Early ficolin-1 is a sensitive prognostic marker for functional outcome in ischemic stroke.

BACKGROUND: Several lines of evidence support the involvement of the lectin pathway of complement (LP) in the pathogenesis of acute ischemic stroke. The aim of this multicenter observational study was to assess the prognostic value of different circulating LP initiators in acute stroke. METHODS: Plasma levels of the LP initiators ficolin-1, -2, and -3 and mannose-binding lectin (MBL) were measured in 80 stroke patients at 6 h only and in 85 patients at 48 h and later. Sixty-one age- and sex-matched healthy individuals served as controls. Stroke severity was measured on admission using the National Institutes of Health Stroke Scale (NIHSS). The outcome was measured at 90 days by the modified Rankin Scale (mRS). RESULTS: Ficolin-1 was decreased in patients compared with controls measured at 6 h (median 0.13 vs 0.33 µg/ml, respectively, p < 0.0001). At 48 h, ficolin-1 was significantly higher (0.45 µg/ml, p < 0.0001) compared to the 6 h samples and to controls. Likewise, ficolin-2 was decreased at 6 h (2.70 vs 4.40 µg/ml, p < 0.0001) but not at 48 h. Ficolin-3 was decreased both at 6 and 48 h (17.3 and 18.23 vs 21.5 µg/ml, p < 0.001 and <0.05, respectively). For MBL no difference was detected between patients and controls or within patients at the different time points. In multivariate analysis, early ficolin-1 was independently associated with unfavorable mRS outcome (adjusted odds ratio (OR): 2.21, confidence interval (CI) 95 % 1.11-4.39, p = 0.023). Early ficolin-1 improved the discriminating ability of an outcome model including NIHSS and age (area under the curve (AUC) 0.95, CI 95 % 0.90-0.99, p = 0.0001). CONCLUSIONS: The ficolins are consumed within 6 h after stroke implicating activation of the LP. Early ficolin-1 is selectively related to 3-month unfavorable outcome.

Heart-fatty acid-binding and tau proteins relate to brain injury severity and long-term outcome in subarachnoid haemorrhage patients.

BACKGROUND: Vasospasm and other secondary neurological insults may follow subarachnoid haemorrhage (SAH). Biomarkers have the potential to stratify patient risk and perhaps serve as an early warning sign of delayed ischaemic injury. METHODS: Serial cerebrospinal fluid (CSF) samples were collected from 38 consecutive patients with aneurysmal SAH admitted to the neurosurgical intensive care unit. We measured heart-fatty acid-binding protein (H-FABP) and tau protein (τ) levels in the CSF to evaluate their association with brain damage, and their potential as predictors of the long-term outcome. H-FABP and τ were analysed in relation to acute clinical status, assessed by the World Federation of Neurological Surgeons (WFNS) scale, radiological findings, clinical vasospasm, and 6-month outcome. RESULTS: H-FABP and τ increased after SAH. H-FABP and τ were higher in patients in poor clinical status on admission (WFNS 4-5) compared with milder patients (WFNS 1-3). Elevated H-FABP and τ levels were also observed in patients with early cerebral ischaemia, defined as a CT scan hypodense lesion visible within the first 3 days after SAH. After the acute phase, H-FABP, and τ showed a delayed increase with the occurrence of clinical vasospasm. Finally, patients with the unfavourable outcome (death, vegetative state, or severe disability) had higher peak levels of both proteins compared with patients with good recovery or moderate disability. CONCLUSIONS: H-FABP and τ show promise as biomarkers of brain injury after SAH. They may help to identify the occurrence of vasospasm and predict the long-term outcome.

Intracerebroventricular injection of interleukin 1 induces high circulating levels of interleukin 6.

