Biomedical subjects

A H Swiergiel

Publications and source records attributed to A H Swiergiel.

At least 19 recordsLinked to original sources

PubMed2004

Brain circuits involved in corticotropin-releasing factor-norepinephrine interactions during stress.

Corticotropin-releasing factor (CRF)- and norepinephrine (NE)-containing neurons in the brain are activated during stress, and both have been implicated in the behavioral responses. NE neurons in the brain stem can stimulate CRF neurons in the hypothalamic paraventricular nucleus (PVN) to activate the hypothalamic-pituitary-adrenocortical axis and may affect other CRF neurons. CRF-containing neurons in the PVN, the amygdala, and other brain areas project to the area of the locus coeruleus (LC), and CRF injected into the LC alters the electrophysiologic activity of LC-NE neurons. Neurochemical studies have indicated that CRF applied intracerebroventricularly or locally activates the LC-NE system, and microdialysis and chronoamperometric measurements indicate increased NE release in LC-NE terminal fields. However, chronoamperometric studies indicated a significant delay in the increase in NE release, suggesting that the CRF input to LC-NE neurons is indirect. The reciprocal interactions between cerebral NE and CRF systems have been proposed to create a "feed-forward" loop. It has been postulated that a sensitization of such a feed-forward loop may underlie clinical depression. However, in the majority of studies, repeated or chronic stress has been shown to decrease the behavioral and the neurochemical responsivity to acute stressors. Repeated stress also seems to decrease the responsivity of LC neurons to CRF. These results do not provide support for a feed-forward hypothesis. However, a few studies using certain tasks have indicated sensitization, and some other studies have suggested that the effect of CRF may be dose dependent. Further investigations are necessary to establish the validity or otherwise of the feed-forward hypothesis.

Animals↗

PubMed2001

The reductions in sweetened milk intake induced by interleukin-1 and endotoxin are not prevented by chronic antidepressant treatment.

Administration of interleukin-1 (IL-1) and endotoxin (lipopolysaccharide, LPS) to rodents can decrease food intake, a behavioral response resembling the diminution of appetite observed in human depression. IL-1 and LPS are known to affect cerebral neurotransmission involving norepinephrine and serotonin, both of which have been implicated in feeding behavior and in the pharmacotherapy of depression in man. The ability of chronic antidepressant treatment to attenuate LPS-induced depressed feeding in rats has been cited as evidence that cytokines may be involved in human depression. Thus, we studied the effects of chronic treatment with the tricyclic antidepressant, imipramine, and the novel antidepressant, venlafaxine, on the sweetened milk intake challenged with intraperitoneally injected IL-1 beta and LPS. Chronic (from 2 to 8 weeks) treatment of the mice with imipramine (10 mg/kg once or twice daily) or venlafaxine (10 and 20 mg/kg/day) did not significantly alter the decreases in milk intake in response to mIL-1 beta or LPS. In some experiments, chronic imipramine slightly decreased body weight and slightly increased milk intake, but not food pellet intake. Venlafaxine had none of these effects. Analysis of variance did not indicate any significant interactions between the antidepressant and IL-1 or LPS treatments. These results indicate that chronic treatment with antidepressants does not significantly alter the responses to IL-1 or LPS in the mouse sweetened milk model of sickness behavior.

Adrenergic Uptake Inhibitors↗

PubMed2000

Hippocampal norepinephrine-like voltammetric responses following infusion of corticotropin-releasing factor into the locus coeruleus.

