The synergic effects of presynaptic calcium channel antagonists purified from spiders on memory elimination of glutamate-induced excitotoxicity in the rat hippocampus trisynaptic circuit.

The hippocampus is a complex area of the mammalian brain and is responsible for learning and memory. The trisynaptic circuit engages with explicit memory. Hippocampal neurons express two types of presynaptic voltage-gated calcium channels (VGCCs) comprising N and P/Q-types. These VGCCs play a vital role in the release of neurotransmitters from presynaptic neurons. The chief excitatory neurotransmitter at these synapses is glutamate. Glutamate has an essential function in learning and memory under normal conditions. The release of neurotransmitters depends on the activity of presynaptic VGCCs. Excessive glutamate activity, due to either excessive release or insufficient uptake from the synapse, leads to a condition called excitotoxicity. This pathological state is common among all neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases. Under these conditions, glutamate adversely affects the trisynaptic circuitry, leading to synaptic destruction and loss of memory and learning performance. This study attempts to clarify the role of presynaptic VGCCs in memory performance and reveals that modulating the activity of presynaptic calcium channels in the trisynaptic pathway can regulate the excitotoxic state and consequently prevent the elimination of neurons and synaptic degradation. All of these can lead to an improvement in learning and memory function. In the current study, two calcium channel blockers-omega-agatoxin-Aa2a and omega-Lsp-IA-were extracted, purified, and identified from spiders (Agelena orientalis and Hogna radiata) and used to modulate N and P/Q VGCCs. The effect of omega-agatoxin-Aa2a and omega-Lsp-IA on glutamate-induced excitotoxicity in rats was evaluated using the Morris water maze task as a behavioral test. The local expression of synaptophysin (SYN) was visualized for synaptic quantification using an immunofluorescence assay. The electrophysiological amplitudes of the field excitatory postsynaptic potentials (fEPSPs) in the input-output and LTP curves of the mossy fiber and Schaffer collateral circuits were recorded. The results of our study demonstrated that N and P/Q VGCC modulation in the hippocampus trisynaptic circuit of rats with glutamate-induced excitotoxicity dysfunction could prevent the destructive consequences of excitotoxicity in synapses and improve memory function and performance.

The effects of lactobacilli (L. rhamnosus, L. reuteri, L. Plantarum) on LPS-induced memory impairment and changes in CaMKII-α and TNF-α genes expression in the hippocampus of rat.

In recent years, some investigations have focused on the relationship between gut microbiota and brain function in healthy and disease conditions. Moreover, changes in the gut microbiome may affect memory, behavior, and cognition. This study aimed to evaluate the effect of lactobacilli on passive avoidance learning, hippocampal CaMKII-α, and TNF-α genes expression in one experimental model of neuroinflammtion. Male wistar rats (220-240 g) received daily oral gavage of different lactobacilli including L. rhamnosus, L. reuteri, and L. plantarum for 21 days. At the next step, behavioral test was performed and 4 hours after acute injection of LPS (1mg/kg, ip) retrieval was evaluated. Then the hippocampi were extracted and kept at _80°C. Finally CaMKII-α and TNF-α mRNA levels were evaluated by Real-time PCR. Our results showed that consumption of L. rhamnosus, L.reuteri, or L. plantarum significantly prevented LPS-induced enhancement of TNF-α mRNA and memory deterioration. Furthermore, L. rhamnosus significantly prevented changes induced by LPS on CaMKII-α mRNA levels. It seems the lactobacilli used in this study can affect brain function and memory performance by their immune-modulatory properties.

Quercetin-Conjugated Superparamagnetic Iron Oxide Nanoparticles Protect AlCl3-Induced Neurotoxicity in a Rat Model of Alzheimer's Disease via Antioxidant Genes, APP Gene, and miRNA-101.

