CaMKIIα mediates spermidine-induced memory enhancement in rats: A potential involvement of PKA/CREB pathway.

Memory consolidation is associated with the regulation of protein kinases, which impact synaptic functions and promote synaptogenesis. The administration of spermidine (SPD) has been shown to modulate major protein kinases associated with memory improvement, including the Ca2+-dependent protein kinase (PKC) and cAMP-dependent protein kinase (PKA), key players in the cAMP response element-binding protein (CREB) activation. Nevertheless, the initial mechanism underlying SPD-mediated memory consolidation remains unknown, as we hypothesize a potential involvement of the memory consolidation precursor, Ca2+/calmodulin-dependent protein kinase II-α (CaMKIIα), in this process. Based on this, our study aimed to investigate potential interactions among PKC, PKA, and CREB activation, mediated by CaMKIIα activation, in order to elucidate the SPD memory consolidation pathway. Our findings suggest that the post-training administration of the CaMKII inhibitor, KN-62 (0.25 nmol, intrahippocampal), prevented the memory enhancement induced by SPD (0.2 nmol, intrahippocampal) in the inhibitory avoidance task. Through western immunoblotting, we observed that phosphorylation of CaMKIIα in the hippocampus was facilitated 15 min after intrahippocampal SPD administration, resulting in the activation of PKA and CREB, 180 min after infusion, suggesting a possible sequential mechanism, since SPD with KN-62 infusion leads to a downregulation in CaMKIIα/PKA/CREB pathway. However, KN-62 does not alter the memory-facilitating effect of SPD on PKC, possibly demonstrating a parallel cascade in memory acquisition via PKA, without modulating CAMKIIα. These results suggest that memory enhancement induced by SPD administration involves crosstalk between CaMKIIα and PKA/CREB, with no PKC interaction.

Use of recombinant S1 protein with hFc for analysis of SARS-CoV-2 adsorption and evaluation of drugs that inhibit entry into VERO E6 cells.

The significant number of deaths and infection caused by the new coronavirus SARS-CoV-2 has created an urgent demand for effective and readily available drugs for the treatment of COVID-19. However, the requirements for biosafety level 3 (NB-3) laboratories for experiments with the virus has made it very challenging for such research to meet this demand. It is known that angiotensin-converting enzyme 2 (ACE2), located on the surface of host cells, serves as the viral receptor for the spike (S) protein of SARS-CoV-2. This protein is a tetramer subdivided into S1 and S2 regions, with the former containing the receptor-binding domain (RBD). Therefore, drugs that interfere with the interaction between the spike and the receptor (as well as accessory proteins) or suppress their expression could inhibit the entry and spread of SARS-CoV-2 between cells. In this context, we standardized the use of recombinant SARS-CoV-2 S1 Protein with hFc (human Fc) for the analysis of binding in VERO E6 cells by flow cytometry, aiming to provide a new tool for identifying drugs and neutralizing antibodies, thus eliminating the need for NB-3 laboratories. Because minocycline (MCL), nimesulide (NMS), and berberine (BBR) have effects related to the ACE2 receptor, inhibit inflammation, and do not suppress the adaptive immune response (crucial for patient recovery), we investigated whether these drugs prevent the absorption of the spike protein into the host cell. For this purpose, we used VERO E6 cells under control conditions, pre-treated with these drugs and exposed to recombinant SARS-CoV-2 S1 Protein with hFC. We found that an exposure time of 30 min and a concentration of 10 µg/mL of spike S1 caused a strong signal detected by flow cytometry, using the secondary anti-hFc antibody conjugated with Alexa Fluor 647. Pre-treatment of cells with BBR for 30 min suppressed the signal from spike-positive cells, suggesting that this alkaloid interferes with spike adsorption on ACE2. The pre-incubation of spike protein with BBR did not alter its adsorption and internalization, indicating that BBR does not directly interact with spike protein. The ACE2 inactivation with a specific antibody inhibited spike protein adsorption and internalization. Furthermore, the pharmacological treatments did not alter the expression of ACE2. Exposure to spike protein increased IFNγ levels and the treatments with MCL and NMS were effective in inhibiting this increase. Taken together, we standardized a technique for analyzing the adsorption of SARS-CoV-2 and studying molecules that inhibit this process. Additionally, we demonstrated that BBR blocks spike entry bypre-binding to the host cell,and that the ACE2 receptor inactivation prevents Spike protein adsorption and penetration into cells.

