Intracerebroventricular streptozotocin induces behavioral impairments and increases short­term C3 gene expression in the hippocampus of Wistar rats.

A non­transgenic rat model based on intracerebroventricular injection of streptozotocin (STZ) has been used as an animal model to investigate mechanisms associated to the late onset of sporadic Alzheimer's disease, such as anatomical and behavioral impairments. However, molecular aspects related to gene expression, mainly in the hippocampus, require more investigation. Thus, this study evaluated the early and late cognitive functions and hippocampal gene expression after STZ administration. Male Wistar rats were divided into 4 groups: STZ (injected bilaterally), control group for the early memory function evaluation (1 month after surgery = phase 1, same volume of vehicle), and the same treatment for the late memory function evaluation (4 months after surgery = phase 2). The animals were observed in the elevated plus maze to assess behaviors related to anxiety, risk­assessment and fear­related memories. The behavioral tests were followed by brain removal and hippocampal dissection for RNA extraction and qRT­PCR to assess the expression levels of 4 Alzheimer's disease related genes: Mapt, Apoe, C3 and Ps­1. Animals from both phases showed increased time percentage and number of entries into the open arms, indicating risk behavior associated with anxiety, and an increased time percentage in the center square for both exposures (re­test) when compared to the control group, suggesting working memory impairment related to an aversive event. Statistical analyses indicated that the STZ group presented alterations in anxiety, memory and risk assessment responses. Additionally, one month after STZ administration, C3 gene assays revealed an increased expression. Therefore, current data indicate that neuroinflammatory events linked to the expression of pro inflammatory cytokines such as C3 are related to memory, anxiety and decision-making alterations.

Unilateral intranigral administration of ß-sitosterol ß-D-glucoside triggers pathological α-synuclein spreading and bilateral nigrostriatal dopaminergic neurodegeneration in the rat.

The spreading and accumulation of α-synuclein and dopaminergic neurodegeneration, two hallmarks of Parkinson's disease (PD), have been faithfully reproduced in rodent brains by chronic, oral administration of ß-sitosterol ß-D-glucoside (BSSG). We investigated whether a single injection of BSSG (6 µg BSSG/µL DMSO) in the left substantia nigra of Wistar rats causes the same effects. Mock DMSO injections and untreated rats formed control groups. We performed immunostainings against the pathological α-synuclein, the dopaminergic marker tyrosine hydroxylase (TH), the neuroskeleton marker ß-III tubulin, the neurotensin receptor type 1 (NTSR1) as non-dopaminergic phenotype marker and Fluro-Jade C (F-J C) label for neurodegeneration. Using ß-galactosidase (ß-Gal) assay and active caspase-3 immunostaining, we assessed cell death mechanisms. Golgi-Cox staining was used to measure the density and types of dendritic spines of striatal medium spiny neurons. Motor and non-motor alterations were also evaluated. The study period comprised 15 to 120 days after the lesion. In the injured substantia nigra, BSSG caused a progressive α-synuclein aggregation and dopaminergic neurodegeneration caused by senescence and apoptosis. The α-synuclein immunoreactivity was also present within microglia cells. Decreased density of dopaminergic fibers and dendritic spines also occurred in the striatum. Remarkably, all the histopathological changes also appeared on the contralateral nigrostriatal system, and α-synuclein aggregates were present in other brain regions. Motor and non-motor behavioral alterations were progressive. Our data show that the stereotaxic BSSG administration reproduces PD α-synucleinopathy phenotype in the rat. This approach will aid in identifying the spread mechanism of α-synuclein pathology and validate anti-synucleinopathy therapies.

Central substance P NK1 receptors are involved in fever induced by LPS but not by IL-1ß and CCL3/MIP-1α in rats.

