Methadone's effects on pentylenetetrazole-induced seizure threshold in mice: NMDA/opioid receptors and nitric oxide signaling

Anticonvulsant effects of noscapine against status epilepticus induced by lithium-pilocarpine in rats: involvement of Nrf2/HO-1 and NLRP3 pathways

This study investigates the efficacy of noscapine in mitigating lithium-pilocarpine-induced Status epilepticus (SE) in rats and explores its impact on Nrf2/HO-1/NLRP3 signaling pathways, along with IL-1β and IL-18 modulation. SE was induced in male rats using lithium (127 mg/kg, intraperitoneal (i.p.)) and pilocarpine (60 mg/kg, i.p.). Noscapine (0.1, 1, 3, 10, 30, 100 mg/kg, i.p.) or its vehicle was administered 30 min before the SE induction. Seizure activity was monitored, and the effective dose of noscapine was identified. Western blotting was performed to analyze the expression levels of Nrf2, HO-1, and NLRP3, while ELISA was used to measure IL-1β and IL-18 levels, all in the hippocampus, which is critically involved in epilepsy pathophysiology. Noscapine at 30 mg/kg significantly (p < 0.01) reduced seizure severity and duration. Molecular analysis revealed that noscapine modulated the Nrf2/HO-1/NLRP3 pathway and reduced levels of pro-inflammatory cytokines IL-1β and IL-18 (p < 0.01). Noscapine exhibits potent anticonvulsive effects in a lithium-pilocarpine model of SE in rats, likely mediated through modulation of the Nrf2/HO-1 pathway and the NLRP3 inflammasome pathways. Further studies are warranted to explore its therapeutic potential in epilepsy.

Additive Anticonvulsive Effects of Sumatriptan and Morphine on Pentylenetetrazole-Induced Clonic Seizures in Mice

Background and Purpose

Sumatriptan protects the brain from damage and enhance the anti-seizure effect of morphine. There is evidence that nitric oxide (NO) may mediate these effects of both drugs. In the present study, we investigated the effects of sumatriptan (0.1-20 mg/kg, intraperitoneal [i.p.]) and morphine (0.1-20 mg/kg, i.p.) alone or in combination on seizure thresholds in an in vivo model of seizure in mice. Using various NO synthase inhibitors as well as the NO precursor, we assessed possible involvement of NO signaling in these effects.

Methods

Clonic seizures were induced in male Naval Medical Research Institute mice by intravenous administration of pentylenetetrazol (PTZ).

Results

Acute sumatriptan administration exerted anti-convulsive effects at 0.5 (p<0.01) and 1 mg/kg (p<0.05), but pro-convulsive effects at 20 mg/kg (p<0.05). Morphine had anti-convulsive effects at 0.5 (p<0.05) and 1 mg/kg (p<0.001), but exerted pro-convulsive effect at 20 mg/kg (p<0.05). Combination treatment with sub-effective doses of sumatriptan (0.1 mg/kg) and morphine (0.1 mg/kg) significantly (p<0.05) exerted an anti-convulsive effect. Co-administration of the NO precursor L-arginine (60 mg/kg) with sub-effective doses of sumatriptan and morphine significantly (p<0.05) increased seizure threshold compared with sumatriptan alone, but not sumatriptan+morphine group. While concomitant administration of either the non-selective NO synthase (NOS) inhibitor L-NG-nitroarginine methyl ester (5 mg/kg) or the selective inducible NOS inhibitor aminoguanidine (50 mg/kg) with combined sub-effective doses of morphine and sumatriptan produced significant anticonvulsive effects, concomitant administration with the selective neuronal NOS inhibitor 7-nitroindazole (30 mg/kg) inhibited this effect.

Conclusions

Our data suggest a possible role for the NO signaling in the anticonvulsive effects of combined sumatriptan and morphine on the PTZ-induced clonic seizures in mice.

Bilateral watershed infarcts due to hypoperfusion in the context of drug abuse: case report

BACKGROUND

Watershed infarcts (WIs) are a distinct type of stroke with a varying clinical presentation that affects the border areas between the territories of two cerebral arteries and are typically associated with hemodynamic impairment and internal carotid artery stenosis. However, there is a paucity of data concerning its association with the history of recreational substance and drug abuse.

METHODS/CASE REPORT

This case report presents a unique instance of bilateral internal watershed infarcts in a 23-year-old male with a history of polysubstance abuse, including methadone and cocaine. The patient's presentation included confusion, lower limb weakness, and systemic complications such as acute liver injury and myonecrosis, underlying the complexity of the clinical scenario.

