Prescription psychostimulants for the treatment of amphetamine-type stimulant use disorder: A systematic review and meta-analysis of randomized placebo-controlled trials.

BACKGROUND AND AIMS: There is currently no standard of care for pharmacological treatment of amphetamine-type stimulant (ATS) use disorder (ATSUD). This systematic review with meta-analysis (PROSPERO CRD42022354492) aimed to pool results from randomized placebo-controlled trials (RCTs) to evaluate efficacy and safety of prescription psychostimulants (PPs) for ATSUD. METHODS: Major indexing sources and trial registries were searched to include records published before 29 August 2022. Eligible studies were RCTs evaluating efficacy and safety of PPs for ATSUD. Risk of bias (RoB) was assessed using the Cochrane RoB 2 tool. Risk ratio (RR) and risk difference were calculated for random-effect meta-analysis of dichotomous variables. Mean difference and standardized mean difference (SMD) were calculated for random-effect meta-analysis of continuous variables. RESULTS: Ten RCTs (n = 561 participants) were included in the meta-analysis. Trials studied methylphenidate (n = 7), with daily doses of 54-180 mg, and dextroamphetamine (n = 3), with daily doses of 60-110 mg, for 2-24 weeks. PPs significantly decreased end-point craving [SMD  -0.29; 95% confidence interval (CI) = -0.55, -0.03], while such a decrease did not reach statistical significance for ATS use, as evaluated by urine analysis (UA) (RR = 0.93; 95% CI = 0.85-1.01). No effect was observed for self-reported ATS use, retention in treatment, dropout following adverse events, early-stage craving, withdrawal and depressive symptoms. In a sensitivity analysis, treatment was associated with a significant reduction in UA positive for ATS (RR = 0.89; 95% CI = 0.79-0.99) after removing studies with a high risk of bias. In subgroup analyses, methylphenidate and high doses of PPs were negatively associated with ATS use by UA, while higher doses of PPs and treatment duration (≥ 20 weeks) were positively associated with longer retention. CONCLUSIONS: Among individuals with amphetamine-type stimulant use disorder, treatment with prescription psychostimulants may decrease ATS use and craving. While effect size is limited, it may increase with a higher dosage of medications.

Bupropion for treatment of amphetamine-type stimulant use disorder: A systematic review and meta-analysis of placebo-controlled randomized clinical trials.

BACKGROUND: This meta-analysis (PROSPERO-ID: CRD42022362962), pooled effect estimates of outcomes, from placebo-controlled randomized clinical trials (RCTs) examining bupropion efficacy and safety for amphetamine-type stimulant use disorder (ATSUD) treatment. METHOD: Electronic databases were searched for records published to October 31st, 2022, including MEDLINE, CINAHL, PsycINFO, EBM Reviews, EMBASE, PubMed, Web of Science, trial registries. Inclusion criteria were RCTs comparing bupropion to placebo in ATSUD. Cochrane RoB2 tool and GRADE evidence certainty assessment were employed. Outcomes included amphetamine-type stimulant (ATS) use by urinalysis, retention in treatment, treatment adherence, ATS craving, addiction severity, depressive symptom severity, drop-out following adverse events (AEs), and serious AEs. Random-effect meta-analysis was conducted presenting standardized mean difference (SMD), risk ratio (RR), and risk difference (RD). RESULTS: Eight RCTs (total N=1239 participants) were included. Bupropion compared to placebo was associated with reduced ATS use (RR: 0.90; 95% CI: 0.84, 0.96), end-of-treatment ATS craving (SMD: -0.38; 95%CI: -0.63, -0.13), and adherence (RR: 0.91; 95%CI: 0.84, 0.99). Subgroup analysis showed greater reduction in ATS use with longer trial duration (12 weeks) (RR: 0.85; 95%CI: 0.78, 0.93) and greater reduction in end-of-treatment ATS craving in studies with mixed ATS use frequency (SMD: -0.46; 95%CI: -0.70, -0.22) and male-only samples (SMD: -1.26; 95%CI: -1.87, -0.65). CONCLUSION: Bupropion showed a significant modest reduction in ATS use and ATS craving (both rated as very low-quality evidence), larger in males (craving), and with longer treatment (ATS use). These results may inform future studies. More research is warranted on who might benefit from bupropion as ATSUD treatment.