Differentiated Embryonic Neurospheres from Familial Alzheimer's Disease Model Show Innate Immune and Glial Cell Responses.

Proteins involved in the Alzheimer's disease (AD), such as amyloid precursor protein (APP) and presenilin-1 (PS1), play critical roles in early development of the central nervous system (CNS), as well as in innate immune and glial cell responses. Familial AD is associated with the presence of APPswe and PS1dE9 mutations. However, it is still unknown whether these mutations cause deficits in CNS development of carriers. We studied genome-wide gene expression profiles of differentiated neural progenitor cells (NPCs) from wild-type and APPswe/PS1dE9 mouse embryo telencephalon. The occurrence of strong innate immune and glial cell responses in APPswe/PS1dE9 neurospheres mainly involves microglial activation, inflammatory mediators and chemokines. APPswe/PS1dE9 neurospheres augmented up to 100-fold CCL12, CCL5, CCL3, C3, CX3CR1, TLR2 and TNF-alpha expression levels, when compared to WT neurospheres. Expression levels of the glia cell marker GFAP and microglia marker Iba-1 were up to 20-fold upregulated in APPswe/PS1dE9 neurospheres. The secretome of differentiated APPswe/PS1dE9 NPCs revealed enhanced chemoattraction of peripheral blood mononuclear cells. When evaluating the inferred protein interaction networks constructed from the array data, an improvement in astrocyte differentiation in APPswe/PS1dE9 neurospheres was evident in view of increased GFAP expression. Transgenic NPCs differentiated into neural phenotypes presented expression patterns of cytokine, glial cells, and inflammatory mediators characteristic of APPswe/PS1dE9 adult animals. Consequently, the neurogenic niche obtained from differentiation of embryonic APPswe/PS1dE9 neurospheres spontaneously presents several alterations observed in adult AD brains. Finally, our data strengthen pathophysiological hypotheses that propose an early neurodevelopmental origin for familial AD.

Efficacy, acceptability, and tolerability of antidepressants for sleep quality disturbances in post-traumatic stress disorder: A systematic review and network meta-analysis.

Sleep quality disturbances are a common occurrence in post-traumatic stress disorder (PTSD) and may remain after evidence-based treatment for PTSD has been implemented. If left untreated, sleep disturbance can perpetuate or aggravate the disorder. A systematic review and network meta-analysis (NMA) of randomized controlled trials (RCTs) was conducted comparing efficacy, acceptability, and tolerability among antidepressants for sleep quality improvement in PTSD, using Cochane's RoB2.0 and GRADE approach for NMA. The Cochrane Library, LILACS, PsycINFO, PTSDpubs, and PubMed Central databases were searched from inception to November 29, 2020, leading to the retrieval of 3733 reports. After the selection process, seven RCTs were included in the review (N = 600). We found low certainty of evidence (LCE) that sertraline may improve sleep quality (measured by PSQI) in adult patients with PTSD (MD -0.48, 95% CrI -0.63 to -0.32). Sertraline was as well accepted (RR 1.12, 95% CrI -0.83 to 1.52, very low certainty [VLCE]) and as well tolerated as placebo (RR 0.58, 95% CrI 0.28 to 1.14, LCE). Mirtazapine (MD -3.35, 95% CrI -9.06 to 2.39, LCE), paroxetine (MD -3.13, 95% CrI -7.47 to 1.26, VLCE), nefazodone (MD -0.25, 95% CrI -5.95 to 5.38, VLCE), and bupropion (MD -2.28, 95% CrI -4.75 to 0.21, VLCE) were similar to placebo for improving sleep quality. These antidepressants resulted in little or no benefit for sleep in PTSD. Although the NMA suggested that sertraline may improve sleep in PTSD compared to placebo, due to the low certainty, these estimates are not robust enough to guide clinical decisions.

Pharmacological treatments for adults with post-traumatic stress disorder: A network meta-analysis of comparative efficacy and acceptability.

