Anti-inflammatory and protective effects of Aripiprazole on TNBS-Induced colitis and associated depression in rats: Role of kynurenine pathway.

BACKGROUND: The prevalence of depression is higher in patients with inflammatory bowel disease (IBD) than in the general population. Inflammatory cytokines and the kynurenine pathway (KP) play important roles in IBD and associated depression. Aripiprazole (ARP), an atypical antipsychotic, shows various anti-inflammatory properties and may be useful in treating major depressive disorder. This study aimed to evaluate the protective effects of ARP on TNBS-induced colitis and subsequent depression in rats, highlighting the role of the KP. MATERIAL AND METHODS: Fifty-six male Wistar rats were used, and all groups except for the normal and sham groups received a single dose of intra-rectal TNBS. Three different doses of ARP and dexamethasone were injected intraperitoneally for two weeks in treatment groups. On the 15th day, behavioral tests were performed to evaluate depressive-like behaviors. Colon ulcer index and histological changes were assessed. The tissue levels of inflammatory cytokines, KP markers, lipopolysaccharide (LPS), nuclear factor-kappa-B (NF-κB), and zonula occludens (ZO-1) were evaluated in the colon and hippocampus. RESULTS: TNBS effectively induced intestinal damages and subsequent depressive-like symptoms in rats. TNBS treatment significantly elevated the intestinal content of inflammatory cytokines and NF-κB expression, dysregulated the KP markers balance in both colon and hippocampus tissues, and increased the serum levels of LPS. However, treatment with ARP for 14 days successfully reversed these alterations, particularly at higher doses. CONCLUSION: ARP could alleviate IBD-induced colon damage and associated depressive-like behaviors mainly via suppressing inflammatory cytokines activity, serum LPS concentration, and affecting the NF-κB/kynurenine pathway.

Effect of high-dose Spirulina supplementation on hospitalized adults with COVID-19: a randomized controlled trial.

Objective: Spirulina (arthrospira platensis) is a cyanobacterium proven to have anti-inflammatory, antiviral, and antioxidant effects. However, the effect of high-dose Spirulina supplementation on hospitalized adults with COVID-19 is currently unclear. This study aimed to evaluate the efficacy and safety of high-dose Spirulina platensis for SARS-CoV-2 infection. Study Design: We conducted a randomized, controlled, open-label trial involving 189 patients with COVID-19 who were randomly assigned in a 1:1 ratio to an experimental group that received 15.2g of Spirulina supplement plus standard treatment (44 non-intensive care unit (non-ICU) and 47 ICU), or to a control group that received standard treatment alone (46 non-ICU and 52 ICU). The study was conducted over six days. Immune mediators were monitored on days 1, 3, 5, and 7. The primary outcome of this study was mortality or hospital discharge within seven days, while the overall discharge or mortality was considered the secondary outcome. Results: Within seven days, there were no deaths in the Spirulina group, while 15 deaths (15.3%) occurred in the control group. Moreover, within seven days, there was a greater number of patients discharged in the Spirulina group (97.7%) in non-ICU compared to the control group (39.1%) (HR, 6.52; 95% CI, 3.50 to 12.17). Overall mortality was higher in the control group (8.7% non-ICU, 28.8% ICU) compared to the Spirulina group (non-ICU HR, 0.13; 95% CI, 0.02 to 0.97; ICU, HR, 0.16; 95% CI, 0.05 to 0.48). In non-ICU, patients who received Spirulina showed a significant reduction in the levels of IL-6, TNF-α, IL-10, and IP-10 as intervention time increased. Furthermore, in ICU, patients who received Spirulina showed a significant decrease in the levels of MIP-1α and IL-6. IFN-γ levels were significantly higher in the intervention group in both ICU and non-ICU subgroups as intervention time increased. No side effects related to Spirulina supplements were observed during the trial. Conclusion: High-dose Spirulina supplements coupled with the standard treatment of COVID-19 may improve recovery and remarkably reduce mortality in hospitalized patients with COVID-19. Clinical Trial Registration: https://irct.ir/trial/54375, Iranian Registry of Clinical Trials number (IRCT20210216050373N1).

Role of hippocampal and prefrontal cortical cholinergic transmission in combination therapy valproate and cannabidiol in memory consolidation in rats: involvement of CREB- BDNF signaling pathways.