Intracerebroventricular (i.c.v.) administration of corticotropin-releasing factor (CRF) increases the activity of noradrenergic neurons in the locus coeruleus (LC) assessed by electrophysiological and neurochemical studies. It has been suggested that this effect of i.c.v. CRF is exerted directly on LC noradrenergic (LC-NE) neurons. Infusion of CRF directly into the LC increases cortical and hippocampal release of norepinephrine (NE) as indicated by in vivo microdialysis studies, but the electrophysiological studies have shown both increases and decreases. The present study used in vivo voltammetry to study changes in the extracellular concentrations of NE in the rat hippocampus in response to infusion of CRF (100 ng) into the LC. When the infusion cannula was located in or very close to the LC, the immediate response to CRF was a small decrease in the NE-like oxidation current, followed by a robust increase after about 6-7 min. The oxidation current reached a peak around 13 min and returned to baseline by about 30 min after CRF infusion. By contrast with CRF, infusion of glutamate into the LC increased the oxidation current with a delay of around 30 s and a peak within 90 s. The responses to LC infusion of CRF in rats treated with DSP-4 to deplete hippocampal NE were substantially smaller than those in untreated rats, suggesting that the oxidation signals in untreated rats reflected changes in concentrations of NE. The response to glutamate was markedly augmented by pretreatment with the NE reuptake inhibitor, desmethylimipramine, suggesting that the observed responses reflected changes in NE. Infusion of the same dose of CRF into brain structures outside the LC did not elicit consistent changes in oxidation current in the hippocampus. The time course of the responses to CRF is compatible with previously reported electrophysiological responses of LC-NE neurons to CRF and with neurochemical evidence indicating that CRF can affect the activity of LC-NE neurons. The results indicate that CRF may act in or close to the LC to induce release of hippocampal NE, but the delayed response to CRF compared with that to glutamate, suggests that CRF does not directly activate LC-NE neurons.

Animals↗

PubMed2000

The role of cyclooxygenases in endotoxin- and interleukin-1-induced hypophagia.

Endotoxin (lipopolysaccharide, LPS) and interleukin-1 (IL-1) reduce food intake in rodents. Cyclooxygenase (COX) inhibitors have long been known to attenuate these responses, but recent work has revealed the existence of two distinct isoforms of the enzyme, COX1 and COX2, with different characteristics and functions. Therefore, we reassessed the COX involvement using inhibitors with different selectivities for COX1 and COX2. Feeding was assessed in nondeprived mice by measuring the intake of sweetened milk in a 30-minute period, as well as daily food pellet intake. LPS and IL-1beta consistently reduced milk intake. Treatment of the mice with the selective COX1 inhibitor, piroxicam, attenuated the hypophagic responses to IL-1 and LPS. Similar results were obtained with diclofenac. The hypophagic responses to LPS and IL-1beta were not affected by the COX2-selective inhibitors nimesulide and NS-398 at doses considered selective for COX2, but were inhibited by higher doses. Pretreatment of the mice with aspirin, an irreversible inhibitor of COX1 and COX2, prevented the hypophagic response to IL-1, 16 h, but not 40 h later. Taken together, these results suggest that COX1 may be the major isozyme involved in the hypophagic responses to LPS and IL-1, but a role for COX2 cannot be excluded. We also studied the combination of a COX inhibitor with the IL-1 receptor antagonist protein. Consistent with earlier results, both the IL-1 receptor antagonist (IL-1ra) and indomethacin attenuated the hypophagic responses to LPS. Combination of the two treatments produced additive results almost completely preventing the hypophagic response. Because indomethacin almost completely prevented the hypophagic response to IL-1, this additivity suggests that there are multiple mechanisms by which LPS induces hypophagia.

Animals↗

PubMed2000

Lack of evidence for a role of serotonin in interleukin-1-induced hypophagia.

Interleukin-1 (IL-1) administration depresses food intake in rodents. IL-1 is known to increase the metabolism of serotonin, which is known to affect feeding behavior. Thus, serotonin is an obvious candidate for a mediator of the hypophagic response to IL-1. Therefore, we tested the ability of serotonergic agonists and antagonists to alter the hypophagic responses to IL-1 and bacterial lipopolysaccharide (LPS). Hypophagia was assessed in ad lib-fed mice by recording the intake of sweetened milk in a 30-min period. Acute intraperitoneal administration of mouse IL-1beta reliably decreased milk intake. This hypophagic response was not affected by any of the serotonin antagonists tested, including 5-HT(1A) (WAY100135 and propranolol), 5-HT(1B) (GR127935), 5-HT(2) (ritanserin, ketanserin, SB206553, and RS102221), mixed 5-HT(1/2) (methysergide and metergoline), and 5-HT(3) (tropisetron) receptor antagonists. The 5-HT(1A) agonists (8-OH-DPAT and ipsapirone) and a 5-HT(1B) agonist (CGS12066B) known to decrease the activity of serotonergic neurons, also had no effect. Mice pretreated with 5,7-dihydroxytryptamine to deplete brain serotonin ate less, but, nevertheless, displayed similar hypophagic responses to mIL-1beta or LPS. The results suggest that serotonin is not involved in the decrease in short-term milk intake induced by mIL-1beta or LPS in mice that have been fed ad lib.

