Spermine protects from LPS-induced memory deficit via BDNF and TrkB activation.

Lipopolysaccharide (LPS) has been long known to promote neuroinflammation and learning and memory deficits. Since spermine, one of the main natural polyamines in the central nervous system, protects from LPS-induced memory deficit by a mechanism that comprises GluN2B receptors, the aim of the present study was to determine whether brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB) receptor and cAMP response element binding (CREB) are involved in this protective effect of spermine. Adult male Swiss albino mice received, immediately after training in the novel object recognition task, saline or LPS (250 µg/kg, i.p.); 5 min later they received saline or spermine (0.3 mg/kg, i.p.) and, when specified, 5 min thereafter saline or the TrkB receptor antagonist ANA-12 (0.5 mg/kg, i.p.) in different flanks. Animals were tested 24 h after training. Spermine protected from LPS-induced memory deficit and this protective effect was reversed by ANA-12. In a subset of animals BDNF, CREB and phospho-CREB immunoreactivity was determined in the hippocampi and cerebral cortex 4 h after spermine injection. Spermine reversed the decrease of mature BDNF levels induced by LPS in both hippocampus and cerebral cortex. Spermine increased phospho-CREB content and phospho-CREB/total CREB ratio in the cerebral cortex of LPS-treated mice. The results support that the protective effect of spermine on LPS-induced memory deficits depends on TrkB receptor activation and is accompanied by restoration of mature BDNF levels in hippocampus and cerebral cortex, as well as increased CREB phosphorylation in the cerebral cortex.

Spermidine improves the persistence of reconsolidated fear memory and neural differentiation in vitro: Involvement of BDNF.

Putrescine, spermidine and spermine are organic cations implicated in learning, memory consolidation, reconsolidation and neurogenesis. These physiological processes are closely related, and convincing evidence indicates that neurogenesis is implicated both, in the establishment and maintenance of remote contextual fear memory. Although brain-derived neurotrophic factor (BDNF) is a key mediator involved in both neurogenesis and memory consolidation, effects of spermidine on persistence of memory after reactivation (reconsolidation) and possible involvement of BDNF have not been investigated. Here, we investigated whether the intrahippocampal infusion of spermidine improves the persistence of reconsolidated contextual fear conditioning memory in rats and whether these possible changes depend on BDNF/TrkB signaling in the hippocampus. The infusion of spermidine immediately and 12h post-reactivation improved fear memory of the animals tested seven but not two days after reactivation. The facilitatory effect of spermidine on the persistence of reconsolidated memory was blocked by the TrkB inhibitor ANA-12 (73.6pmol/site) and accompanied by mature BDNF level increase in the hippocampus, indicating that it depends on the BDNF/TrkB pathway. We also investigated whether spermidine alters BDNF levels and neural progenitor cell differentiation in vitro. Spermidine increased BDNF levels in vitro, facilitating neuritogenesis and neural migration. Spermidine-induced neuritogenesis in vitro was also blocked by ANA-12 (10µM). Since spermidine increases BDNF levels and facilitates neural differentiation in vitro, similar mechanisms may be involved in spermidine-induced facilitation of the persistence of reconsolidated memory.

Intrahippocampal infusion of spermidine improves memory persistence: Involvement of protein kinase A.

Spermidine (SPD) is an endogenous aliphatic amine that modulates GluN2B-containing NMDA receptors and improves memory. Recent evidence suggests that systemic SPD improves the persistence of the long term memory of fear. However, the role of hippocampal polyamines and its binding sites in the persistence of fear memory is to be determined, as well as its putative underlying mechanisms. This study investigated whether the intrahippocampal (i.h.) infusion of spermidine or arcaine, modulators of polyamine binding site at GluN2B-containing NMDA receptors, alters the persistence of the memory of contextual fear conditioning task in rats. We also investigated whether protein synthesis and cAMP dependent protein kinase (PKA) play a role in SPD-induced improvement of the fear memory persistence. While 12h post-training infusion of spermidine facilitated, arcaine and the inhibitor of protein synthesis (anisomycin) impaired the memory of fear assessed 7days after training. The infusion of arcaine, anisomycin or a selective PKA inhibitor (H-89), at doses that have no effect on memory per se, prevented the SPD-induced improvement of memory persistence. H-89 prevented the stimulatory effect of SPD on phospho-PKA/total-PKA ratio. These results suggests that the improvement of fear memory persistence induced by spermidine involves GluN2B-containing NMDA receptors, PKA pathway and protein synthesis in rats.

