The effect of fluvoxamine and sertraline on the opioid withdrawal syndrome: a combined in vivo cerebral microdialysis and behavioural study

Amelioration of morphine withdrawal syndrome by systemic and intranasal administration of mesenchymal stem cell-derived secretome in preclinical models of morphine dependence

BACKGROUND

Morphine is an opiate commonly used in the treatment of moderate to severe pain. However, prolonged administration can lead to physical dependence and strong withdrawal symptoms upon cessation of morphine use. These symptoms can include anxiety, irritability, increased heart rate, and muscle cramps, which strongly promote morphine use relapse. The morphine-induced increases in neuroinflammation, brain oxidative stress, and alteration of glutamate levels in the hippocampus and nucleus accumbens have been associated with morphine dependence and a higher severity of withdrawal symptoms. Due to its rich content in potent anti-inflammatory and antioxidant factors, secretome derived from human mesenchymal stem cells (hMSCs) is proposed as a preclinical therapeutic tool for the treatment of this complex neurological condition associated with neuroinflammation and brain oxidative stress.

METHODS

Two animal models of morphine dependence were used to evaluate the therapeutic efficacy of hMSC-derived secretome in reducing morphine withdrawal signs. In the first model, rats were implanted subcutaneously with mini-pumps which released morphine at a concentration of 10 mg/kg/day for seven days. Three days after pump implantation, animals were treated with a simultaneous intravenous and intranasal administration of hMSC-derived secretome or vehicle, and withdrawal signs were precipitated on day seven by i.p. naloxone administration. In this model, brain alterations associated with withdrawal were also analyzed before withdrawal precipitation. In the second animal model, rats voluntarily consuming morphine for three weeks were intravenously and intranasally treated with hMSC-derived secretome or vehicle, and withdrawal signs were induced by morphine deprivation.

RESULTS

In both animal models secretome administration induced a significant reduction of withdrawal signs, as shown by a reduction in a combined withdrawal score. Secretome administration also promoted a reduction in morphine-induced neuroinflammation in the hippocampus and nucleus accumbens, while no changes were observed in extracellular glutamate levels in the nucleus accumbens.

CONCLUSION

Data presented from two animal models of morphine dependence suggest that administration of secretome derived from hMSCs reduces the development of opioid withdrawal signs, which correlates with a reduction in neuroinflammation in the hippocampus and nucleus accumbens.

Structure-based discovery of conformationally selective inhibitors of the serotonin transporter

The serotonin transporter (SERT) removes synaptic serotonin and is the target of anti-depressant drugs. SERT adopts three conformations: outward-open, occluded, and inward-open. All known inhibitors target the outward-open state except ibogaine, which has unusual anti-depressant and substance-withdrawal effects, and stabilizes the inward-open conformation. Unfortunately, ibogaine's promiscuity and cardiotoxicity limit the understanding of inward-open state ligands. We docked over 200 million small molecules against the inward-open state of the SERT. Thirty-six top-ranking compounds were synthesized, and thirteen inhibited; further structure-based optimization led to the selection of two potent (low nanomolar) inhibitors. These stabilized an outward-closed state of the SERT with little activity against common off-targets. A cryo-EM structure of one of these bound to the SERT confirmed the predicted geometry. In mouse behavioral assays, both compounds had anxiolytic- and anti-depressant-like activity, with potencies up to 200-fold better than fluoxetine (Prozac), and one substantially reversed morphine withdrawal effects.

Disulfiram attenuates morphine or methadone withdrawal syndrome in mice

Taking opioids is often accompanied by the development of dependence. Unfortunately, treatment of opioid dependence is difficult, particularly because of codependence - for example, on alcohol or other drugs of abuse. In the presented study, we analyzed the potential influence of disulfiram, a drug used to aid the management of alcoholism, on opioid abstinence syndrome, which occurs as a result of opioid withdrawal. Opioid dependence in mice was induced by subcutaneous administration of either morphine or methadone at a dose of 48 mg/kg for 10 consecutive days. To trigger a withdrawal syndrome, the opioid receptor antagonist, naloxone, was administered at a dose of 1 mg/kg (subcutaneous), and the severity of withdrawal signs was assessed individually. Interruption of chronic treatment with morphine or methadone by naloxone has led to the occurrence of opioid abstinence signs such as jumping, paw tremor, wet-dog shakes, diarrhea, teeth chattering, ptosis, and piloerection. Importantly, pretreatment with disulfiram (25, 50, and 100 mg/kg) reduced the intensity of withdrawal signs induced by naloxone in morphine or methadone-treated mice. These findings show the effectiveness of disulfiram in reducing opioid abstinence signs.

