Adenosine A2A receptors control generalization of contextual fear in rats.

Fear learning is essential to survival, but traumatic events may lead to abnormal fear consolidation and overgeneralization, triggering fear responses in safe environments, as occurs in post-traumatic stress disorder (PTSD). Adenosine A2A receptors (A2AR) control emotional memory and fear conditioning, but it is not known if they affect the consolidation and generalization of fear, which was now investigated. We now report that A2AR blockade through systemic administration of the A2AR antagonist SCH58261 immediately after contextual fear conditioning (within the consolidation window), accelerated fear generalization. Conversely, A2AR activation with CGS21680 decreased fear generalization. Ex vivo electrophysiological recordings of field excitatory post-synaptic potentials (fEPSPs) in CA3-CA1 synapses and of population spikes in the lateral amygdala (LA), showed that the effect of SCH58261 is associated with a reversion of fear conditioning-induced decrease of long-term potentiation (LTP) in the dorsal hippocampus (DH) and with increased amplitude of LA LTP in conditioned animals. These data suggest that A2AR are engaged during contextual fear consolidation, controlling long-term potentiation mechanisms in both DH and LA during fear consolidation, impacting on fear generalization; this supports targeting A2AR during fear consolidation to control aberrant fear processing in PTSD and other fear-related disorders.

Increased ATP Release and Higher Impact of Adenosine A2A Receptors on Corticostriatal Plasticity in a Rat Model of Presymptomatic Parkinson's Disease.

Extracellular ATP can be a danger signal, but its role in striatal circuits afflicted in Parkinson's disease (PD) is unclear and was now investigated. ATP was particularly released at high stimulation intensities from purified striatal nerve terminals of mice, which were endowed with different ATP-P2 receptors (P2R), although P2R antagonists did not alter corticostriatal transmission or plasticity. Instead, ATP was extracellularly catabolized into adenosine through CD73 to activate adenosine A2A receptors (A2AR) modulating corticostriatal long-term potentiation (LTP) in mice. In the presymptomatic phase of a 6-hydroxydopamine rat model of PD, ATP release from striatal nerve terminals was increased and was responsible for a greater impact of CD73 and A2AR on corticostriatal LTP. These observations identify increased ATP release and ATP-derived formation of extracellular adenosine bolstering A2AR activation as a key pathway responsible for abnormal synaptic plasticity in circuits involved in the onset of PD motor symptoms. The translation of these findings to humans prompts extending the use of A2AR antagonists from only co-adjuvants of motor control in Parkinsonian patients to neuroprotective drugs delaying the onset of motor symptoms.

Functional interplay between adenosine A2A receptor and NMDA preconditioning in fear memory and glutamate uptake in the mice hippocampus.

N-methyl D-aspartate (NMDA) administered at subtoxic dose plays a protective role against neuronal excitotoxicity, a mechanism described as preconditioning. Since the activation of adenosinergic receptors influences the achievement of NMDA preconditioning in the hippocampus, we evaluated the potential functional interplay between adenosine A1 and A2A receptors (A1R and A2AR) activities and NMDA preconditioning. Adult male Swiss mice received saline (NaCl 0.9 g%, i.p.) or a nonconvulsant dose of NMDA (75 mg/kg, i.p.) and 24 h later they were treated with the one of the ligands: A1R agonist (CCPA, 0.2 mg/kg, i.p.) or antagonist (DPCPX, 3 mg/kg, i.p.), A2AR agonist (CGS21680, 0.05 mg/kg, i.p.) or antagonist (ZM241385, 0.1 mg/kg, i.p.) and subjected to contextual fear conditioning task. Binding properties and content of A2AR and glutamate uptake were assessed in the hippocampus of mice subjected to NMDA preconditioning. Treatment with CGS21680 increased the time of freezing during the exposure of animals to the new environment. NMDA preconditioning did not affect the freezing time of mice per se, but it prevented the response observed after the activation of A2AR. Furthermore, the activation of A2AR by CGS21680 after the preconditioning blocked the increase of glutamate uptake induced by NMDA preconditioning. The immunodetection of A2AR in total hippocampal homogenates showed no significant differences evoked by NMDA preconditioning and did not alter A2AR maximum binding for the selective ligand [3H]CGS21680. These results demonstrate changes in A2AR functionality in mice following NMDA preconditioning.

