The Inflammation/NF-κB and BDNF/TrkB/CREB Pathways in the Cerebellum Are Implicated in the Changes in Spatial Working Memory After Both Morphine Dependence and Withdrawal in Rat.

We aimed to explore the impact of the cerebellum on the decline in spatial working memory following morphine dependence and withdrawal. Two groups of male Wistar rats received intraperitoneal injections of either saline (1 ml/kg) or morphine (10 mg/kg) twice daily for 10 days, serving as the control and dependent groups. Additionally, a withdrawal group underwent a 30-day withdrawal period after the dependence phase. Spatial working memory was assessed using a Y maze test. ELISA and western blot were used to assess protein levels in the cerebellum. On day 1, morphine impaired spatial working memory, deteriorated further after 10 days of morphine use, and nearly returned to its initial level following a 30-day withdrawal period. On day 10, significant increases in TNF-α, IL-1ß, and CXCL12 and a notable decrease in IL-10 levels were detected in the morphine-dependent group, which did not completely restore in the withdrawal group. The protein levels of CXCR4, TLR4, P2X7R, and NF-κB sharply increased in the morphine-dependent group. However, these levels almost returned to normal after withdrawal. In the morphine-dependent group, BDNF decreased, while TrkB and CREB1 increased noticeably. Nevertheless, after withdrawal, TrkB and CREB1 but not BDNF levels returned to normal. In the morphine-dependent group, both CACNA1 and KCNMA1 decreased significantly and after withdrawal, only KCNMA1 showed partial restoration, while CACNA1 did not. It can be concluded that inflammation/NF-κB and BDNF/TrkB/CREB pathways play key roles in neural adaptation within the cerebellum, contributing to the decline in spatial working memory after both morphine dependence and withdrawal.

Brain Renin-Angiotensin System: From Physiology to Pathology in Neuronal Complications Induced by SARS-CoV-2.

Angiotensin-converting enzyme 2 (ACE2), a key enzyme in the renin-angiotensin system (RAS), is expressed in various tissues and organs, including the central nervous system (CNS). The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease-2019 (COVID-19), binds to ACE2, which raises concerns about the potential for viral infection in the CNS. There are numerous reports suggesting a link between SARS-CoV-2 infection and neurological manifestations. This study aimed to present an updated review of the role of brain RAS components, especially ACE2, in neurological complications induced by SARS-CoV-2 infection. Several routes of SARS-CoV-2 entry into the brain have been proposed. Because an anosmia condition appeared broadly in COVID-19 patients, the olfactory nerve route was suggested as an early pathway for SARS-CoV-2 entry into the brain. In addition, a hematogenous route via disintegrations in the blood-brain barrier following an increase in systemic cytokine and chemokine levels and retrograde axonal transport, especially via the vagus nerve innervating lungs, have been described. Common nonspecific neurological symptoms in COVID-19 patients are myalgia, headache, anosmia, and dysgeusia. However, more severe outcomes include cerebrovascular diseases, cognitive impairment, anxiety, encephalopathy, and stroke. Alterations in brain RAS components such as angiotensin II (Ang II) and ACE2 mediate neurological manifestations of SARS-CoV-2 infection, at least in part. Downregulation of ACE2 due to SARS-CoV-2 infection, followed by an increase in Ang II levels, leads to hyperinflammation and oxidative stress, which in turn accelerates neurodegeneration in the brain. Furthermore, ACE2 downregulation in the hypothalamus induces stress and anxiety responses by increasing corticotropin-releasing hormone. SARS-CoV-2 infection may also dysregulate the CNS neurotransmission, leading to neurological complications observed in severe cases of COVID-19. It can be concluded that the neurological manifestations of COVID-19 may be partially associated with changes in brain RAS components.

Alpha-pinene moderates memory impairment induced by kainic acid via improving the BDNF/TrkB/CREB signaling pathway in rat hippocampus.