BACKGROUND: The purpose of this study was to compare efficacy and acceptability among drug treatments for adults with post-traumatic stress disorder (PTSD) through a systematic review, random-effects pairwise and network meta-analyses. METHODS: Double-blind randomized controlled trials comparing pharmacological interventions for adults with PTSD were searched from database inception through Aug. 28, 2018, on Cochrane (Central), Embase, LILACS, PILOTS, PsycINFO, PubMed, and Web of Science. Clinical trial registries and the websites of pharmaceutical companies were also searched. The GRADE system was used to assess the quality of the evidence. RESULTS: The systematic review included 58 studies comprising 6766 patients randomized to 26 different interventions. Regarding efficacy, topiramate (SMD = -0.57; 95%CrI: -1.07,-0.10), risperidone (SMD = -0.53; 95%CrI: -0.93,-0.15), quetiapine (SMD = -0.59; 95%CrI: -1.06,-0.11), paroxetine (SMD = -0.35; 95%CrI: -0.48,-0.21), venlafaxine (SMD = -0.25; 95%CrI: -0.44,-0.05), fluoxetine (SMD = -0.28; 95%CrI: -0.46,-0.08), and sertraline (SMD = -0.21; 95%CrI: -0.33,-0.09) outperformed placebo. Moreover, phenelzine (RR = 3.39; 95%CrI: 1.43,11.09), lamotrigine (RR = 4.39; 95%CrI: 1.18,26.38), and fluoxetine (RR = 1.28%CrI: 1.01,1.59) outperformed placebo in terms of acceptability. CONCLUSIONS: The NMA supports topiramate, risperidone, quetiapine, paroxetine, venlafaxine, fluoxetine and sertraline as effective pharmacological choices for the treatment of PTSD. Quetiapine and topiramate have the shortcoming of relying on a few small studies, but the clinically meaningful change in symptoms is noteworthy and merits further investigation. Among the pharmacological treatments with evidence of efficacy compared to placebo, fluoxetine achieved a relatively high rank regarding acceptability. To the best of our knowledge, this is the largest contemporary NMA on the subject and the addition of new medications is an important extension of previous meta-analyses, enabling a larger number of drug comparisons.

Spermidine-induced improvement of memory consolidation involves PI3K/Akt signaling pathway.

Spermidine (SPD) is an endogenous polyamine that plays a facilitatory role in memory acquisition and consolidation. Memory consolidation occurs immediately after learning and again around 3-6 hours later. Current evidence indicates that the polyamine binding site at the NMDA receptor (NMDAr) mediates the effects of SPD on memory. While NMDAr activation increases brain-derived neurotrophic factor (BDNF) release, no study has investigated whether BDNF-activated signaling pathways, such as the phosphatidylinositol 3-kinase (PI3K)/Akt pathway play a role in SPD-induced improvement of memory consolidation. Therefore, the aim of the current study was to evaluate whether the TrkB receptor and the PI3K/Akt pathway are involved in the facilitatory effect of SPD on memory consolidation. Male Wistar rats were trained in the contextual conditioned fear task. SPD, ANA-12 (TrkB antagonist), and LY294002 (PI3K inhibitor) were administered immediately after training. The animals were tested 24 h after training. We found that SPD improved fear memory consolidation and that both ANA-12 and LY294002 prevented the facilitatory effect of SPD on memory. These results suggest that SPD-induced improvement of memory consolidation involves the activation of the TrkB receptor and PI3K/Akt pathway.

Nectandra grandiflora essential oil and its isolated sesquiterpenoids minimize anxiety-related behaviors in mice through GABAergic mechanisms.