Evaluating preferences for online psychological interventions to decrease cannabis use in young adults with psychosis: An observational study.

Innovative technology-based solutions have the potential to improve access to clinically proven interventions for cannabis use disorder (CUD) in individuals with first episode psychosis (FEP). High patient engagement with app-based interventions is critical for achieving optimal outcomes. 104 individuals 18 to 35 years old with FEP and CUD from three Canadian provinces completed an electronic survey to evaluate preferences for online psychological intervention intensity, participation autonomy, feedback related to cannabis use, and technology platforms and app functionalities. The development of the questionnaire was informed by a qualitative study that included patients and clinicians. We used Best-Worst Scaling (BWS) and item ranking methodologies to measure preferences. Conditional logistic regression models for BWS data revealed high preferences for moderate intervention intensity (e.g., modules with a length of 15 min) and treatment autonomy that included preferences for using technology-based interventions and receiving feedback related to cannabis use once a week. Luce regression models for rank items revealed high preferences for smartphone-based apps, video intervention components, and having access to synchronous communications with clinicians and gamification elements. Results informed the development of iCanChange (iCC), a smartphone-based intervention for the treatment of CUD in individuals with FEP that is undergoing clinical testing.

Depression and Outcomes of Methadone and Buprenorphine Treatment Among People with Opioid Use Disorders: A Literature Review.

Objective: Depression is the most common psychiatric comorbidity among people with opioid use disorders (OUDs). However, whether and how comorbid depression is associated with the outcomes of opioid agonist therapy (OAT) remains poorly understood. The objective of this review was to identify and describe the association between depression and main outcomes (opioid use and treatment retention) of methadone and buprenorphine treatment among people with OUDs. Methods: A literature review was conducted by searching five electronic databases (MEDLINE, PubMed, Embase, Evidence-Based Medicine Reviews [EBMR], and Cumulative Index of Nursing and Allied Health Literature [CINAHL] Complete) from January 1970 to April 2019. Two independent reviewers screened titles and abstracts of the identified records by using pre-established eligibility criteria. Next, full texts were reviewed and studies that met inclusion criteria were selected. Finally, a descriptive synthesis of extracted data was performed. Results: In total, 12,296 records were identified and 18 studies that met inclusion criteria were retained. Of these, six studies reported reduced opioid use and seven reported increased opioid use during methadone or buprenorphine treatment. In addition, three studies reported an increased retention rate and four documented a decreased retention rate during methadone or buprenorphine treatment. The remaining studies did not find any significant association between depression and opioid use or treatment retention. Overall, the evidence did not demonstrate a consistent association between depression and outcomes of methadone or buprenorphine treatment. Conclusions: Although the inconsistent nature of the current evidence prohibited us from drawing definitive conclusions, we posit that the presence of depression among OUDs patients may not always predict negative outcomes related to retention and drug use during the course of OAT. Particularly, the hypothesis that adequate treatment of depression can improve treatment retention is promising and is in line with the call for increased efforts to provide integrated care for comorbid mental health disorders and addiction. Future studies with rigorous methodology are essential to better characterize the complex interplay between depression, OAT, and OUDs.

Mental Illnesses-Associated Fxr1 and Its Negative Regulator Gsk3ß Are Modulators of Anxiety and Glutamatergic Neurotransmission.