Introduction: The potential benefits of natural ingredients in the alleviation of neurodegenerative disorders are of great interest. Alpha-pinene (APN) is an essential oil belonging to monoterpenes with multiple beneficial effects. In this study, the possible improving effects of alpha-pinene on memory impairment induced by kainic acid and the underlying molecular mechanisms were examined. Methods: Memory impairment was induced by i.c.v. injection of kainic acid (KA) in male Wistar rats. Alpha-pinene (50 mg/kg/day, i.p.) was injected for 21 days, including 14 days before the KA injection and seven days afterward. Spatial working memory and inhibitory avoidance (IA) memory performance were assessed five and even days following KA injection, respectively. The hippocampal protein levels of brain-derived neurotrophic factor (BDNF), tropomyosin-like receptor kinase B (TrkB), cAMP response element binding protein (CREB), and neuronal loss in the CA1 region were also examined. Results: Results revealed that the i.c.v. injection of KA triggered memory impairment, which was notably diminished by alpha-pinene pre-and post-treatment. Histopathological evaluation revealed that alpha-pinene significantly moderated the attenuation in CA1 alive neurons induced by KA injection. Western blotting analysis confirmed that alpha-pinene pre-and post-treatment significantly reversed the KA-induced decreases in the hippocampal levels of BDNF, TrkB, phosphorylated TrkB, CREB, and phosphorylated CREB. Discussion: These findings suggest that alpha-pinene pre-and post-treatment moderate memory impairment induced by KA by restoring the BDNF/TrkB/CREB signaling pathway in the rat hippocampus.

Alpha-Pinene Exerts Antiseizure Effects by Preventing Oxidative Stress and Apoptosis in the Hippocampus in a Rat Model of Temporal Lobe Epilepsy Induced by Kainate.

Oxidative stress and apoptosis following seizures play pivotal roles in the consequences of repeated seizures. Beneficial effects of alpha-pinene (APN) have been reported in some experimental models of neurodegenerative diseases. However, its neuroprotective efficacy in a rat model of temporal lobe epilepsy (TLE) induced by kainic acid (KA) has remained unexplored. We aimed to explore the possible antiseizure effects of APN pretreatment and underlying molecular mechanisms in a rat model of TLE induced by KA. TLE was induced in male Wistar rats by intracerebroventricular injection of KA. APN at a dose of 50 mg/kg/day was intraperitoneally injected for 2 weeks before induction of TLE. One day after the induction of TLE, behavioral expressions of seizure were recorded and scored using Racine's scale. Furthermore, the hippocampal levels of oxidative stress markers, B-cell lymphoma 2 (Bcl2), BCL2-associated X protein (BAX), and c-Jun N-terminal kinase (JNK) protein levels were also assessed. Histopathological assessment in the hippocampus was performed with Nissl staining 5 days following induction of TLE. The results revealed that APN pretreatment alleviated epileptic seizures, diminished oxidative stress indicators, blocked the mitochondrial apoptotic pathway via decreasing BAX and raising BCL2 protein levels in the hippocampus at least partly through inhibiting JNK activity, and decreased neuronal death in the CA3 and hilus regions. These findings reveal that APN pretreatment mitigates KA-induced seizures by blocking oxidative stress and neuronal damage factors. It can be concluded that APN has a potent potential to be considered an antiseizure medication, but it needs further investigation.

Repeated Use of Morphine Induces Anxiety by Affecting a Proinflammatory Cytokine Signaling Pathway in the Prefrontal Cortex in Rats.