RESULTS

The investigation revealed no evidence of arterial stenosis or thrombosis, leading to the conclusion that the infarctions were likely precipitated by a total loss of consciousness due to substance abuse-related cerebral hypoperfusion and vasoconstriction. Methadone and cocaine, both implicated in vasoconstriction, lowering the seizure threshold and contributing to QTc prolongation, thus leading to loss of consciousness, were identified as potential triggers for the episode.

CONCLUSIONS

In the young adult population, it is important to consider drug abuse as an etiological trigger for watershed infarcts, whereas the multi-system involvement and atypical presentation highlight the need for a comprehensive approach.

Pharmacological evidence for the possible involvement of the NMDA receptor pathway in the anticonvulsant effect of tramadol in mice

Background

Previous studies have shown controversial results regarding the pro- or anticonvulsant effects of tramadol. Additionally, the underlying mechanism of seizure induction or alleviation by tramadol has not been fully understood. In the current study, the effects of tramadol on pentylenetetrazole (PTZ)-induced seizure and the possible involvement of the N-methyl-D-aspartate (NMDA) pathway were assessed in mice.

Methods

Male Naval Medical Research Institute (NMRI) mice were treated with intravenous infusion of PTZ in order to induce clonic seizures and determine seizure threshold. Tramadol was injected intraperitoneally (0.1-150 mg/kg) 30 minutes prior to elicitation of seizures. The possible effects of intraperitoneal injections of NMDA receptor antagonists, ketamine (0.5 mg/kg) and MK-801 (0.5 mg/kg) on the anticonvulsant property of tramadol were investigated subsequently.

Results

Tramadol (1-100 mg/kg) increased PTZ-induced seizure threshold in a dose-dependent, time-independent manner, with optimal anticonvulsant effect at a dose of 100 mg/kg. Acute administration of either ketamine (0.5 mg/kg) or MK-801 (0.5 mg/kg) potentiated the anticonvulsant effect of a subeffective dose of tramadol (0.3 mg/kg).

Conclusion

These results suggest a possible role of the NMDA pathway in the anticonvulsant effect of tramadol.

Influence of methadone on the anticonvulsant efficacy of valproate sodium gabapentin against maximal electroshock seizure in mice by regulation of brain MDA TNF-α

Methadone is the most frequently used opioid therapy worldwide, with controversial effects on oxidative stress homeostasis. This study investigated the effects of intraperitoneal (i.p.) co-administration of methadone (0.1, 0.3, 1, and 3 mg/kg) and valproate sodium (300 mg/kg) or gabapentin (50 mg/kg) in the mice maximal electroshock (MES)-induced seizure model. The adverse effect of drugs was assessed using the chimney test. The levels of tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) contents were measured in mice brains after a single seizure. Administration of methadone alone resulted in a significant reduction in the duration of hind limb extension (HLE) than that in the control group. Methadone pretreatment at doses of 0.1 and 0.3 mg/kg i.p. decreased, and at doses of 1 and 3 mg/kg i.p. had an increasing effect on anticonvulsant efficacy of gabapentin. Pretreatment with all doses of methadone significantly decreased the valproate anticonvulsive efficacy. At doses of 1 and 3 mg/kg i.p. methadone per se increased brain MDA levels after MES-induced seizure. Administration of methadone (0.3 mg/kg i.p.) enhanced and at 3 mg/kg decreased gabapentin effect on brain MDA level, but their co-treatment did not lead to further increase in MDA. Methadone at 0.3–3 mg/kg enhanced the effect of sodium valproate on MDA levels in the brain, but at all doses significantly potentiated its effect on brain TNF-α levels. The drugs did not produce any side effects on motor coordination in experimental animals. In conclusion, methadone showed different effects on anticonvulsant actions of gabapentin and valproate through regulation of brain levels of MDA and TNF-α.

Neuroprotective effect of sumatriptan in pentylenetetrazole-induced seizure is mediated through N-methyl-D-aspartate/nitric oxide and cAMP response element-binding protein signaling pathway

Seizure occurs as a result of uncontrolled electrical disturbances within the brain. Various biomolecules such as N-methyl-D-aspartate (NMDA), nitric oxide (NO), and cAMP response element-binding protein (CREB) have been implicated in the pathophysiology of seizure. Sumatriptan is a specific 5-Hydroxytryptamine 1B/1D receptor agonist and has neuroprotective effects in various neuropsychiatric disorders. In the current study, we tried to investigate the possible interaction of sumatriptan with NMDA/NO and CREB signaling pathway in PTZ induced seizure. For this purpose, various agonist and antagonist of NMDA such as MK-801 and Ketamine, NO precursor L-ARG, and NOS inhibitors L-NAME and 7-NI were co-administered with sumatriptan in PTZ induced seizure model. The level of nitrite in mice hippocampus was determined by Griess reaction. The gene expression of NR1, NR2A, NR2B, and CREB were quantified by quantitative real time-polymerase chain reaction (qRT-PCR). Furthermore, the involved neuronal nitric oxide synthase (nNOS) protein expression was examined via western blot analysis. Effective dose of sumatriptan (1.2 mg/kg) alone and subeffective dose of sumatriptan (0.3 mg/kg) in combination with NMDA and/or NO antagonist showed significant (P < 0.001) anticonvulsant activity in mice. Furthermore, sumatriptan significantly inhibited the PTZ-induced mRNA expression of NR2A (P < 0.0001), NR2B (P < 0.05), and CREB (P < 0.01). Also, the expression of nNOS protein in PTZ treated group was reversed by sumatriptan (P < 0.01). Hence, current findings suggest that the anticonvulsant effect of sumatriptan was due to down regulation of NMDA/NO and CREB signaling pathway.