Nectandra grandiflora Ness (Lauraceae) essential oil (EO) main constituent, the sesquiterpenoid (+)-dehydrofukinone (DHF), has sedative and anticonvulsant effects through GABAergic mechanisms. Other DHF-related sesquiterpenoids have been identified in the EO, such as, dehydrofukinone epoxide (DFX), eremophil-11-en-10-ol (ERM) and selin-11-en-4-α-ol (SEL). However, the neuronal effects of these compounds in mammals remain unknown. Therefore, the aim of this study was to evaluate the anxiolytic potential of the N. grandiflora EO and the isolated compounds in in mice. For this purpose, mice were administered orally with vehicle, 10, 30 or 100 mg/kg EO, DHF, DFX, ERM or SEL or 1 mg/kg diazepam. Locomotion and ethological parameters in the open field (OF) and elevated plus maze (EPM) were recorded. We also examined the effect of DFX, ERM and SEL on the membrane potential and calcium influx in synaptosomes, and the presence of the compounds in the cortical tissue using gas chromatography. EOs and isolated compounds reduced anxiety-related parameters in the EPM (open arms time and entries, end activity, head dipping) and OF (center time and entries, total rearing, unprotected rearing, sniffing, grooming) without alter ambulation or induce sedation. Flumazenil (2 mg/kg, i.p.) altered the anxiolytic-like effect of all treatments and vanished the DFX, ERM and SEL-induced changes in membrane potential. However, FMZ did not blocked the DFX-, ERM- and SEL-induced inhibition of calcium influx. Therefore, our results suggest that N. grandiflora EO and isolated compounds induced anxiolytic-like effect in mice due to positive modulation of GABAa receptors and/or inhibition of neuronal calcium influx.

A rapid method for identification and quantification of prostaglandins in cerebral tissues by UHPLC-ESI-MS/MS for the lipidomic in vivo studies.

An analytical method utilizing liquid chromatography coupled to mass spectrometry with electrospray ionization has been developed for the identification of prostaglandins (PGs) in cerebral tissues. The five compounds identified (thromboxane B2, prostaglandin E2, prostaglandin D2, 6-keto-prostaglandin F1 alpha and prostaglandin F2 alpha) are cellular mediators of inflammation and are involved in a variety of physiological and pathological processes by acting on membrane receptors on the surfaces of target cells. The parameters of the electrospray ionization interface were optimized to obtain the highest possible sensitivity for all compounds studied. The limits of detection ranged from 0.25 to 1.09 µg L-1, and the limits of quantification ranged from 0.83 to 3.64 µg L-1. The method was validated and applied to samples of brain tissue from five mice. The sample concentrations of the four prostaglandins quantified ranged from 375 ȵg L-1for prostaglandin E2 to 6602 µg L-1 for prostaglandin D2. An advantage of this work that should be emphasized is the fast response of the method, which allows to obtaining the lipid profile after a 3 min chromatographic run.

(+)-Dehydrofukinone modulates membrane potential and delays seizure onset by GABAa receptor-mediated mechanism in mice.

(+)-Dehydrofukinone (DHF), isolated from Nectandra grandiflora (Lauraceae) essential oil, induces sedation and anesthesia by modulation of GABAa receptors. However, no study has addressed whether DHF modulates other cellular events involved in the control of cellular excitability, such as seizure behavior. Therefore, the aim of the present study was to investigate the effect of DHF on cellular excitability and seizure behavior in mice. For this purpose, we used isolated nerve terminals (synaptosomes) to examine the effect of DHF on the plasma membrane potential, the involvement of GABAa receptors and the downstream activation of Ca2+ mobilization. Finally, we performed an in vivo assay in order to verify whether DHF could impact on seizures induced by pentylenetetrazole (PTZ) in mice. The results showed that DHF induced a GABA-dependent sustained hyperpolarization, sensitive to flumazenil and absent in low-[Cl-] medium. Additionally, (1-100µM) DHF decreased KCl-evoked calcium mobilization over time in a concentration-dependent manner and this effect was prevented by flumazenil. DHF increased the latency to myoclonic jerks (10mg/kg), delayed the onset of generalized tonic-clonic seizures (10, 30 and 100mg/kg), and these effects were also blocked by the pretreatment with flumazenil. Our data indicate that DHF has anticonvulsant properties and the molecular target underlying this effect is likely to be the facilitation of GABAergic neuronal inhibition. The present study highlights the therapeutic potential of the natural compound DHF as a suppressor of neuronal excitability.

Cyclooxygenase-2 inhibitors differentially attenuate pentylenetetrazol-induced seizures and increase of pro- and anti-inflammatory cytokine levels in the cerebral cortex and hippocampus of mice.