Genetic variants of the fragile X mental retardation syndrome-related protein 1 (FXR1) have been associated to mood regulation, schizophrenia, and bipolar disorders. Nonetheless, genetic association does not indicate a functional link of a given gene to neuronal activity and associated behaviors. In addition, interaction between multiple genes is often needed to sculpt complex traits such as behavior. Thus, modulation of neuronal functions by a given gene product, such as Fxr1, has to be thoroughly studied in the context of its interactions with other gene products. Glycogen synthase kinase-3 beta (GSK3ß) is a shared target of several psychoactive drugs. In addition, interaction between functional polymorphisms of GSK3b and FXR1 has been implicated in mood regulation in healthy subjects and bipolar patients. However, the mechanistic underpinnings of this interaction remain unknown. We used somatic CRISPR/Cas9 mediated knockout and overexpression to investigate the impact of Fxr1 and its regulator Gsk3ß on neuronal functions directly in the adult mouse brain. Suppression of Gsk3ß or increase of Fxr1 expression in medial prefrontal cortex neurons leads to anxiolytic-like responses associated with a decrease in AMPA mediated excitatory postsynaptic currents. Furthermore, Fxr1 and Gsk3ß modulate glutamatergic neurotransmission via regulation of AMPA receptor subunits GluA1 and GluA2 as well as vesicular glutamate transporter VGlut1. These results underscore a potential mechanism underlying the action of Fxr1 on neuronal activity and behaviors. Association between the Gsk3ß-Fxr1 pathway and glutamatergic signaling also suggests how it may contribute to emotional regulation in response to mood stabilizers, or in illnesses like mood disorders and schizophrenia.

A COX/5-LOX Inhibitor Licofelone Revealed Anticonvulsant Properties Through iNOS Diminution in Mice.

Licofelone is a COX/5-LOX inhibitor, which recently was approved as an effective treatment for osteoarthritis. Beside its analgesic and anti-inflammatory effects, some reports show neuro-protective properties for this agent in central nervous system. Several lines of evidence declare the involvement of COX or LOX isoenzymes in epileptic disorders. To set the foundation for future research into the neurobiology of licofelone as a potential therapeutic agent, we studied the effect of licofelone in an animal model of epilepsy. Although different neurotransmitters and neuro-modulators like nitric oxide were introduced as suggested targets of licofelone, the underlying mechanisms of central effects of this drug are not still fully understood. We have utilized pentylenetetrazole-induced clonic seizure model to investigate the behavioral consequences of licofelone administration and its possible mechanisms in seizure susceptibility. Licofelone revealed anticonvulsant properties at the dose of 10 mg/kg (i.p) or higher in mice. Pre-treatment with NO (nitric oxide) donor, L-arginine, reversed this anticonvulsant effects dose dependently. L-NAME, as a non-selective nitric oxide synthase (NOS) inhibitor, potentiated the anticonvulsant effects of licofelone. A neuronal NOS inhibitor, 7-NI did not affect seizure threshold alone or in combination with licofelone. Using non-effective doses of selective inhibitors of inducible NOS, aminoguanidine or 1400W, significantly increased the seizure threshold when were accompanied by licofelone in low doses. These data support the involvement of NO as an important role player in the central neuro-protective properties of licofelone. Furthermore, it implies that down regulation of iNOS seems crucial for anticonvulsant properties of this COX/5-LOX inhibitor in seizure susceptibility.

Protective effects of lithium chloride on seizure susceptibility: Involvement of α2-adrenoceptor.

For more than 60years, lithium has been the mainstay in the treatment of mental disorders as a mood stabilizer. In addition to the antimanic and antidepressant responses, lithium also shows some anticonvulsant properties. In spite of the ascertained neuroprotective effects of this alkali metal, the underlying mechanisms through which lithium regulates behavior are still poorly understood. Among different targets, some authors suggest neuromodulatory effects of lithium are the consequences of interaction of this agent with the brain neurotransmitters including adrenergic system. In order to study the involvement of α2-adrenergic system in anticonvulsant effect of lithium, we used a model of clonic seizure induced by pentylenetetrazole (PTZ) in male NMRI mice. Injection of a single effective dose of lithium chloride (30mg/kg, i.p.) significantly increased the seizure threshold (p<0.01). The anticonvulsant effect of an effective dose of lithium was prevented by pre-treatment with low and per se non-effective dose of clonidine [α2-adrenoceptor agonist] (0.05, 0.1 and 0.25mg/kg). On the other hand, yohimbine [α2-adrenoceptor antagonist] augmented the anticonvulsant effect of sub-effective dose of lithium (10mg/kgi.p.) at relatively low doses (0.1, 0.5, 1 and 2.5mg/kg). Moreover, UK14304 [a potent and selective α2-adrenoceptor agonist] (0.05 and 0.1mg/kg) and RX821008 [a potent and selective α2D-adrenoceptor antagonist] (0.05, 0.1 and 0.25mg/kg) repeated the same results confirming that these modulatory effects are conducted specifically through the α2D-adrenoceptors. In summary, our findings demonstrated that α2-adrenoceptor pathway could be involved in the anticonvulsant properties of lithium chloride in the model of chemically induced clonic seizure.