IL-1 is known to have a central role in the induction of acute-phase response, and some of its activities (including induction of some acute-phase proteins) were reported to be mediated by an induction of IL-6. Administration to rats of 200 ng of human rIL-1 by intracerebroventricular injection resulted in a more marked induction of circulating IL-6 than the same dose of IL-1 administered systemically (intravenously or intraperitoneally). Induction of serum IL-6 by centrally administered IL-1 was also observed in hypophysectomized or adrenalectomized rats, suggesting that activation of the hypothalamus-pituitary-adrenal axis is not essential for this effect of IL-1. IL-6 induction was also observed after pretreatment with indomethacin, indicating that the effect was dissociated from the pyrogenic activity of IL-1. Induction of IL-6 by a central action could represent a novel pathway in IL-1-induced acute-phase response.

Leukocyte recruitment in the cerebrospinal fluid of mice with experimental meningitis is inhibited by an antibody to junctional adhesion molecule (JAM).

The mechanisms that govern leukocyte transmigration through the endothelium are not yet fully defined. Junctional adhesion molecule (JAM) is a newly cloned member of the immunoglobulin superfamily which is selectively concentrated at tight junctions of endothelial and epithelial cells. A blocking monoclonal antibody (BV11 mAb) directed to JAM was able to inhibit monocyte transmigration through endothelial cells in in vitro and in vivo chemotaxis assays. In this study, we report that BV11 administration was able to attenuate cytokine-induced meningitis in mice. The intravenous injection of BV11 mAb significantly inhibited leukocyte accumulation in the cerebrospinal fluid and infiltration in the brain parenchyma. Blood-brain barrier permeability was also reduced by the mAb. We conclude that JAM may be a new target in limiting the inflammatory response that accompanies meningitis.

Targeted deletions of complement lectin pathway genes improve outcome in traumatic brain injury, with MASP-2 playing a major role.

The lectin pathway (LP) of complement activation is believed to contribute to brain inflammation. The study aims to identify the key components of the LP contributing to TBI outcome as possible novel pharmacological targets. We compared the long-term neurological deficits and neuropathology of wild-type mice (WT) to that of mice carrying gene deletions of key LP components after experimental TBI. WT or MASP-2 (Masp2-/-), ficolin-A (Fcna-/-), CL-11 (Colec11-/-), MASP-1/3 (Masp1-/-), MBL-C (Mbl2-/-), MBL-A (Mbl1-/-) or MBL-/- (Mbl1-/-/Mbl2-/-) deficient male C57BL/6J mice were used. Mice underwent sham surgery or TBI by controlled cortical impact. The sensorimotor response was evaluated by neuroscore and beam walk tests weekly for 4 weeks. To obtain a comparative analysis of the functional outcome each transgenic line was rated according to a health score calculated on sensorimotor performance. For selected genotypes, brains were harvested 6 weeks after injury for histopathological analysis. MASP-2-/-, MBL-/- and FCN-A-/- mice had better outcome scores compared to WT. Of these, MASP-2-/- mice had the best recovery after TBI, showing reduced sensorimotor deficits (by 33% at 3 weeks and by 36% at 4 weeks). They also showed higher neuronal density in the lesioned cortex with a 31.5% increase compared to WT. Measurement of LP functional activity in plasma from MASP-2-/- mice revealed the absence of LP functional activity using a C4b deposition assay. The LP critically contributes to the post-traumatic inflammatory pathology following TBI with the highest degree of protection achieved through the absence of the LP key enzyme MASP-2, underlining a therapeutic utility of MASP-2 targeting in TBI.

Imaging T-cell movement in the brain during experimental cerebral malaria.

T-cells are known to play a role in the pathology associated with experimental cerebral malaria, although it has not previously been possible to examine their behaviour in brain. Using multiphoton laser scanning microscopy, we have examined the migration and movement of these cells in brain tissue. We believe that this approach will help define host-parasite interactions and examine how intervening in these relationships affects the development of cerebral pathology.

Neuroprotective effect of C1-inhibitor following traumatic brain injury in mice.