Substance P (SP) is a neuropeptide that can modulate inflammatory mediator release through activation of NK(1) receptors (NK(1)R). Some studies have also suggested the involvement of SP in lipopolysaccharide (LPS)-induced fever. However, the precise contribution of this neuropeptide to the pathways activated during fever is unknown. In this study we investigated the effect of a selective NK(1)R antagonist, SR140333B, on the febrile response induced by LPS and cytokines. Our results show that the systemic injection of SR140333B did not modify the fever induced by LPS at a dose that is able to reduce protein extravasation induced by SP in the skin. On the other hand, intracerebroventricular administration of SR140333B significantly reduced the fever induced by peripheral injection of LPS. These data emphasize an important role for SP in the central nervous system during the febrile response to LPS, and are reinforced by the fact that intracerebroventricular injection of SP also induced fever in a dose-dependent manner in captopril-treated rats. Considering that the febrile response can result from the generation of several endogenous pyrogens, among them interleukin (IL)-1ß and macrophage inflammatory protein-1α (CCL3/MIP-1α), we also examined the effect of SR140333B on the fever induced by these cytokines which act through prostaglandin-dependent and -independent mechanisms, respectively. Surprisingly, SR140333B did not modify the febrile response to IL-1ß or CCL3/MIP-1α. Altogether these data suggest that the central action of SP is essential for LPS-, but not for IL-1ß- or CCL3/MIP-1α-induced fever.

Behavioral profile and Fos activation of serotonergic and non-serotonergic raphe neurons after central injections of serotonin in the pigeon (Columba livia).

Central injections of serotonin (5-HT) in food-deprived/refed pigeons evoke a sequence of hypophagic, hyperdipsic and sleep-like responses that resemble the postprandial behavioral sequence. Fasting-refeeding procedures affect sleep and drinking behaviors "per se". Here, we describe the behavioral profile and long-term food/water intake following intracerebroventricular (ICV) injections of 5-HT (50, 150, 300 nmol/2 µl) in free-feeding/drinking pigeons. The patterns of Fos activity (Fos+) in serotonergic (immunoreactive to tryptophan hydroxylase, TPH+) neurons after these treatments were also examined. 5-HT ICV injections evoked vehement drinking within 15 min, followed by an intense sleep. These effects did not extend beyond the first hour after treatment. 5-HT failed to affect feeding behavior consistently. The density of double-stained (Fos+/TPH+) cells was examined in 6 brainstem areas of pigeons treated with 5-HT (5-HTW) or vehicle. Another group received 5-HT and remained without access to water during 2h after treatment (5-HTØ). In the pontine raphe, Fos+ density correlated positively to sleep, and increased in both the 5-HTW and 5-HTØ animals. In the n. linearis caudalis, Fos+ and Fos+/TPH+ labeling was negatively correlated to sleep and was reduced in 5-HTØ animals. In the A8 region, Fos+/TPH+ labeling was reduced in 5-HTW and 5-HTØ animals, was positively correlated to food intake and negatively correlated to sleep. These data indicate that hyperdipsic and hypnogenic effects of ICV 5-HT in pigeons may result from the inhibition of a tonic activity of serotonergic neurons, which is possibly relevant to the control of postprandial behaviors, and that these relationships are shared functional traits of the serotonergic circuits in amniotes.

Restorative effect of intracerebroventricular insulin-like growth factor-I gene therapy on motor performance in aging rats.

Insulin-like growth factor-I (IGF-I) is a powerful neuroprotective molecule in the brain and spinal cord. We have previously shown that intracerebroventricular (i.c.v.) IGF-I gene therapy is an effective strategy to increase IGF-I levels in the cerebrospinal fluid (CSF). Since aging in rats is associated with severe motor function deterioration, we implemented i.c.v. IGF-I gene therapy in very old rats (30-31 months) and assessed the beneficial impact on motor performance. We used recombinant adenovectors (RAds) expressing either green fluorescent protein (GFP) or rat IGF-I. Injection in the lateral or fourth ventricle led to high transgene expression in the ependymal cell layer in the brain and cervical spinal cord. RAd-IGF-I-injected rats but not RAd-GFP-injected controls, showed significantly increased levels of CSF IGF-I. Motor tests showed the expected age-related decline in aged rats. Seventeen-day IGF-I gene therapy induced a significant improvement in motor performance in the aged but not in the young animals. These results show that IGF-I is an effective restorative molecule in the aging brain and spinal cord. The data also reveal that the ependymal route constitutes a promising approach for implementing protective IGF-I gene therapy in the aging CNS.