Effect of biliary cirrhosis on neurogenic relaxation of rat gastric fundus and anococcygeus muscle: role of nitric oxide pathway.

BACKGROUND: Cirrhosis, associated with a host of hemodynamic abnormalities, could affect the gastrointestinal (GI) tract motility. On the other hand, the nonadrenergic noncholinergic (NANC) neurotransmission has been shown to play a pivotal role in GI tract motility and has been linked with release of nitric oxide (NO) on electrical stimulation. In this study, we investigated the effect of biliary cirrhosis on the neurogenic relaxation of rat gastric fundus and anococcygeus muscle and also the possible role of nitric oxide system in this manner. METHODS: Isolated gastric fundus and anococcygeus strips of sham-operated and biliary cirrhotic (4 weeks after bile duct ligation) rats were mounted under tension in a standard organ bath. Electrical stimulation was applied to obtain NANC-mediated relaxations in precontracted gastric fundus and anococcygeus muscle. The neurogenic relaxations were examined in the presence of different doses of NO synthase inhibitor, N (w)-Nitro-L-Arginine Methyl Ester (L-NAME). The concentration-dependent relaxant responses to the NO donor sodium nitroprusside were also evaluated. RESULTS: The neurogenic relaxation of both gastric fundus and anococcygeus muscle was significantly (P < 0.001) increased in cirrhotic animals. L-NAME (0.03-1,000 µM) inhibited relaxations in both groups in a dose-dependent manner (P < 0.001), but cirrhotic groups were more resistant to the inhibitory effects of L-NAME (P < 0.01). Sodium nitroprusside-mediated relaxations were similar in two groups. CONCLUSIONS: This study for the first time demonstrated that cirrhosis increases the NO-mediated neurogenic relaxation of both rat gastric fundus and anococcygeus muscle, suggesting a crucial role for the neurogenic NO in the pathophysiology of disturbed GI motility in cirrhosis.

Nitric oxide mediates the anticonvulsant effects of thalidomide on pentylenetetrazole-induced clonic seizures in mice.

Thalidomide is an old glutamic acid derivative which was initially used as a sedative medication but withdrawn from the market due to the high incidence of teratogenicity. Recently, it has reemerged because of its potential for counteracting number of diseases, including neurodegenerative disorders. Other than the antiemetic and hypnotic aspects, thalidomide exerts some anticonvulsant properties in experimental settings. However, the underlying mechanisms of thalidomide actions are not fully realized yet. Some investigations revealed that thalidomide could elicit immunomodulatory or neuromodulatory properties by affecting different targets, including cytokines (such as TNF α), neurotransmitters, and nitric oxide (NO). In this regard, we used a model of clonic seizure induced by pentylenetetrazole (PTZ) in male NMRI mice to investigate whether the anticonvulsant effect of thalidomide is affected through modulation of the l-arginine-nitric oxide pathway or not. Injection of a single effective dose of thalidomide (10 mg/kg, i.p. or higher) significantly increased the seizure threshold (P<0.05). On the one hand, pretreatment with low and per se noneffective dose of l-arginine [NO precursor] (10, 30 and 60 mg/kg) prevented the anticonvulsant effect of thalidomide. On the other hand, NOS inhibitors [l-NAME and 7-NI] augmented the anticonvulsant effect of a subeffective dose of thalidomide (1 and 5 mg/kg, i.p.) at relatively low doses. Meanwhile, several doses of aminoguanidine [an inducible NOS inhibitor] (20, 50 and 100 mg/kg) failed to alter the anticonvulsant effect of thalidomide significantly. In summary, our findings demonstrated that the l-arginine-nitric oxide pathway can be involved in the anticonvulsant properties of thalidomide, and the role of constitutive nNOS is prominent in the reported neuroprotective feature.

Role of nitric oxide in additive anticonvulsant effects of agmatine and morphine.