Selegiline reverses aß25₋35-induced cognitive deficit in male mice.

Alzheimer's disease (AD) is biochemically characterized by the occurrence of extracellular deposits of amyloid beta peptide (Aß) and intracellular deposits of the hyperphosphorylated tau protein, which are causally related to the pathological hallmarks senile plaques and neurofibrillary tangles. Monoamine oxidase B (MAO-B) activity, involved in the oxidation of biogenic monoamines, is particularly high around the senile plaques and increased in AD patients in middle to late clinical stages of the disease. Selegiline is a selective and irreversible MAO-B inhibitor and, although clinical trials already shown the beneficial effect of selegiline on cognition of AD patients, its mechanism of action remains to be elucidated. Therefore, we first investigated whether selegiline reverses the impairment of object recognition memory induced by Aß25-35 in mice, an established model of AD. In addition, we investigated whether selegiline alters MAO-B and MAO-A activities in the hippocampus, perirhinal and remaining cerebral cortices of Aß25-35-injected male mice. Acute (1 and 10 mg/kg, p.o., immediately post-training) and subchronic (10 mg/kg, p.o., seven days after Aß25-35 injection and immediately post-training) administration of selegiline reversed the cognitive impairment induced by Aß25-35 (3 nmol, i.c.v.). Acute administration of selegiline (1 mg/kg, p.o.) in combination with Aß25-35 (3 nmol) decreased MAO-B activity in the perirhinal and remaining cerebral cortices. Acute administration of selegiline (10 mg/kg, p.o.) decreased MAO-B activity in hippocampus, perirhinal and remaining cerebral cortices, regardless of Aß25-35 or Aß35-25 treatment. MAO-A activity was not altered by selegiline or Aß25-35. In summary, the current findings further support a role for cortical monoaminergic transmission in the cognitive deficits observed in AD.

Piracetam prevents scopolamine-induced memory impairment and decrease of NTPDase, 5'-nucleotidase and adenosine deaminase activities.

Piracetam improves cognitive function in animals and in human beings, but its mechanism of action is still not completely known. In the present study, we investigated whether enzymes involved in extracellular adenine nucleotide metabolism, adenosine triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase and adenosine deaminase (ADA) are affected by piracetam in the hippocampus and cerebral cortex of animals subjected to scopolamine-induced memory impairment. Piracetam (0.02 µmol/5 µL, intracerebroventricular, 60 min pre-training) prevented memory impairment induced by scopolamine (1 mg/kg, intraperitoneal, immediately post-training) in the inhibitory avoidance learning and in the object recognition task. Scopolamine reduced the activity of NTPDase in hippocampus (53 % for ATP and 53 % for ADP hydrolysis) and cerebral cortex (28 % for ATP hydrolysis). Scopolamine also decreased the activity of 5'-nucleotidase (43 %) and ADA (91 %) in hippocampus. The same effect was observed in the cerebral cortex for 5'-nucleotidase (38 %) and ADA (68 %) activities. Piracetam fully prevented scopolamine-induced memory impairment and decrease of NTPDase, 5'-nucleotidase and adenosine deaminase activities in synaptosomes from cerebral cortex and hippocampus. In vitro experiments show that piracetam and scopolamine did not alter enzymatic activity in cerebral cortex synaptosomes. Moreover, piracetam prevented scopolamine-induced increase of TBARS levels in hippocampus and cerebral cortex. These results suggest that piracetam-induced improvement of memory is associated with protection against oxidative stress and maintenance of NTPDase, 5'-nucleotidase and ADA activities, and suggest the purinergic system as a putative target of piracetam.

Spermidine-induced improvement of memory involves a cross-talk between protein kinases C and A.