5,7-Dihydroxytryptamine↗

PubMed1999

Behavioral responses to stress are intact in CRF-deficient mice.

Corticotropin-releasing factor (CRF) has been implicated in endocrine and behavioral responses associated with stress. We have now studied the behavior of mice lacking the CRF gene (CRFko), comparing them to wild-type (WT) mice. Behaviors were observed in untreated mice, as well as following restraint or intraperitoneal administration of mouse interleukin-1beta (mIL-1beta). In the multicompartment chamber (MCC), the behaviors of CRFko and WT mice were very similar, and prior restraint and IL-1beta induced similar decreases in stimulus-contact times in both genotypes. In the elevated plus maze (EPM), restraint decreased the number of open arm entries but the behavior of both genotypes was very similar. In the open field (OF), the changes in locomotor activity in response to restraint were similar in both genotypes, although CRFko mice displayed slightly increased locomotor activity compared to WT mice. In both the MCC and the EPM, grooming behavior was increased by restraint, and was higher in the CRFko than in the WT mice. Compared to WT mice, CRFko mice had lower basal plasma concentrations of corticosterone which did not increase significantly following footshock. Thus, CRFko mice showed a clear dichotomy; the stress-related activation of the hypothalamo-pituitary-adrenal (HPA) axis was absent, whereas the stress-related behavioral responses thought to be mediated by brain CRF were unaffected. These results suggest that when mice develop in the absence of CRF, another factor (or factors) assumes the behavioral functions normally ascribed to brain CRF, but not activation of the HPA axis. Alternatively, the natural modulator of behavior may not be CRF, but some other molecule that can act on receptors sensitive to CRF. Thus, redundant CNS mechanisms appear to be involved in stress-related behaviors.

Animals↗

PubMed1999

Stress-induced behaviors require the corticotropin-releasing hormone (CRH) receptor, but not CRH.

Corticotropin-releasing hormone (CRH) is a central regulator of the hormonal stress response, causing stimulation of corticotropin and glucocorticoid secretion. CRH is also widely believed to mediate stress-induced behaviors, implying a broader, integrative role for the hormone in the psychological stress response. Mice lacking the CRH gene exhibit normal stress-induced behavior that is specifically blocked by a CRH type 1 receptor antagonist. The other known mammalian ligand for CRH receptors is urocortin. Normal and CRH-deficient mice have an identical distribution of urocortin mRNA, which is confined to the region of the Edinger-Westphal nucleus, and is absent from regions known to mediate stress-related behaviors. Since the Edinger-Westphal nucleus is not known to project to any brain regions believed to play a role in anxiety-like behavior, an entirely different pathway must be postulated for urocortin in the Edinger-Westphal nucleus to mediate these behaviors in CRH-deficient mice. Alternatively, an unidentified CRH-like molecule other than CRH or urocortin, acting through the CRH receptors in brain regions believed to mediate stress-induced behaviors, may mediate the behavioral response to stress, either alone or in concert with CRH.

Animals↗

PubMed1999

The roles of IL-1, IL-6, and TNFalpha in the feeding responses to endotoxin and influenza virus infection in mice.

Influenza infection or administration of bacterial endotoxin (lipopolysaccharide, LPS) results in diminished feeding and loss of body weight. It has been suggested that these effects may be mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and/or tumor necrosis factor-alpha (TNFalpha). To assess the potential role of these cytokines, we tested the ability of the naturally occurring IL-1-receptor antagonist (IL-1ra), a monoclonal antibody to mouse IL-6 (IL-6mAb), and a TNF binding protein fragment (TNFbp) to antagonize hypophagia induced by intraperitoneally (ip) injected mouse IL-1beta or LPS or by inoculation with influenza virus. Feeding was assessed by measuring the daily intake of food pellets and sweetened milk in a 30-min period. The hypophagia induced by mIL-1beta or LPS was not affected by pretreatment with IL-6mAb. The effects of IL-1beta were blocked by IL-1ra but unaffected by TNFbp. TNFbp and IL-1ra given separately both exhibited a tendency to attenuate LPS-induced hypophagia. The effectiveness of TNFbp plus IL-1ra treatment was similar to that of the individual antagonists. However, combined treatment with TNFbp, IL-1ra, and IL-6mAb almost completely prevented the depressing effect of LPS on milk intake. The antagonists were also tested in influenza virus-inoculated mice. IL-1ra was delivered chronically by osmotic minipumps and was supplemented by treatment with TNFbp and IL-6mAb. The treatments slightly attenuated the effects of the virus on milk intake 48 h after the inoculation and delayed the decrease in body weight. However, over the entire course of the experiment, the treatment produced very small, statistically nonsignificant, attenuations of the depressions in milk and food pellet intake. Similar results were obtained with TNFbp alone or the combination of IL-6mAb and TNFbp. The results suggest that IL-1beta, TNFalpha, and IL-6 contribute to the hypophagia induced by LPS. However, antagonism of all three cytokines was not sufficient to prevent the decreases in feeding and loss of body weight induced by influenza virus infection.