Pharmacogenetic analysis of opioid dependence treatment dose and dropout rate

BACKGROUND

Currently, no pharmacogenetic tests for selecting an opioid-dependence pharmacotherapy have been approved by the US Food and Drug Administration.

OBJECTIVES

Determine the effects of variants in 11 genes on dropout rate and dose in patients receiving methadone or buprenorphine/naloxone (ClinicalTrials.gov Identifier: NCT00315341).

METHODS

Variants in six pharmacokinetic genes (CYP1A2, CYP2B6, CYP2C19, CYP2C9, CYP2D6, CYP3A4) and five pharmacodynamic genes (HTR2A, OPRM1, ADRA2A, COMT, SLC6A4) were genotyped in samples from a 24-week, randomized, open-label trial of methadone and buprenorphine/naloxone for the treatment of opioid dependence (n = 764; 68.7% male). Genotypes were then used to determine the metabolism phenotype for each pharmacokinetic gene. Phenotypes or genotypes for each gene were analyzed for association with dropout rate and mean dose.

RESULTS

Genotype for 5-HTTLPR in the SLC6A4 gene was nominally associated with dropout rate when the methadone and buprenorphine/naloxone groups were combined. When the most significant variants associated with dropout rate were analyzed using pairwise analyses, SLC6A4 (5-HTTLPR) and COMT (Val158Met; rs4860) had nominally significant associations with dropout rate in methadone patients. None of the genes analyzed in the study was associated with mean dose of methadone or buprenorphine/naloxone.

CONCLUSIONS

This study suggests that functional polymorphisms related to synaptic dopamine or serotonin levels may predict dropout rates during methadone treatment. Patients with the S/S genotype at 5-HTTLPR in SLC6A4 or the Val/Val genotype at Val158Met in COMT may require additional treatment to improve their chances of completing addiction treatment. Replication in other methadone patient populations will be necessary to ensure the validity of these findings.

Effects of alkaloid-rich extract from Mitragyna speciosa (Korth.) Havil. on naloxone-precipitated morphine withdrawal symptoms and local field potential in the nucleus accumbens of mice

ETHNOPHARMACOLOGICAL RELEVANCE

Mitragyna speciosa (Korth.) Havil. (M. speciosa) is among the most well-known plants used in ethnic practice of Southeast Asia. It has gained increasing attention as a plant with potential to substitute morphine in addiction treatment program. However, its action on the central nervous system is controversial.

AIM OF THE STUDY

This study investigated the effects of M. speciosa alkaloid extract on naloxone-precipitated morphine withdrawal and neural signaling in the nucleus accumbens (NAc, brain reward center) of mice.

MATERIALS AND METHODS

The effects of M. speciosa alkaloid extract and mitragynine, a pure major constituent, on naloxone-precipitated morphine withdrawal were examined. Male Swiss Albino (ICR) mice were rendered dependent on morphine before injection with naloxone, a nonspecific opioid antagonist, to induce morphine withdrawal symptoms. The intensity of naloxone-precipitated morphine withdrawal was assessed from jumping behavior and diarrhea induced during a period of morphine withdrawal. To test possible addictive effect of M. speciosa alkaloid extract, mice were implanted with intracranial electrode into the NAc for local field potential (LFP) recording. Following M. speciosa alkaloid extract (80mg/kg) and morphine (15mg/kg) treatment, LFP power spectra and spontaneous motor activity were analyzed in comparison to control levels.

RESULTS

One-way ANOVA and multiple comparisons revealed that M. speciosa alkaloid extract (80 and 100mg/kg) significantly decreased the number of jumping behavior induced by morphine withdrawal whereas mitragynine did not. Additionally, M. speciosa alkaloid extract significantly decreased dry and wet fecal excretions induced by morphine withdrawal. LFP analysis revealed that morphine significantly decreased alpha (9.7-12Hz) and increased low gamma (30.3-44.9Hz) and high gamma (60.5-95.7Hz) powers in the NAc whereas M. speciosa alkaloid extract did not. Spontaneous motor activity was significantly increased by morphine but not M. speciosa alkaloid extract.

CONCLUSIONS

Taken together, M. speciosa alkaloid extract, but not mitragynine, attenuated the severity of naloxone-precipitated morphine withdrawal symptoms. Neural signaling in the NAc and spontaneous motor activity were sensitive to morphine but not M. speciosa alkaloid extract. Therefore, treatment with the M. speciosa alkaloid extract may be useful for opiate addiction treatment program.