The anticonvulsant effects of agmatine, an endogenous polyamine and a metabolite of l-arginine, have been shown in various experimental seizure models. Agmatine also potentiates the anti-seizure activity of morphine. The present study aimed to investigate a possible involvement of nitric oxide (NO) pathway in the protection by agmatine and morphine co-administration against pentylenetetrazole (PTZ) -induced seizure in male mice. To this end, the thresholds for the clonic seizures induced by the intravenous administration of PTZ, a GABA antagonist, were assessed. Intraperitoneal administration of morphine at lower dose (1mg/kg) increased the seizure threshold. Also intraperitoneal administration of agmatine (5 and 10mg/kg) increased the seizure threshold significantly. Combination of subeffective doses of morphine and agmatine led to potent anticonvulsant effects. Non-effective doses of morphine (0.1 and 0.5mg/kg) were able to induce anticonvulsant effects in mice pretreated with agmatine (3mg/kg). Concomitant administration of either the non-selective nitric oxide synthase (NOS) inhibitor L-NAME (1, 5mg/kg, i.p.) or the selective NOS inhibitor 7-NI (15, 30mg/kg, i.p.), with an ineffective combination of morphine (0.1mg/kg) plus agmatine (1mg/kg) produced significant anticonvulsant impacts. Moreover, the NO precursor, l-arginine (30, 60mg/kg, i.p.), inhibited the anticonvulsant action of agmatine (3mg/kg) plus morphine (0.5mg/kg) co-administration. Our results indicate that pretreatment of animals with agmatine enhances the anticonvulsant effects of morphine via a mechanism which may involve the NO pathway.

Quercetin prevents experimental glucocorticoid-induced osteoporosis: a comparative study with alendronate.

Glucocorticoid-induced osteoporosis (GIO) is the most common type of secondary osteoporosis. The aim of this study was to compare the efficacy of quercetin, a plant-derived flavonoid, with alendronate in the prevention of GIO. Fifty-six Sprague-Dawley rats were randomly distributed among 7 groups (8 rats per group) and treated for 6 weeks with one of the following: (i) normal saline; (ii) 40 mg methylprednisolone sodium succinate (MP)/kg body mass; (iii) MP + 40 µg alendronate/kg; (iv) MP + 50 mg quercetin/kg; (v) MP + 40 µg alendronate/kg + 50 mg quercetin/kg; (vi) MP + 150 mg quercetin/kg; and (vii) MP + 40 µg alendronate/kg + 150 mg quercetin/kg. MP and alendronate were injected subcutaneously and quercetin was administered by oral gavage 3 days a week. At the end of the study, femur breaking strength was significantly decreased as a consequence of MP injection. This decrease was completely compensated for in groups receiving 50 mg quercetin/kg plus alendronate, and 150 mg quercetin/kg with or without alendronate. Quercetin noticeably elevated osteocalcin as a bone formation marker, while alendronate did not show such an effect. In addition, administration of 150 mg quercetin/kg increased femoral trabecular and cortical thickness by 36% and 22%, respectively, compared with the MP-treated group. These data suggest that 150 mg quercetin/kg, alone or in combination with alendronate, can completely prevent GIO through its bone formation stimulatory effect.

Quercetin improves bone strength in experimental biliary cirrhosis.

AIM: Metabolic bone disorders and reduced bone mass are common complications in patients with biliary cirrhosis. As a result of there being no clear etiology, no specific therapy has been established yet. Previous studies have reported that quercetin, a plant-derived flavonoid, might improve bone quality. The present study was designed to investigate the effect of quercetin on bone strength of biliary cirrhotic rats. METHODS: Twenty-four male Sprague-Dawley rats aged 6-7 months were randomized into three groups of eight. One group served as control (sham operated), while the other two groups underwent a complete bile duct ligation (BDL). Four weeks after the operation, serum bilirubin, alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase were measured in animal blood samples to confirm the occurrence of cirrhosis in the BDL rats. Then, one of the BDL groups received placebo and the other one was injected once a day with 150 µmol/kg of quercetin for 4 weeks. At the end of the study, femora were removed and tested for bone strength and histomorphometric parameters. The serum levels of osteocalcin, C-terminal cross-linked telopeptide of type I collagen, calcium and phosphorus were determined as bone turnover markers. RESULTS: Femur breaking strength was dramatically lower in the BDL group compared with control. However, receiving quercetin could reverse the deteriorating effect of cirrhosis on bone strength of BDL rats. Quercetin could noticeably elevate osteocalcin as a bone formation marker. CONCLUSION: These data suggest that quercetin can significantly improve bone strength particularly due to increasing bone formation in biliary cirrhosis.