We examined the role of toll-like receptors (TLRs) and proinflammatory cytokine signaling pathways in the prefrontal cortex (PFC) in anxiety-like behaviors after repeated use of morphine. Morphine (10 mg/kg) was used twice daily for 8 days to induce morphine dependence in male Wistar rats. On day 8, opioid dependence was confirmed by measuring naloxone-precipitated withdrawal signs. On days 1 and 8, anxiety-like behaviors were evaluated using a light/dark box test. Expression of TLR1 and 4, proinflammatory cytokines, and some of the downstream signaling molecules was also evaluated in the bilateral PFC at mRNA and protein levels following morphine dependence. The results revealed that morphine caused anxiolytic-like effects on day 1 while induced anxiety following 8 days of repeated injection. On day 8, a significant decrease in TLR1 expression was detected in the PFC in morphine-dependent rats, but TLR4 remained unaffected. Repeated morphine injection significantly increased IL1-ß, TNFα, and IL6 expression, but decreased IL1R and TNFR at mRNA and protein levels except for IL6R at the protein level in the PFC. The p38α mitogen-activated protein (MAP) kinase expression significantly increased but the JNK3 expression decreased in the PFC in morphine-dependent rats. Repeated injection of morphine also significantly increased the NF-κB expression in the PFC. Further, significant increases in Let-7c, mir-133b, and mir-365 were detected in the PFC in morphine-dependent rats. We conclude that TLR1 and proinflammatory cytokines signaling pathways in the PFC are associated with the anxiogenic-like effects of morphine following its chronic use in rats via a MAP kinase/NF-κB pathway.

Differential expression of H19, BC1, MIAT1, and MALAT1 long non-coding RNAs within key brain reward regions after repeated morphine treatment.

Morphine-induced analgesic tolerance and dependence are significant limits of pain control; however, the exact molecular mechanisms underlying morphine tolerance and dependence have remained unclear. The role of long non-coding RNAs (lncRNAs) in morphine tolerance and dependence is yet to be determined. We aimed to explore the association of specific lncRNAs expression in key brain reward regions after repeated injection of morphine. Male Wistar rats received subcutaneous injections of twice-daily morphine (10 mg/kg) or saline (1 mL/kg) for eight days. On day 8 of the repeated injections, induction of morphine analgesic tolerance and dependence was confirmed through a hotplate test and a naloxone-precipitated withdrawal analysis, respectively. Expression of H19, BC1, MIAT1, and MALAT1 lncRNAs was determined from the midbrain, striatum, hypothalamus, prefrontal cortex (PFC), and hippocampus by real-time PCR on day 8 of the repeated injections. The H19 expression was significantly different between morphine-treated and control saline-treated rats in all investigated areas except for the hippocampus. The BC1 expression significantly altered in the midbrain, hypothalamus, and hippocampus, but not in the striatum and PFC after repeated morphine treatment. The MIAT1 and MALAT1 expression site-specifically altered in the midbrain, hypothalamus, and striatum; however, no significant changes were detected in their expression in the PFC and hippocampus after repeated morphine treatment. We conclude that alterations in the expression of these lncRNAs in the brain reward regions especially in the midbrain, striatum and hypothalamus may have critical roles in the development of morphine dependence and tolerance, which need to be considered in future researches.

Mesoporous silica SBA-15 decreases hyperammonemia and affects the gene expression of mitogen-activated protein kinases in the prefrontal cortex of rats with bile duct ligation.

OBJECTIVES: We aim to examine possible ammonia lowering effects of mesoporous silica SBA-15 in rats after the common bile duct ligation (BDL). We also evaluate the effect of SBA-15 treatments during 28 days of BDL on locomotion and rearing behavior, as well as on the gene expression of Jnk3 and p38alpha (p38α) mitogen-activated protein kinases in the prefrontal cortex (PFC). MATERIALS AND METHODS: SBA-15 was prepared with the hydrothermal method from the surfactant P123 and tetraethyl orthosilicate (TEOS), and calcined at 550 ºC. Then, the product was characterized by FT-IR, XRD, SEM, and BJH-BET techniques. Male Wistar rats in sham control and a group with BDL received saline but another group with BDL received SBA-15 during 28 days of BDL. We examined all groups of rats weekly for locomotion and rearing behavior; then on day 28, we sacrificed all rats, collected the blood sample, and finally dissected the PFC from the whole brain. RESULTS: The SBA-15 treatments had no effect on locomotion but improved rearing behavior on days 7 and 14 of BDL. Biochemical analysis indicated that the SBA-15 treatments in rats with BDL significantly decreased hyperammonemia. The results also revealed that the SBA-15 treatments in rats with BDL significantly restored the decreased Jnk3 gene expression, and increased the p38α gene expression in the PFC. CONCLUSION: We conclude that SBA-15 can be used as an ammonia lowering agent in hepatic encephalopathy; however, its improving effects on locomotion and neuroinflammation, as well as signaling molecules in the brain need more investigations.