Guanosine Promotes Proliferation in Neural Stem Cells from Hippocampus and Neurogenesis in Adult Mice.

Neural stem cells can generate new neurons in the mouse adult brain in a complex multistep process called neurogenesis. Several factors regulate this process, including neurotransmitters, hormones, neurotrophic factors, pharmacological agents, and environmental factors. Purinergic signaling, mainly the adenosinergic system, takes part in neurogenesis, being involved in cell proliferation, migration, and differentiation. However, the role of the purine nucleoside guanosine in neurogenesis remains unclear. Here, we examined the effect of guanosine by using the neurosphere assay derived from neural stem cells of adult mice. We found that continuous treatment with guanosine increased the number of neurospheres, neural stem cell proliferation, and neuronal differentiation. The effect of guanosine to increase the number of neurospheres was reduced by removing adenosine from the culture medium. We next traced the neurogenic effect of guanosine in vivo. The intraperitoneal treatment of adult C57BL/6 mice with guanosine (8 mg/kg) for 26 days increased the number of dividing bromodeoxyuridine (BrdU)-positive cells and also increased neurogenesis, as identified by measuring doublecortin (DCX)-positive cells in the dentate gyrus (DG) of the hippocampus. Antidepressant-like behavior in adult mice accompanied the guanosine-induced neurogenesis in the DG. These results provide new evidence of a pro-neurogenic effect of guanosine on neural stem/progenitor cells, and it was associated in vivo with antidepressant-like effects.

Combined effects of caloric restriction and fish oil attenuated anti-depressant and anxiolytic-like effects of fish oil: association with hippocampal BDNF concentrations.

Omega-3-enriched fish oil (FO) and caloric restriction (CR) are nutritional therapeutic approaches that exert an important impact on brain function, behavior, memory, and neuroprotection. Here, we investigate the synergic effects of both therapeutic approaches combined (CR + FO) on behavior (memory, anxiety-like behavior, antidepressant-like behavior), as well as its association with hippocampal brain-derived neurotrophic factor (BDNF) concentrations. Adult male Wistar rats were divided into four dietary groups: Control group (C) - chow ad libitum; CR group - 30 % CR, considering C group food intake; FO group - FO-enriched chow ad libitum; and CR + FO group - FO-enriched 30 % CR chow. After 12 weeks of dietary treatment, behavioural analysis set was conducted, and hippocampal BDNF concentrations were measured. FO group presented anxiolytic-like and antidepressant-like behaviors as well as improved memory in the Morris' water maze. These effects were attenuated by the combined CR + FO treatment. FO group also presented higher BDNF concentrations. There was a positive association between the number of entries in the platform quadrant in the MWM and hippocampal BDNF concentrations (ß = 0.39; R² = 0.15; p = 0.042) and an inverse association between forced swim immobility time and BDNF concentrations (ß = -0.39; R² = 0.15; p = 0.041). Taken together, our data showed that the 12-week FO dietary treatment promoted anxiolytic-like and antidepressant-like behaviors as well as memory improvement, and these effects were associated with BDNF concentrations. Synergic effects of interventions attenuated FO-related behavioral responses and BDNF concentrations and probably reduced hippocampal neuroplasticity.

Atorvastatin Prevents Early Oxidative Events and Modulates Inflammatory Mediators in the Striatum Following Intranasal 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Administration in Rats.

Atorvastatin is a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor with cholesterol-lowering, anti-inflammatory, and antioxidant properties. Increasing evidence show atorvastatin acts as a protective agent against insults in the central nervous system (CNS). The regular use of statins has been associated with a reduced risk of Parkinson's disease (PD) development. Here, we evaluated early events involved in the neurotoxicity induced by intranasal (i.n.) infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in rats and the potential of atorvastatin to prevent these early toxic events. Male Wistar rats were pretreated orally with atorvastatin (10 mg/kg/day) or vehicle once a day during seven consecutive days. Twenty-four hours after atorvastatin administration, animals received a single bilateral i.n. infusion of MPTP (1 mg/nostril), and 6 h later, the striatum and the hippocampus were collected to evaluate early oxidative stress parameters and inflammatory cytokines. Atorvastatin prevented MPTP-induced increase in reactive species (RS) generation and in glutathione levels in the striatum. Atorvastatin also prevented the reduction in mitochondrial respiratory chain complex I and II activities evoked by MPTP in the striatum. Atorvastatin per se reduced the levels of the cytokines TNF-α and IL-1ß, and surprisingly, it reduced IL-10 and nerve growth factor levels in the striatum. However, the anti-inflammatory IL-10 levels increased in the striatum following atorvastatin plus MPTP treatment. These effects were not observed in the hippocampus. Our findings reinforce and extend the notion of the neuroprotective effects of atorvastatin in a PD model and indicate the modulation of oxidative and inflammatory responses as the mechanisms associated with therapeutic action of atorvastatin in PD.