5-HT(3) receptor mediates the dose-dependent effects of citalopram on pentylenetetrazole-induced clonic seizure in mice: involvement of nitric oxide.

Citalopram is a selective serotonin reuptake inhibitor (SSRI), widely used in the treatment of depressive disorders. It has been shown that citalopram affects seizure susceptibility. Although the exact mechanism of these effects are not yet fully understood, recent data suggest that 5HT(3) receptors and nitric oxide (NO) might participate in the central effects of SSRIs. In this study in a mouse model of clonic seizure induced by pentylenetetrazole we investigated whether 5-HT(3) receptors are involved in the effects of citalopram on seizure threshold. In our experiments, citalopram at lower doses (0.5 and 1mg/kg, i.p) significantly increased the seizure threshold and at higher doses (≥25mg/kg) showed proconvulsive effects. Moreover, mCPBG (a 5-HT(3) receptor agonist) at low and non-effective doses augmented while non-effective doses of tropisetron prevented the anticonvulsive properties of citalopram. On the other hand, Low doses of nitric oxide synthase inhibitors l-NAME and 7-NI alone or in combination with lower doses of 5-HT(3) receptor agonist enhanced the anticonvulsive property of citalopram, while l-arginine (NO precursor) alone or in combination with tropisetron blocked the protective effect of citalopram. In summary, our findings demonstrate that 5-HT(3) receptor mediates the anticonvulsant properties of low doses of citalopram, whereas it seems that the proconvulsive effect is mostly mediated through the NO pathway and can be totally blocked by NOS inhibitors. This could propose a new approach toward finding the mechanism of citalopram activity, curtailing the adverse effects of citalopram and perhaps managing the convulsions as a vicious consequence of citalopram overdose.

Sildenafil attenuates TNBS-induced colitis in rats: possible involvement of cGMP and KATP channels.

The involvement of cGMP/KATP pathway in effects of sildenafil on experimental colitis was investigated. Sildenafil significantly attenuated colonic injury markers. These effects were reversed by the addition of glibenclamide or ODQ, indicating the involvement of ATP-sensitive potassium channels (KATP) and cGMP, respectively.

Additive anticonvulsant effects of agmatine and lithium chloride on pentylenetetrazole-induced clonic seizure in mice: involvement of α2-adrenoceptor.

After 60 years, lithium is still the mainstay in the treatment of mood disorders and widely used in clinic. In addition to its mood stabilizer effects, lithium also shows some anticonvulsant properties. Similar to lithium, agmatine also plays a protective role in the CNS against seizures and has been reported to enhance the effect of different antiepileptic agents. Moreover, both agmatine and lithium have modulatory effects on α(2)-adrenoceptors. So, we designed this study: 1) to investigate whether agmatine and lithium show an additive effect against clonic seizures induced by pentylenetetrazole; 2) to assess whether this additive effect is mediated through the α(2)-adrenoceptor or not. In our study, acute administration of a single effective dose of lithium chloride (30 mg/kg, i.p.) increased the seizure threshold. Pre-treatment with low and, per se, non-effective doses of agmatine (1 and 3mg/kg) potentiated a sub-effective dose of lithium (10mg/kg). Interestingly, the anticonvulsant effects of these effective combinations of lithium and agmatine were prevented by pre-treatment with low and non-effective doses of yohimbine [α(2)-adrenoceptor antagonist] (0.1 and 0.5mg/kg). On the other hand, clonidine [α(2)-adrenoceptor agonist] augmented the anticonvulsant effect of a sub-effective combination of lithium (5mg/kg i.p.) and agmatine (1mg/kg) at relatively low doses (0.1 and 0.25mg/kg). In summary, our findings demonstrate that agmatine and lithium chloride exhibit additive anticonvulsant properties which seem to be mediated through α(2)-adrenoceptor.

The role of 5-HT(3) receptors in the additive anticonvulsant effects of citalopram and morphine on pentylenetetrazole-induced clonic seizures in mice.