Seizures increase prostaglandin and cytokine levels in the brain. However, it remains to be determined whether cyclooxygenase-2 (COX-2) derived metabolites play a role in seizure-induced cytokine increase in the brain and whether anticonvulsant activity is shared by all COX-2 inhibitors. In this study we investigated whether three different COX-2 inhibitors alter pentylenetetrazol (PTZ)-induced seizures and increase of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), interferon-γ (INF-γ), tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) levels in the hippocampus and cerebral cortex of mice. Adult male albino Swiss mice received nimesulide, celecoxib or etoricoxib (0.2, 2 or 20mg/kg in 0.1% carboxymethylcellulose (CMC) in 5% Tween 80, p.o.). Sixty minutes thereafter the animals were injected with PTZ (50mg/kg, i.p.) and the latency to myoclonic jerks and to generalized tonic-clonic seizures were recorded. Twenty minutes after PTZ injection animals were killed and cytokine levels were measured. PTZ increased cytokine levels in the cerebral cortex and hippocampus. While celecoxib and nimesulide attenuated PTZ -induced increase of proinflammatory cytokines in the cerebral cortex, etoricoxib did not. Nimesulide was the only COX-2 inhibitors that attenuated PTZ-induced seizures. This effect coincided with an increase of IL-10 levels in the cerebral cortex and hippocampus, constituting circumstantial evidence that IL-10 increase may be involved in the anticonvulsant effect of nimesulide.

EP2 receptor agonist ONO-AE1-259-01 attenuates pentylenetetrazole- and pilocarpine-induced seizures but causes hippocampal neurotoxicity.

Epilepsy is a common and devastating neurological disease affecting more than 50 million people worldwide. Accumulating experimental and clinical evidence suggests that inflammatory pathways contribute to the development of seizures in various forms of epilepsy. In this context, while the activation of the PGE2 EP2 receptor causes early neuroprotective and late neurotoxic effects, the role of EP2 receptor in seizures remains unclear. We investigated whether the systemic administration of the highly selective EP2 agonist ONO-AE1-259-01 prevented acute pentylenetetrazole (PTZ)- and pilocarpine-induced seizures. The effect of ONO-AE1-259-01 on cell death in the hippocampal formation of adult male mice seven days after pilocarpine-induced status epilepticus (SE) was also evaluated. ONO-AE1-259-01 (10µg/kg, s.c.) attenuated PTZ- and pilocarpine-induced seizures, evidenced by the increased latency to seizures, decreased number and duration of seizures episodes and decreased mean amplitude of electrographic seizures. ONO-AE1-259-01 and pilocarpine alone significantly increased the number of pyknotic cells per se in all hippocampal subfields. The EP2 agonist also additively increased pilocarpine-induced pyknosis in the pyramidal cell layer of CA1 but reduced pilocarpine-induced pyknosis in the granule cell layer of the dentate gyrus (DG). Although the systemic administration of ONO-AE1-259-01 caused a significant anticonvulsant effect in our assays, this EP2 agonist caused extensive cell death. These findings limit the likelihood of EP2 receptor agonists being considered as novel potential anticonvulsant drugs.

A Nonrewarding NMDA Receptor Antagonist Impairs the Acquisition, Consolidation, and Expression of Morphine Conditioned Place Preference in Mice.

N-methyl-D-aspartate (NMDA) receptor antagonists block morphine-induced conditioned place preference (CPP). Although polyamines are endogenous modulators of the NMDA receptor, it is not known whether polyaminergic agents induce CPP or modulate morphine-induced CPP. Here, we examined whether polyamine ligands modify morphine CPP acquisition, consolidation, and expression. Adult male albino Swiss mice received saline (0.9 % NaCl, intraperitoneally (i.p.)) or morphine (5 mg/kg, i.p.) and were respectively confined to a black or a white compartment for 30 min for four consecutive days for CPP induction. The effect of arcaine (3 mg/kg, i.p.) or spermidine (30 mg/kg, i.p.), respectively, an antagonist and an agonist of the polyamine-binding site at the NMDA receptor, on the acquisition, consolidation, and expression of morphine CPP was studied. In those experiments designed to investigate whether spermidine prevented or reversed the effect of arcaine, spermidine (30 mg/kg, i.p.) was administered 15 min before or 15 min after arcaine, respectively. Arcaine and spermidine did not induce CPP or aversion per se. Arcaine (3 mg/kg, i.p.) impaired the acquisition, consolidation, and expression of morphine CPP. Spermidine prevented the impairing effect of arcaine on the acquisition of morphine CPP but not the impairing effect of arcaine on consolidation or expression of morphine CPP. These results suggest that arcaine may impair morphine CPP acquisition by modulating the polyamine-binding site at the NMDA receptor. However, the arcaine-induced impairment of consolidation and expression of morphine CPP seems to involve other mechanisms.