Spermidine (SPD) is an endogenous aliphatic amine with polycationic structure that modulates NMDA receptor activity and improves memory. Recent evidence suggests that cAMP-dependent protein kinase (PKA) and cAMP response element-binding protein (CREB) play a role in SPD-induced improvement of memory. In the current study, we determined whether the calcium-dependent protein kinase (PKC) signaling pathway is involved in SPD-induced facilitation of memory of inhibitory avoidance task in adult rats. The post-training administration of the PKC inhibitor, 3-[1-(dimethylaminopropyl)indol-3-yl]-4-(indol-3-yl)maleimide hydrochloride [GF 109203X, 2.5 ρmol, intrahippocampal (ih)] with SPD (0.2 nmol, ih) prevented memory improvement induced by SPD. Intrahippocampal administration of SPD (0.2 nmol) facilitated PKC phosphorylation in the hippocampus, 30 min after administration. GF 109203X prevented not only the stimulatory effect of SPD on PKC but also PKA and CREB phosphorylation. These results suggest that memory enhancement induced by the ih administration of SPD involves the cross-talk between PKC and PKA/CREB, with sequential activation of PKC and PKA/CREB pathways, in rats.

Trypanosoma evansi: concentration of 3-nitrotyrosine in the brain of infected rats.

Nitric oxide (NO) is involved in many physiological processes, such as blood pressure control, neurotransmission, inhibition of platelet and neutrophil adherence, and the ability to kill tumor cells and parasites. The indirect determination of NO can be made by detection of 3-nitrotyrosine (3-NT) residues. The aim of this study was to measure the concentration of 3-NT in the brain of rats experimentally infected with Trypanosoma evansi. Twenty-four were inoculated intraperitoneally with cryopreserved blood containing 1×10(6) trypomastigotes per animal. Twenty-four animals were used as negative controls and received 0.2 mL of saline by the same route. The experimental groups (group C and T) were established according to the time after infection and the degree of parasitemia as follows: four control subgroups (C3, C5, C10 and C20) with six non-inoculated animals each and four test subgroups (T3, T5, T10 and T20) with six animals infected with T. evansi in each group. The animals were anesthetized with isoflurane and subsequently euthanized at the days 3 (C3, T3), 5 (C5, T5), 10 (C10, T10) and 20 (C20, T20) post-infection (PI). The brain was removed and dissected into cerebellum, cerebral cortex, striatum and hippocampus. Concentration of 3-NT in the brain was determined by Slot blot technique. At the day 3 PI no changes were observed in the concentration of 3-NT among the groups. There was a significant reduction (p<0.05) of 3-NT concentration in the striatum and cerebellum at the days 5 and 10 PI, respectively. At the day 20 PI a significant increase (p<0.05) of 3-NT was observed in the cerebellum, cerebral cortex and hippocampus from the infected animals. Therefore, T. evansi infection caused changes in the concentrations of 3-NT in the central nervous system (CNS), which may be related to clinical signs and infection management.

Spermidine, a positive modulator of the NMDA receptor, facilitates extinction and prevents the reinstatement of morphine-induced conditioned place preference in mice.

RATIONALE: Individuals with opioid use disorders often relapse into drug-seeking behavior after recalling memories linked to the drug use experience. Improving extinction efficacy has been used as a strategy to treat substance use disorders and suppress relapse. Although N-methyl-D-aspartate receptor (NMDAr) agonists facilitate acquisition, consolidation, and extinction, no study has addressed whether spermidine (SPD), a natural polyamine ligand of the NMDA receptor, facilitates the extinction and reinstatement of morphine-induced conditioned place preference (CPP). OBJECTIVES AND METHODS: The aim of the present study was to investigate the effect of SPD, an NMDAr agonist, on the extinction and reinstatement of morphine-induced CPP in mice. Adult male albino Swiss mice received saline (0.9% NaCl) or morphine (5 mg/kg) intraperitoneally (i.p.) and were respectively confined to a black or a white compartment for 30 min for four consecutive days for CPP induction. SPD (10-30 mg/kg, i.p.) or ifenprodil (NMDAr antagonist, 0.1-1 mg/kg, i.p.) were injected 15 min before extinction training. RESULTS: SPD and ifenprodil facilitated the extinction of morphine-induced CPP. SPD treatment during the extinction period impaired reinstatement induced by a priming dose of morphine (1.25 mg/kg). Ifenprodil (0.1 mg/kg) prevented the facilitatory effect of spermidine on the extinction of morphine-induced CPP but did not prevent reinstatement induced by morphine. CONCLUSIONS: These results suggest that SPD facilitated the extinction of morphine-induced CPP by modulating the polyamine binding site of the NMDA receptor. Our findings reveal important effects of SPD and ifenprodil on the re-exposure-induced decrease in morphine-induced CPP, which may be promising for developing novel pharmacological strategies to treat opioid use disorder.