PURPOSE: Cognitive disorders are associated with valproate and drugs used to treat neuropsychological diseases. Cannabidiol (CBD) has beneficial effects on cognitive function. This study examined the effects of co-administration of CBD and valproate on memory consolidation, cholinergic transmission, and cyclic AMP response element-binding protein (CREB)-brain-derived neurotrophic factor (BDNF) signaling pathway in the prefrontal cortex (PFC) and hippocampus (HPC). METHODS: One-trial, step-through inhibitory test was used to evaluate memory consolidation in rats. The intra-CA1 injection of physostigmine and atropine was performed to assess the role of cholinergic transmission in this co-administration. Phosphorylated CREB (p-CREB)/CREB ratio and BDNF levels in the PFC and HPC were evaluated. RESULTS: Post-training intraperitoneal (i.p.) valproate injection reduced memory consolidation; however, post-training co-administration of CBD with valproate ameliorated memory impairment induced by valproate. Post-training intra-CA1 injection of physostigmine at the ineffective doses in memory consolidation (0.5 and 1 µg/rat), plus injection of 10 mg/kg of CBD as an ineffective dose, improved memory loss induced by valproate, which was associated with BDNF and p-CREB level enhancement in the PFC and HPC. Conversely, post-training intra-CA1 injection of ineffective doses of atropine (1 and 2 µg/rat) reduced the positive effects of injection of CBD at a dose of 20 mg/kg on valproate-induced memory loss associated with BDNF and p-CREB level reduction in the PFC and HPC. CONCLUSION: The results indicated a beneficial interplay between valproate and CBD in the process of memory consolidation, which probably creates this interaction through the BDNF-CREB signaling pathways in the cholinergic transmission of the PFC and HPC regions.

Cross state-dependent memory retrieval between tramadol and ethanol: involvement of dorsal hippocampal GABAA receptors.

RATIONALE: Tramadol and ethanol, as psychoactive agents, are often abused. Discovering the molecular pathways of drug-induced memory creation may contribute to preventing drug addiction and relapse. OBJECTIVE: The tramadol- and ethanol-induced state-dependent memory (SDM) and cross-SDM retrieval between tramadol and ethanol were examined in this study. Moreover, because of the confirmed involvement of GABAA receptors and GABAergic neurotransmission in memory retrieval impairment, we assessed cross-SDM retrieval between tramadol and ethanol with a specific emphasis on the role of the GABAA receptors. The first hypothesis of this study was the presence of cross-SDM between tramadol and ethanol, and the second hypothesis was related to possible role of GABAA receptors in memory retrieval impairment within the dorsal hippocampus. The cannulae were inserted into the hippocampal CA1 area of NMRI mice, and a step-down inhibitory avoidance test was used to evaluate state dependence and memory recovery. RESULTS: The post-training and/or pre-test administration of tramadol (2.5 and 5 mg/kg, i.p.) and/or ethanol (0.5 and 1 g/kg, i.p.) induced amnesia, which was restored after the administration of the drugs 24 h later during the pre-test period, proposing ethanol and tramadol SDM. The pre-test injection of ethanol (0.25 and 0.5 g/kg, i.p.) with tramadol at an ineffective dose (1.25 mg/kg) enhanced tramadol SDM. Moreover, tramadol injection (1.25 and 2.5 mg/kg) with ethanol at the ineffective dose (0.25 g/kg) promoted ethanol SDM. Furthermore, the pre-test intra-CA1 injection of bicuculline (0.0625, 0.125, and 0.25 µg/mouse), a GABAA receptor antagonist, 5 min before the injection of tramadol (5 mg/kg) or ethanol (1 g/kg) inhibited tramadol- and ethanol-induced SDM dose-dependently. CONCLUSION: The findings strongly confirmed cross-SDM between tramadol and ethanol and the critical role of dorsal hippocampal GABAA receptors in the cross-SDM between tramadol and ethanol.

Ameliorative Effect of Cannabidiol on Topiramate-Induced Memory Loss: The Role of Hippocampal and Prefrontal Cortical NMDA Receptors and CREB/BDNF Signaling Pathways in Rats.