Molecular mechanisms underlying actions of certain long noncoding RNAs in Alzheimer's disease.

Long non-coding RNAs (lncRNAs) are a group of non-protein coding RNAs that have more than 200 nucleotides. LncRNAs play an important role in the regulation of protein-coding genes at the transcriptional and post-transcriptional levels. They are found in most organs, with a high prevalence in the central nervous system. Accumulating data suggests that lncRNAs are involved in various neurodegenerative disorders, including the onset and progression of Alzheimer's disease (AD). Recent insights suggest lncRNAs, such as BACE1-AS, 51A, 17A, NDM29 and AS-UCHL1, are dysregulated in AD tissues. Furthermore, there are ongoing efforts to explore the clinical usability of lncRNAs as biomarkers in the disease. In this review, we explore the mechanisms by which aberrant expressions of the most studied lncRNAs contribute to the neuropathologies associated with AD, including amyloid ß plaques and neurofibrillary tangles. Understanding the molecular mechanisms of lncRNAs in patients with AD will reveal novel diagnosis strategies and more effective therapeutic targets.

Anxiety in rats with bile duct ligation is associated with activation of JNK3 mitogen-activated protein kinase in the hippocampus.

We examine the anxiety-like behaviors in rats with bile duct ligation (BDL), as well as its relationship with the expression of JNK3 and P38 MAPKs in rat hippocampus. Male Wistar rats undergo either sham operation or BDL as a rat model of cirrhotic HE. The anxiety-like behaviors are determined using a light/dark box test two hours befor the surgery on day 1 and on days 7, 14, 21 and 28 of BDL. The gene and protein expression levels of JNK3 and p38 in the hippocampus were examined respectively with qPCR and western blotting methods on day 28 of BDL. The results revealed that anxiety was increased in the cirrhotic HE model rats during 28 days of BDL. The molecular data indicated that the gene expression of Jnk3 and protein levels of JNK3, as well as phospho-JNK3, significantly increased in the hippocampus of the cirrhotic HE model rats compared to the sham control group. However, the results revealed no significant changes in the gene expression and the protein levels of p38 as well as phospho-p38 in the hippocampus of the cirrhotic HE model rats compared to the sham control group. We conclude that the increases in the expression and activation of JNK3 MAPK in the hippocampus may underlie, at least partly, the anxiety-like behaviors in rats with cirrhotic HE.

Calcium-dependent kinases in the brain have site-specific associations with locomotion and rearing impairments in rats with bile duct ligation.

We study the impairment of locomotion and rearing behavior in rats with a common bile duct ligation (BDL), and the possible involvement of the PKCγ and CamKIIα gene expression in the brain. Male Wistar rats undergo either sham operation or BDL to induce a rat model of cirrhotic hepatic encephalopathy (HE). Six groups of the animals were divided into three sets of sham-operated and BDL groups. In the first set, locomotion and rearing behavior were assessed on days 1, 7, 14, 21 and 28 of BDL. On day 28 of BDL, blood samples were collected from the second set of the animals for biochemical analysis, and the rats in the third set were used to extract the PFC, the hippocampus, and the cerebellar cortex for examining the Pkcγ and CamKIIα gene expression. The results showed that locomotion and rearing were decreased during 28 days of BDL with the most significant change on the 28th day. Biochemical analysis of the blood revealed hyperammonemia, increases in liver enzymes, and a decrease in albumin indicating liver damage and induction of cirrhotic HE. The results also showed that both of the Pkcγ and CamKIIα gene expressions were increased in the PFC but decreased in the hippocampus. However, the Pkcγ gene expression was decreased but the CamKIIα gene expression was increased in the cerebellar cortex. It can be concluded that the Ca2+-dependent kinases in different brain areas have a site-specific association with the impairment of locomotion and rearing behavior in the cirrhotic HE model rats.