Ursolic acid affords antidepressant-like effects in mice through the activation of PKA, PKC, CAMK-II and MEK1/2.

BACKGROUND: Ursolic acid has been shown to display antidepressant-like effects in mice through the modulation of monoaminergic systems. In this study, we sought to investigate the involvement of signaling pathways on the antidepressant-like effects of ursolic acid. METHODS: Mice were treated orally with ursolic acid (0.1mg/kg) and, 45min later they received the followings inhibitors by intracerebroventricular route: H-89 (PKA inhibitor, 1µg/mouse), KN-62 (CAMK-II inhibitor, 1µg/mouse), chelerythrine (PKC inhibitor, 1µg/mouse), U0126 (MEK1/2 inhibitor, 5µg/mouse), PD98059 (MEK1/2 inhibitor, 5µg/mouse), wortmannin (PI3K irreversible inhibitor, 0.1µg/mouse) or LY294002 (PI3K inhibitor, 10 nmol/mouse). Immobility time of mice was registered in the tail suspension test (TST). RESULTS: The anti-immobility effect of ursolic acid in the TST was abolished by the treatment of mice with H-89, KN-62, chelerythrine, U0126 or PD98059, but not with wortmannin or LY294002. CONCLUSIONS: These results suggest that activation of PKA, PKC, CAMK-II, MEK1/2 may underlie the antidepressant-like effects of ursolic acid.

Angiotensin II type 1/adenosine A 2A receptor oligomers: a novel target for tardive dyskinesia.

Tardive dyskinesia (TD) is a serious motor side effect that may appear after long-term treatment with neuroleptics and mostly mediated by dopamine D2 receptors (D2Rs). Striatal D2R functioning may be finely regulated by either adenosine A2A receptor (A2AR) or angiotensin receptor type 1 (AT1R) through putative receptor heteromers. Here, we examined whether A2AR and AT1R may oligomerize in the striatum to synergistically modulate dopaminergic transmission. First, by using bioluminescence resonance energy transfer, we demonstrated a physical AT1R-A2AR interaction in cultured cells. Interestingly, by protein-protein docking and molecular dynamics simulations, we described that a stable heterotetrameric interaction may exist between AT1R and A2AR bound to antagonists (i.e. losartan and istradefylline, respectively). Accordingly, we subsequently ascertained the existence of AT1R/A2AR heteromers in the striatum by proximity ligation in situ assay. Finally, we took advantage of a TD animal model, namely the reserpine-induced vacuous chewing movement (VCM), to evaluate a novel multimodal pharmacological TD treatment approach based on targeting the AT1R/A2AR complex. Thus, reserpinized mice were co-treated with sub-effective losartan and istradefylline doses, which prompted a synergistic reduction in VCM. Overall, our results demonstrated the existence of striatal AT1R/A2AR oligomers with potential usefulness for the therapeutic management of TD.

Caffeine alleviates progressive motor deficits in a transgenic mouse model of spinocerebellar ataxia.