Sinoaortic denervation prevents enhanced heat loss induced by central cholinergic stimulation during physical exercise.

The present study investigated whether the effects of central cholinergic stimulation on thermoregulation during exercise are modulated by arterial baroreceptors. Wistar rats were submitted to sinoaortic denervation (SAD) or sham denervation (SHAM) and then fitted with a chronic guide cannula into the lateral cerebral ventricle. After 2 weeks, a catheter was implanted into the ascending aorta, and a temperature sensor was implanted into the peritoneal cavity. Two days later, the rats were submitted to exercise on a treadmill at 18 m/min until fatigued. Thermoregulatory and cardiovascular responses were measured after injection of 2 µL of 10mM physostigmine (Phy) or 0.15M NaCl solution (Sal) into the cerebral ventricle. In SHAM rats, Phy injection induced a greater exercise-induced increase in blood pressure and lower increase in heart rate than Sal treatment. In the SAD group, the attenuation of heart rate in response to Phy was blocked despite an exaggerated increase in blood pressure. SHAM rats treated with Phy had a higher increase in tail skin temperature compared to Sal injection (31.9 ± 0.4 °C Phy-SHAM vs. 30.1 ± 0.6 °C Sal-SHAM, 5 min after injection; p<0.05), resulting in a lower exercise-induced increase in core temperature. In contrast, SAD blocked the Phy injection effects in thermoregulatory responses during exercise (tail temperature: 30.1 ± 1.2 °C Phy-SAD vs. 29.5 ± 1.2 °C Sal-SAD, 5 min, p = 0.65). Therefore, we conclude that the enhancement of cutaneous heat loss induced by central cholinergic stimulation during exercise is mediated primarily by arterial baroreceptors.

Ontogenetic role of angiontensin-converting enzyme in rats: thirst and sodium appetite evaluation.

We investigated the influence of captopril (an angiotensin converting enzyme inhibitor) treatment during pregnancy and lactation period on hydromineral balance of the male adult offspring, particularly, concerning thirst and sodium appetite. We did not observe significant alterations in basal hydromineral (water intake, 0.3M NaCl intake, volume and sodium urinary concentration) or cardiovascular parameters in adult male rats perinatally treated with captopril compared to controls. However, male offspring rats that perinatally exposed to captopril showed a significant attenuation in water intake induced by osmotic stimulation, extracellular dehydration and beta-adrenergic stimulation. Moreover, captopril treatment during perinatal period decreased the salt appetite induced by sodium depletion. This treatment also attenuated thirst and sodium appetite aroused during inhibition of peripheral angiotensin II generation raised by low concentration of captopril in the adult offspring. Interestingly, perinatal exposure to captopril did not alter water or salt intake induced by i.c.v. administration of angiotensin I or angiotensin II. These results showed that chronic inhibition of angiotensin converting enzyme during pregnancy and lactation modifies the regulation of induced thirst and sodium appetite in adulthood.

The ependymal route for insulin-like growth factor-1 gene therapy in the brain.

