mechanisms of thermoregulation in fever rather than with the temperature itself. The differences in the reaction patterns of neurosecretory nuclei are compared with changes in their vasopressin-synthetizing function during fever.

Pyrogenicity of interferon and its inducer in rabbits.

The effects of intracerebral administration of interferon (IFN) or its inducer polyriboinosinic acid-polyribocytidylic acid (poly I:C) on thermoregulatory responses were assessed in conscious rabbits. Administration of IFN (10(2)-10(6) IU) or poly I:C (0.012-12 micrograms) into the preoptic anterior hypothalamus or the third cerebral ventricle caused a dose-dependent fever in rabbits at three ambient temperatures (Ta) tested. In the cold (Ta = 8 degrees C), the fever was due to increased metabolism, whereas in the heat (Ta = 32 degrees C) the fever was due to a reduction in respiratory evaporative heat loss and ear skin blood flow. At the moderate environmental temperature (Ta = 22 degrees C), the fever was due to increased metabolism and cutaneous vasoconstriction. Compared with the febrile responses induced by cerebroventricular route injection of IFN or poly I:C, the hypothalamic route of injection required a much lower dose of IFN or poly I:C to produce a similar fever. Furthermore, the fever induced by intrahypothalamic injection of IFN or poly I:C was reduced by pretreatment of animals with a systemic dose of indomethacin (an inhibitor of all prostaglandins formation) or cycloheximide (an inhibitor of protein synthesis). The data indicate that IFN or its inducer may act through the endogenous release of a prostaglandin or a protein factor of an unknown chemical nature in the preoptic anterior hypothalamic region to induce fever in rabbits. The fever induced by IFN or its inducer is brought about by a decrease in heat loss and/or an increase in heat production in rabbits.

Effects of endogenous pyrogen and prostaglandin E2 on hypothalamic neurons in rat brain slices.

We investigated the effects of endogenous pyrogen and prostaglandin E2 (PGE2) on the preoptic and anterior hypothalamic (POAH) neurons using brain slice preparations from the rat. Partially purified endogenous pyrogen did not change the activities of most of the neurons in the POAH region when applied locally through a micropipette attached to the recording electrode in proximity to the neurons. This indicates that partially purified endogenous pyrogen does not act directly on the neuronal activity in the POAH region. The partially purified endogenous pyrogen, applied into a culture chamber containing a brain slice, facilitated the activities in 24% of the total neurons tested, regardless of the thermal specificity of the neurons. Moreover, PGE2 added to the culture chamber facilitated 48% of the warm-responsive, 33% of the cold-responsive, and 29% of the thermally insensitive neurons. The direction of change in neuronal activity induced by partially purified endogenous pyrogen appears to be almost the same as that induced by PGE2 when these substances were applied by perfusion to the same neuron in the culture chamber. These results suggest that partially purified pyrogen applied to the perfusate of the culture chamber stimulates some constituents of brain tissue to synthesize and release prostaglandin, which in turn affects the neuronal activity of the POAH region.

Autonomic thermoregulation after separation of the preoptic area from the hypothalamus in rats.

To clarify the role of the hypothalamic preoptic area in autonomic thermoregulation, the preoptic area (POA) of rats was disconnected from the rest of the brain-stem by bilateral microknife cuts which spared or included the medial forebrain bundle. The animals' metabolic responses to exogenous norepinephrine (0.5 mg/kg, im) were then measured at ambient temperatures of 25 degrees and 15 degrees C. Oxygen uptake and colonic and tail skin temperatures were also measured at ambient temperatures of 34 degrees, 25 degrees, and 15 degrees C. Finally, the febrile response to a challenge with live Salmonella enteritidis was studied. Except for a slightly higher oxygen uptake at all ambient temperatures in the rats in which the medial forebrain bundle was cut, no differences were found in any of the variables studied between the POA-disconnected and the sham-operated animals. We conclude, therefore, that the POA is not essential for the integration of autonomic thermoregulatory responses in the rat.