OBJECTIVE: Machado-Joseph disease (MJD) is a neurodegenerative spinocerebellar ataxia (SCA) associated with an expanded polyglutamine tract within ataxin-3 for which there is currently no available therapy. We previously showed that caffeine, a nonselective adenosine receptor antagonist, delays the appearance of striatal damage resulting from expression of full-length mutant ataxin-3. Here we investigated the ability of caffeine to alleviate behavioral deficits and cerebellar neuropathology in transgenic mice with a severe ataxia resulting from expression of a truncated fragment of polyglutamine-expanded ataxin-3 in Purkinje cells. METHODS: Control and transgenic c57Bl6 mice expressing in the mouse cerebella a truncated form of human ataxin-3 with 69 glutamine repeats were allowed to freely drink water or caffeinated water (1g/L). Treatments began at 7 weeks of age, when motor and ataxic phenotype emerges in MJD mice, and lasted up to 20 weeks. Mice were tested in a panel of locomotor behavioral paradigms, namely rotarod, beam balance and walking, pole, and water maze cued-platform version tests, and then sacrificed for cerebellar histology. RESULTS: Caffeine consumption attenuated the progressive loss of general and fine-tuned motor function, balance, and grip strength, in parallel with preservation of cerebellar morphology through decreasing the loss of Purkinje neurons and the thinning of the molecular layer in different folia. Caffeine also rescued the putative striatal-dependent executive and cognitive deficiencies in MJD mice. INTERPRETATION: Our findings provide the first in vivo demonstration that caffeine intake alleviates behavioral disabilities in a severely impaired animal model of SCA. Ann Neurol 2017;81:407-418.

Agmatine attenuates reserpine-induced oral dyskinesia in mice: Role of oxidative stress, nitric oxide and glutamate NMDA receptors.

Dyskinesia consists in a series of trunk, limbs and orofacial involuntary movements that can be observed following long-term pharmacological treatment in some psychotic and neurological disorders such as schizophrenia and Parkinson's disease, respectively. Agmatine is an endogenous arginine metabolite that emerges as neuromodulator and a promising agent to manage diverse central nervous system disorders by modulating nitric oxide (NO) pathway, glutamate NMDA receptors and oxidative stress. Herein, we investigated the effects of a single intraperitoneal (i.p.) administration of different agmatine doses (10, 30 or 100mg/kg) against the orofacial dyskinesia induced by reserpine (1mg/kg,s.c.) in mice by measuring the vacuous chewing movements and tongue protusion frequencies, and the duration of facial twitching. The results showed an orofacial antidyskinetic effect of agmatine (30mg/kg, i.p.) or the combined administration of sub-effective doses of agmatine (10mg/kg, i.p.) with the NMDA receptor antagonists amantadine (1mg/kg, i.p.) and MK801 (0.01mg/kg, i.p.) or the neuronal nitric oxide synthase (NOS) inhibitor 7-nitroindazole (7-NI; 0.1mg/kg, i.p.). Reserpine-treated mice displayed locomotor activity deficits in the open field and agmatine had no effect on this response. Reserpine increased nitrite and nitrate levels in cerebral cortex, but agmatine did not reverse it. Remarkably, agmatine reversed the decrease of dopamine and non-protein thiols (NPSH) levels caused by reserpine in the striatum. However, no changes were observed in striatal immunocontent of proteins related to the dopaminergic system including tyrosine hydroxylase, dopamine transporter, vesicular monoamine transporter type 2, pDARPP-32[Thr75], dopamine D1 and D2 receptors. These results indicate that the blockade of NO pathway, NMDAR and oxidative stress are possible mechanisms associated with the protective effects of agmatine against the orofacial dyskinesia induced by reserpine in mice.

Developmental exposure to manganese induces lasting motor and cognitive impairment in rats.

Exposure to high manganese (Mn) levels may damage the basal ganglia, leading to a syndrome analogous to Parkinson's disease, with motor and cognitive impairments. The molecular mechanisms underlying Mn neurotoxicity, particularly during development, still deserve further investigation. Herein, we addressed whether early-life Mn exposure affects motor coordination and cognitive function in adulthood and potential underlying mechanisms. Male Wistar rats were exposed intraperitoneally to saline (control) or MnCl2 (5, 10 or 20 mg/kg/day) from post-natal day (PND) 8-12. Behavioral tests were performed on PND 60-65 and biochemical analysis in the striatum and hippocampus were performed on PND14 or PND70. Rats exposed to Mn (10 and 20 mg/kg) performed significantly worse on the rotarod test than controls indicating motor coordination and balance impairments. The object and social recognition tasks were used to evaluate short-term memory. Rats exposed to the highest Mn dose failed to recognize a familiar object when replaced by a novel object as well as to recognize a familiar juvenile rat after a short period of time. However, Mn did not alter olfactory discrimination ability. In addition, Mn-treated rats displayed decreased levels of non-protein thiols (e.g. glutathione) and increased levels of glial fibrillary acidic protein (GFAP) in the striatum. Moreover, Mn significantly increased hippocampal glutathione peroxidase (GPx) activity. These findings demonstrate that acute low-level exposure to Mn during a critical neurodevelopmental period causes cognitive and motor dysfunctions that last into adulthood, that are accompanied by alterations in antioxidant defense system in both the hippocampus and striatum.