Spermine improves recognition memory deficit in a rodent model of Huntington's disease.

Huntington's disease (HD) is a progressive neurodegenerative disorder associated with motor and cognitive impairment. Intrastriatal administration of quinolinic acid (QA) causes neurodegeneration, glial proliferation and cognitive impairment in animals, which are similar to these seen in human HD. Since polyamines improve memory in cognitive tasks, we now tested if the post-training intrastriatal administration of spermine, an agonist of the polyamine site at the NMDA receptor, reverses the deficits in the object recognition task induced by QA. Bilateral striatal injections of QA (180 or 360 nmol/site) caused object recognition impairment, neuronal death and reactive astrogliosis. A single injection of spermine (0.1 and 1 nmol/site), 5 days after QA injection, reversed QA-induced impairment of object recognition task. Spermine (0.1 nmol/site) also inhibited QA-induced reactive astrogliosis measured by a semi-quantitative determination of GFAP immunolabelling, but did not alter neuronal death, measured by a semi-quantitative determination of fluoro-Jade C staining. These results suggest that polyamine binding sites may be considered a novel therapeutic target to prevent reactive astrogliosis and mnemonic deficits in HD.

Taurine Protects from Pentylenetetrazole-Induced Behavioral and Neurochemical Changes in Zebrafish.

Epilepsy is a common neurological disorder characterized by recurrent unprovoked seizures, which culminate in various neurobehavioral and neurochemical changes. Taurine (TAU) is an amino sulfonic acid which acts an endogenous inhibitory neuromodulator. Moreover, TAU displays intrinsic antioxidant activity, contributing to its beneficial actions in the CNS. Here, we evaluated whether TAU pretreatment protects from pentylenetetrazole (PTZ)-induced behavioral alterations and oxidative stress-related parameters in zebrafish brain tissue. Fish were pretreated with 42, 150, and 400 mg/L TAU (40 min) and further exposed to 10 mM PTZ (20 min) to analyze the seizure-like behaviors. As a positive control, another group was previously treated with 75 µM diazepam (DZP). Afterwards, biochemical experiments were performed. All TAU concentrations tested decreased seizure intensity in the first 150 s. Importantly, 150 mg/L TAU attenuated seizure-like behavioral scores, decreased seizure intensity, reduced the frequency of clonic-like seizures (score 4), and increased the latency to score 4. TAU (150 mg/L) also prevented oxidative stress in PTZ-challenged fish by decreasing lipid peroxidation and protein carbonylation and preventing changes on nonprotein thiol levels. No significant changes were observed in MTT assay and LDH activity. Differently than observed in DZP group, TAU did not affect the overall swimming activity of fish, suggesting different mechanisms of action. Collectively, we show that TAU attenuates PTZ-induced seizure-like behaviors and brain oxidative stress in zebrafish, suggesting the involvement of antioxidant mechanisms in neuroprotection.

Antinociceptive effect of novel trihalomethyl-substituted pyrazoline methyl esters in formalin and hot-plate tests in mice.