BACKGROUND: The goal of the study was to evaluate the effects of Cl-inhibitor (C1-INH), an endogenous glycoprotein endowed with multiple anti-inflammatory actions, on cognitive and histological outcome following controlled cortical impact (CCI) brain injury. METHODS: Male C57B1/6 mice (n=48) were subjected to CCI brain injury. After brain injury, animals randomly received an intravenous infusion of either C1-INH (15 U either at 10 minutes or 1 hour postinjury) or saline (equal volume, 150 microl at 10 min postinjury). Uninjured control mice received identical surgery and saline injection without brain injury. Cognitive function was evaluated at 4 weeks postinjury using the Morris Water Maze. Mice were subsequently sacrificed, the brains were frozen and serial sections were cut. Traumatic brain lesion was assessed by dividing the area of the ipsilateral hemisphere for the area of the contralateral one at the level of the injured area of the brain. FINDINGS: Brain-injured mice receiving C1-INH at 10 min postinjury showed attenuated cognitive dysfunction compared to brain-injured mice receiving saline (p < 0.01). These mice also showed a significantly reduced traumatic brain lesion compared to mice receiving saline (p < 0.01). Mice receiving C1-INH at 1 hour post injury did not show a significant improvement in either cognitive or histological outcome. Conclusions Our results suggest that administration of C1-INH at 10 minutes postinjury attenuates cognitive deficits and histological damage associated with traumatic brain injury.

Effect of traumatic brain injury on cognitive function in mice lacking p55 and p75 tumor necrosis factor receptors.

BACKGROUND: Tumor necrosis factor (TNF)-alpha has been suggested to play both a deleterious and beneficial role in neurobehavioral dysfunction and recovery following traumatic brain injury (TBI). The goal of this study was to evaluate the specific role of tumor necrosis factor (TNF) receptors p55 and p75 in mediating cognitive outcome following controlled cortical impact (CCI) brain injury by comparing post-traumatic cognitive function in mice with genetically engineered deletion of the gene for either p55 (-/-) or p75 (-/-) receptors. METHOD: Male C57B1/6 mice (WT, n=29), and mice genetically engineered to delete p55 TNF (p55 (-/-), n=8) or p75 TNF (p75 (-/-), n=23) receptors were used. They were anesthetized with intraperitoneal (i.p.) administration of sodium pentobarbital (65 mg/kg) and subjected to CCI brain injury of moderate severity. Sham-injured control mice were anesthetized and surgically prepared similarly but they received no impact. Assessment of mRNA expression of inflammatory, proapoptotic and antiapoptotic genes was done by real time-polymerase chain reaction (RT-PCR). Cognitive outcome was evaluated at 4 weeks postinjury using the Morris water maze (MWM). FINDINGS: mRNA expression of inflammatory, proapoptotic and antiapoptotic genes prior to TBI did not reveal any baseline difference between p55 and p75 (-/-) mice. WT mice showed greater baseline expression of inflammatory genes. The learning ability of p55 (-/-) brain-injured mice was significantly better than that observed in p75 (-/-) brain-injured mice (p < 0.05). Cognitive learning in WT control mice fell between the p55 (-/-) and p75 (-/-) mice. CONCLUSIONS: These data suggest that TNF-alpha may both exacerbate cognitive dysfunction via p55 receptor and attenuate it via p75 receptor.

Interleukin-1beta immunoreactivity and microglia are enhanced in the rat hippocampus by focal kainate application: functional evidence for enhancement of electrographic seizures.