Adenosine A1 receptor activation modulates N-methyl-d-aspartate (NMDA) preconditioning phenotype in the brain.

N-methyl-d-aspartate (NMDA) preconditioning is induced by subtoxic doses of NMDA and it promotes a transient state of resistance against subsequent lethal insults. Interestingly, this mechanism of neuroprotection depends on adenosine A1 receptors (A1R), since blockade of A1R precludes this phenomenon. In this study we evaluated the consequences of NMDA preconditioning on the hippocampal A1R biology (i.e. expression, binding properties and functionality). Accordingly, we measured A1R expression in NMDA preconditioned mice (75mg/kg, i.p.; 24h) and showed that neither the total amount of receptor, nor the A1R levels in the synaptic fraction was altered. In addition, the A1R binding affinity to the antagonist [(3)H] DPCPX was slightly increased in total membrane extracts of hippocampus from preconditioned mice. Next, we evaluated the impact of NMDA preconditioning on A1R functioning by measuring the A1R-mediated regulation of glutamate uptake into hippocampal slices and on behavioral responses in the open field and hot plate tests. NMDA preconditioning increased glutamate uptake into hippocampal slices without altering the expression of glutamate transporter GLT-1. Interestingly, NMDA preconditioning also induced antinociception in the hot plate test and both effects were reversed by post-activation of A1R with the agonist CCPA (0.2mg/kg, i.p.). NMDA preconditioning or A1R modulation did not alter locomotor activity in the open field. Overall, the results described herein provide new evidence that post-activation of A1R modulates NMDA preconditioning-mediated responses, pointing to the importance of the cross-talk between glutamatergic and adenosinergic systems to neuroprotection.

Nitric oxide, a new player in L-DOPA-induced dyskinesia?

L-3,4-Dihydroxyphenylalanine (L-DOPA) remains the most effective symptomatic treatment of Parkinson's disease (PD). However, the long-term use of L-DOPA causes, in combination with disease progression, the development of motor complications termed L-DOPA-induced dyskinesia (LID). LID is the result of profound modifications in the functional organization of the basal ganglia circuitry. There is increasing evidence of the involvement of non-dopaminergic systems on the pathophysiology of LID. This raises the possibility of novel promising therapeutic approaches in the future, including agents that interfere with glutamatergic, serotonergic, adenosine, adrenergic, and cholinergic neurotransmission that are currently in preclinical testing or clinical development. Herein, we summarize the current knowledge of the pharmacology of LID in PD. More importantly, this review attempts to highlight the role of nitric oxide (NO) in PD and provide a comprehensive picture of recent preclinical findings from our group and others showing its potential involvement in dyskinesia.

Depression as a Glial-Based Synaptic Dysfunction.

Recent studies combining pharmacological, behavioral, electrophysiological and molecular approaches indicate that depression results from maladaptive neuroplastic processes occurring in defined frontolimbic circuits responsible for emotional processing such as the prefrontal cortex, hippocampus, amygdala and ventral striatum. However, the exact mechanisms controlling synaptic plasticity that are disrupted to trigger depressive conditions have not been elucidated. Since glial cells (astrocytes and microglia) tightly and dynamically interact with synapses, engaging a bi-directional communication critical for the processing of synaptic information, we now revisit the role of glial cells in the etiology of depression focusing on a dysfunction of the "quad-partite" synapse. This interest is supported by the observations that depressive-like conditions are associated with a decreased density and hypofunction of astrocytes and with an increased microglia "activation" in frontolimbic regions, which is expected to contribute for the synaptic dysfunction present in depression. Furthermore, the traditional culprits of depression (glucocorticoids, biogenic amines, brain-derived neurotrophic factor, BDNF) affect glia functioning, whereas antidepressant treatments (serotonin-selective reuptake inhibitors, SSRIs, electroshocks, deep brain stimulation) recover glia functioning. In this context of a quad-partite synapse, systems modulating glia-synapse bidirectional communication-such as the purinergic neuromodulation system operated by adenosine 5'-triphosphate (ATP) and adenosine-emerge as promising candidates to "re-normalize" synaptic function by combining direct synaptic effects with an ability to also control astrocyte and microglia function. This proposed triple action of purines to control aberrant synaptic function illustrates the rationale to consider the interference with glia dysfunction as a mechanism of action driving the design of future pharmacological tools to manage depression.