Citalopram, a selective serotonin reuptake inhibitor (SSRI), is frequently used in the treatment of major depressive disorders. In addition to its antidepressant features, citalopram shows some anticonvulsive properties at lower doses, whereas higher doses, ingested in cases of suicide, have been associated with seizures. Moreover, some reports support the enhancing effect of morphine on different responses of SSRIs such as analgesic and anticonvulsant properties. Although the exact mechanisms of these additive effects are not yet fully understood, 5-HT(3) receptor has recently been shown to play an important role in the central effects of SSRIs and morphine. In this regard, we used a model of clonic seizures induced by pentylenetetrazole (PTZ) in male NMRI mice to investigate whether morphine and citalopram exhibit additive anticonvulsant effects and, if so, whether this effect is mediated through modulation of 5-HT(3) receptors. In our study, citalopram at lower doses (0.5 and 1 mg/kg, ip) significantly increased the seizure threshold (P<0.01) and at a higher dose (50 mg/kg) had proconvulsive effects. Moreover, morphine at low and noneffective doses had additive effects on the anticonvulsive properties of citalopram. This additive effect was prevented by pretreatment with low and noneffective doses of tropisetron (a 5-HT(3) receptor antagonist) and augmented by 1-(m-chlorophenyl)-biguanide (mCPBG, a 5-HT(3) receptor agonist). Moreover, low doses of morphine (0.1 and 0.5 mg/kg) alone or in combination with potent doses of 5-HT(3) receptor agonist or antagonist could not alter the proconvulsive properties of citalopram at higher dose (50 mg/kg), ruling out the contribution of 5-HT(3) to this effect. In summary, our findings demonstrate that 5-HT(3) receptor mediates the additive anticonvulsant properties of morphine and low-dose citalopram. This could constitute a new approach to augmenting the efficacy and curtailing the adverse effects of citalopram.

A role for opioid system in the proconvulsant effects of sildenafil on the pentylenetetrazole-induced clonic seizure in mice.

There are several lines of evidence that opioidergic and nitrergic systems could modulate the seizure threshold. We previously have shown that sildenafil had proconvulsant effects in a model of clonic seizure induced by pentylenetetrazole (PTZ) or bicuculline. In the present study, we examined whether the opioid system participates in the action of sildenafil on the PTZ-induced clonic seizures in mice. Sildenafil (1, 5, 10 and 20 mg/kg, i.p.) significantly decreased the seizure threshold in a dose-dependent manner, whereas morphine had both anticonvulsant and proconvulsant effects at low (0.5, 1, and 3 mg/kg, s.c.) and high (60 mg/kg, s.c.) doses. A sub-effective dose of sildenafil (5 mg/kg) combined with a dose of morphine (7.5 mg/kg) which was sub-effective for its proconvulsant effects significantly decreased the seizure threshold. Although naltrexone at 0.5 and 1 mg/kg had no effect on the seizure threshold, it significantly prevented both the proconvulsant effects of sildenafil as well as the anticonvulsant and proconvulsant effects of morphine on the PTZ-induced seizure thresholds. Our data suggested a role for opioidergic system in the proconvulsant effects of sildenafil on the PTZ-induced clonic seizures in mice.

Administration of lithium and magnesium chloride inhibited tolerance to the anticonvulsant effect of morphine on pentylenetetrazole-induced seizures in mice.