Using immunocytochemistry and ELISA, we investigated the production of interleukin (IL)-1beta in the rat hippocampus after focal application of kainic acid inducing electroencephalographic (EEG) seizures and CA3 neuronal cell loss. Next, we studied whether EEG seizures per se induced IL-1beta and microglia changes in the hippocampus using bicuculline as a nonexcitotoxic convulsant agent. Finally, to address the functional role of this cytokine, we measured the effect of human recombinant (hr)IL-1beta on seizure activity as one marker of the response to kainate. Three and 24 hr after unilateral intrahippocampal application of 0.19 nmol of kainate, IL-1beta immunoreactivity was enhanced in glia in the injected and the contralateral hippocampi. At 24 hr, IL-1beta concentration increased by 16-fold (p < 0.01) in the injected hippocampus. Reactive microglia was enhanced with a pattern similar to IL-1beta immunoreactivity. Intrahippocampal application of 0.77 nmol of bicuculline methiodide, which induces EEG seizures but not cell loss, enhanced IL-1beta immunoreactivity and microglia, although to a less extent and for a shorter time compared with kainate. One nanogram of (hr)IL-1beta intrahippocampally injected 10 min before kainate enhanced by 226% the time spent in seizures (p < 0.01). This effect was blocked by coinjection of 1 microgram (hr)IL-1beta receptor antagonist or 0.1 ng of 3-((+)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate, selective antagonists of IL-1beta and NMDA receptors, respectively. Thus, convulsant and/or excitotoxic stimuli increase the production of IL-1beta in microglia-like cells in the hippocampus. In addition, exogenous application of IL-1beta prolongs kainate-induced hippocampal EEG seizures by enhancing glutamatergic neurotransmission.

Central endotoxin induces different patterns of interleukin (IL)-1 beta and IL-6 messenger ribonucleic acid expression and IL-6 secretion in the brain and periphery.

Centrally injected endotoxin induced high levels of interleukin (IL)-6 in serum, but the mechanisms of this induction and the signal conveying the information from the brain to the periphery are not yet known. To help characterize the pathway of centrally mediated induction of IL-6 in periphery, the cytokine levels were measured in rat serum and cerebrospinal fluid at different times after intracerebro-ventricular endotoxin (LPS, 2.5 micrograms/rat). In the same experiments, IL-6 and IL-1 beta messenger RNA (mRNA) expression, measured by Northern blot analysis, were evaluated in the periphery (adrenals, lymph nodes, and mononuclear cells) and brain (hypothalamus, hippocampus and striatum). In serum, IL-6 levels were highest after 2h; then they rapidly decreased. IL-6 mRNA showed the same time-course in adrenals and lymph nodes. The pattern in the central nervous system was different: in the cerebrospinal fluid, IL-6 was detectable starting from 2h, reaching a plateaux at 4-8h and remaining detectable until 16 h. IL-6 mRNA expression in the brain areas showed a similar time-course, reaching a maximum at 4-8 h. IL-1 beta mRNA induction started at the same time in brain and periphery, i.e. 1 h after LPS, but the maximal effect was reached at 2 h in mononuclear cells, adrenals, and lymph nodes, and at 8 h in brain regions. The results indicate that circulating IL-6 induced by central LPS is produced mainly peripherally and that synthesis of IL-6 and IL-1 beta are regulated differently in the brain and periphery.

Interferon-gamma potentiates interleukin (IL)-6 and tumor necrosis factor-alpha but not IL-1beta induced by endotoxin in the brain.

Because interferon-gamma (IFN gamma) is present in the central nervous system during neurologic diseases associated with inflammation, its effect on endotoxin-induced cytokines was studied. Cerebrospinal fluid (CSF) and serum levels of interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF alpha), their messenger RNA expression in brain areas (hypothalamus, hippocampus, and striatum) and in spleen were evaluated 2 and 8 h after endotoxin [lipopolysaccharide (LPS), 25 microg/rat i.c.v.], IFN gamma (2.5 microg/rat i.c.v.) or after their coadministration in rats. CSF and serum IL-1beta levels were increased by LPS alone and IFN gamma coadministration did not furtherly increase them. IFN gamma potentiated LPS effect on IL-6 and TNF alpha levels in both CSF and serum. LPS and IFN-gamma coadministration did not alter IL-1beta messenger RNA expression induced by LPS in brain areas and in spleen, but it potentiated that of IL-6 and TNF alpha. The present in vivo data show that i.c.v. coadministration of LPS and IFN gamma results in a potentiation of cytokine production (IL-6 and TNF alpha) which may trigger a cascade of events relevant to neurodegenerative processes. This action is independent of IL-1beta because the production of this cytokine is not altered by IFN gamma treatment.