The aim of the present study was to evaluate the antinociceptive potential of four novel pyrazoline methyl ester compounds on chemical and thermal models of pain in mice. The following 5-trihalomethylated-4,5-dihydro-1H-pyrazole methyl ester compounds were tested: 3-methyl-5-trifluoromethyl-(MPF3), 4-methyl-5-trifluoromethyl-(MPF4), 3-methyl-5-trichloromethyl-(MPCl3) and 4-methyl-5-trichloromethyl-(MPCl4). MPF3, MPF4, MPCl3 and MPCl4 (0.03-1.0 mmol/kg) given intraperitoneally decreased neurogenic and inflammatory phases of nociception in the formalin test. Moreover, MPF3, MPF4, MPCl3, MPCl4 (0.1-1.0 mmol/kg) and dipyrone (1.5 mmol/kg) also produced a dose-dependent antinociceptive effect in the hot-plate test. However, MPF3, MPF4, MPCl3 and MPCl4 did not impair motor coordination in the rotarod test or spontaneous locomotion in the open field test. The antinociceptive effect of MPF4 (1.0 mmol/kg, i.p.) was reversed by the opioid receptor antagonist naloxone (2 mg/kg, i.p.), but not by the alpha(2)-adrenergic receptor antagonist yohimbine (0.15 mg/kg, i.p.) or by p-chlorophenylalanine ethyl ester (PCPA, 300 mg/kg, i.p.) treatment. In contrast to morphine (5 mg/kg, i.p.), MPF4 given daily for up to 8 days did not generate a tolerance to its antinociceptive effect. However, similar to morphine (11 mg/kg, i.p.), MPF4 reduced gastrointestinal transit in mice. Taken together these results demonstrate that these novel pyrazoline methyl esters tested may be promising prototypes of additional mild analgesics.

Antinociceptive action of 4-methyl-5-trifluoromethyl-5-hydroxy-4, 5-dihydro-1H-pyrazole methyl ester in models of inflammatory pain in mice.

AIMS: The aim of the present study was to evaluate the antinociceptive effect of the novel pyrazoline methyl ester: 4-methyl-5-trifluoromethyl-5-hydroxy-4,5-dihydro-1H-pyrazole methyl ester (MPF4). MAIN METHODS: The effect of MPF4 was assessed in two models of pain: arthritic pain caused by Complete Freund's Adjuvant (CFA) and postoperative pain caused by surgical incision in mice. KEY FINDINGS: MPF4 given intraperitoneally (1.0 mmol/kg, i.p.) produced marked antinociception in inflammatory allodynia caused by CFA. The antinociceptive effect produced by MPF4 was reversed with the pre-treatment of animals with naloxone or naltrindole. Oral administration of MPF4 (1.0 mmol/kg, p.o), dipyrone (1.0 mmol/kg, p.o.) and morphine (0.026 mmol/kg, p.o.) also produced an anti-allodynic effect. However, none of the compounds evaluated reversed the paw edema produced by CFA. Moreover, MPF4, dipyrone and morphine also produced an anti-allodynic effect in the surgical incisional pain model. The maximal inhibitions obtained with preemptive drug treatment were 66+/-7%, 73+/-9% and 88+/-8% for MPF4 (1.0 mmol/kg, p.o.), dipyrone (1.0 mmol/kg, p.o.) and morphine (0.026 mmol/kg, p.o.), respectively. The maximal inhibitions obtained with curative drug treatment were 53+/-9%, 83+/-7% and 84+/-7%, for MPF4, dipyrone and morphine, respectively. Unlike indomethacin, MPF4 did not induce gastric lesions at the dose that caused the highest antinociception (1.0 mmol/kg, p.o). The anti-allodynic action of MPF4, dipyrone and morphine was not associated with impairment of motor activity. SIGNIFICANCE: The results of the present study suggest that MPF4 represents a potential target for the development of new drugs to treat persistent inflammatory pain.

Design and microwave-assisted synthesis of 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles: novel agents with analgesic and anti-inflammatory properties.

In this work, we reported the synthesis and evaluation of the analgesic and anti-inflammatory properties of novel 3- or 4-substituted 5-trifluoromethyl-5-hydroxy-4,5-dihydro-1H-1-carboxyamidepyrazoles (where 3-/4-substituent=H/H, Me/H, Et/H, Pr/H, i-Pr/H, Bu/H, t-Bu/H, Ph/H, 4-Br-Ph/H and H/Me) designed in the exploration of the bioisosteric replacement of benzene present in salicylamide with a 5-trifluoromethyl-4,5-dihydro-1H-pyrazole scaffold. Target compounds were synthesized from the cyclocondensation of 4-alkoxy-1,1,1-trifluoromethyl-3-alken-2-ones with semicarbazide hydrochloride through a rapid one-pot reaction via microwave irradiation. In addition to spectroscopic data, the structure of the compounds was supported by X-ray diffraction. Subcutaneous administration of the 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles decreased pain-related behavior during neurogenic and inflammatory phases of the formalin test in mice. Moreover, the more active analgesic compounds (3-/4-=Et/H and H/Me) significantly decreased carrageenan-induced paw edema in mice. The data obtained in this work suggest that the synthesized compounds could be promising candidates for the future development of novel analgesic and anti-inflammatory agents.