Exposure to GSM 900-MHz mobile radiation impaired inhibitory avoidance memory consolidation in rat: Involvements of opioidergic and nitrergic systems.

The use of mobile phones is increasing, and the main health concern is the possible deleterious effects of radiation on brain functioning. The present study aimed to examine the effects of exposure to a global system for mobile communication (GSM) with mobile phones on inhibitory avoidance (IA) memory performance as well as the involvement of endogenous opioids and nitric oxide (NO) in this task. Male Wistar rats, 10-12 weeks old, were used. The results showed that four weeks of mobile phone exposure impaired IA memory performance in rats. The results also revealed that post-training, but not pre-training, as well as pre-test intracerebroventricular (i.c.v.) injections of naloxone (0.4, 4 and 40 ng/rat), dose-dependently recovered the impairment of IA memory performance induced by GSM radiation. Additionally, the impairment of IA memory performance was completely recovered in the exposed animals with post-training treatment of naloxone (40 ng/rat) plus pre-test i.c.v. injections of L-arginine (100 and 200 nmol/rat). However, pre-test i.c.v. injections of L-NAME (10 and 20 nmol/rat), impaired IA memory performance in the animals receiving post-training naloxone (40 ng/rat). In the animals receiving post-training naloxone treatment, the impairment of IA memory performance due to pre-test i.c.v. injections of L-NAME was recovered by the pre-test co-administration of L-arginine. It was concluded that the recovery from impairment of IA memory in GSM-exposed animals with post-training naloxone treatment was the result of blockade of the opioidergic system in early memory consolidation as well as activation of the nitrergic system in the retrieval phase of memory.

Association of morphine-induced analgesic tolerance with changes in gene expression of GluN1 and MOR1 in rat spinal cord and midbrain.

OBJECTIVES: We aimed to examine association of gene expression of MOR1 and GluN1 at mRNA level in the lumbosacral cord and midbrain with morphine tolerance in male Wistar rats. MATERIALS AND METHODS: Analgesic effects of morphine administrated intraperitoneally at doses of 0.1, 1, 5 and 10 mg/kg were examined using a hot plate test in rats with and without a history of 15 days morphine (10 mg/kg) treatment. Morphine-induced analgesic tolerance was also assessed on days 1, 5, 10 and 15 of chronic morphine injections. Two groups with history of 15 days injections of saline or morphine (10 mg/kg) were decapitated on day 15 and their lumbosacral cord and midbrain were dissected for evaluating MOR1 and GluN1 gene expression. RESULTS: The results of the hot plate test showed that morphine (5 and 10 mg/kg) induced significant analgesia in naïve rats but its analgesic effects in rats receiving 15 days injections of morphine (10 mg/kg) was decreased, indicating tolerance to morphine analgesia. The results also showed that the GluN1 gene expression in tolerant rats was decreased by 71% in the lumbosacral cord but increased by 110 % in the midbrain compared to the control group. However, no significant change was observed for the MOR1 gene expression in both areas. CONCLUSION: It can be concluded that tolerance following administration of morphine (10 mg/kg) for 15 days is associated with site specific changes in the GluN1 gene expression in the spinal cord and midbrain but the MOR1 gene expression is not affected.

Comparative study on the interaction of two binuclear Pt (II) complexes with human serum albumin: Spectroscopic and docking simulation assessments.