Increased cytokine release from peripheral blood cells after acute stroke.

Cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha can play pathogenetic or protective roles in stroke. They are increased in the brain after experimental ischemia and in the CSF of patients with stroke. However, their presence in the periphery is still controversial. To determine the source and time-course of cytokines in blood of stroke patients, IL-6 and TNF-alpha release from blood cells and serum levels were determined in 40 patients on days 1 through 2, 4, 10, 30, and 90 after stroke. Twenty healthy age-matched volunteers were used as controls. IL-6 and TNF-alpha release from stimulated blood cells was increased in stroke patients, compared to controls. A peak response (+224%) was observed at day 4 for IL-6, while TNF-alpha release was largely and significantly increased (about three-fold compared to controls) from day 1 to 2 until day 90 after stroke. The increase in IL-6 release was significantly higher in ischemic, compared to hemorrhagic strokes, at days 1 and 4. Circulating IL-6 was increased at each time point. The ischemic processes in the CNS induces a long-lasting activation of IL-6 and TNF-alpha production in peripheral blood cells, which are a major source of serum cytokines after stroke.

Neuroprotection by complement (C1) inhibitor in mouse transient brain ischemia.

The authors investigated the effect of the C1 inhibitor (C1-INH), the only known inhibitor of complement C1, in a murine model of transient focal ischemia. Ischemia was induced by intraluminal occlusion of the middle cerebral artery. After 2 hours, reperfusion was produced by removing the nylon monofilament occluding the artery. The effect of 15 U C1-INH (intravenously) was evaluated in terms of general and focal neurologic deficits, ischemic volume, neutral red staining (to identify the brain areas subject to ischemic damage), and glial fibrillary acidic protein immunoreactivity (to show astrocytic response). Forty-eight hours after ischemia, C1-INH significantly improved general and focal deficits by 36% and 54%, respectively, and significantly reduced infarct volume (CI-INH, 6.69% +/- 2.93%; saline, 24.24% +/- 8.24%) of total brain. Neutral red staining further showed the strong protective effect of C1-INH in cortex, hippocampus, and striatum. Astrocyte activation induced by ischemia was not affected by C1-INH. These findings show that C1-INH displayed a potent neuroprotective action by effectively reducing ischemia-reperfusion injury.

Cross tolerance between ketamine and morphine to some pharmacological and biochemical effects.

Whether morphine and ketamine induced cross-tolerance to some of their common pharmacological and biochemical effects, namely analgesia and enhancement of metabolites of dopamine (DA) in the striatum and limbic area of the rat was analysed. Ketamine was given at the dose of 100 mg/kg, twice a day for 8 days. After this treatment, a challenge dose of morphine (15 mg/kg, i.p.) still induced analgesia comparable to that induced by morphine alone, showing no cross-tolerance to this effect. In contrast, the challenge dose of morphine given to ketamine-tolerant rats no longer enhanced metabolism of DA, indicating the appearance of cross-tolerance to this effect. A high degree of tolerance to morphine was obtained after the subcutaneous implantation of rats with pellets of morphine; a challenge dose of ketamine to morphine-tolerant rats induced marked analgesia, with no cross-tolerance to this pharmacological effect, while cross-tolerance was present to the biochemical effect. The existence of a high degree of reciprocal cross-tolerance in both areas and on both metabolites of DA is consistent with the hypothesis of action at a common receptor; the lack of cross-tolerance to the analgesic effect indicates that analgesia is achieved by a different mechanism for the two drugs.