The opioid antagonist naltrexone decreases seizure-like activity in genetic and chemically induced epilepsy models

OBJECTIVE

A significant number of epileptic patients fail to respond to available anticonvulsive medications. To find new anticonvulsive medications, we evaluated FDA-approved drugs not known to be anticonvulsants. Using zebrafish larvae as an initial model system, we found that the opioid antagonist naltrexone exhibited an anticonvulsant effect. We validated this effect in three other epilepsy models and present naltrexone as a promising anticonvulsive candidate.

METHODS

Candidate anticonvulsant drugs, determined by our prior transcriptomics analysis of hippocampal tissue, were evaluated in a larval zebrafish model of human Dravet syndrome (scn1Lab mutants), in wild-type zebrafish larvae treated with the pro-convulsant drug pentylenetetrazole (PTZ), in wild-type C57bl/6J acute brain slices exposed to PTZ, and in wild-type mice treated with PTZ in vivo. Abnormal locomotion was determined behaviorally in zebrafish and mice and by field potential in neocortex layer IV/V and CA1 stratum pyramidale in the hippocampus.

RESULTS

The opioid antagonist naltrexone decreased abnormal locomotion in the larval zebrafish model of human Dravet syndrome (scn1Lab mutants) and wild-type larvae treated with the pro-convulsant drug PTZ. Naltrexone also decreased seizure-like events in acute brain slices of wild-type mice, and the duration and number of seizures in adult mice injected with PTZ.

SIGNIFICANCE

Our data reveal that naltrexone has anticonvulsive properties and is a candidate drug for seizure treatment.

Effects of Sodium Selenite and Vitamin E on the Development of Morphine Dependency in Mice

Background: Antioxidant drugs may be useful in preventing morphine-induced dependency bysuppressing oxidative stress. Vitamin E which has many essential roles in the body is a powerfulantioxidant. On the other hand, selenium is an essential trace element that plays a strong rolein various biochemical pathways. The aim of this study was to investigate the effects of sodiumselenite and vitamin E on morphine-induced dependency in mice. Methods: Ninety male mice, weighing 20 to 30 g, were randomly divided into 10 groups and weretreated as follows: a) saline and b) morphine groups were pretreated (for 2 days) with normalsaline (10 ml.kg-1.day-1, ip) then daily doses of normal saline (10 ml.kg-1.day-1, ip) and morphine(50 mg.kg-1.day-1) were added to the injections for the following 4 days, respectively. c, d, e)sodium selenite, f, g, h) vitamin E, i) vitamin E solvent (almond oil) and j) co-administrationgroups were pretreated (for 2 days) with sodium selenite (0.25, 0.5, 1 mg.kg-1.day-1, ip), vitaminE (20, 40, 60 IU.kg-1.day-1, ip), vitamin E solvent (10 ml.kg-1.day-1, ip) and combination of thedrugs respectively, then morphine doses (50 mg.kg-1.day-1, ip) were added to the injections forthe following 4 days. Withdrawal symptoms were evaluated after injecting naloxone (4 mg/kg/day). Biochemical evaluations were also performed. Results: The results showed that co-administration of sodium selenite and vitamin E (at lowdoses) significantly reduced morphine dependency (p < 0.05). Conclusion: The synergistic effect of sodium selenite and vitamin E can be a suitable andefficient approach to reduce dependency.

Clinical characteristics and time trends of hospitalized methadone exposures in the United States based on the Toxicology Investigators Consortium (ToxIC) case registry: 2010-2017

Background

Methadone is well known for its long duration of action and propensity for mortality after an overdose. The present research was aimed at evaluating the clinical manifestations and time trends of methadone exposure in patients in US hospitals.

Methods

We queried the American College of Medical Toxicology’s Toxicology Investigators Consortium case registry for all cases of methadone exposure between January 1, 2010, and December 31, 2017. The collected information included demographic features, clinical presentations, therapeutic interventions, poisoning type (acute, chronic, or acute on chronic), and the reason(s) for exposure. Descriptive data and relative frequencies were used to investigate the participants’ characteristics.