I.c.v. administration of the peptide insulin-like growth factor-1 (IGF-1) has been shown to be an effective neuroprotective strategy in the brain of different animal models, a major advantage being the achievement of high concentrations of IGF-1 in the brain without altering serum levels of the peptide. In order to exploit this therapeutic approach further, we used high performance recombinant adenoviral (RAd) vectors expressing their transgene under the control of the potent mouse cytomegalovirus immediate early (mCMV) promoter, to transduce brain ependymal cells with high efficiency and to achieve effective release of transgenic IGF-1 into the cerebrospinal fluid (CSF). We constructed RAd vectors expressing either a chimeric green fluorescent protein fused to HSV-1 thymidine kinase (TK/GFP)(fus), or the cDNA encoding rat IGF-1, both driven by the mCMV promoter. The vectors were injected into the lateral ventricles of young rats and chimeric GFP expression in brain sections was assessed by fluorescence microscopy. The ependymal cell marker vimentin was detected by immunofluorescence and nuclei were labeled with the DNA dye 4',6-diamidino-2-phenylindole. Blood and CSF samples were drawn at different times post-vector injection. In all cerebral ventricles, vimentin immunoreactive cells of the ependyma were predominantly transduced by RAd-(TK/GFP)(fus), showing nuclear and cytoplasmic expression of the transgene. For tanycytes (TK/GFP)(fus) expression was evident in their cytoplasmic processes as they penetrated deep into the hypothalamic parenchyma. I.c.v. injection of RAd-IGF-1 induced high levels of IGF-1 in the CSF but not in serum. We conclude that the ependymal route constitutes an effective approach for implementing experimental IGF-1 gene therapy in the brain.

The analgesic actions of centrally administered celecoxib are mediated by endogenous opioids.

Celecoxib is a selective inhibitor of cyclooxygenase-2 (COX-2) and blocks prostaglandin (PG) biosynthesis associated with inflammatory conditions. In a model of peripherally induced inflammatory pain in rats, celecoxib, given systemically, induced a state of hypoalgesia where the nociceptive threshold was raised above basal values, an effect not observed after treatment with non-selective inhibitors of COX (indomethacin, piroxicam). Here, we have assessed the possibility that these atypical effects of celecoxib could be mediated by action at a site in the CNS. Inflammation and hyperalgesia were induced in one hind paw of rats by intraplantar injection of carrageenan (250microg). Nociceptive thresholds to mechanical stimulation were measured in the inflammed and contralateral paws for 6h after carrageenan injection. Celecoxib, SC236 (selective COX-2 inhibitors), indomethacin (non-selective COX inhibitor), SC560 (selective COX-1 inhibitor) or morphine were given by i.c.v. injection, 30 min before carrageenan. Celecoxib, SC236 or morphine-induced hypoalgesia whereas, after indomethacin or SC 560, the nociceptive threshold only returned to basal values. Naltrexone, also given i.c.v., reversed the hypoalgesia after celecoxib or morphine. Bestatin, an inhibitor of metabolism of endogenous opioid peptides, given i.c.v., potentiated the analgesic effects of a low dose of celecoxib. Taken together, these data indicate that celecoxib could act centrally after systemic administration to produce its characteristic profile of analgesia in this model of peripheral inflammatory pain. Moreover, this atypical analgesia appeared to be mediated by endogenous opioids rather than by inhibition of PG biosynthesis.

Facilitation of contextual fear memory extinction and anti-anxiogenic effects of AM404 and cannabidiol in conditioned rats.

The present study investigated the central effects of the eCB uptake/metabolism inhibitor AM404 and the phytocannabinoid cannabidiol (CBD) on the extinction of contextual fear memories in rats. Rats were conditioned and 24 h later subjected to three consecutive 9-min non-reinforced exposures to the conditioning context (extinction sessions, 24 h intervals). AM404 or CBD was injected i.c.v. 5 min before each extinction session and a 3-min drug-free test of contextual memory was performed 24 h after the last extinction session. AM404 (1.0 microg/microl, i.c.v.) and CBD (2.0 microg/microl, i.c.v.) facilitated extinction of contextual fear memory, with persistent effects. These responses were antagonized by the CB1-selective antagonist SR141716A (0.2 mg/kg, i.p.), but not by the TRPV1-selective antagonist capsazepine (5.0 microg/microl, i.c.v.). The effect of the anxiolytic drug Diazepam (DZP) on the extinction of contextual fear memory was also investigated. In contrast with the CBD and AM404 results, DZP induced a general reduction in the expression of conditioned freezing. Both AM404 and CBD induced anti-anxiogenic effect in the fear-potentiated plus-maze test, whereas DZP was anxiolytic in conditioned and unconditioned rats. In conclusion, CBD, a non-psychoactive phytocannabinoid could be an interesting pharmacological approach to reduce the anxiogenic effects of stress and promote the extinction of fear memories.