The sympathetic nervous system tonically inhibits peripheral interleukin-1beta and interleukin-6 induction by central lipopolysaccharide.

To study the role of the sympathetic nervous system in the induction of inflammatory cytokines elicited by central lipopolysaccharide, sympathetic chemical denervation was performed by intraperitoneal injection of 6-hydroxydopamine. Rats received the neurotoxin according to the following schedule: 50 mg/kg on days 1 and 2, 100 mg/kg on days 3, 4 and 7. On day 8, lipopolysaccharide (2.5 microg/6 microl/rat) was injected intracerebroventricularly and rats were killed 2 h later. 6-Hydroxydopamine reduced noradrenaline and dopamine content in the spleen by 88.7% and 88.8% respectively, without affecting striatal contents indicating that the chemical sympathectomy had been effective and selective. In sympathectomized rats, lipopolysaccharide raised interleukin-1beta and interleukin-6 serum levels more than in control rats given the vehicle. Tumour necrosis factor-alpha serum levels in sympathectomized rats were no different from those in vehicle-treated rats. Interleukin-1beta and interleukin-6 messenger RNA expression, measured by northern blot analysis, was clearly detectable in adrenals and spleen of rats given lipopolysaccharide. Sympathectomy increased lipopolysaccharide-induced interleukin-1beta and interleukin-6 messenger RNA in adrenals and spleen. Corticosterone basal levels were raised by central lipopolysaccharide and not further changed by sympathectomy. The present study shows that sympathetic nervous system denervation enhances the synthesis and production of peripheral interleukin-1beta and interleukin-6 in rats given central lipopolysaccharide and suggests a tonic inhibitory control of the sympathetic nervous system on these inflammatory cytokines.

Glutamate release in the nucleus tractus solitarius induced by peripheral lipopolysaccharide and interleukin-1 beta.

The involvement of vagal afferents in the communication pathway from the immune system to the brain was studied. Glutamate was measured in the nucleus tractus solitarius, the brain area receiving glutamatergic vagal afferents, after peripheral injection of lipopolysaccharide or interleukin-1 beta. Intraperitoneal or intravenous saline or intraperitoneal heat-inactivated interleukin-1 beta increased glutamate release, measured by brain microdialysis in freely-moving rats at 20 min (137 +/- 19%, 126 +/- 10% and 133 +/- 6%, respectively), without inducing any other change up to 3 h after injection. Intraperitoneal lipopolysaccharide (10 micrograms/rat) increased glutamate at 20 min (132 +/- 10%) and at 60 min (208 +/- 26%). To compare lipopolysaccharide effectiveness by the two routes, serum levels of interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha were measured. Intravenous lipopolysaccharide induced each cytokine more rapidly and efficiently than intraperitoneal lipopolysaccharide. Perfusion with tetrodotoxin (1 microM) in the dialysis probe decreased glutamate basal levels by approximately 20% and completely prevented lipopolysaccharide effects, showing the neuronal component of the glutamate measured. Except for the 20-min increase, intravenous lipopolysaccharide (10 micrograms/rat) did not affect glutamate release. Intraperitoneal interleukin-1 beta (4 micrograms/rat) increased glutamate release at 20 min (126 +/- 6%) and at 40 min (150 +/- 18%). These data indicate that vagal glutamatergic system in the nucleus tractus solitarius is activated by intraperitoneal injections of immunoactive compounds.

Functional and histological consequences of quinolinic and kainic acid-induced seizures on hippocampal somatostatin neurons.