Cannabidiol (CBD) is a promising neurological agent with potential beneficial effects on memory and cognitive function. The combination of CBD and topiramate in the treatment of some neurological diseases has been of great interest. Since Topiramate-induced memory loss is a major drawback of its clinical application and the overall effect of the combination of CBD and topiramate on memory is still unclear, here we investigated the effect of CBD on topiramate-induced memory loss and the underlying molecular mechanisms. A one trial step-through inhibitory test was used to evaluate memory consolidation in rats. Moreover, the role of N-methyl-D-aspartate receptors (NMDARs) in the combination of CBD and topiramate in memory consolidation was evaluated through the intra-CA1 administration of MK-801 and NMDA. Western blot analysis was used to evaluate variations in brain-derived neurotrophic factor (BDNF) and phosphorylated cyclic AMP response element-binding protein (pCREB)/CREB ratio in the prefrontal cortex (PFC) and hippocampus (HPC). While the intraperitoneal (i.p.) administration of topiramate (50, 75, and 100 mg/kg) significantly reduced inhibitory time latency, the i.p. administration of CBD (20 and 40 mg/kg) could effectively reverse these effects. Similarly, the sub-effective doses of NMDA plus CBD (10 mg/kg) could improve the topiramate-induced memory loss along with an enhancement in BDNF and pCREB expression in the PFC and HPC. Contrarily, the administration of sub-effective doses of the NMDAR antagonist (MK-801) diminished the protective effects of CBD (20 mg/kg) on topiramate-induced memory loss associated with decreased BDNF and pCREB levels in the PFC and HPC. These findings suggest that CBD can improve topiramate-induced memory impairment, partially by the NMDARs of the PFC and HPC, possibly regulated by the CREB/BDNF signaling pathway.

Kynurenine pathway and its role in neurologic, psychiatric, and inflammatory bowel diseases.

Tryptophan metabolism along the kynurenine pathway is of central importance for the immune function. It prevents hyperinflammation and induces long-term immune tolerance. Accumulating evidence also demonstrates cytoprotective and immunomodulatory properties of kynurenine pathway in conditions affecting either central or peripheral nervous system as well as other conditions such as inflammatory bowel disease (IBD). Although multilevel association exists between the inflammatory bowel disease (IBD) and various neurologic (e.g., neurodegenerative) disorders, it is believed that the kynurenine pathway plays a pivotal role in the development of both IBD and neurodegenerative disorders. In this setting, there is strong evidence linking the gut-brain axis with intestinal dysfunctions including IBD which is consistent with the fact that the risk of neurodegenerative diseases is higher in IBD patients. This review aims to highlight the role of kynurenine metabolic pathway in various neurologic and psychiatric diseases as well as relationship between IBD and neurodegenerative disorders in the light of the kynurenine metabolic pathway.

Dorsal hippocampal CA1 NMDA receptors mediate the interactive effects of quetiapine and lithium on memory retention in male rats.

Objectives: Lithium and quetiapine are administered simultaneously as a treatment for bipolar disorder. The concurrent use of these two drugs has been observed to affect the neurobiological mechanisms underlying learning and memory. To clarify the precise mechanisms involved, we evaluated the possible role of the dorsal hippocampal CA1 NMDA receptors in the interactive effects of lithium and quetiapine in memory consolidation. Materials and Methods: The dorsal hippocampal CA1 regions of adult male Wistar rats were bilaterally cannulated, and a single-trial step-through inhibitory avoidance apparatus was used to assess memory consolidation. Results: Post-training administration of certain doses of lithium (20, 30, and 40 mg/kg, IP) diminished memory consolidation. Post-training administration of higher doses of quetiapine (5, 10, and 20 mg/kg, IP) augmented memory consolidation. Post-training administration of certain doses of quetiapine (2.5, 5, 10, and 20 mg/kg) dose-dependently restored lithium-induced memory impairment. Post-training microinjection of ineffective doses of the NMDA (10-5 and 10-4 µg/rat, intra-CA1) plus an ineffective dose of quetiapine (2.5 mg/kg) restored the lithium-induced memory impairment. Post-training microinjection of ineffective doses of the noncompetitive NMDA receptor antagonist, MK-801 (0.0625 and 0.0125 µg/rat, intra-CA1), diminished the quetiapine-induced (10 mg/kg) memory improvement in lithium-induced memory impairment. Conclusion: These findings suggest a functional interaction between lithium and quetiapine through hippocampal CA1 NMDA receptor mechanisms in memory consolidation.

Correction to: Evaluation of curcumin effect on Il6, Sirt1, TNFα and NFkB expression of liver tissues in diabetic mice with STZ.

[This corrects the article DOI: 10.1007/s40200-022-01090-4.].

Evaluation of curcumin effect on Il6, Sirt1, TNFα and NFkB expression of liver tissues in diabetic mice with STZ.