Alzheimer's disease (AD) is a neurodegenerative disease with cognitive impairment. Oxidative stress in neurons is considered as a reason for development of AD. Antioxidant agents such as quercetin slow down AD progression, but the usage of this flavonoid has limitations because of its low bioavailability. We hypothesized that quercetin-conjugated superparamagnetic iron oxide nanoparticles (QT-SPIONs) have a better neuroprotective effect on AD than free quercetin and regulates the antioxidant, apoptotic, and APP gene, and miRNA-101. In this study, male Wistar rats were subjected to AlCl3, AlCl3 + QT, AlCl3 + SPION, and AlCl3 + QT-SPION for 42 consecutive days. Behavioral tests and qPCR were used to evaluate the efficiency of treatments. Results of behavioral tests revealed that the intensity of cognitive impairment was decelerated at both the middle and end of the treatment period. The effect of QT-SPIONs on learning and memory deficits were closely similar to the control group. The increase in expression levels of APP gene and the decrease in mir101 led to the development of AD symptoms in rats treated with AlCl3 while these results were reversed in the AlCl3 + QT-SPIONs group. This group showed similar results with the control group. QT-SPION also decreased the expression levels of antioxidant enzymes along with increases in expression levels of anti-apoptotic genes. Accordingly, the antioxidant effect of QT-SPION inhibited progression of cognitive impairment via sustaining the balance of antioxidant enzymes in the hippocampus of AD model rats.

Lidocaine Reversible Inactivation of the Central Nucleus of Amygdala Impairs Acquisition, Consolidation, and Retrieval of Morphine State-Dependent Learning in Rat.

BACKGROUND/AIMS: Morphine causes state-dependent learning that its mechanism and brain-related structures are not fully understood. This study aimed to determine whether lidocaine reversible inactivation of the central nucleus of the amygdala (CeA) could affect acquisition, consolidation, and retrieval of morphine state-dependent learning. METHODS: One hundred twenty male Wistar rats were allocated into 15 experimental groups. Subcutaneous administration of morphine (5 mg/kg) induced morphine state-dependent learning. Intra-CeA injection of Lidocaine hydrochloride was performed 5 min before each morphine session for transient inactivation of the CeA. The step-through latency and the time spent in the dark compartment were measured using passive avoidance learning task. RESULTS: Our results showed that pretraining, posttraining, and pretest inhibition of the CeA severely impaired acquisition, consolidation, and retrieval of morphine state-dependent learning. CONCLUSION: These data revealed the involvement of the CeA in different stages of memory and morphine state-dependent learning.

The role of nucleus accumbens shell on acquisition and retrieval stages of morphine state dependent learning.

AIM: In the present study, the effect of transient inactivation of the shell subregion of the nucleus accumbens (NAC shell) by lidocaine on the acquisition and retrieval stages of passive avoidance learning (PAL) and memory and morphine state-dependent learning (SDL) in male wistar rats was investigated. METHODOLOGY: Adult male wistar rats weighing (220-250 g) were used. Lidocaine hydrochloride was bilaterally injected into the shell area of the nucleus accumbens 5 min before of subcutaneous morphine administration. RESULTS: pre-training and pre-test infusion of lidocaine into the NAC shell significantly impaired PAL and memory. Furthermore, Pre-training administration of morphine (5 mg/kg, s.c.) in a step-through passive avoidance task induced state-dependent learning with impaired memory retrieval on the test day. The impairment of memory was restored after pre-test administration of the same dose of morphine. This phenomenon has been named as morphine state dependent learning (SDL). Moreover, Pre-training and pre-test inactivation of the NAC shell impaired morphine SDL. CONCLUSIONS: The results suggest the role of NAC shell as a common structure in the PAL and morphine SDL. It is suggested that NAC shell as a common area plays a critical role in the acquisition and retrieval stages of PAL and also morphine SDL.

Agmatine attenuates methamphetamine-induced passive avoidance learning and memory and CaMKII-α gene expression deteriorations in hippocampus of rat.

Methamphetamine (METH) abuse is one the most worldwide problems with wide-ranging effects on the central nervous system (CNS). Chronic METH abuse can associate with cognitive abnormalities and neurodegenerative changes in the brain. Agmatine, a cationic polyamine, has been proposed as a neuromodulator that modulates many effects of abused drugs. The aim of this study was to determine if agmatine can decrease the impairment effect of METH on memory and hippocampal CaMKII-α gene expression, a gene that plays a major role in memory. Male wistar rats (200-220 g) were allocated into 7 groups, including 5 groups of saline, METH (1, 2 mg/kg), Agmatine (5, 10 mg/kg) and 2 groups of agmatine (5, 10 mg/kg) with higher doses of METH (2 mg/kg) for 5 consecutive days (n = 8 in each group). All injections were done intraperitoneally and agmatine was administrated 10 min before METH treatment. Furthermore, Passive avoidance learning (PAL) test was assessed on the 5th day. Retention test was done 24 h after training and the rats were sacrificed immediately. Hippocampi were removed and stored at -80 °C. Finally, hippocampal CaMKII-α gene expression was measured using Quantitative Real-time PCR. Our data showed that chronic METH dose-dependently impaired PAL retrieval, as it decreased step-through latency (STL) and increased time spent in the dark compartment (TDC). While Agmatine with a higher dose (10 mg/kg) significantly decreased impairment effect of METH (2 mg/kg) on PAL and memory. Also, molecular results revealed that METH (2 mg/kg) markedly decreased hippocampal CaMKII-α gene expression while agmatine (10 mg/kg) co-adminstration prevented it. Taken together, the results propose that agmatine may provide a potential therapy for learning and memory deficits induced by METH.