Changes in endogenous somatostatin after quinolinic and kainic acids were investigated by measuring somatostatin-like peaks by in vivo voltammetry and by assessing the distribution of somatostatin-positive neurons by immunocytochemistry. Kainic acid (0.19 nmol/0.5 microliter) or quinolinic acid (120 nmol/0.5 microliter) in doses inducing comparable electroencephalographic seizure patterns, were injected into the hippocampus of freely moving rats. Somatostatin-like peaks were measured every 6 min for 3 h by a carbon fiber electrode implanted in the proximity of the injection needle. Kainic acid kept somatostatin-like peaks significantly higher than saline from 48 min after the injection till the end of the recording. Somatostatin-like peaks were dramatically elevated by quinolinic acid, reaching a maximum of 482% 60 min after the injection. Three days later, administration of kainic acid resulted in selective degeneration of CA3 pyramidal neurons but did not affect the number of somatostatin-positive cells, while quinolinic acid induced cell loss in all pyramidal layers and complete degeneration of somatostatin-positive cells in the whole hippocampus. Thus, the quantitative difference in somatostatin release in response to doses of kainic and quinolinic acids inducing comparable electroencephalographic seizure patterns was reflected in a substantial difference in the neurodegenerative consequences. In both models, the release of somatostatin in response to seizures may be interpreted as a "defense" mechanism aimed at reducing the spread of excitation in the tissue.

Changes in the serotonergic system during the sleep-wake cycle: simultaneous polygraphic and voltammetric recordings in hypothalamus using a telemetry system.

Changes in the serotonergic system in the posterior hypothalamus of freely moving rats were related to sleep and wakefulness using in vivo voltammetry (with carbon fiber microelectrodes) and polygraphic recordings. By using an optoelectronic telemetry system for the voltammetric signals, electrical cross-talk between the two settings was avoided and simultaneous neurochemical and electro-physiological recordings could be made so that a detailed time course of events could be obtained. Extracellular levels of the serotonin metabolite, 5-hydroxy-indoleacetic acid, measured every 2 min, increased with wakefulness and decreased with sleep: levels were significantly lower during desynchronized sleep than slow wave sleep. In vivo voltammetry associated with the optoelectronic telemetry system appears to be a useful tool for studying the relationship between neurochemical changes and electrophysiological events.

Hypothalamic serotonergic activity correlates better with brain temperature than with sleep-wake cycle and muscle tone in rats.

The activity of the serotonergic system varies in phase with the sleep-wake cycle, which is associated with changes in several physiological functions, including electroencephalographic activity, brain temperature, and locomotion. The aim of the present study was to clarify which of these parameters correlates better with serotonergic activity in spontaneous conditions. Voltammetric recordings by telemetry of serotonergic metabolism in the medial preoptic area and polygraphic recordings of sleep-wake activity (by means of electroencephalographic delta band, brain cortical temperature and neck electromyographic activity recordings) were simultaneously performed in freely moving rats. Univariate analyses of variance revealed that each variable under investigation was statistically correlated with serotonergic metabolism. When the variables were entered into the model simultaneously, both partial correlation and step-wise multiple regression analyses indicated that the highest correlation exists between serotonergic metabolism and brain cortical temperature. The present data show that serotonergic activity in the medial preoptic area is closely linked to physiological changes in brain temperature.

Impaired central stress-induced release of noradrenaline in rats with heart failure: a microdialysis study.

Sympathetic hyperactivity in rats with heart failure is associated with increased extracellular noradrenaline in the hypothalamic paraventricular nucleus at rest. However, it is unknown how this nucleus responds to stressful stimuli. In the present study we therefore examined the basal and stress-induced release of noradrenaline in the paraventricular nucleus of conscious Sprague-Dawley rats with heart failure measured by in vivo microdialysis. Basal noradrenaline concentration in the paraventricular nucleus of rats with heart failure was more than double that in sham-operated controls. Immobilization stress decreases noradrenaline levels in the paraventricular nucleus of rats with heart failure to 57% of baseline, while it increased in sham-operated controls to 228%. However, serum corticosterone was similarly elevated at 30 and 90 min post-stress in both experimental groups. We have shown that heart failure causes an impairment of the central noradrenergic system's response to acute sympatho-excitation but does not affect the hypothalamo-pituitary-adrenocortical response.