Background: Curcumin is active ingredient of turmeric The main purpose of this study is evaluating impact of curcumin on suger, hypoalgesia and inflammatory factors in diabetic mice. Materials and methods: Male mice divided into six groups of 6. One group as a negative and the other five groups injected with Streptozotocin (STZ) (200 mg/kg). Diabetic mice in each group given different treatments for twenty-one days.After that, blood sugar and neuroathy studies have been done and tissue samples the liver were studied for gene expression. Result: Curcumin reduced blood sugar, but the rate of hypoglycemia was significantly lower than metformin group P > 0.05, and the comparison of the synergistic effect of curcumin and metformin with metformin was not significant P > 0.05. Also, in neuropathy studies, the groups which recieved curcumin and metformin have shown a significant difference with diabetic group P < 0.01, Also, by evaluating inflammatory factors, there was a significant difference in the expression of TNF-a, IL-6 and NfkB, but there is no significant difference in the expression of Sirt1 P < 0.05. Conclusions: The analgesic effect of curcumin was quite evident, probably due to the significant impact of this herbal drug in reducing the expression of inflammatory genes NF-kB, IL6, and TNF-α. Supplementary Information: The online version contains supplementary material available at 10.1007/s40200-022-01090-4.

The Effects of Vitamin D3 and Melatonin Combination on Pentylenetetrazole- induced Seizures in Mice.

BACKGROUND: Epileptic seizures are associated with the overproduction of free radicals in the brain leading to neuronal cell death. Therefore, reduction of oxidative stress may inhibit seizure- induced neuronal cell damage. The current study evaluated the effects of Vit D3 and melatonin and their combination on pentylenetetrazol (PTZ)-induced tonic-clonic seizures in mice. METHODS: Animals were divided into six groups. Group I was administered with normal saline (0.5 ml, intraperitoneally (i.p.)) on the 15th day of the experiment. Group II was injected with PTZ (60 mg/kg dissolved in 0.5 ml normal saline, i.p) on the 15th day. Groups III-IV were treated with diazepam (4 mg/kg/day), Vit D3 (6000 IU/kg/day), melatonin (20 mg/kg/day), and Vit D3 (6000 IU/kg/day)/melatonin (20 mg/kg/day), respectively, and were then injected with PTZ (60 mg/kg) on the 15th day of the experiment. Immediately after the injection of PTZ on the 15th day, mice were observed for a 30-min period to measure seizure latency and duration. For determination of oxidative stress markers, malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were measured in mouse brains. RESULTS: Treatment with Vit D3, melatonin, and Vit D3/melatonin significantly increased seizure latency and decreased seizure duration. The brain level of MDA was lower, and SOD activity was greater than in the PTZ group. Mice treated with Vit D3/melatonin had lower seizure duration than other treated groups. CONCLUSIONS: The combination of Vit D3 and melatonin may reduce seizure frequency in epileptic patients; this effect may result from various mechanisms, including inhibition of oxidative stress.

Oral administration of phenylalanine molecularly imprinted polymer (MIP) benefits PKU mouse model.

Phenylketonuria (PKU) is a rare genetic disorder caused by a defect in the metabolism of phenylalanine (Phe). Currently, the most commonly used treatment for PKU is dietary Phe restriction. Problems associated with Phe restricted diets include lack of universal availability, high treatment costs, and reduced adherence to continued treatment with age and finally the development of psychological and neurological problems in a significant proportion of patients despite early start of treatment. One possible approach to decreasing blood Phe level, is inhibition of GI tract absorption of this amino acid. We had previously shown that a Phe selective molecularly imprinted polymer was able to bind Phe in the GI tract and attenuate its plasma concentration. In this work, we used different orally administered Phe selective molecularly imprinted polymer doses in a PKU mouse model to further study the effects of this treatment on biochemical profile and cognitive function in test animals. Treatments started 21 days postnatally. After 3 weeks, brain and plasma amino acid profiles and brain monoaminergic neurotransmitter concentrations were measured. Behavioral profile was also evaluated. Treatment with 2% and 5% Phe selective molecularly imprinted polymer significantly reduced levels of blood Phe in PKU model animals (46% and 48% respectively) meanwhile levels of other amino acids remained unchanged. Brain dopamine concentrations in hippocampus was effectively restored by supplementation of Phe selective molecularly imprinted polymer. Finally, polymer treatment improved locomotor dysfunction in PKU model animals. Our data suggest that the Phe selective molecularly imprinted polymer can be a new candidate for treatment of PKU patients. Take home message: Orally administered Phenylalanine Selective Molecularly Imprinted Polymer is able to inhibit absorption of phenylalanine from the GI tract and may offer a new treatment, in conjunction with dietary restriction, for PKU patients.

Cross state-dependent memory retrieval between cannabinoid CB1 and serotonergic 5-HT1A receptor agonists in the mouse dorsal hippocampus.