Human serum albumin (HSA) principally tasks as a transport carrier for a vast variety of natural compounds and pharmaceutical drugs. In the present study, two structurally related binuclear Pt (II) complexes containing cis, cis-[Me2Pt (µ-NN) (µ-dppm) PtMe2] (1), and cis, cis-[Me2Pt(µ-NN)(µ dppm) Pt((CH2)4)] (2) in which NN=phthalazine and dppm=bis (diphenylphosphino) methane were used to investigate their interaction with HSA, using UV-Vis absorption spectroscopy, fluorescence, circular dichroism and molecular dynamic analyses. The spectroscopic results suggest that upon binding to HSA, the binuclear Pt (II) complexes could effectively induce structural alteration of this protein. These complexes can bind to HSA with the binding affinities of the following order: complex 2>complex 1. Moreover, the thermodynamic parameters of binding between these complexes and HSA suggested the existence of entropy-driven spontaneous interaction, which mostly dominated with the hydrophobic forces. The ANS fluorescence results also indicated that two binuclear Pt (II) complexes were competing for the binding to the hydrophobic regions on HSA. In addition, competitive displacement assay and docking simulation study revealed that complexes 1 and 2 bind to the drug binding sites II and I on HSA, respectively. Furthermore, complex 2, with the higher binding affinity for HSA, shows more denaturing effect on this protein. Considering the protein structural damages in the pathway of harmful side effects of platinum drugs, complex 1 with the moderate binding affinity and low denaturing effect might be of high significance.

Morphine-Induced Analgesic Tolerance Effect on Gene Expression of the NMDA Receptor Subunit 1 in Rat Striatum and Prefrontal Cortex.

INTRODUCTION: Morphine is a potent analgesic but its continual use results in analgesic tolerance. Mechanisms of this tolerance remain to be clarified. However, changes in the functions of µ-opioid and N-Methyl-D-aspartate (NMDA) receptors have been proposed in morphine tolerance. We examined changes in gene expression of the NMDA receptor subunit 1 (NR1) at mRNA levels in rat striatum and prefrontal cortex (PFC) after induction of morphine tolerance. METHODS: Morphine (10 mg/kg, IP) was injected in male Wistar rats for 7 consecutive days (intervention group), but control rats received just normal saline (1 mL/kg, IP). We used a hotplate test of analgesia to assess induction of tolerance to analgesic effects of morphine on days 1 and 8 of injections. Later, two groups of rats were sacrificed one day after 7 days of injections, their whole brains removed, and the striatum and PFC immediately dissected. Then, the NR1 gene expression was examined with a semi-quantitative RT-PCR method. RESULTS: The results showed that long-term morphine a administration induces tolerance to analgesic effect of the opioid, as revealed by a significant decrease in morphine-induced analgesia on day 8 compared to day 1 of the injections (P<0.001). The results also showed that the NR1 gene expression at mRNA level in rats tolerant to morphine was significantly increased in the striatum (P<0.01) but decreased in the PFC (P<0.001). CONCLUSION: Therefore, changes in the NR1 gene expression in rat striatum and PFC have a region-specific association with morphine-induced analgesic tolerance.

Extending Time Profile of Morphine-Induced Analgesia Using a Chitosan-Based Molecular Imprinted Polymer Nanogel.

Chitosan-based molecular imprinted polymer (CS-MIP) nanogel is prepared in the presence of morphine template, fully characterized and used as a new vehicle to extend duration of morphine analgesic effect in Naval Medical Research Institute mice. The CS-MIP nanogel with ≈25 nm size range exhibits 98% loading efficiency, and in vitro release studies show an initial burst followed by an extended slow release of morphine. In order to study the feasibility of CS-MIP nanogel as morphine carrier, 20 mice are divided into two groups randomly and received subcutaneous injection of morphine-loaded CS-MIP and morphine (10 mg kg-1 ) dissolved in physiologic saline. Those received injection of morphine-loaded CS-MIP show slower and long lasting release of morphine with 193 min effective time of 50% (ET50) analgesia compared to 120 min ET50 in mice received morphine dissolved in physiologic saline. These results suggest that CS-MIP nanogel can be a possible strategy as morphine carrier for controlled release and extension of its analgesic efficacy.