Antidepressant- and anxiolytic-like activities of an oil extract of propolis in rats.

PURPOSE: Propolis biological effects are mainly attributed to its polyphenolic constituents such as flavonoids and phenolic acids that were recently described in the chemical composition of an extract of propolis obtained with edible vegetal oil (OEP) by our group. The aim of this study was to evaluate the effect of OEP on the behavior of rats. MATERIALS AND METHODS: An in vivo open field (OF), elevated Plus-maze (EPM), and forced swimming (FS) tests were performed to evaluate locomotor activity, anxiolytic- and antidepressant effects of the extract. Besides, oxidative stress levels were measured in rat blood samples after the behavioral assays by evaluation of the Trolox equivalent antioxidant capacity (TEAC) and nitric oxide levels. RESULTS: OEP increased locomotion in the OF test (50mg/kg) and central locomotion and open arm entries in the OF and EPM tests (10-50mg/kg) and decreased the immobility time in the FS test (10-50mg/kg). Moreover, OEP reduced nitric oxide levels in response to swim stress induced in rats. CONCLUSION: OEP exerted stimulant, anxiolytic and antidepressant effects on the Central Nervous System and antioxidant activity in rats, highlighting propolis as a potential therapeutic compound for behavior impairment of anxiety and depression.

Cellular prion protein is present in dopaminergic neurons and modulates the dopaminergic system.

Cellular prion protein (PrP(C) ) is widely expressed in the brain. Although the precise role of PrP(C) remains uncertain, it has been proposed to be a pivotal modulator of neuroplasticity events by regulating the glutamatergic and serotonergic systems. Here we report the existence of neurochemical and functional interactions between PrP(C) and the dopaminergic system. PrP(C) was found to co-localize with dopaminergic neurons and in dopaminergic synapses in the striatum. Furthermore, the genetic deletion of PrP(C) down-regulated dopamine D1 receptors and DARPP-32 density in the striatum and decreased dopamine levels in the prefrontal cortex of mice. This indicates that PrP(C) affects the homeostasis of the dopaminergic system by interfering differently in different brain areas with dopamine synthesis, content, receptor density and signaling pathways. This interaction between PrP(C) and the dopaminergic system prompts the hypotheses that the dopaminergic system may be implicated in some pathological features of prion-related diseases and, conversely, that PrP(C) may play a role in dopamine-associated brain disorders.

Mechanisms involved in abdominal nociception induced by either TRPV1 or TRPA1 stimulation of rat peritoneum.

Abdominal pain is a frequent symptom of peritoneal cavity irritation, but little is known about the role of the receptors for irritant substances, transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), in this painful condition. Thus, we investigated the abdominal nociception caused by peritoneal stimulation with TRPV1 (capsaicin) and TRPA1 (allyl isothiocyanate, AITC) agonists and their mechanisms in rats. The intraperitoneal (i.p.) injection of either capsaicin or AITC (0.03-10 mg/kg) induced short-term (up to 20 min) and dose-dependent abdominal nociception, and also produced c-fos expression in spinal afferents of the dorsal horn. TRPV1 antagonism prevented (94 ± 4% inhibition) nociception induced by capsaicin but not by AITC. In contrast, the TRPA1 antagonism almost abolished AITC-induced nociception (95 ± 2% inhibition) without altering the capsaicin response. Moreover, nociception induced by either capsaicin or AITC was reduced by the desensitisation of TRPV1-positive sensory fibres with resiniferatoxin (73 ± 18 and 76 ± 15% inhibitions, respectively) and by the NK1 receptor antagonist aprepitant (56 ± 5 and 53 ± 8% inhibitions, respectively). Likewise, the i.p. injections of capsaicin or AITC increased the content of substance P in the peritoneal fluid. Nevertheless, neither the mast cell membrane stabiliser cromoglycate, nor the H1 antagonist promethazine, nor depletion of peritoneal macrophages affected abdominal nociception induced either by capsaicin or AITC. Accordingly, neither capsaicin nor AITC increased the histamine content in the peritoneal fluid or provoked peritoneal mast cell degranulation in vitro. Collectively, our findings suggest that TRPV1 and TRPA1 stimulation in the peritoneum produces abdominal nociception that is mediated by sensory fibres activation.