Understanding the neurobiological mechanisms of drug-related learning and memory formation may help the treatment of cognitive disorders. Dysfunction of the cannabinoid and serotonergic systems has been demonstrated in learning and memory disorders. The present paper investigates the phenomenon called state-dependent memory (SDM) induced by ACPA (a selective cannabinoid CB1 receptor agonist) and 8-OH-DPAT (a nonselective 5-HT1A receptor agonist) with special focus on the role of the 5-HT1A receptor in the effects of both ACPA and 8-OH-DPAT SDM and cross state-dependent memory retrieval between ACPA and 8-OH-DPAT in a step-down inhibitory avoidance task. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated, and all drugs were microinjected into the intended injection sites. A single-trial step-down inhibitory avoidance task was used to assess memory retrieval and state-dependence. Post-training and/or pre-test microinjections of ACPA (1 and 2 ng/mouse) and 8-OH-DPAT (0.5 and 1 µg/mouse) dose-dependently induced amnesia. Pre-test administration of the same doses of ACPA and 8-OH-DPAT reversed the post-training ACPA- and 8-OH-DPAT-induced amnesia, respectively. This phenomenon has been named SDM. 8-OH-DPAT (1 µg/mouse) reversed the amnesia induced by ACPA (0.5, 1, and 2 ng/mouse) and induced ACPA SDM. ACPA (2 ng/mouse) reversed the amnesia induced by 8-OH-DPAT (0.25, 0.5, and 1 µg/mouse) and induced 8-OH-DPAT SDM. Pre-test administration of a 5-HT1A receptor antagonist, (S)-WAY 100,135 (0.25 and 0.5 µg/mouse), 5 min before ACPA and 8-OH-DPAT dose-dependently inhibited ACPA- and 8-OH-DPAT-induced SDM, respectively. The present study results demonstrated ACPA- and 8-OH-DPAT- induced SDM. Overall, the data revealed that dorsal hippocampal 5-HT1A receptor mechanisms play a pivotal role in modulating cross state-dependent memory retrieval between ACPA and 8-OH-DPAT.

Noscapine protects the H9c2 cardiomyocytes of rats against oxygen-glucose deprivation/reperfusion injury.

Noscapine is an antitumor alkaloid derived from Papaver somniferum plants. Our previous study has demonstrated that exposure of noscapine on primary murine fetal cortical neurons exposed to oxygen-glucose deprivation/reperfusion (OGD/R) has neuroprotective effects. In current study, the effects of noscapine on cardiomyocytes (H9c2 cells) damage caused by 120 minutes (min) of OGD/R were evaluated and we determined whether the addition of BD1047, sigma-one receptor antagonist, prevents the protective effects of noscapine in H9c2 cells through the production of nitric oxide (NO) and apoptosis. To initiate OGD, H9c2 cells was transferred to glucose-free DMEM, and placed in a humidified incubation chamber. Cell viability was assessed with noscapine (1-5 µM) in the presence or absence of BD1047, 24 hours (h) after OGD/R. Cell viability, NO production and apoptosis ratio were evaluated by the MTT assay, the Griess method and the quantitative real-time PCR. Noscapine considerably improved the survival of H9c2 cells compared to OGD/R. Also, noscapine was extremely capable of reducing the concentrations of NO and Bax/Bcl-2 ratio expression. While the BD1047 administration alone diminished cell viability and increased the Bax/Bcl-2 ratio and NO levels. The addition of noscapine in the presence of BD1047 did not increase the cell viability relative to noscapine alone. Noscapine exerted cardioprotective effects exposed to OGD/R-induced injury in H9c2 cells, at least partly via attenuation of NO production and Bax/Bcl-2 ratio, which indicates that the sigma-one receptor activation is involved in the protection by noscapine of H9c2 cells injured by OGD/R.

Hippocampal and prefrontal cortical NMDA receptors mediate the interactive effects of olanzapine and lithium in memory retention in rats: the involvement of CAMKII-CREB signaling pathways.