Anticancer activity assessment of two novel binuclear platinum (II) complexes.

In the current study, two binuclear Pt (II) complexes, containing cis, cis-[Me2Pt (µ-NN) (µ-dppm) PtMe2] (1), and cis,cis-[Me2Pt(µ-NN)(µ dppm) Pt((CH2)4)] (2) in which NN=phthalazine and dppm=bis (diphenylphosphino) methane were evaluated for their anticancer activities and DNA/purine nucleotide binding properties. These Pt (II) complexes, with the non-classical structures, demonstrated a significant anticancer activity against Jurkat and MCF-7 cancer cell lines. The results of ethidium bromide/acridine orange staining and Caspase-III activity suggest that these complexes were capable to stimulate an apoptotic mechanism of cell death in the cancer cells. Using different biophysical techniques and docking simulation analysis, we indicated that these complexes were also capable to interact efficiently with DNA via a non-intercalative mechanism. According to our results, substitution of cyclopentane (in complex 2) with two methyl groups (in complex 1) results in significant improvement of the complex ability to interact with DNA and subsequently to induce the anticancer activity. Overall, these binuclear Pt (II) complexes are promising group of the non-classical potential anticancer agents which can be considered as molecular templates in designing of highly efficient platinum anticancer drugs.

Hepatic encephalopathy induces site-specific changes in gene expression of GluN1 subunit of NMDA receptor in rat brain.

We investigate changes in gene expression of GluN1 subunit of N-Methyl-D-Aspartate (NMDA) receptor in the prefrontal cortex (PFC), hippocampus and striatum in a rat model of hepatic encephalopathy (HE). We used male Wistar rats in which HE was induced after a common bile duct ligation (BDL). The animals were divided into three sets, and each set included three groups of control, sham operated and BDL. In the first set of animals, blood samples collected for biochemical analysis on day 21 of BDL. In the second set, changes in nociception threshold was assessed on day 21 of BDL using a hotplate test. In the third set, whole brain extracted, and the PFC, the hippocampus and the striatum in each rat were immediately dissected. We used a semi-quantitative RT-PCR method for evaluating the GluN1 gene expression. The biochemical analyses showed that plasma levels of ammonia and bilirubin in BDL rats were significantly increased compared to the sham control group on day 21 of BDL (P < 0.01). Nociception threshold was also increased in rats with BDL compared to sham group (P < 0.001). The results revealed that the GluN1 gene expression at mRNA levels in BDL group was decreased by 19 % in the PFC (P < 0.05) but increased by 82 % in the hippocampus (P < 0.01) compared to the sham control group; however, no significant change was observed in the striatum. It can be concluded that HE affects the GluN1 gene expression in rat brain with a site-specific pattern, and the PFC and hippocampus are more sensitive areas than striatum.

ATP-sensitive Potassium Channels and L-type Calcium Channels are Involved in Morphine-induced Hyperalgesia after Nociceptive Sensitization in Mice.

INTRODUCTION: We investigated the role of ATP-sensitive potassium channels and L-type calcium channels in morphine-induced hyperalgesia after nociceptive sensitization. METHODS: We used a hotplate apparatus to assess pain behavior in male NMRI mice. Nociceptive sensitization was induced by three days injection of morphine and five days of drug free. On day 9 of the schedule, pain behavior test was performed for evaluating the effects of morphine by itself and along with nimodipine, a blocker of L-type calcium channels and diazoxide, an opener of ATP-sensitive potassium channels. All drugs were injected through an intraperitoneal route. RESULTS: The results showed that morphine (7.5, 10 and 15 mg/kg) induced analgesia in normal mice, which was prevented by naloxone (1 mg/kg). After nociceptive sensitization, analgesic effect of morphine (10 and 15 mg/kg) was significantly decreased in sensitized mice. The results showed that nimodipine (2.5, 5, 10 and 20 mg/kg) had no significant effect on pain behavior test in either normal or sensitized mice. However, nimodipine (20 mg/ kg) along with morphine (10 and 15 mg/kg) caused more decrease in morphine analgesia in sensitized mice. Furthermore, diazoxide by itself (0.25, 1, 5 and 20 mg/kg) had also no significant effect on pain behavior in both normal and sensitized mice, but at dose of 20 mg/kg along with morphine (10 and 15 mg/kg) decreased analgesic effect of morphine in sensitized mice. DISCUSSION: It can be concluded that potassium and calcium channels have some roles in decrease of analgesic effect of morphine after nociceptive sensitization induced by pretreatment of morphine.