Animals↗

PubMed1999

Endotoxin- and interleukin-1-induced hypophagia are not affected by adrenergic, dopaminergic, histaminergic, or muscarinic antagonists.

Endotoxin (lipopolysaccharide, LPS) and interleukin-1 (IL-1) administration induce hypophagia in rodents. Both IL-1 and LPS are known to activate cerebral norepinephrine and serotonin metabolism, and IL-1 affects that of acetylcholine and histamine. Each of these neurotransmitters has been implicated in feeding behavior. Therefore, the ability of specific antagonists of the above neurotransmitter systems to counteract feeding responses to peripherally injected mIL-1beta and LPS was studied. Feeding was assessed in nondeprived mice by measuring the intake of sweetened milk in a 30-min period, as well as daily food pellet intake. LPS and mIL-1beta reliably reduced milk intake, and often reduced food pellet intake and body weight. Treatment of the mice with peripherally administered alpha-adrenergic (phentolamine or prazosin) or 3-adrenergic antagonists (propranolol), either alone or in combination, did not significantly alter the hypophagic responses to mIL-1beta or LPS. Mice in which cerebral norepinephrine was depleted with DSP-4 or 6-hydroxydopamine also displayed the usual hypophagia in response to mIL-1beta and LPS. The hypophagic responses to mIL-1beta and LPS were not affected by the histaminergic antagonists, pyrilamine (H1), cimetidine (H2), thioperamide (H3), or the histamine-depleting agent, alpha-fluoromethylhistidine, nor by the muscarinic cholinergic antagonist, scopolamine. The responses to mIL-l1 were also unaffected by the dopamine receptor antagonist, haloperidol, the opioid receptor antagonist, naloxone, and the NO synthase inhibitor, L-NAME. These results suggest that adrenergic, dopaminergic, histaminergic, cholinergic, opioid or nitric oxide systems are not essential for the hypophagia induced by IL-1, and that multiple redundant pathways may be involved in illness-related hypophagia.

Adrenergic Antagonists↗

PubMed1999

CRF-deficient mice respond like wild-type mice to hypophagic stimuli.

Corticotropin-releasing factor (CRF) has been implicated in physiological processes associated with stress, including changes in feeding behavior. Intracerebroventricular (ICV) administration of CRF and urocortin have been shown to depress feeding, and antagonism of CRF receptors has been reported to attenuate hypophagic responses to many treatments, suggesting that brain CRF may mediate these responses. We have now studied feeding behavior of mice lacking the CRF gene (CRFko), comparing them to wild-type (CRFwt) mice. Feeding was assessed in nondeprived mice by measuring the intake of sweetened milk in a 30-min period and the food pellet intake over 24 h. ICV administration of CRF or urocortin (1 microg, but not lower doses) depressed milk and food pellet intake in normal mice. Physical restraint for 30 min, or administration of mouse interleukin-1beta (mIL-1beta, 100 ng, IP), lipopolysaccharide (LPS, 1 microg, IP), or the serotonergic agonist (d-fenfluramine, 4 mg/kg, IP) reliably reduced milk intake. LPS also reduced food pellet intake. The responses to restraint, IL-1, LPS, and fenfluramine were indistinguishable between the CRFwt and CRFko mice. These results suggest that CRF is not essential for the reduction in sweetened milk intake that occurs following restraint, LPS, IL-1, or d-fenfluramine administration to mice.