Evidence that exercise-induced heat storage is dependent on adrenomedullary secretion.

To investigate the influence of medullary adrenal secretion on thermoregulation during exercise, Phy (Eserine, 5x10(-3) M) was injected into the lateral cerebral ventricle of normal (INT) or bilaterally adrenodemedullated (ADM) untrained rats. Body temperature (Tb) and metabolic rate were measured in the rats while they were exercising on a treadmill (20 m min(-1), 5% inclination) until fatigue or while they were at rest after drug injection. In resting rats, Phy increased oxygen consumption in both INT or ADM rats without any effect on core temperature. During the dynamic phase of exercise (first 20 min), ADM attenuated the exercise-induced increase in core temperature (0.86+/-0.12 degrees C ADM Sal vs 1.48+/-0.21 degrees C INT Sal), thus reducing heat storage (HS) levels. Icv injection of Phy in ADM rats significantly reduced the increase in Tb (0.012+/-0.10 degrees C min(-1) Phy vs 0.042+/-0.006 degrees C min(-1) Sal; p<0.02) and HS (65.8+/-56.1 cal Phy vs 207.7+/-32.7 cal Sal; p<0.04) compared to ADM Sal rats. In conclusion, the exercise-induced increase in heat storage was attenuated by adrenodemedullation in rats. Furthermore, the activation of heat loss mechanisms by the central cholinergic system during exercise occurs independently of adrenal medullary secretion suppression and can be improved by previous adrenodemedullation. Our data indicate the existence of a dual mechanism of heat loss control during the dynamic phase of exercise: one involving sympathoadrenal system activation that impairs heat loss and another that counteracts the increased sympathoadrenal activity through the hypothalamic cholinergic system to promote heat loss.

Effects of nociceptin/orphanin FQ in the acquisition of contextual and tone fear conditioning in rats.

Nociceptin, or orphanin FQ (N/OFQ), the endogenous ligand of NOP receptors, is known to regulate learning and memory processes. To verify the role of N/OFQ in the acquisition of contextual (CFC) and tone fear conditioning (TFC), Wistar male rats received intracerebroventricular injections of N/OFQ (0.1-5.0 nmol) before training, and were tested 24 and 48 hr later to access the freezing response to context and tone, respectively. The intermediate doses (1.0 and 2.5 nmol) impaired the CFC test, sparing TFC. The highest dose (5.0 nmol) reduced freezing during both tests, a result that may be due to nonspecific effects. The posttraining injection of N/OFQ (1 or 5 nmol) did not interfere with CFC and TFC, suggesting a specific effect of the peptide in acquisition processes. Moreover, the impairment observed with N/OFQ (1 nmol) in CFC cannot be attributed to a state-dependent learning because it was not reversed by its pretest administration. The data support the negative role of N/OFQ in the acquisition of aversively motivated tasks, which encompass a spatial component and depend on the hippocampus.

Protective effect of nitric oxide synthase inhibition or antioxidants on brain oxidative damage caused by intracerebroventricular arginine administration.