Antinociceptive and antidepressant-like effects of the crude extract of Vitex megapotamica in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Vitex megapotamica (Spreng) Moldenke has been used in South American folk medicine to treat inflammatory diseases. However, the effects of V. megapotamica on animal models of nociception and depression have not been evaluated. AIM OF THE STUDY: This study investigated whether the crude leaf extract of V. megapotamica exhibits antinociceptive and antidepressant-like effects in a Freund's adjuvant-induced chronic inflammation and depression model. MATERIALS AND METHODS: Chronic inflammation was induced in rats by the intraplantar administration of complete Freund's adjuvant (CFA; 100µl). The effect of oral crude extract of V. megapotamica (VmE; 3-30mg/kg, p.o.) on nociception (thermal hyperalgesia, mechanical allodynia and arthritis score), inflammation (edema, myeloperoxidase activity), immobility (forced swimming test), locomotor activity (open field), gastrointestinal transit, hyperalgesia and naloxone-precipitated morphine withdrawal syndrome was evaluated. Naloxone (0.4mg/kg, i.p.) was used to investigate the involvement of opioid system in the currently described effects of VmE. RESULTS: Crude extract caused antinociceptive/antidepressant-like effects in the CFA-induced chronic inflammation model, which was prevented by naloxone. The VmE extract (10mg/kg, p.o.) did not alter the locomotor activity, gastrointestinal function and inflammatory parameters and did not cause hyperalgesia. CONCLUSION: V. megapotamica induces opioid-dependent antinociception and antidepressant-like effect, without anti-inflammatory activity. The results support the use of VmE as analgesic and antidepressant.

Modulation of learning and memory by natural polyamines.

Spermine and spermidine are natural polyamines that are produced mainly via decarboxylation of l-ornithine and the sequential transfer of aminopropyl groups from S-adenosylmethionine to putrescine by spermidine synthase and spermine synthase. Spermine and spermidine interact with intracellular and extracellular acidic residues of different nature, including nucleic acids, phospholipids, acidic proteins, carboxyl- and sulfate-containing polysaccharides. Therefore, multiple actions have been suggested for these polycations, including modulation of the activity of ionic channels, protein synthesis, protein kinases, and cell proliferation/death, within others. In this review we summarize these neurochemical/neurophysiological/morphological findings, particularly those that have been implicated in the improving and deleterious effects of spermine and spermidine on learning and memory of naïve animals in shock-motivated and nonshock-motivated tasks, from a historical perspective. The interaction with the opioid system, the facilitation and disruption of morphine-induced reward and the effect of polyamines and putative polyamine antagonists on animal models of cognitive diseases, such as Alzheimer's, Huntington, acute neuroinflammation and brain trauma are also reviewed and discussed. The increased production of polyamines in Alzheimer's disease and the biphasic nature of the effects of polyamines on memory and on the NMDA receptor are also considered. In light of the current literature on polyamines, which include the description of an inborn error of the metabolism characterized by mild-to moderate mental retardation and polyamine metabolism alterations in suicide completers, we can anticipate that polyamine targets may be important for the development of novel strategies and approaches for understanding the etiopathogenesis of important central disorders and their pharmacological treatment.

Spermidine-induced improvement of reconsolidation of memory involves calcium-dependent protein kinase in rats.