Systemic delivery of selective EP1 and EP3 receptor antagonists attenuates pentylenetetrazole-induced seizures in mice.

Neuroinflammation plays a major role in brain excitability and may contribute to the development of epilepsy. Prostaglandin E2 (PGE2) is a direct mediator of inflammatory responses and, through EP receptors, plays an important role in neuronal excitability. Pharmacological evidence supports that centrally-administered EP1 and EP3 receptor antagonists reduced acutely evoked seizures in rats. Translation of these findings would benefit from evidence of efficacy with a more clinically relevant route of delivery and validation in another species. In the current study we investigated whether the systemic administration of EP1 and EP3 agonists and antagonists modulate pentylenetetrazole (PTZ)-induced seizures in mice. In addition, it was examined whether these compounds alter Na+, K+-ATPase activity, an enzyme responsible for the homeostatic ionic equilibrium and, consequently, for the resting membrane potential in neurons. While the systemic administration of EP1 and EP3 antagonists (ONO-8713 and ONO-AE3-240, respectively) attenuated, the respective agonists (ONO-DI-004 and ONO-AE-248) potentiated PTZ-induced seizures (all compounds injected at the dose of 10 µg/kg, s.c., 30 min before PTZ challenge). Co-administration of either EP1 or EP3 agonist with the respective antagonists nullified the anticonvulsant effects of EP1/3 receptor blockade. In addition, EP1 and EP3 agonists exacerbated PTZ-induced decrease of Na+, K+-ATPase activity in both cerebral cortex and hippocampus, whereas, EP1 and EP3 antagonists prevented PTZ-induced decrease of Na+, K+-ATPase activity in both structures. Our findings support and extend evidence that EP1 and EP3 receptors may be novel targets for the development of anticonvulsant drugs.

Intra-amygdala administration of polyamines modulates fear conditioning in rats.

Amygdalar NMDA receptor activation has been implicated in the acquisition of fear memories in rats. However, little is known about the role of endogenous modulators of the NMDA receptor, such as polyamines, in pavlovian fear-conditioning learning. Therefore, in the present study we investigated whether the immediate pretraining or post-training bilateral infusion of arcaine, an antagonist of the NMDA receptor polyamine-binding site, or spermidine, an agonist of the NMDA receptor polyamine-binding site, into the amygdala affected classical fear conditioning in rats. Bilateral microinjections of arcaine (0.0002-0.2 nmol) decreased, whereas spermidine (0.002-20 nmol) increased, contextual and auditory fear conditioning. Arcaine coadministration, at a dose that had no effect per se, reversed the facilitatory effect of spermidine. These results provide evidence that endogenous and exogenous polyamines modulate the acquisition or early consolidation (or both) of the fear-conditioning task in the amygdala.

Hypothermic and antipyretic effects of 3-methyl- and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole-1-carboxyamides in mice.

The effect of novel pyrazolines, 3-methyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole-1-carboxyamide (MPCA) and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole-1-carboxyamide (PPCA) on body temperature and endotoxin-induced fever was investigated in mice. The subcutaneous (s.c.) administration of 1.5 mmol/kg dipyrone, MPCA or PPCA and the intracerebroventricular (i.c.v.) administration of 225 nmol dipyrone reduced basal rectal temperature. Intracerebroventricular administration of 225 nmol MPCA or PPCA did not alter basal rectal temperature. The administration of 0.15 mmol/kg (s.c.) or 25 nmol (5 microl) dipyrone (i.c.v.), MPCA or PPCA had no effect on basal rectal temperature, but reversed lipopolysaccharide-induced fever. These results suggest that MPCA and PPCA cause antipyresis, which is similar to that caused by dipyrone, and may be useful antipyretic agents.

Alpha 2-adrenoceptors and 5-HT receptors mediate the antinociceptive effect of new pyrazolines, but not of dipyrone.