We have previously demonstrated that acute arginine administration induces oxidative stress and compromises energy metabolism in rat hippocampus. In the present study, we initially investigated the effect of intracerebroventricular infusion of arginine (0.1, 0.5 and 1.5 mM solution) on Na(+),K(+)-ATPase activity and on some parameters of oxidative stress, namely thiobarbituric acid-reactive substances (TBA-RS) and total radical-trapping antioxidant parameter (TRAP) in the hippocampus of rats. Results showed that 1.5 mM arginine solution significantly increases TBA-RS and reduces Na(+),K(+)-ATPase activity and TRAP in the rat hippocampus. We also evaluated the influence of the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), and antioxidants, namely alpha-tocopherol plus ascorbic acid, on the effects elicited by arginine on Na(+),K(+)-ATPase activity, TBA-RS and TRAP. Results showed that treatment with alpha-tocopherol plus ascorbic acid per se did not alter these parameters but prevented these effects. Furthermore, intracerebroventricular infusion of L-NAME prevented the inhibition caused by arginine on Na(+),K(+)-ATPase activity, as well as the increased of TBA-RS. Our findings indicate that intracerebroventricular infusion of arginine induces oxidative stress in rat hippocampus and that the inhibition of Na(+),K(+)-ATPase activity caused by this amino acid was probably mediated by NO and/or its derivatives ONOO(-) and/or other free radicals. Finally, we suggest that the administration of antioxidants should be considered as an adjuvant therapy to specific diets in hyperargininemia.

Intracerebroventricular administration of Shiga toxin type 2 induces striatal neuronal death and glial alterations: an ultrastructural study.

Shiga toxin (Stx) from enterohemorrhagic Escherichia coli (STEC) is the main cause of hemorrhagic colitis which may derive to hemolytic-uremic syndrome (HUS). HUS is characterized by acute renal failure, thrombocytopenia and microangiopathic hemolytic anemia. Mortality in the acute stage has been lower than 5% of total affected argentine children with endemic HUS. Common signs of severe CNS involvement leading to death included seizures, alteration of consciousness, hemiparesis, visual disturbances, and brainstem symptoms. The main purpose of the present work was to study the direct involvement of Stx2 in brain cells by intracerebroventricular (i.c.v.) administration of Stx2. Immunodetection of Stx2 was confirmed by immunoelectron cytochemistry in different subsets and compartments of affected caudate putamen cells of corpus striatum. Transmission electron microscopy (TEM) studies revealed apoptotic neurons, glial ultrastructural alterations and demyelinated fibers. The i.c.v. microinfusion was applied for the first time in rats to demonstrate the direct action of Stx2 in neurons and glial cells. The toxin may affect brain neuroglial cells without the involvement of proinflammatory or systemic neurotoxic elements.

Involvement of nitric oxide in cocaine-induced erections and ejaculations after paradoxical sleep deprivation.

OBJECTIVES: As nitric oxide (NO) is involved in penile erectile (PE) function and also influences the sleep-wake cycle, we speculated that NO could play a role in PE and ejaculation of paradonical sleep deprivation (PSD) rats. METHODS: Animals were pretreated with N(G)-nitro-L-arginine methyl ester (L-NAME, ip) and L-arginine (ip and icv) prior to saline or cocaine injection. RESULTS: Cocaine-induced PE in 90% of PSD rats, 60% of which ejaculated. L-NAME reduced the frequency of erection, but had no effect in the proportion of PSD-cocaine-injected rats displaying this response. L-NAME had no effect in saline groups. L-Arginine in PSD-saline rats reduced the proportion of animals displaying PE at the highest dose and reduced the frequency of PE at all doses in both saline and cocaine groups. The icv administration of L-arginine reduced PE only in PSD-cocaine rats. Results indicate that common to both drugs, whether it was NO synthase (NOS) inhibitor or NO precursor, was their capacity to strongly reduce PE frequency in cocaine-treated rats. Moreover, L-arginine (ip) played a relevant inhibitory role in the erection displayed by PSD rats. CONCLUSIONS: Our findings suggest that the stimulating effects of PSD associated or not with cocaine on erection can be modified by alterations in the NO system.

The inhibition of different types of potassium channels underlies the antidepressant-like effect of adenosine in the mouse forced swimming test.