Alteration in messenger RNA neurotrophin 4 and tyrosine kinase receptors B expression levels following spinal cord injury.

BACKGROUND: Neurotrophins as polypeptide growth factors have important roles during nervous system development and are involved in neuronal differentiation and survival and spinal cord reorganization. Neurotrophins have been recognized as factors which are involved in the development of damaged axons and increase the axon growth ability and neuroplasticity. Spinal cord injury (SCI) is associated with numerous physiological damages, leading to neuron death, axon extended destruction healthy and intact neurons demyelination, inflammation, cell death and severe motor/sensory defects. The aim of this study was to investigate the alteration in messenger RNA neurotrophin 4 and tyrosine kinase receptors B expression levels following SCI. METHODS: In this research, to know expression level alterations of neurotrophin 4 mRNA and its receptor Trk- B at 6 hours and 1, 3, 7 and 10 days after SCI, we developed competitive RT-qPCR. mRNA was extracted from T9 injury site (epicenter, rostral and caudal to the epicenter) and reversed to cDNA. RESULTS: The results showed that the expression of these genes changed after SCI. The NT4 mRNA expression level in the rostral to the epicenter decreased after enhancement in the 1st 6 hours. At the epicenter and in the caudal to the epicenter, it decreased. mRNA expression level of Trk-B decreased after an increase in the initial hours in all the areas. CONCLUSIONS: The present results showed that NT4 and Trk-B are expressed temporary and spatially following SCI and the adjustment of these neurotrophins rate in SCI may provide therapeutic benefits.

Portulaca oleracea L. prevents lipopolysaccharide-induced passive avoidance learning and memory and TNF-α impairments in hippocampus of rat.

There is a growing body of evidence that neuroinflammation can impair memory. It has been indicated that Portulaca oleracea Linn. (POL), possess anti-inflammatory activity and might improve memory disruption caused by inflammation. In this study the effect of pre-treatment with the hydro-alcoholic extract of POL on memory retrieval investigated in lipopolysaccharide (LPS) treated rats. Male Wistar rats (200-220g) received either a control diet or a diet containing of POL (400mg/kg, p.o.) for 14days. Then, they received injections of either saline or LPS (1mg/kg, i.p.). In all the experimental groups, 4h following the last injection, passive avoidance learning (PAL) and memory test was performed. The retention test was done 24h after the training and then the animals were sacrificed. Hippocampal TNF-α levels measured using ELISA as one criteria of LPS-induced neuroinflammation. The results indicated that LPS significantly impaired PAL and memory and increased TNF-α levels in hippocampus tissue. Pre-treatment with POL improved memory in control rats and prevented memory and TNF-α deterioration in LPS treated rats. Taken together, the results of this study suggest that the hydro-alcoholic extract of POL may improve memory deficits in LPS treated rats, possibly via inhibition of TNF-α and anti-inflammatory activity.

Nurr1 and PPARγ protect PC12 cells against MPP(+) toxicity: involvement of selective genes, anti-inflammatory, ROS generation, and antimitochondrial impairment.