In this study, we determined whether the calcium-dependent protein kinase (PKC) signaling pathway is involved in the improvement of fear memory reconsolidation induced by the intrahippocampal administration of spermidine in rats. Male Wistar rats were trained in a fear conditioning apparatus using a 0.4-mA footshock as an unconditioned stimulus. Twenty-four hours after training, animals were re-exposed to the apparatus in the absence of shock (reactivation session). Immediately after the reactivation session, spermidine (2-200 pmol/site), the PKC inhibitor 3-[1-(dimethylaminopropyl)indol-3-yl]-4-(indol-3-yl) maleimide hydrochloride (GF 109203X, 0.3-30 pg/site), the antagonist of the polyamine-binding site at the NMDA receptor, arcaine (0.2-200 pmol/site), or the PKC activator phorbol 12-myristate 13-acetate (PMA, 0.02-2 nmol/site) was injected. While the post-reactivation administration of spermidine (20 and 200 pmol/site) and PMA (2 nmol/site) improved memory reconsolidation, GF 109203X (1, 10, and 30 pg/site) and arcaine (200 pmol/site) impaired it. GF 109203X (0.3 pg/site) impaired memory reconsolidation in the presence of spermidine (200 pmol/site). PMA (0.2 nmol/site) prevented the arcaine (200 pmol/site)-induced impairment of memory reconsolidation. Anisomycin (2 µg/site) also impaired memory reconsolidation in the presence of spermidine (200 pmol/site). Drugs had no effect when they were administered in the absence of reactivation. These results suggest that the spermidine-induced enhancement of memory reconsolidation involves PKC activation.

Montelukast potentiates the anticonvulsant effect of phenobarbital in mice: an isobolographic analysis.

Although leukotrienes have been implicated in seizures, no study has systematically investigated whether the blockade of CysLT1 receptors synergistically increases the anticonvulsant action of classic antiepileptics. In this study, behavioral and electroencephalographic methods, as well as isobolographic analysis, are used to show that the CysLT1 inverse agonist montelukast synergistically increases the anticonvulsant action of phenobarbital against pentylenetetrazole-induced seizures. Moreover, it is shown that LTD4 reverses the effect of montelukast. The experimentally derived ED50mix value for a fixed-ratio combination (1:1 proportion) of montelukast plus phenobarbital was 0.06±0.02 µmol, whereas the additively calculated ED50add value was 0.49±0.03 µmol. The calculated interaction index was 0.12, indicating a synergistic interaction. The association of montelukast significantly decreased the antiseizure ED50 for phenobarbital (0.74 and 0.04 µmol in the absence and presence of montelukast, respectively) and, consequently, phenobarbital-induced sedation at equieffective doses. The demonstration of a strong synergism between montelukast and phenobarbital is particularly relevant because both drugs are already used in the clinics, foreseeing an immediate translational application for epileptic patients who have drug-resistant seizures.

Spermine reverses lipopolysaccharide-induced memory deficit in mice.

BACKGROUND: Lipopolysaccharide (LPS) induces neuroinflammation and memory deficit. Since polyamines improve memory in various cognitive tasks, we hypothesized that spermine administration reverses LPS-induced memory deficits in an object recognition task in mice. The involvement of the polyamine binding site at the N-methyl-D-aspartate (NMDA) receptor and cytokine production in the promnesic effect of spermine were investigated. METHODS: Adult male mice were injected with LPS (250 µg/kg, intraperitoneally) and spermine (0.3 to 1 mg/kg, intraperitoneally) or ifenprodil (0.3 to 10 mg/kg, intraperitoneally), or both, and their memory function was evaluated using a novel object recognition task. In addition, cortical and hippocampal cytokines levels were measured by ELISA four hours after LPS injection. RESULTS: Spermine increased but ifenprodil decreased the recognition index in the novel object recognition task. Spermine, at doses that did not alter memory (0.3 mg/kg, intraperitoneally), reversed the cognitive impairment induced by LPS. Ifenprodil (0.3 mg/kg, intraperitoneally) reversed the protective effect of spermine against LPS-induced memory deficits. However, spermine failed to reverse the LPS-induced increase of cortical and hippocampal cytokine levels. CONCLUSIONS: Spermine protects against LPS-induced memory deficits in mice by a mechanism that involves GluN2B receptors.

Effect of morphine on the persistence of long-term memory in rats.