It was previously shown that the acute administration of adenosine elicits an antidepressant-like effect in the mouse forced swimming test (FST) by a mechanism dependent on the inhibition of the L-arginine-nitric oxide (NO)-guanylate cyclase pathway. Taken into account that the stimulation of this pathway is associated with the activation of K(+) channels, this study investigated the involvement of different types of K(+) channels in the effect of adenosine in the FST. Intracerebroventricular treatment of mice with tetraethylammonium (TEA, a non-specific inhibitor of K(+) channels, 25 pg/site), glibenclamide (an ATP-sensitive K(+) channel inhibitor, 0.5 pg/site), charybdotoxin (a large- and intermediate-conductance calcium-activated K(+) channel inhibitor, 25 pg/site) or apamin (a small-conductance calcium-activated K(+) channel inhibitor, 10 pg/site) was able to potentiate the action of subeffective doses of adenosine (1 mg/kg, i.p.) and fluoxetine (a serotonin reuptake inhibitor, 10 mg/kg, i.p.). Furthermore, the administration of adenosine or fluoxetine and the K(+) channel inhibitors, alone or in combination, did not affect the ambulatory behavior. Moreover, the reduction in the immobility time elicited by active doses of adenosine (10 mg/kg, i.p.) or fluoxetine (32 mg/kg, i.p.) in the FST was prevented by the pretreatment of mice with cromakalim (a K(+) channel opener, 10 microg/site, i.c.v.), without affecting the locomotion in an open-field. Together these results indicate that the modulatory effects of adenosine and fluoxetine on neuronal excitability, via inhibition of K(+) channels, may represent the final pathway of their antidepressant-like effects in the FST.

Activation of the central cholinergic pathway increases post-exercise tail heat loss in rats.

The aim of this study was to evaluate the effects of stimulation of the central cholinergic pathway on the regulation of post-exercise tail heat loss in rats. Either 2.0microL of 25x10(-3)M physostigmine (Phy) or 0.15M NaCl solution (Sal) were injected into the right lateral cerebral ventricle of both resting (n=8) and post-exercising rats (n=6; 24mmin(-1); 25min; 5% inclination). Tail temperature (Ttail) was measured using a thermistor taped to the tail, and intraperitoneal temperature, an index of core temperature (Tc), was recorded using a telemetry sensor implanted into the peritoneal cavity. In resting rats, Phy induced an increase in both Ttail (26.8+/-0.3 degrees C Phy versus 25.2+/-0.6 degrees C Sal; P<0.05) and in heat loss index (0.26+/-0.03 Phy versus 0.14+/-0.05 Sal; P<0.05; 30min after injection), and a decrease in Tc compared to the Sal injection group (36.6+/-0.2 degrees C Phy versus 37.0+/-0.2 degrees C Sal; P<0.05). In post-exercising rats, Phy injection attenuated the decrease in both T(tail) (28.3+/-0.8 degrees C Phy versus 26.4+/-0.6 degrees C Sal; P<0.05) and heat loss index (0.37+/-0.07 Phy versus 0.19+/-0.02 Sal; P<0.05) without altering Tc. We conclude that activation of the central cholinergic pathway increases post-exercise tail heat loss in rats.

Differential susceptibility following beta-amyloid peptide-(1-40) administration in C57BL/6 and Swiss albino mice: Evidence for a dissociation between cognitive deficits and the glutathione system response.