Although morphine has an anticonvulsant effect in several animal models of seizures, its potential clinical application in epilepsy may be hindered by its adverse effects like opioid tolerance. The present study evaluated the development of tolerance to the anticonvulsant effect of morphine in a model of clonic seizures induced with pentylenetetrazole (PTZ) in male Swiss mice. We also examined whether administration of either lithium chloride (LiCl) or magnesium chloride (MgCl(2)) was able to prevent the probable tolerance. Our data demonstrated that the anticonvulsant effect of a potent dose of morphine (1mg/kg) was abolished in chronic morphine-treated mice (mice administered the same dose of morphine intraperitoneally twice daily for 4 days). Four days of pretreatment with low and noneffective doses of MgCl(2) (2 and 5mg/kg) and LiCl (5mg/kg) inhibited the development of tolerance to the anticonvulsant effect of morphine (1mg/kg, ip). Moreover, a single acute injection of the aforementioned agents at the same doses reversed the expression of tolerance to the anticonvulsant effects of morphine (1mg/kg, ip). Chronic 17-day treatment with LiCl (600 mg/L in drinking water) also inhibited the development of tolerance to the anticonvulsant effects of 1mg/kg morphine. These results demonstrate that the anticonvulsant effect of morphine is subject to tolerance after repeated administration. Both development and expression of tolerance are inhibited by either LiCl or MgCl(2). As both LiCl and MgCl(2) can modulate the function of N-methyl-d-aspartate (NMDA) receptors, we discuss how NMDA receptor functioning might be involved in the effects of LiCl and MgCl(2) on the development of tolerance to the anticonvulsant effect of morphine.

Adenosine A2A receptors and uric acid mediate protective effects of inosine against TNBS-induced colitis in rats.

Inflammatory bowel disease comprises chronic recurrent inflammation of gastrointestinal tract. This study was conducted to investigate inosine, a potent immunomodulator, in 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced chronic model of experimental colitis, and contribution of adenosine A(2A) receptors and the metabolite uric acid as possible underlying mechanisms. Experimental colitis was rendered in rats by a single colonic administration of 10 mg of TNBS. Inosine, potassium oxonate (a hepatic uricase inhibitor), SCH-442416 (a selective adenosine A(2A) receptor antagonist), inosine+potassium oxonate, or inosine+SCH-442416 were given twice daily for 7 successive days. At the end of experiment, macroscopic and histopathologic scores, colonic malondialdehyde (MDA), Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-1beta (IL-1ß) levels, and myeloperoxidase (MPO) activity were assessed. Plasma uric acid level was measured throughout the experiment. Both macroscopic and histological features of colonic injury were markedly ameliorated by either inosine, oxonate or inosine+oxonate. Likewise, the elevated amounts of MPO and MDA abated as well as those of TNF-α and IL-1ß (P<0.05). SCH-442416 partially reversed the effect of inosine on theses markers, while inosine+oxonate showed a higher degree of protection than each treatment alone (P<.0.05). No significant difference was observed between TNBS and SCH-442416 groups. Uric acid levels were significantly higher in inosine or oxonate groups compared to control. Inosine+oxonate resulted in an even more elvelated uric acid level than each treatment alone (P<0.05). Inosine elicits notable anti-inflammatory effects on TNBS-induced colitis in rats. Uric acid and adenosine A(2A) receptors contribute to these salutary properties.

Inhibition of NMDA receptor/NO signaling blocked tolerance to the anticonvulsant effect of morphine on pentylenetetrazole-induced seizures in mice.

Although morphine has anticonvulsant effect in several animal models of seizure, its potential clinical application in epilepsy may be hindered by its adverse effects like the phenomenon of opioid tolerance. The present study evaluated the development of tolerance to the anticonvulsant effect of morphine in a model of clonic seizure induced by pentylenetetrazole (PTZ) in male Swiss mice. We also examined whether N-methyl-d-aspartate (NMDA) receptor/nitrergic system blockage was able to prevent the probable tolerance. Our data demonstrated that anticonvulsant effects of a potent dose of morphine (1mg/kg) was abolished in chronic morphine-treated mice (with the same dose of morphine twice daily, 4 days, i.p.). Chronic pretreatment with low and non-effective doses of different NMDA antagonists ifenprodil (0.5mg/kg), MK-801 (0.05mg/kg) and ketamine (0.5mg/kg) as well as the non-selective nitric oxide (NO) synthase inhibitor l-NAME (2mg/kg) inhibited the development of tolerance to the anticonvulsant effect of morphine (1mg/kg). Moreover, a single acute injection of the above mentioned agents at the same doses reversed the expression of tolerance to the anticonvulsant effects of morphine (1mg/kg). These results demonstrate that anticonvulsant effect of morphine can be subject to tolerance after repeated administration. Both development and expression of tolerance are inhibited by NMDA receptor/nitrergic system blockage, suggesting a role for NMDA receptor/NO signaling in the development of tolerance to the anticonvulsant effect of morphine.