In this study, we investigated whether spinal noradrenergic and serotonergic systems are involved in the antinociception induced by the novel pyrazolines 3-methyl- and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-1-pyrazole-1-carboxyamide (MPCA and PPCA, respectively), and the pyrazolinone dipyrone in the acetic acid writhing (stretching) test in mice. Intrathecal (i.t.) administration of methysergide (3 and 10 microg) and yohimbine (3 microg), but not of prazosin (0.3 and 1 microg) prevented the antinociceptive action of MPCA and PPCA (500 micromol/kg, s.c.). Dipyrone-induced antinociception (500 micromol/kg, s.c.) was not affected by methysergide or adrenoceptor antagonists. These results suggest that spinal 5-HT receptors and alpha2-adrenoceptors are involved in the antinociception induced by MPCA and PPCA, but not in that elicited by dipyrone.

Ebselen blocks the quinolinic acid-induced production of thiobarbituric acid reactive species but does not prevent the behavioral alterations produced by intra-striatal quinolinic acid administration in the rat.

Ebselen (EBS) is a seleno-organic compound with glutathione peroxidase-like activity which is neuroprotective in acute stroke ischemia. In this study, we investigated the effect of EBS on quinolinic acid (QA)-induced neurotoxicity. EBS inhibited QA-induced production of thiobarbituric acid reactive species (TBARS) by striatal homogenates in vitro with an IC(50) of 1.85 microM. Intra-striatal injection of QA (360 nmol) increased striatal content of TBARS and induced convulsions and contralateral rotational behavior. Intra-striatal pre-injection of EBS (10 nmol) 15 min before QA abolished QA-induced TBARS production but did not alter QA-induced behavioral effects. The present findings suggest that EBS acts on post-receptor events, neutralizing free radicals produced by overstimulation of N-methyl-D-aspartate receptors.

Spermidine improves fear memory persistence.

Persistence is the most characteristic attribute of long-term memory (LTM). For memory persistence, a second late event of consolidation, that occurs around 12h after the acquisition, is necessary. Although the N-methyl-d-aspartate (NMDA) receptor has been involved in the persistence of memory, whether endogenous modulators of the NMDA receptor actually modulate memory persistence is unknown. In the current study we investigated whether spermidine and arcaine, respectively agonist and antagonist of polyamine binding site at NMDA receptor, alter the persistence of the memory of contextual fear conditioning task in rats. While 12h post-training administration of spermidine (10 and 30mg/kg, i.p.) facilitated, arcaine (10mg/kg, i.p.) impaired the memory of fear assessed 2 and 7 days after training. Arcaine (0.1mg/kg) prevented the facilitatory effect of spermidine (10mg/kg, i.p.), and spermidine (1mg/kg), prevented the memory impairment induced by arcaine (10mg/kg, i.p.) when tested 2 and 7 days after training. These results suggest that endogenous polyamines improve the persistence of fear memory.

Monoterpenoid terpinen-4-ol exhibits anticonvulsant activity in behavioural and electrophysiological studies.

Terpinen-4-ol (4TRP) is a monoterpenoid alcoholic component of essential oils obtained from several aromatic plants. We investigated the psychopharmacological and electrophysiological activities of 4TRP in male Swiss mice and Wistar rats. 4TRP was administered intraperitoneally (i.p.) at doses of 25 to 200 mg/kg and intracerebroventricularly (i.c.v.) at concentrations of 10, 20, and 40 ng/2 µL. For in vitro experiments, 4TRP concentrations were 0.1 mM and 1.0 mM. 4TRP (i.p.) inhibited pentylenetetrazol- (PTZ-) induced seizures, indicating anticonvulsant effects. Electroencephalographic recordings showed that 4TRP (i.c.v.) protected against PTZ-induced seizures, corroborating the behavioural results. To determine whether 4TRP exerts anticonvulsant effects via regulation of GABAergic neurotransmission, we measured convulsions induced by 3-mercapto-propionic acid (3-MP). The obtained results showed involvement of the GABAergic system in the anticonvulsant action exerted by 4TRP, but flumazenil, a selective antagonist of the benzodiazepine site of the GABAA receptor, did not reverse the anticonvulsant effect, demonstrating that 4TRP does not bind to the benzodiazepine-binding site. Furthermore, 4TRP decreased the sodium current through voltage-dependent sodium channels, and thus its anticonvulsant effect may be related to changes in neuronal excitability because of modulation of these channels.