Considerable evidence supports the role of oxidative stress in the pathogenesis of Alzheimer's disease (AD). Previous studies suggest that the central nervous system (CNS) administration of beta-amyloid peptide, the major constituent of senile plaque in AD, induces oxidative stress in rodents which may contribute to the learning and memory deficits verified in the beta-amyloid model of AD. In the present study, we compared the effects of a single intracerebroventricular (i.c.v.) injection of aggregated beta-amyloid peptide-(1-40) (Abeta(1-40)) (400pmol/mouse) on spatial learning and memory performance, synaptic density and the glutathione (GSH)-dependent antioxidant status in adult male C57BL/6 and Swiss albino mice. Seven days after Abeta(1-40) administration, C57BL/6 and Swiss mice presented similar spatial learning and memory impairments, as evaluated in the water maze task, although these impairments were not found in Abeta(40-1)-treated mice. Moreover, a similar decline of synaptophysin levels was observed in the hippocampus (HC) and prefrontal cortex (PFC) of both Swiss and C57BL/6 mice treated with Abeta(1-40), which suggests synaptic loss. C57BL/6 mice presented lower levels of glutathione-related antioxidant defences (total glutathione (GSH-t) levels, glutathione peroxidase (GPx) and glutathione reductase (GR) activity) in the HC and PFC in comparison to Swiss mice. Despite the reduced basal GSH-dependent antioxidant defences observed in C57BL/6 mice, Abeta(1-40) administration induced significant alterations in the brain antioxidant parameters only in Swiss mice, decreasing GSH-t levels and increasing GPx and GR activity in the HC and PFC 24h after treatment. These results indicate strain differences in the susceptibility to Abeta(1-40)-induced changes in the GSH-dependent antioxidant defences in mice, which should be taken into account in further studies using the Abeta model of AD in mice. In addition, the present findings suggest that the spatial learning and memory deficits induced by beta-amyloid peptides in rodents may not be entirely related to glutathione-dependent antioxidant response.

Central nitric oxide inhibition modifies metabolic adjustments induced by exercise in rats.

The influence of the central nervous system on metabolic function is of interest in situations deviating from basal states, such as during exercise. Our previous study in rats demonstrated that central nitric oxide (NO) blockade increases metabolic rate, reducing mechanical efficiency during exercise. To assess the role of brain nitric oxide in the plasma glucose, lactate and free fatty acids (FFAs) concentrations of rats submitted to an incremental exercise protocol on a treadmill until fatigue, 1.43 micromol (2 microl) of N(omega)-nitro-l-arginine methyl ester (L-NAME, n=6), a NO synthase inhibitor, or 2 microl of 0.15M NaCl (SAL, n=6) was injected into the lateral cerebral ventricle (icv) of male Wistar rats immediately before exercise (starting at 10 m/min, with increments of 1m/min every 3 min until fatigue, 10% inclination). Blood samples were collected through a chronic jugular catheter at rest and during exercise until fatigue. During exercise, the L-NAME-treated animals had the following metabolic response compared to controls: (1) an increased hyperglycemic response during the first 60% of time to fatigue; (2) higher plasma lactate levels; and (3) a significant transitory increase in plasma free fatty acids during the dynamic phase of exercise that returned to basal levels earlier than controls during the steady state phase of exercise. In addition L-NAME-treated rats fatigued earlier than controls. The data indicate that the inhibition of the brain nitrergic system induced by icv L-NAME treatment disrupted the accuracy of the neural mechanism that regulates plasma glucose and free fatty acids mobilization during exercise in rats.

Potential participation of cystatin C in rapid eye movement sleep (REMS) modulation.

It has been hypothesized that proteins modulate rapid eye movement sleep (REMS). Studies have shown an increase in the liberation of proteins in the mesencephalic reticular formation of cats during REMS. It has also been determined that protein-synthesis inhibitors diminish REMS and that protease-inhibitors increase this sleep phase. These and other studies support the importance of "di novo" protein molecules in sleep, and in particular, in REMS regulation. In this context, it is important to determine the role of endogenous proteases and their endogenous inhibitors in sleep regulation. In this study, we found that Cystatin C (CC), an endogenous protease inhibitor, diminishes wakefulness and increases REMS. We have also found an increase in CC expression after REMS deprivation and a tendency to decrease after a 2 h period of REMS rebound. We further showed that REMS deprivation increases the expression of Cathepsin H (CH), a protease inhibited by CC. These results suggest that naturally occurring protease-inhibitors enhance REMS, perhaps by facilitating the availability of proteins.