Animals↗

PubMed1998

The role of cytokines in infection-related behavior.

Infections are associated with a specific behavioral pattern that includes hypomotility, hypophagia, increased sleep, decreased libido, and decreased exploration. This behavioral response is considered adaptive and important for the survival of the animal. A similar behavioral pattern was observed following treatment with endotoxin (lipopolysaccharide [LPS]) and cytokines, such as interleukin-1 (IL-1). Because the secretion of these cytokines is induced by LPS and infections, it is possible that they mediate the behavioral responses to infection. We have studied ingestive behavior and locomotor activity in mice following infection with influenza virus, or injection of LPS, IL-1, or IL-6. A lethal dose of influenza virus, LPS, IL-1a and IL-1b each decreased the intake of sweetened condensed milk and 24-hour food pellet intake and decreased locomotor activity. Mouse IL-6 was ineffective. A sublethal dose of influenza virus decreased food pellet intake and locomotor activity, but did not significantly alter milk intake. Indomethacin prevented the behavioral responses to IL-1, and attenuated those to LPS, but had only a very small effect on those to influenza virus. Similar results were obtained with the IL-1-receptor antagonist (IL-1ra); it completely prevented the responses to IL-1, attenuated those to LPS, but, even after chronic high dose administration, attenuated the effects of influenza virus infection only slightly. Our results suggest that while IL-1 may play an important role in the responses to infection, IL-6 does not. Moreover, IL-1 cannot be the only factor contributing to the altered behavior of LPS-injected or influenza virus-infected mice.

Animals↗

PubMed1998

Cortical catecholamine secretion following intravenous nitroprusside infusion: a voltammetric study.

Intravenous administration of sodium nitroprusside (NP) decreases blood pressure and activates noradrenergic neurons in the locus coeruleus (LC). Microdialysis studies have shown that NP infusion is accompanied by increased extracellular concentrations of norepinephrine (NE) in the medial prefrontal cortex. The present study used in vivo voltammetry to obtain a finer temporal analysis of the NP-induced changes in the extracellular concentrations of catecholamine-like compounds in the LC terminal fields in the rat medial prefrontal cortex. Intravenous infusion of rats with NP caused a rapid decrease in blood pressure that lasted for the duration of the infusion but rapidly reversed when the infusion was terminated. After a delay of between about 2 and 8 min (mean 5 min), there was an increase in extracellular concentrations of a NE-like substance. Presumed cortical release of NE lasted for several minutes but had almost returned to baseline by the time the NP infusion was terminated at 15 min. In many cases, the first peak was followed by a second one, usually of smaller amplitude but more prolonged than the first one. There was no clear response to the cessation of infusion of NP. The time course of the initial response is comparable to the previously reported electrophysiological response of LC-NE neurons to NP. In rats treated with DSP-4 to deplete cortical NE, blood pressure was reduced as in untreated rats, but no voltammetric response to NP infusion was observed. These results suggest that activation of the NE-LC neurons by NP results in a delayed synaptic release of NE in the cerebral cortex which attenuates within several minutes.

Animals↗

PubMed1998

Intracerebroventricular infusion of CRF increases extracellular concentrations of norepinephrine in the hippocampus and cortex as determined by in vivo voltammetry.

Previous studies have indicated that intracerebroventricular (i.c.v.) infusions of corticotropin-releasing factor (CRF) activate locus coeruleus (LC) noradrenergic neurons and increase the metabolism and extracellular concentrations of norepinephrine (NE) in several brain regions, suggesting increased release. To examine the temporal aspects and mechanism of the presumed release of NE, CRF was infused i.c.v. and the oxidation current was recorded using carbon fiber voltammetric electrodes placed in rat hippocampus or cortex. The CRF (1 microg, i.c.v.) caused a significant increase of oxidation current with a delay of approximately 5 min, and a peak at approximately 35 min. Similar responses were observed in the medial prefrontal cortex. The hippocampal response was markedly attenuated when CRF was infused into rats pretreated with DSP-4 to deplete NE, suggesting that the observed changes in current resulted from oxidation of NE. The increase of NE-like current did not occur when 25 microg alpha-helical CRF9-41 (ahCRF) was injected immediately before 1 microg CRF, suggesting that the response was mediated by cerebral CRF-receptors. Subcutaneous pretreatment with the ganglionic blocker, chlorisondamine, at a dose of 3 mg/kg had no effect on the voltammetric response to CRF, but a 6 mg/kg dose completely prevented the response. The beta-adrenoceptor antagonists, S-propranolol (5 mg/kg), nadolol (5 and 10 mg/kg), and timolol (5 mg/kg) attenuated the NE response to i.c.v. CRF to varying degrees. When chlorisondamine (3 microg) or nadolol (5 microg) were given i.c.v. before the CRF, the hippocampal responses were not blocked. These results suggest peripheral actions of ganglionic and beta-adrenergic blockers. We conclude that peripheral autonomic mechanisms, and probably both central and peripheral beta-adrenoceptors, contribute to the increased secretion of hippocampal NE in response to i.c.v. CRF.