Parkinson's disease (PD) can degenerate dopaminergic (DA) neurons in midbrain, substantia-nigra pars compacta. Alleviation of its symptoms and protection of normal neurons against degeneration are the main aspects of researches to establish novel therapeutic strategies. PPARγ as a member of PPARs have shown neuroprotection in a number of neurodegenerative disorders such as Alzheimer's disease and PD. Nuclear receptor related 1 protein (Nurr1) is, respectively, member of NR4A family and has received great attentions as potential target for development, maintenance, and survival of DA neurons. Based on neuroprotective effects of PPARγ and dual role of Nurr1 in anti-inflammatory pathways and development of DA neurons, we hypothesize that PPARγ and Nurr1 agonists alone and in combined form can be targets for neuroprotective therapeutic development for PD in vitro model. 1-Methyl-4-phenylpyridinium (MPP(+)) induced neurotoxicity in PC12 cells as an in vitro model for PD studies. Treatment/cotreatment with PPARγ and Nurr1 agonists 24 h prior to MPP(+) induction enhanced the viability of PC12 cell. The viability of PC12 cells was determined by MTS test. Mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (ROS) were detected by flow cytometry. In addition, the relative expression of four genes including TH (the marker of DA neurons), Ephrin A1, Nurr1, and Ferritin light chain were assessed by RT-qPCR. In the MPP(+)-pretreated PC12 cells, PPARγ and Nurr1 agonists and their combined form resulted in a decrease in the cell death rate. Moreover, production of intracellular ROS and MMP modulated by MPP(+) was decreased by PPARγ and Nurr1 agonists' treatment alone and in the combined form.

Omega-3 fatty acids prevent LPS-induced passive avoidance learning and memory and CaMKII-α gene expression impairments in hippocampus of rat.

BACKGROUND: Neuroinflammation is considered to be a major factor in several neurodegenerative diseases. Recently, the polyunsaturated fatty acid omega-3 has been shown to have anti-inflammatory effects and might play an effective role in improving memory impairment due to inflammation. In order to test this, we stimulated neuroinflammation in an animal model and induced memory dysfunction as measured by reduced retention of passive avoidance learning (PAL) and altered expression of CaMKII-α, a gene known to be crucial for memory formation. We then investigated whether treatment with dietary omega-3 prevents inflammation-induced memory dysfunction in this model. METHODS: Male wistar rats (200-220 g) were fed either a control diet or a diet containing omega-3 (400mg/kg, po) for 1 month prior. Rats then received injection of either saline or LPS (500 µg/kg, ip) and were subjected to the PAL acquisition task. The retention test was performed 24h later, and animals were sacrificed immediately. Hippocampi were dissected and stored at -80°C. Finally, TNF-α levels and CaMKII-α gene expression were measured by ELISA and qRT-PCR, respectively. RESULTS: We found that LPS treatment significantly impaired PAL and memory, increased TNF-α levels and impaired CaMKII-α gene expression. In control and LPS-injected animals, pre-treatment with omega-3 improved performance on the PAL task and increased CAMKII-α gene expression. CONCLUSION: Taken together, these data suggest that dietary omega-3 may improve cognitive function and provide a potential therapy for memory impairment due to neuroinflammation.

Role of hippocampal CA1 area gap junction channels on morphine state-dependent learning.

Morphine produces a state dependent learning. The hippocampus is involved in this kind of learning. Gap junctions (GJs) are involved in some of the effects of morphine and exist in different areas of the hippocampus. We investigated the effects of blocking GJ channels of the hippocampal CA1 area, by means of pre-test bilateral injection of carbenoxolone (CBX), on morphine state dependent learning, using a passive avoidance task. Post-training subcutaneous administrations of morphine (0.5, 2.5, 5 and 7.5 mg/kg) dose-dependently impaired memory retrieval. Pre-test administration of morphine (0.5, 2.5, 5 and 7.5 mg/kg) induced a state-dependent retrieval of the memory acquired under post-training morphine influence. Pre-test injections of CBX (25, 75 and 150 nM) dose dependently prevented memory retrieval by post-training (7.5 mg/kg) and pre-test (0.5, 2.5, 5, 7.5 mg/kg) injections of morphine. The results suggest that intercellular coupling via GJ channels of the hippocampal CA1 area modulates morphine state dependent learning.

Orexin-1 receptor mediates long-term potentiation in the dentate gyrus area of freely moving rats.