RATIONALE: Current evidence suggests that pharmacological manipulation around 12 h after training alters the persistence of long-term memory. However, no study has addressed whether opioids modulate the persistence of fear. The current study examined whether morphine alters the persistence of the memory of contextual fear conditioning. METHODS: Male adult Wistar rats were injected with saline (NaCl 0.9 %, intraperitoneally (i.p.)) or morphine (3 and/or 10 mg/kg, i.p.) 6, 9, 12, or 24 h post-training and tested 2 or 7 days after training, when freezing responses were assessed. The involvement of state dependence and opioid receptors in the effect of morphine was investigated by respectively injecting naloxone (1 mg/kg, i.p.) 30 min before morphine, and morphine (10 mg/kg, i.p.) 30 min before testing. RESULTS: Morphine (10 mg/kg, i.p., 12 h post-training) did not alter freezing to context in animals tested 2 days after training but impaired freezing to context when testing was carried out 7 or 14 days after training. Morphine (10 mg/kg, i.p.) administration 6, 9, or 24 h post-training did not alter freezing measured 2 or 7 days after training. Pre-test morphine improved recall but did not alter the deleterious effect of 12 h post-training morphine. The deleterious effect of morphine was prevented by naloxone, indicating that opioid receptors are involved in this effect. CONCLUSIONS: Our findings indicate an inhibitory role for opioid receptors in memory persistence. This is relevant from both the experimental and clinical point of views, since it may have implications for the prevention of post-traumatic stress disorder (PTSD).

Inhibition of the polyamine system counteracts ß-amyloid peptide-induced memory impairment in mice: involvement of extrasynaptic NMDA receptors.

In Alzheimer's disease (AD), the ß-amyloid peptide (Aß) has been causally linked to synaptic dysfunction and cognitive impairment. Several studies have shown that N-Methyl-D-Aspartate receptors (NMDAR) activation is involved in the detrimental actions of Aß. Polyamines, like spermidine and spermine, are positive modulators of NMDAR function and it has been shown that their levels are regulated by Aß. In this study we show here that interruption of NMDAR modulation by polyamines through blockade of its binding site at NMDAR by arcaine (0.02 nmol/site), or inhibition of polyamine synthesis by DFMO (2.7 nmol/site), reverses Aß25-35-induced memory impairment in mice in a novel object recognition task. Incubation of hippocampal cell cultures with Aß25-35 (10 µM) significantly increased the nuclear accumulation of Jacob, which is a hallmark of NMDAR activation. The Aß-induced nuclear translocation of Jacob was blocked upon application of traxoprodil (4 nM), arcaine (4 µM) or DFMO (5 µM), suggesting that activation of the polyamine binding site at NMDAR located probably at extrasynaptic sites might underlie the cognitive deficits of Aß25-35-treated mice. Extrasynaptic NMDAR activation in primary neurons results in a stripping of synaptic contacts and simplification of neuronal cytoarchitecture. Aß25-35 application in hippocampal primary cell cultures reduced dendritic spine density and induced alterations on spine morphology. Application of traxoprodil (4 nM), arcaine (4 µM) or DFMO (5 µM) reversed these effects of Aß25-35. Taken together these data provide evidence that polyamine modulation of extrasynaptic NMDAR signaling might be involved in Aß pathology.

Commentary on Kaushik et al.: Prostaglandin D2 is crucial for seizure suppression and postictal sleep. Novel evidence supporting a role for prostanoid receptors in seizure control.

Accumulating clinical and experimental evidence suggests a role for prostaglandins (PGs) in epilepsy and isolated seizures. Prostaglandin levels are increased in the hippocampus of epileptic patients and in the cerebrospinal fluid of children with febrile seizures. Moreover, increased PGD2, PGE2 and PGF2α levels are found in the brain after chemically-induced seizures and in spontaneously epileptic mice. However, whether prostaglandins facilitate or decrease seizures has been a matter of debate in the literature. Both pro- and anticonvulsant activities have been described for most of prostaglandins, except for PGD2 and DP receptor agonists, for which a consistent anticonvulsant action has been reported. The study by Kaushik and colleagues elegantly extends this view by showing that hematopoietic PGD synthase (H-PGDS) and DP1 receptors are essential for seizure suppression and that lipocalin-type prostaglandin D synthase (L-PGDS)/PGD2/DP1 system regulates sleep that follows PTZ-induced seizures using knockout animals. This commentary discusses the experimental approach of the studies that have implicated prostaglandins and their receptors in seizures, the interesting approach and results of Kaushik and colleagues, and the challenges of considering PGD2 signaling as a therapeutic target in epilepsy.