RATIONALE: Treatment of bipolar disorder (BPD) with lithium and olanzapine concurrent administration is a major medicine issue with the elusive neurobiological mechanisms underlying the cognitive function. OBJECTIVE: To clarify the precise mechanisms involved, the possible role of the hippocampus (HPC) and prefrontal cortical (PFC) NMDA receptors and CAMKII-CREB signaling pathway in the interactive effects of lithium and olanzapine in memory consolidation was evaluated. The dorsal hippocampal CA1 regions of adult male Wistar rats were bilaterally cannulated and a step-through inhibitory avoidance apparatus was used to assess memory consolidation. The changes in p-CAMKII/CAMKII and p-CREB/CREB ratio in the HPC and the PFC were measured by Western blot analysis. RESULTS: Post-training administration of lithium (20, 30, and 40 mg/kg, i.p.) dose-dependently decreased memory consolidation whereas post-training administration olanzapine (2 and 5 mg/kg, i.p.) increased memory consolidation. Post-training administration of certain doses of olanzapine (1, 2, and 5 mg/kg, i.p.) dose-dependently improved lithium-induced memory impairment. Post-training administration of ineffective doses of the NMDA (10-5 and 10-4 µg/rat, intra-CA1) plus an ineffective dose of olanzapine (1 mg/kg, i.p.) dose-dependently improved the lithium-induced memory impairment. Post-training microinjection of ineffective doses of the NMDA (10-5 and 10-4 µg/rat, intra-CA1) dose-dependently potentiated the memory improvement induced by olanzapine (1 mg/kg, i.p.) on lithium-induced memory impairment which was associated with the enhancement of the levels of p-CAMKII and p-CREB in the HPC and the PFC. Post-training microinjection of ineffective doses of the noncompetitive NMDA receptor antagonist, MK-801 (0.0625 and 0.0125 µg/rat, intra-CA1), dose-dependently decreased the memory improvement induced by olanzapine (5 mg/kg, i.p.) on lithium-induced memory impairment which was related to the reduced levels of HPC and PFC CAMKII-CREB. CONCLUSION: The results strongly revealed that there is a functional interaction among lithium and olanzapine through the HPC and the PFC NMDA receptor mechanism in memory consolidation which is mediated with the CAMKII-CREB signaling pathway.

Cross state-dependency of learning between 5-HT1A and/or 5-HT7 receptor agonists and muscimol in the mouse dorsal hippocampus.

BACKGROUND: Dysfunction of the serotonergic and GABAergic systems in cognitive disorders has been revealed. Understanding the neurobiological mechanisms of drug-associated learning and memory formation may help treatment of cognitive disorders. AIMS: The aim of the present study was to investigate: 1) 8-OH-DPAT (5-HT1A agonist), AS19 (5-HT7 agonist) and muscimol (GABA-A agonist) on memory retrieval and state of memory, 2) cross state-dependent learning between 8-OH-DPAT and/or AS19 and muscimol. METHODS: The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated, and all drugs were microinjected into the intended sites of injection. A single-trial step-down inhibitory avoidance task was used for the evaluation of memory retrieval and state of memory. RESULTS: Post-training and/or pre-test 8-OH-DPAT, AS19 and muscimol induced amnesia. Pre-test microinjection of the same doses of 8-OH-DPAT, AS19 and muscimol reversed the post-training 8-OH-DPAT-, AS19- and muscimol-induced amnesia, respectively. This event has been named state-dependent learning (SDL). The amnesia induced by 8-OH-DPAT was reversed by muscimol and induced 8-OH-DPAT SDL. The amnesia induced by muscimol was reversed by 8-OH-DPAT and induced muscimol SDL. The amnesia induced by AS19 was reversed by muscimol and induced AS19 SDL. The amnesia induced by muscimol was reversed by AS19 and induced muscimol SDL. Pre-test administration of a selective GABA-A receptor antagonist, bicuculline, 5 min before muscimol, 8-OH-DPAT and AS19 dose-dependently inhibited muscimol-, 8-OH-DPAT- and AS19-induced SDL, respectively. CONCLUSIONS: The results strongly revealed a cross SDL among 8-OH-DPAT and/or AS19 and muscimol in the dorsal hippocampal CA1 regions.

Cross state-dependency of learning between tramadol and MK-801 in the mouse dorsal hippocampus: involvement of nitric oxide (NO) signaling pathway.