Adrenergic beta-Antagonists↗

PubMed1997

Modifications of operant thermoregulatory behavior of the young pig by environmental temperature and food availability.

Piglets (Sus scrofa domesticus) were weaned at 14 days and acclimated to 10 ("cold animals") or 35 degrees C ("warm animals"). Cold animals were either fed ad lib. (10HH) or maintained on a high (10H) or low (10L) nutrition plane. Warm animals were maintained on a high (35H), low (35L), or a very low (35LL) nutrition plane. After 3 weeks of acclimation, operant thermoregulatory behavior (animals pressed a lever to turn on a heater) at 15 degrees C was assessed immediately following or 22 h after a meal. It was found that cold piglets or those on low nutrition planes produced more heat reinforcements than warm piglets and those on high nutrition planes. All animals tested 22 h after a meal produced more reinforcements than when tested immediately after a meal. Rectal temperature before the sessions of operant heating was lower in cold animals and those on low nutrition planes than in warm animals and those on high nutrition planes, but the difference dissipated after 90 min of access to heat. Piglets were then "deacclimated" for 24 h at 25 degrees C and their behavior observed once again. Deacclimation eliminated the effect of acclimation temperature on body temperature and behavior but it did not eliminate the effect due to nutrition. There was no interaction between temperature of acclimation and nutrition. The experiments demonstrate that the body temperature of the pig is independently affected by environmental temperature, the quantity of food eaten by the animal, and a possibility to use behavior. The behavioral drive is to reach body temperature which can be defined as a thermal set-point (temperature at which there is no need for a thermoregulatory response to occur) for behavioral thermoregulatory responses. Adaptation to different environmental conditions does not affect this behavioral set-point, but it can involve a temporary shift in the set points for specific autonomic thermoregulatory responses.

Acclimatization↗

PubMed1997

The role of cytokines in the behavioral responses to endotoxin and influenza virus infection in mice: effects of acute and chronic administration of the interleukin-1-receptor antagonist (IL-1ra).

Following infection with influenza virus, animals display decreased locomotor activity and feeding behavior and loss of body weight. It has been suggested that these effects may be mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), induced by the infection. To assess the potential role of IL-1, we tested the ability of a naturally occurring IL-1-receptor antagonist (IL-1ra) to antagonize the changes in feeding behavior induced by IL-1, endotoxin (lipopolysaccharide, LPS), and infection with influenza virus. Feeding behavior was assessed by measuring the daily intake of food pellets and sweetened milk in a 30-min period. Acute injection of IL-1 beta decreased milk intake, but mouse IL-6 and mouse TNF-alpha did not. However, TNF-alpha decreased food pellet intake slightly, especially when it was injected at the beginning of the dark phase. The reductions in milk intake induced by mouse IL-1 beta were largely prevented by IL-1ra pretreatment (100 micrograms/mouse i.p.). The LPS-induced reductions in milk intake were attenuated, but not blocked, by IL-1ra treatment (300 micrograms/mouse). LPS still induced significant decrements in the presence of the antagonist. In influenza virus-infected mice, IL-1ra was administered either by repeated subcutaneous (s.c.) injections, or by continuous s.c. infusion from osmotic minipumps. These IL-1ra treatments produced small, but statistically significant, attenuations of the depression in milk and food pellet intake in the virus-infected mice. In several experiments, IL-1ra treatment increased the survival of influenza virus-infected mice. Thus the attenuation of the hypophagia may have been caused by this IL-1ra-induced increase in survival. The results suggest that IL-1 contributes to sickness behavior induced by LPS and influenza virus infection, but it is not the only factor involved.