N-methyl-D-aspartate receptors involved in morphine-induced hyperalgesia in sensitized mice.

The aim of this study was to investigate role of the N-Methyl-D-Aspartate (NMDA) receptors in the decrease of morphine analgesia in mice after nociceptive sensitization. We used a hot plate test to assess effects of morphine on pain behavior in male NMRI mice. All drugs were administered through an intraperitoneal route. Sensitization schedule composed of 3-days pre-treatment of morphine (20mg/kg) followed by 5-days washout. The results showed that morphine (5, 7.5, 10 and 15mg/kg) induced a significant analgesia in normal mice. However, the analgesic effects of morphine significantly decreased at higher dose (15mg/kg) in sensitized mice. Injections of either a competitive NMDA receptor antagonist, D-AP5 (0, 0.25, 0.5 and 1mg/kg) or an NMDA receptor channel blocker (30, 60 and 120mg/kg) alone had no effect on pain behavior. However, injections of D-AP5 (1mg/kg), along with morphine over 3-days of the sensitization schedule, significantly prevented the decrease in the analgesic effect of the opioid at doses of 7.5 and 10mg/kg on the hot plate test. Similarly, injections of MgSO4 (120mg/kg), along with morphine over 3-days of the sensitization schedule, significantly prevented the decrease in analgesic effect of morphine at doses of 10 and 15mg/kg. It can be concluded that NMDA receptors are influenced by morphine during the sensitization schedule, which in turn may affect morphine analgesia after the schedule. This may further support the potential effectiveness of NMDA blockade during repeated use of morphine for control of chronic pain.

Anxiolytic-Like Effects and Increase in Locomotor Activity Induced by Infusions of NMDA into the Ventral Hippocampus in Rat: Interaction with GABAergic System.

INTRODUCTION: In this study, we investigated the role of N-Methyl-D-Aspartate (NMDA) receptors in the ventral hippocampus (VH) and their possible interactions with GABAA system on anxiety-like behaviors. METHODS: We used an elevated-plus maze test (EPM) to assess anxiety-like behaviors and locomotor activity in male Wistar rats. RESULTS: The results showed that intra-VH infusions of different doses of NMDA (0.25 and 0.5 µg/rat) increased locomotor activity, and also induced anxiolytic-like behaviors, as revealed by a tendency to increase percentage of open arm time (%OAT), and a significant increase in percentage of open arm entries (%OAE). The results also showed that intra-VH infusions of muscimol (0.5 and 1 µg/rat) or bicuculline (0.5 and 1 µg/rat) did not significantly affect anxiety-like behaviors, but bicuculline at dose of 1 µg/rat increased locomotor activity. Intra-VH co-infusions of muscimol (0.5 µg/rat) along with low doses of NMDA (0.0625 and 0.125 µg/rat) showed a tendency to increase %OAT, %OAE and locomotor activity; however, no interaction was observed between the drugs. Interestingly, intra-VH co-infusions of bicuculline (0.5 µg/rat) along with effective doses of NMDA (0.25 and 0.5 µg/rat) decreased %OAT, %OAE and locomotor activity, and a significant interaction between two drugs was observed. DISCUSSION: It can be concluded that GABAergic system may mediate the anxiolytic-like effects and increase in locomotor activity induced by NMDA in the VH.