RATIONALE: Tramadol, an atypical µ-opioid receptor agonist, as a psychoactive drug, is frequently abused by human beings. Understanding the neurobiological mechanisms of drug-associated learning and memory formation may help prevent drug addiction and relapse. Previous study revealed that dorsal hippocampus (CA1) plays a crucial role in the retrieval of tramadol-associated memory and that its role depends on the expression of CA1 N-methyl-D-aspartate (NMDA) receptors (Jafari-Sabet et al. Can J Physiol Pharmacol 96:45-50, 2018). OBJECTIVE: To clarify the exact mechanisms involved, the activation of CA1 nitric oxide (NO) signaling pathway by L-arginine (a nitric oxide precursor) on the interaction between tramadol and MK-801 in memory retrieval was examined. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated and a single-trial step-down inhibitory avoidance apparatus was used for the assessment of memory retrieval. RESULTS: Post-training and/or pre-test microinjection of tramadol (0.5 and 1 µg/mouse) and/or a non-competitive NMDA receptor antagonist, MK-801 (0.25 and 0.5 µg/mouse), induced amnesia which were reversed when the same doses of the drugs were administered 24 h later in a pre-test session, suggesting tramadol state-dependent learning (SDL) and MK-801 SDL. The amnesia induced by post-training microinjection of tramadol (1 µg/mouse) was reversed by pre-test microinjection of MK-801 (0.25 and 0.5 µg/mouse). Pre-test microinjection of MK-801 (0.125 and 0.25 µg/mouse) with an ineffective dose of tramadol (0.25 µg/mouse) potentiated tramadol SDL. The amnesia induced by post-training microinjection of MK-801 (0.5 µg/mouse) was reversed by pre-test microinjection of tramadol (0.5 and 1 µg/mouse). Pre-test microinjection of tramadol (0.25 and 0.5 µg/mouse) with an ineffective dose of MK-801 (0.125 µg/mouse) potentiated MK-801 SDL. Pre-test microinjection of ineffective doses of L-arginine (0.125, 025, and 0.5 µg/mouse) improved amnesia induced by the co-administration of tramadol and MK-801. Pre-test microinjection of L-arginine (0.125, 025, and 0.5 µg/mouse) could not reverse amnesia induced by post-training microinjection of tramadol while same doses of L-arginine improved MK-801 response on tramadol SDL. CONCLUSION: The results strongly propose that activation of CA1 NO signaling pathway has a pivotal role in cross SDL among tramadol and MK-801.

NMDA receptors in the dorsal hippocampal area are involved in tramadol state-dependent memory of passive avoidance learning in mice.

The precise neurobiological mechanisms of tramadol abuse underlying the cognitive function are still unknown. The aim of the present study was to examine the possible effects of intra-CA1 injections of N-methyl-d-aspartate (NMDA), a glutamate NMDA receptor (NMDAR) agonist, and d,l-2-amino-5-phosphonopentanoic acid (DL-AP5), a competitive NMDAR antagonist, on tramadol state-dependent memory. A single-trial step-down passive avoidance task was used for the assessment of memory retrieval in adult male NMRI mice. Post-training i.p. administration of an atypical µ-opioid receptor agonist, tramadol (2.5 and 5 mg/kg), dose-dependently induced impairment of memory retention. Pre-test injection of tramadol (2.5 and 5 mg/kg) induced state-dependent retrieval of the memory acquired under post-training administration of tramadol (5 mg/kg) influence. Pre-test intra-CA1 injection of NMDA (10-5 and 10-4 µg/mouse) 5 min before the administration of tramadol (5 mg/kg, i.p.) dose-dependently inhibited tramadol state-dependent memory. Pre-test intra-CA1 injection of DL-AP5 (0.25 and 0.5 µg/mouse) reversed the memory impairment induced by post-training administration of tramadol (5 mg/kg). Pre-test administration of DL-AP5 (0.25 and 0.5 µg/mouse) with an ineffective dose of tramadol (1.25 mg/kg) restored the retrieval and induced tramadol state-dependent memory. It can be concluded that dorsal hippocampal NMDAR mechanisms play an important role in the modulation of tramadol state-dependent memory.

Cross state-dependency of learning between arachidonylcyclopropylamide (ACPA) and muscimol in the mouse dorsal hippocampus.