Our data analysis was performed using SPSS version 19 and Prism software. The trends and clinical manifestations of methadone poisoning over the time period of the study were specifically investigated.

Results

Nine hundred and seventy-three patients who met our inclusion criteria, with a mean age of 41.9 ± 16.6 years (range: 11 months-78 years) were analyzed. Five hundred eighty-two (60.2%) were male. The highest rate of methadone poisoning was observed in 2013. There was an increasing rate of methadone exposures in 2010–2013, followed by a decline in 2014–2017. The most common clinical manifestations in methadone-poisoned patients were coma (48.6%) and respiratory depression (33.6%). The in-hospital mortality rate of methadone poisoning was 1.4%.

Conclusion

ToxIC Registry data showed that inpatient methadone exposures enhanced from 2010 to 2013, after which a reduction occurred in the years 2014 to 2017.

Acupuncture at Gastric Back-Shu and Front-Mu Acupoints Enhances Gastric Motility via the Inhibition of the Glutamatergic System in the Hippocampus

Acupuncture strongly alleviates gastrointestinal symptoms and especially promotes gastrointestinal motility. However, the mechanism underlying these processes is poorly understood. This study was designed to examine the effect of electroacupuncture (EA) at gastric back-shu (BL21) and front-mu (RN12) acupoints on gastric motility in functional dyspepsia (FD) rats and to investigate the mechanisms of its effects on the glutamatergic system in the hippocampus. We found that EA at RN12 or BL21 enhanced gastric motility in FD rats, whereas EA at the combination of RN12 and BL21 showed an additional effect. Microdialysis combined with HPLC showed that EA reduced the glutamate content in the hippocampus, and the NMDAR-NO-cGMP signalling pathway was downregulated, as determined by Western blot assays, in FD rats. In addition, we found that decreased gastric motility was significantly restored by the hippocampal infusion of an NMDAR, nNOS, or sGC antagonist. Interestingly, EA had no further effects on gastric motility in the presence of these antagonists in FD rats. Taken together, these results suggest that the hippocampal glutamatergic system is involved in the regulation of gastric motility by EA at RN12 and BL21.

Nitric oxide and glutamate are contributors of anti-seizure activity of rubidium chloride: A comparison with lithium

The neuro-protective effects of rubidium and lithium as alkali metals have been reported for different central nervous system dysfunctions including mania and depression. The aim of this study was evaluating as well as comparing the effects of rubidium chloride (RbCl) and lithium chloride (LiCl) on different seizures paradigms in mice and determining the involvement of NMDA receptors and nitrergic pathway. To assess the seizures threshold, animals received intravenous pentylenetetrazole (PTZ, 0.5%; 1 mL/min). Male NMRI mice (6-8 weeks) received intraperitoneal (i.p.) injections of different doses of RbCl and LiCl. Doses greater than 10 mg/kg of RbCl showed a significant anticonvulsant activity 60 min after administration; the anticonvulsant effects of LiCl was observed at the doses more than 5 mg/kg and after 30 min in PTZ-induced seizure threshold. But, RbCl (10, 20 mg/kg, i.p) or LiCl (5, 10 mg/kg, i.p) injection did not induce protection against maximal electroshock (MES) or intraperitoneal injection of PTZ lethal dose (80 mg/kg)-induced seizure models. Pre-treatment with L-NAME (non-selective nitric oxide synthase (NOS) inhibitor, 10 mg/kg; i.p.) and 7-nitroindazole (selective neuronal NOS inhibitor, 30 mg/kg; i.p.) enhanced the anticonvulsive effects of both RbCl (5 mg/kg, i.p.) and LiCl (1 mg/kg, i.p.) in PTZ-induced seizure threshold model. Injection of MK-801 (NMDA receptor antagonist, 0.05 mg/kg; i.p.) before RbCl (5 mg/kg, i.p.; P < 0.001) and LiCl (1 mg/kg, i.p.; P < 0.001) administration increased the anti-seizure activity. But, treatment with L-arginine (precursor of nitric oxide, 100 mg/kg; i.p.) decreased the seizure threshold of both RbCl (20 mg/kg, i.p.; P < 0.001) and LiCl (10 mg/kg, i.p.; P < 0.001). Measurement of nitrite levels in hippocampus of animals revealed a remarkable reduction after treatment with RbCl (20 mg/kg, i.p; P < 0.05) and LiCl (10 mg/kg, i.p; P < 0.01). To conclude, rubidium may protect central nervous system against seizures in PTZ-induced seizures threshold model through NMDA/nitrergic pathways with a similarity to lithium effects in mice.