Orexin neurons, localized in the lateral hypothalamus area, synthesize two neuropeptides called orexin A and orexin B and send their axons to hippocampal formation including dentate gyrus (DG). Orexin A and orexin B act as endogenous ligands for two G-protein coupled receptors called orexin-1 and orexin-2 receptors (OX1R and OX2R). In the dentate gyrus (DG) region, OX1R, which has high affinity for orexin A, is expressed. Conflicting results have been reported regarding the effect of orexinergic system on synaptic plasticity. When given alone, SB-334867-A, a non-peptide OX1R antagonist, is a suitable drug to assess the natural and physiological significance of endogenous orexins. In the present research, we studied the effects of DG-OX1Rs antagonization on long-term potentiation (LTP) using two different high frequency stimulation (HFS) protocols i.e. 200 and 400 Hz in freely moving rats. The results showed that inactivation of DG-OX1Rs impair LTP induction in both HFS protocols which lasts beyond 24 h. This occurs with respect to both the population excitatory post-synaptic potential slope and population spike amplitude. Our findings suggest that endogenous orexins are involved in the expression of LTP, at least through DG-OX1Rs.

Copines-1, -2, -3, -6 and -7 show different calcium-dependent intracellular membrane translocation and targeting.

The copines are a family of C2- and von Willebrand factor A-domain-containing proteins that have been proposed to respond to increases in intracellular calcium by translocating to the plasma membrane. The copines have been reported to interact with a range of cell signalling and cytoskeletal proteins, which may therefore be targeted to the membrane following increases in cellular calcium. However, neither the function of the copines, nor their actual movement to the plasma membrane, has been fully established in mammalian cells. Here, we show that copines-1, -2, -3, -6 and -7 respond differently to a methacholine-evoked intracellular increase in calcium in human embryonic kidney cell line-293 cells, and that their membrane association requires different levels of intracellular calcium. We demonstrate that two of these copines associate with different intracellular vesicles following calcium entry into cells, and identify a novel conserved amino acid sequence that is required for their membrane translocation in living cells. Our data show that the von Willebrand factor A-domain of the copines modulates their calcium sensitivity and intracellular targeting. Together, these findings suggest a different set of roles for the members of this protein family in mediating calcium-dependent processes in mammalian cells.

The effect of antagonization of orexin 1 receptors in CA1 and dentate gyrus regions on memory processing in passive avoidance task.

The hippocampal formation plays an essential role in associative learning like passive avoidance (PA) learning. It has been shown; orexin-containing terminals and orexin receptors densely are distributed in the hippocampal formation. We have previously demonstrated that antagonization of orexin 1 receptor (OX1R) in CA1 region of hippocampus and dentate gyrus (DG) impaired spatial memory processing. Although, there are few studies concerning function of orexinergic system on memory processing in PA task, but there is no study about physiological function of OX1R on this process. To address this, the OX1R antagonist, SB-334867-A, was injected into DG or CA1 regions of hippocampus and evaluated the influence of OX1R antagonization on acquisition, consolidation and retrieval in PA task. Our results show that, SB-334867-A administration into CA1 region impaired memory retrieval but not PA acquisition and consolidation. However, SB-334867-A administration into DG region impaired acquisition and consolidation but not PA memory retrieval. Therefore, it seems that endogenous orexins play an important role in learning and memory in the rat through OX1Rs.

Effect of the GABAergic system on memory formation and state-dependent learning induced by morphine in rats.

In the present study, the effects of intraperitoneal injections of GABA(A) receptor agonist and antagonist on memory formation and morphine state-dependent learning were investigated in rats. Pre-training administration of morphine (1-15 mg/kg) in a step-down passive avoidance task induced state-dependent learning with impaired memory retrieval on the test day. The impairment of memory was restored after the pre-test administration of the same dose of morphine. The pre-test administration of the GABA(A) receptor agonist, muscimol (0.01, 0.05 and 0.1 mg/kg), significantly decreased state-dependent retrieval induced by pre-test morphine (5 mg/kg). The state-dependency effect of morphine (1 mg/kg) was significantly potentiated by the pre-test administration of the GABA(A) receptor antagonist, bicuculline (0.125, 0.25 and 0.5 mg/kg). Furthermore, the pre-training injection of muscimol (0.01 mg/kg) impaired memory retrieval which was restored by pre-test morphine (1, 3 and 5 mg/kg) administration. However, the pre-training administration of bicuculline did not affect retention by itself. In addition, amnesia induced by pre-training morphine (5 mg/kg) was significantly reversed in rats which had received pre-test injections of muscimol (0.01, 0.05 and 0.1 mg/kg). Pre-test injections of bicuculline (0.125, 0.25 and 0.5 mg/kg) significantly decreased morphine-induced amnesia. It is concluded that the GABA(A) receptor mechanisms may be involved in the memory formation and it is postulated that these receptors may play an important role in morphine state-dependent learning.