The aim of the present study was to examine cross state-dependent learning between ACPA (a selective cannabinoid CB1 receptor agonist) and muscimol (a selective GABAA receptor agonist) in the step-down inhibitory avoidance learning task. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated, and all drugs were microinjected into the intended sites of injection. Post-training and/or pre-test administration of ACPA (1 and 2ng/mouse) dose-dependently induced amnesia. Pre-test microinjection of the same doses of ACPA reversed the post-training ACPA-induced amnesia. This event has been named ACPA state-dependent learning (SDL). Post-training and/or pre-test microinjection of muscimol (0.05 and 0.1µg/mouse) dose-dependently induced amnesia. Pre-test administration of the same doses of muscimol reversed the post-training muscimol-induced amnesia, suggesting muscimol SDL. The amnesia induced by post-training administration of ACPA was reversed by pre-test administration of muscimol (0.05 and 0.1µg/mouse). Furthermore, the pre-test microinjection of muscimol (0.025 and 0.05µg/mouse) with an ineffective dose of ACPA (0.5ng/mouse) significantly restored memory retrieval and induced ACPA SDL. In another series of experiments, the amnesia induced by post-training administration of muscimol was reversed by pre-test administration of ACPA (1 and 2ng/mouse). Moreover, pre-test microinjection of ACPA (0.5 and 1ng/mouse) with an ineffective dose of muscimol (0.025µg/mouse) significantly restored memory retrieval and induced muscimol SDL. It is important to note that pre-test intra-CA1 injection of a selective GABAA receptor antagonist, bicuculline (0.125 and 0.25µg/mouse), 5min before the administration of muscimol (0.1µg/mouse) or ACPA (2ng/mouse) dose-dependently inhibited muscimol- and ACPA-induced SDL, respectively. Pre-test intra-CA1 administration of bicuculline (0.0625, 0.125 and 0.25µg/mouse) by itself did not affect memory retention. In conclusion, the data strongly revealed a cross SDL among ACPA and muscimol in the dorsal hippocampal CA1 regions.

Tramadol state-dependent memory: involvement of dorsal hippocampal muscarinic acetylcholine receptors.

The effects on tramadol state-dependent memory of bilateral intradorsal hippocampal (intra-CA1) injections of physostigmine, an acetylcholinesterase inhibitor, and atropine, a muscarinic acetylcholine receptor antagonist, were examined in adult male NMRI mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention. Post-training intra-CA1 administration of an atypical µ-opioid receptor agonist, tramadol (0.5 and 1 µg/mouse), dose dependently impaired memory retention. Pretest injection of tramadol (0.5 and 1 µg/mouse, intra-CA1) induced state-dependent retrieval of the memory acquired under the influence of post-training tramadol (1 µg/mouse, intra-CA1). A pretest intra-CA1 injection of physostigmine (1 µg/mouse) reversed the memory impairment induced by post-training administration of tramadol (1 µg/mouse, intra-CA1). Moreover, pretest administration of physostigmine (0.5 and 1 µg/mouse, intra-CA1) with an ineffective dose of tramadol (0.25 µg/mouse, intra-CA1) also significantly restored retrieval. Pretest administration of physostigmine (0.25, 0.5, and 1 µg/mouse, intra-CA1) by itself did not affect memory retention. A pretest intra-CA1 injection of the atropine (1 and 2 µg/mouse) 5 min before the administration of tramadol (1 µg/mouse, intra-CA1) dose dependently inhibited tramadol state-dependent memory. Pretest administration of atropine (0.5, 1, and 2 µg/mouse, intra-CA1) by itself did not affect memory retention. It can be concluded that dorsal hippocampal muscarinic acetylcholine receptor mechanisms play an important role in the modulation of tramadol state-dependent memory.

Pentoxifylline Increases Antiadhesion Effect of Streptokinase on Postoperative Adhesion Formation: Involvement of Fibrinolytic Pathway.

Pentoxifylline reduces peritoneal adhesions and increases peritoneal fibrinolysis in rodents. Furthermore, the activation of the fibrinolytic system by streptokinase leading to degradation of fibrin is effective in the prevention of adhesion formation. We have investigated the effects of pentoxifylline and streptokinase alone and/or coadministration on postoperative intra-abdominal adhesion formation in adult female NMRI mice. Drugs were administered from the day of surgery until 10 days after surgery. At relaparotomy 11 days after surgery, the abdomen was opened, and the adhesions were graded in a blinded fashion utilizing the classification system described. Oral gavage administration of lower doses of pentoxifylline (3.125, 6.25, and 12.5 mg/kg) had no significant effect on postsurgical adhesion formation, while the higher doses of pentoxifylline (25 and 50 mg/kg) significantly decreased postsurgical adhesion formation. Moreover, intraperitoneal injection of lower doses of streptokinase (9.375, 18.75, and 37.5 unit/kg, i.p.) had no significant effect on postsurgical adhesion formation, while the higher doses of streptokinase (75 and 150 unit/kg) significantly decreased postsurgical adhesion formation. In other series of experiments, coadministration of lower doses of pentoxifylline and streptokinase doses, which were ineffective when given alone, significantly decreased postsurgical intra-abdominal adhesion formation compared with streptokinase control group. The results suggest that pentoxifylline may interfere with streptokinase in the reduction of postoperative intra-abdominal adhesion formation by enhancing local fibrinolytic activity.