Animals↗

PubMed1997

A new design of carbon fiber microelectrode for in vivo voltammetry using fused silica.

Voltammetric probes were constructed from stainless steel and fused silica tubing sheathing carbon fibers. Electrochemical tests were carried out to compare these electrodes with commercially available glass-sealed IVEC-5 electrodes. Electrodes of both types displayed a similar declining baseline and calculated coefficients of stabilization (tangent of baseline during a stable period). There were no significant differences in sensitivity between the two designs of electrodes to norepinephrine (NE) and dopamine (DA). All tested electrodes showed linear current responses to increasing concentrations of NE and DA. Fused silica (FS type) electrodes are suitable for electrochemical measurements (in vivo voltammetry) and display characteristics similar to those of commercially available IVEC-5 glass-sealed carbon fiber microelectrodes. Manufacture of FS type electrodes in a biochemical laboratory is easy and does not require any special equipment (such as a micropipette puller) or glass-handling skills. An additional fused silica tube can be glued to the electrode for microinjections. The electrodes are very robust, easy to handle and can be mounted on the arms of standard stereotaxic instruments. The electrodes can be made long enough to reach the deepest parts of brain of large animals.

Microelectrodes↗

PubMed1996

Peripheral administration of interleukin-1 increases extracellular concentrations of norepinephrine in rat hypothalamus: comparison with plasma corticosterone.

Peripheral administration of interleukin-1 (IL-1) activates the hypothalamo-pituitary-adrenocortical (HPA) axis and also activates norepinephrine (NE) metabolism in the hypothalamus. Because there is evidence that hypothalamic NE can activate CRF secretion, it has been proposed that changes in hypothalamic noradrenergic activity are instrumental in the IL-1-induced activation of the HPA axis. We have examined this hypothesis by assessing the release of hypothalamic NE using in vivo microdialysis following intravenous (IV) or intraperitoneal (IP) injection of human IL-1 beta and comparing the responses with those in plasma corticosterone. The results indicate that extracellular concentrations of NE in the hypothalamus increased following IV and IP administration of IL-1 beta. The elevation was more rapid following IV IL-1 beta, and reached a peak at 1 h, whereas the slower and smaller increase following IP IL-1 beta did not reach a peak until 2 h. The results were similar in both anesthetized and unanesthetized rats. In unanesthetized rats, plasma corticosterone increased shortly following IV or IP IL-1 beta administration, but the peak concentration following IV IL-1 beta was significantly earlier (around 1 h) than that following IP IL-1 beta (around 2 h). The hypothalamic noradrenergic responses followed a pattern similar to that of plasma corticosterone with either route of IL-1 beta administration, but they were not identical. The results are consistent with the possibility that a central noradrenergic mechanism mediates the activation of the HPA axis by peripherally administered IL-1 beta. However, appreciable differences in the time courses of the responses may indicate the involvement of other factors.

Animals↗

PubMed1996

The role of cerebral noradrenergic systems in the Fos response to interleukin-1.

Peripheral administration of interleukin-1 (IL-1) has been shown to activate induction of Fos in the brain, but the mechanism is not known. Because cerebral noradrenergic systems have been implicated in Fos induction, we studied the IL-1-induced appearance of Fos in mice pretreated with 6-hydroxydopamine (6-OHDA) which depleted cerebral norepinephrine (NE) by more than 90%, but did not significantly alter dopamine. Intraperitoneally injected IL-1 beta increased Fos in several brain regions, but most obviously in the hypothalamic paraventricular nucleus (PVN). Pretreatment with 6-OHDA substantially reduced the IL-1-induced Fos increase in the PVN which was no longer statistically significant. When the 6-OHDA treatment was preceded by administration of desmethylimipramine which prevents NE depletion, IL-1 treatment increased Fos in the PVN, suggesting that the effect of 6-OHDA was indeed related to the depletion of NE. These results suggest that the noradrenergic innervation of the PVN is involved in the IL-1-induced induction of Fos in the PVN. By contrast with previous experiments is rats, the IL-1-induced increase in plasma corticosterone was not significantly altered by the 6-OHDA pretreatment in mice.

Adrenergic Uptake Inhibitors↗