Atorvastatin improves cognitive, emotional and motor impairments induced by intranasal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in rats, an experimental model of Parkinson's disease.

Affective disorders and memory impairments precede the classical motor symptoms seen in Parkinson's disease (PD) and the currently approved antiparkinsonian agents do not alleviate the non-motor symptoms as well as the underlying dopaminergic neuron degeneration. On the other hand, there is increasing evidence that inflammation plays a key role in the pathophysiology of PD and that the anti-inflammatory actions of statins are related to their neuroprotective properties against different insults in the CNS. The present data indicates that the oral treatment with atorvastatin (10mg/kg/day), once a day during 7 consecutive days, was able to prevent short-term memory impairments and depressive-like behavior of rats assessed in the social recognition and forced swimming tests at 7 and 14 days, respectively, after a single intranasal (i.n.) administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (1mg/nostril). Importantly, at this time no significant alterations on the locomotor activity of the animals were observed in the open field test. Moreover, atorvastatin was found to protect against the long-lasting motor deficits evaluated in activity chambers and the loss of dopaminergic neurons in the substantia nigra pars compacta observed at 21 days after i.n. MPTP administration. At this time, despite the absence of spatial memory deficits in the water maze and in concentrations of the cytokines TNF-α, IL-1ß and IL-10 in striatum and hippocampus following i.n. MPTP administration, atorvastatin treatment resulted in a significant increase in the striatal and hippocampal levels of nerve growth factor (NGF). These findings reinforce and extend the notion of the neuroprotective potential of atorvastatin and suggest that it may represent a new therapeutic tool for the management of motor and non-motor symptoms of PD.

Role of nicotine on cognitive and behavioral deficits in sepsis-surviving rats.

Sepsis and its complications are important causes of mortality in intensive care units and sepsis survivors may present long-term cognitive and emotional impairments, including memory deficits and anxiety symptoms. In the present study, we investigated whether repeated nicotine administration can affect the behavioral changes in sepsis-surviving rats. Male Wistar rats were divided in two groups: sham-operated and experimental sepsis induced by cecal ligation and puncture (CLP). The animals were injected subcutaneously with nicotine (0.1 mg/kg) or vehicle once a day during 1 week before and/or 1 week after sepsis induction. Thirty minutes after the last administration (i.e., 7 days after surgery), the animals were tested in the open field, elevated plus-maze and step-down inhibitory avoidance tasks. The repeated nicotine treatment did not affect the survival rate in the sepsis group (50%). Moreover, no significant changes on locomotor activity were observed in the sepsis group while the treatment with nicotine during 1 week after surgery reduced the locomotion of sepsis-surviving rats in the open field. It is important to note that both schedules of nicotine treatment (prior and/or after CLP) improved the sepsis-induced anxiogenic-like responses. Interestingly, nicotine was able to improve short- and long-term inhibitory avoidance memory impairments, observed in sepsis survivors, only when administered during 2 consecutive weeks (i.e., prior and after CLP). Taken together, these results indicate that repeated nicotine administration does not alter the survival rate in rats submitted to CLP and provide new evidence that nicotine can improve long-lasting memory impairments and anxiogenic-like responses in sepsis-surviving animals.

Ghrelin as a neuroprotective and palliative agent in Alzheimer's and Parkinson's disease.

Ghrelin is a gastric hormone that stimulates growth hormone (GH) secretion and food intake to regulate energy homeostasis and body weight by binding to its receptor, GH secretagogue receptor (GHSR1a), which is most highly expressed in the pituitary and hypothalamus. Nowadays there is considerable evidence showing that the GHSR1a is also expressed in numerous extra-hypothalamic neuronal populations and the physiological role of ghrelin is by far wider than considered before including learning and memory, anxiety, depression and neuroprotection. The present review attempts to provide a comprehensive picture of the role of ghrelin in the central nervous system and to highlight recent findings showing its potential as an innovative therapeutic agent in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease.