The atypical antidepressant mirtazapine attenuates expression of morphine-induced place preference and motor sensitization

Modulation of morphine antinociceptive and rewarding effect by mirtazapine in an animal model of osteoarthritic pain

People with chronic pain mitigate their suffering by the action of opioids. Adverse reactions aside, opioids are not exempt from potential complications like addiction and abuse, which have posed a global public health problem lately. Finding new therapeutic strategies to improve analgesia and to reduce opioid side effects has become a priority. In this regard, the association of different adjuvant therapies has been postulated. Despite preclinical and clinical evidence supporting the use of antidepressants as analgesics, it is not clear whether they could help reduce the risk of addiction in combination with opioids. To further explore this idea a model of chronic osteoarthritis pain was employed, and a combination of mirtazapine and morphine was used in a chronic regimen in male and female rats. The effects on the development of tactile allodynia, movement-evoked pain, reward, analgesic tolerance, naloxone-induced withdrawal symptoms, impaired locomotor activity and anxiety were evaluated under a 25-day experimental protocol. Additionally, protein expression of μ-opioid receptors and clusterin (related with substance abuse) was evaluated in plasma and in brain structures of the reward system. Chronic morphine caused analgesic tolerance, reward and naloxone-induced withdrawal symptoms. The combination reduced the analgesic tolerance and prevented the development of withdrawal symptoms but showed sex-based differences regarding reward. Increased levels of clusterin in plasma were observed in females treated with morphine, but not with combined therapy. The combination of mirtazapine and morphine could be a promising strategy to improve the management of long-term opioid treatment and its risk of abuse, especially in females.

IUPHAR review - Data-driven computational drug repurposing approaches for opioid use disorder

Opioid Use Disorder (OUD) is a chronic and relapsing condition characterized by the misuse of opioid drugs, causing significant morbidity and mortality in the United States. Existing medications for OUD are limited, and there is an immediate need to discover treatments with enhanced safety and efficacy. Drug repurposing aims to find new indications for existing medications, offering a time-saving and cost-efficient alternative strategy to traditional drug discovery. Computational approaches have been developed to further facilitate the drug repurposing process. In this paper, we reviewed state-of-the-art data-driven computational drug repurposing approaches for OUD and discussed their advantages and potential challenges. We also highlighted promising repurposed candidate drugs for OUD that were identified by computational drug repurposing techniques and reviewed studies supporting their potential mechanisms of action in treating OUD.

Mirtazapine Was Effective for a Patient With Benzodiazepine Dependence

OBJECTIVE

Benzodiazepine (BZD) dependence has become a social problem and results in poor outcomes. Only a few evidence-based treatments for pharmacotherapy, including antidepressants, are recommended.

METHODS

We reported about a 71-year-old man with onset of blindness at 50 years of age due to pigmentary degeneration of the retina developed insomnia at age 59 years, characterized by nocturnal and early morning awakenings.

RESULTS

Mirtazapine was effective to not only treat sleep disturbance but also a craving for BZD.

CONCLUSIONS

The increases of dopamine, norepinephrine, and serotonin signaling by mirtazapine may be related to the effectiveness in reducing BZD dependence.

Mirtazapine-induced decrease in cocaine sensitization is enhanced by environmental enrichment in rats

Several studies have reported that mirtazapine attenuated the induction and expression of cocaine-induced locomotor sensitization. Animals placed in enriched housing environments have shown a decrease in cocaine-induced locomotor activity and sensitization. In addition, it has been suggested that a pharmacological treatment combined with a behavioral intervention increases the efficacy of the former. Thus, the objective of this study was to determine if dosing of mirtazapine in an enriched housing environment enhanced the mirtazapine-induced decrease on the induction and expression of cocaine-induced locomotor sensitization. Wistar male rats were dosed with cocaine (10 mg/kg, i.p.). During the drug-withdrawal phase, mirtazapine (30 mg/kg, i.p.) was administered under standard and enriched housing environmental conditions. The environmental enrichment consisted of housing the animals in enclosures with plastic toys, tunnels, and running wheels. After each administration, locomotor activity for each animal was recorded for 30 min. The study found that treatment with mirtazapine in an enriched housing environment produced an enhanced and persistent attenuation of the induction and expression of cocaine-induced locomotor sensitization. Additionally, it reduced the duration of cocaine-induced locomotor activity in the expression phase of locomotor sensitization. Dosing of mirtazapine in an enriched housing environment enhanced the effectiveness of mirtazapine to decrease cocaine-induced locomotor sensitization. This suggests the potential use of enriched environments to enhance the effect of mirtazapine.

Mirtazapine decreased induction and expression of cocaine + nicotine-induced locomotor sensitisation in rats

Objectives: Concurrent abuse of cocaine and nicotine is considered a public health problem. To date, no effective therapy has been known to reduce the reinforcing effects of concurrent use of cocaine and nicotine. Mirtazapine, an antagonist of the α₂-adrenoceptor and the 5-HT_2A/C and the 5-HT₃ receptors has proven effective in reducing the cocaine, nicotine and methamphetamine behavioural effects in humans and animals. Our study evaluated the effect of mirtazapine on enhancing locomotor activity during the induction and expression of locomotor sensitisation induced by a cocaine + nicotine mixture.Methods: Wistar rats were dosed with cocaine, nicotine or cocaine + nicotine combination. Mirtazapine (30 mg/kg, i.p.) was administered during the extinction phase.Results: Mirtazapine decreased cocaine + nicotine-induced locomotor activity and induction and expression of locomotor sensitisation. In addition, we found that co-administration of mecamylamine and mirtazapine significantly enhanced the effect of mirtazapine on cocaine + nicotine-induced locomotor activity during induction and expression of behavioural sensitisation.Conclusions: Our results suggest that mirtazapine demonstrated efficacy in decreasing the psycho-stimulant effects of concurrent use of cocaine and nicotine.

Nortriptyline Enhances Morphine-Conditioned Place Preference in Neuropathic Rats: Role of the Central Noradrenergic System

BACKGROUND

Combination drug therapy is commonly used to treat chronic pain conditions such as neuropathic pain, and antidepressant is often used together with opioid analgesics. While rewarding is an intrinsic property of opioid analgesics, it is unknown whether the use of an antidepressant would influence opioid reward, which may contribute to opioid addiction. In this study, we examined whether nortriptyline (a tricyclic antidepressant and a first-line medication for neuropathic pain) would enhance the morphine rewarding property in both naive and chronic constriction sciatic nerve injury (CCI) rats.

METHODS

The rewarding effect of these drugs was assessed using conditioned place preference (CPP). The real-time polymerase chain reaction, western blot, and enzyme-linked immunosorbent assay analysis were used to investigate the function of central noradrenergic system.

RESULTS

In naive rats, coadministration of nortriptyline with morphine did not change the acquisition of morphine-induced CPP. However, nortriptyline enhanced the acquisition, delayed the extinction, and augmented the reinstatement of morphine-induced CPP in CCI rats. In CCI rats treated with both nortriptyline and morphine, the expression of α2A-adrenergic receptors, norepinephrine transporter, and tyrosine hydroxylase was markedly decreased in the locus coeruleus, whereas the norepinephrine concentration in the nucleus accumbens was remarkably increased.

CONCLUSIONS

These results demonstrate that nortriptyline enhanced morphine reward when both drugs were used to treat neuropathic pain in rats and that this behavioral phenotype is likely to be mediated by upregulation of the central noradrenergic system. These findings may have implications in opioid therapy commonly used for chronic pain management.

Mirtazapine attenuates cocaine seeking in rats

BACKGROUND

Relapse to cocaine use is a major problem in the clinical treatment of cocaine addiction. Antidepressants have been studied for their therapeutic potential to treat cocaine use disorder. Research has suggested that antidepressants attenuate both drug craving and the re-acquisition of drug-seeking and drug-taking behaviors. This study examined the efficacy of mirtazapine, an antidepressant/anxiolytic, in decreasing cocaine seeking in rats.

METHODS

We used the cocaine self-administration paradigm to assess the effects of mirtazapine on rats trained to self-administer cocaine or food under a fixed-ratio schedule. Mirtazapine (30 mg/kg, i.p.) was administered during extinction.

RESULTS

Mirtazapine significantly attenuated non-reinforced lever-press responses during extinction. Moreover, the mirtazapine dosed for 30 days during extinction produced sustained attenuation of lever-press responses during re-acquisition of cocaine self-administration, without changing food-seeking behavior. Our results showed that mirtazapine attenuated the re-acquisition of cocaine-seeking responses.

CONCLUSION

Our study pointed to the efficacy of mirtazapine in reducing the risk of drug relapse during abstinence, suggesting for its potential use as a novel pharmacological agent to treat drug abuse.

Dose- and time-dependent effects of mirtazapine on the expression of cocaine-induced behavioral sensitization in rats

Relapse to cocaine use is a major problem in the clinical treatment of cocaine dependence. Antidepressant medications have been studied as potential therapeutic drugs to relieve a cocaine dependence disorder. Mirtazapine is an antidepressant implicated in reducing behavioral alterations induced by drugs of abuse. We have reported elsewhere that 30mg/kg mirtazapine administered for 30 days during cocaine extinction significantly attenuated the induction and expression of cocaine-induced locomotor sensitization and decreased the duration of the cocaine-induced locomotor effect. This study focused on exploring whether different mirtazapine dosing regimens could optimize and/or improve the effect of 30mg/kg mirtazapine administered for 30 days on cocaine-induced locomotor activity during the expression phase of behavioral sensitization. Our study revealed that the daily dosing regimen with a fixed dose of mirtazapine (30mg/kg ip) over 60 days improved the decrease in cocaine-induced locomotor activity and behavioral sensitization obtained by dosing of 30mg mirtazapine for 30 days. In addition, it showed that a dosing regimen of 30mg/Kg mirtazapine for 30 days managed to reduce cocaine toxicity. These results suggested that dosage of mirtazapine for 30 consecutive days may be an effective therapy.

Mirtazapine and ketanserin alter preference for gambling-like schedules of reinforcement in rats

Drug and behavioral addictions have overlapping features, e.g., both manifest preference for larger, albeit costlier, reinforcement options in cost/benefit decision-making tasks. Our prior work revealed that the mixed-function serotonergic compound, mirtazapine, attenuates behaviors by rats motivated by abused drugs. To extend this work to behavioral addictions, here we determined if mirtazapine and/or ketanserin, another mixed-function serotonin-acting compound, can alter decision-making in rats that is independent of drug (or food)-motivated reward. Accordingly, we developed a novel variable-ratio task in rats wherein intracranial self-stimulation was used as the positive reinforcer. Using lever pressing for various levels of brain stimulation, the operant task provided choices between a small brain stimulation current delivered on a fixed-ratio schedule (i.e., a predictable reward) and a large brain stimulation delivered following an unpredictable number of responses (i.e., a variable-ratio schedule). This task allowed for demonstration of individualized preference and detection of shifts in motivational influences during a pharmacological treatment. Once baseline preference was established, we determined that pretreatment with mirtazapine or ketanserin significantly decreased preference for the large reinforcer presented after gambling-like schedules of reinforcement. When the rats were tested the next day without drug, preference for the unpredictable large reinforcer option was restored. These data demonstrate that mirtazapine and ketanserin can reduce preference for larger, costlier reinforcement options, and illustrate the potential for these drugs to alter behavior.

Pharmacologically distinct pramipexole-mediated akinesia vs. risk-taking in a rat model of Parkinson's disease

Pramipexole and ropinirole are dopamine agonists that are efficacious in treating motor disturbances of neuropathologies, e.g., Parkinson's disease and restless legs syndrome. A significant portion of treated patients develop impulsive/compulsive behaviors. Current treatment is dose reduction or switching to an alternative dopamine replacement, both of which can undermine the motor benefits. Needed is a preclinical model that can assist in identifying adjunct treatments to dopamine agonist therapy that reduce impulsive/compulsive behaviors without interfering with motor benefits of the dopamine agonist. Toward that objective, the current study implemented a rat model of Parkinson's disease to behaviorally profile chronically administered pramipexole. This was accomplished with male Sprague-Dawley rats wherein (i) 6-hydroxydopamine-induced lesions of the dorsolateral striatum produced Parkinson's disease-like akinesia, measured in the forelimbs, (ii) intracranial self-stimulation-mediated probability discounting indicated impulsivity/risk-taking, and (iii) two doses of pramipexole were continuously administered for 14-28days via osmotic minipumps to mirror the chronic, stable exposure achieved with extended release formulations. The atypical antidepressant, mirtazapine, is known to reduce behaviors associated with drug addiction in rats; thus, we demonstrated model utility here by determining the effects of mirtazapine on pramipexole-induced motor improvements versus probability discounting. We observed that forelimb akinesia subsequent to striatal lesions was attenuated by both pramipexole doses tested (0.3 and 1.2mg/kg/day) within 4h of pump implant dispensing 0.3mg/kg/day and 1h by 1.2mg/kg/day. By contrast, 12-14days of infusion with 0.3mg/kg/day did not alter discounting, but increases were obtained with 1.2mg/kg/day pramipexole, with 67% of 1.2mg/kg/day-treated rats meeting categorical criteria for 'high risk-taking'. Insertion of a second minipump delivering mirtazapine did not alter motor function during 14days of co-administration with pramipexole, but was sufficient to attenuate risk-taking. These outcomes revealed distinct probability discounting and anti-akinesia profiles for pramipexole, indicating that pharmacotherapy, (e.g., mirtazapine treatments), can be developed that reduce risk-taking while leaving motor benefits intact.

Mirtazapine prevents induction and expression of cocaine-induced behavioral sensitization in rats

Cocaine abuse is a major health problem worldwide. Treatment based on both 5-HT2A/C and 5-HT3 receptor antagonists attenuate not only the effects of cocaine abuse but also the incentive/motivational effect related to cocaine-paired cues. Mirtazapine, an antagonist of postsynaptic α2-adrenergic, 5-HT2A/C and 5HT3 receptors and inverse agonist of the 5-HT2C receptor, has been shown to effectively modify, at the preclinical and clinical levels, various behavioral alterations induced by drugs abuse. Therefore, it is important to assess whether chronic dosing of mirtazapine alters locomotor effects of cocaine as well as induction and expression of cocaine sensitization. Our results reveal that a daily mirtazapine regimen administered for 30days effectively induces a significant attenuation of cocaine-dependent locomotor activity and as well as the induction and expression of behavioral sensitization. These results suggest that mirtazapine may be used as a potentially effective therapy to attenuate induction and expression of cocaine-induced locomotor sensitization.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Using conditioned place preference to identify relapse prevention medications

Stimuli, including contexts, which predict the availability or onset of a drug effect, can acquire conditioned incentive motivational properties. These conditioned properties endure after withdrawal, and can promote drug-seeking which may result in relapse. Conditioned place preference (CPP) assesses the associations between drugs and the context in which they are experienced. Here, we review the potential utility of CPP procedures in rodents and humans to evaluate medications that target conditioned drug-seeking responses. We discuss the translational potential of the CPP procedure from rodents to humans, and review findings with FDA-approved treatments that support the use of CPP to develop relapse-reduction medications. We also discuss challenges and methodological questions in applying the CPP procedure to this purpose. We argue that an efficient and valid CPP procedure in humans may reduce the burden of full clinical trials with drug-abusing patients that are currently required for testing promising treatments.

Mirtazapine, and mirtazapine-like compounds as possible pharmacotherapy for substance abuse disorders: evidence from the bench and the bedside

Understanding substance use disorders (SUDs) and the problems associated with abstinence has grown in recent years. Nonetheless, highly efficacious treatment targeting relapse prevention has remained elusive, and there remains no FDA-approved pharmacotherapy for psychostimulant dependence. Preclinical and clinical investigations assessing the utility of classical antidepressants, which block monoamine reuptake, show mixed and often contradictory results. Mirtazapine (Remeron®) is a unique FDA-approved antidepressant, with negligible affinity for reuptake proteins, indirectly augments monoamine transmission presumably through antagonist activity at multiple receptors including the norepinephrine (NE)(α2), and serotonin (5-HT)(2A/C) receptors. Historically, mirtazapine was also considered to be a 5-HT(2C) antagonist, but recent evidence indicates that mirtazapine is an inverse agonist at this receptor subtype. Suggesting a promising role for mixed-action serotonergic drugs for addiction pharmacotherapy, mirtazapine attenuates psychostimulant-induced behaviors in several rodent models of substance abuse, and antagonizes methamphetamine-induced biochemical and electrophysiological alterations in rats. Preclinical findings are confirmed through published case studies documenting successful outcomes with mirtazapine therapy across a number of SUDs. To date, a large scale clinical trial assessing the utility of mirtazapine in substance abuse pharmacotherapy has yet to be conducted. However, as reviewed here, accumulating preclinical and clinical evidence argues that mirtazapine, or compounds that emulate aspects of its pharmacological profile, may prove useful in helping treat addictions.