The role of serotonin in drug use and addiction

The use of psychoactive drugs is a wide spread behaviour in human societies. The systematic use of a drug requires the establishment of different drug use-associated behaviours which need to be learned and controlled. However, controlled drug use may develop into compulsive drug use and addiction, a major psychiatric disorder with severe consequences for the individual and society. Here we review the role of the serotonergic (5-HT) system in the establishment of drug use-associated behaviours on the one hand and the transition and maintenance of addiction on the other hand for the drugs: cocaine, amphetamine, methamphetamine, MDMA (ecstasy), morphine/heroin, cannabis, alcohol, and nicotine. Results show a crucial, but distinct involvement of the 5-HT system in both processes with considerable overlap between psychostimulant and opioidergic drugs and alcohol. A new functional model suggests specific adaptations in the 5-HT system, which coincide with the establishment of controlled drug use-associated behaviours. These serotonergic adaptations render the nervous system susceptible to the transition to compulsive drug use behaviours and often overlap with genetic risk factors for addiction. Altogether we suggest a new trajectory by which serotonergic neuroadaptations induced by first drug exposure pave the way for the establishment of addiction.

Novel pharmacotherapeutic strategies for treatment of opioid-induced neonatal abstinence syndrome

The non-medical use of prescription drugs, in general, and opioids, in particular, is a national epidemic, resulting in enormous addiction rates, healthcare expenditures, and overdose deaths. Prescription opioids are overly prescribed, illegally trafficked, and frequently abused, all of which have created a new opioid addiction pathway, adding to the number of opioid-dependent newborns requiring treatment for neonatal abstinence syndrome (NAS), and contributing to challenges in effective care in maternal and fetal/neonatal (M-F/N) medicine. The standard of care for illicit or prescription opioid dependence during pregnancy is opioid agonist (methadone or buprenorphine) substitution therapy, which are also frequently abused. The next generation of pharmacotherapies for the treatment of illicit or prescription opioid addiction in the M-F/N interactional dyad must take into consideration the interplay between genetic, epigenetic, and environmental factors. Addiction to illicit drugs during pregnancy presents unique challenges to effectively treat the mother, and the developing fetus and infant after delivery. New pharmacotherapies should be safe to the developing fetus, effective in treating the physical and psychological consequences of addiction in the mother, and reduce the incidence and severity of NAS in the infant after birth. More pharmacotherapeutic options should be available to the physician such that a more individualized rather than a one-drug/strategy-fits-all approach can be used. A myriad of new and exciting pharmacotherapeutic strategies for the treatment of opioid dependence and addiction are on the horizon. This review focuses on such three strategies: (i) pharmacotherapeutic targeting of the serotonergic system; (ii) mixed opioid immunotherapeutics (vaccines); (iii) pharmacogenomics as a therapeutic strategy to insure personalized care. We review and discuss how these strategies may offer additional treatment modalities for the treatment of M-F/N during pregnancy and the treatment of the infant after birth.

Inhibition of G protein-activated inwardly rectifying K+ channels by different classes of antidepressants

Various antidepressants are commonly used for the treatment of depression and several other neuropsychiatric disorders. In addition to their primary effects on serotonergic or noradrenergic neurotransmitter systems, antidepressants have been shown to interact with several receptors and ion channels. However, the molecular mechanisms that underlie the effects of antidepressants have not yet been sufficiently clarified. G protein-activated inwardly rectifying K⁺ (GIRK, Kir3) channels play an important role in regulating neuronal excitability and heart rate, and GIRK channel modulation has been suggested to have therapeutic potential for several neuropsychiatric disorders and cardiac arrhythmias. In the present study, we investigated the effects of various classes of antidepressants on GIRK channels using the Xenopus oocyte expression assay. In oocytes injected with mRNA for GIRK1/GIRK2 or GIRK1/GIRK4 subunits, extracellular application of sertraline, duloxetine, and amoxapine effectively reduced GIRK currents, whereas nefazodone, venlafaxine, mianserin, and mirtazapine weakly inhibited GIRK currents even at toxic levels. The inhibitory effects were concentration-dependent, with various degrees of potency and effectiveness. Furthermore, the effects of sertraline were voltage-independent and time-independent during each voltage pulse, whereas the effects of duloxetine were voltage-dependent with weaker inhibition with negative membrane potentials and time-dependent with a gradual decrease in each voltage pulse. However, Kir2.1 channels were insensitive to all of the drugs. Moreover, the GIRK currents induced by ethanol were inhibited by sertraline but not by intracellularly applied sertraline. The present results suggest that GIRK channel inhibition may reveal a novel characteristic of the commonly used antidepressants, particularly sertraline, and contributes to some of the therapeutic effects and adverse effects.

Sequential and opposing alterations of 5-HT(1A) receptor function during withdrawal from chronic morphine

Addiction is a brain chronic relapsing disorder associated with emotional distress. The serotonergic system and especially the 5-HT(1A) receptor crucially regulate emotional behaviors both in humans and rodents. Using [(35)S]GTPγS autoradiography in mice, we show that 5-HT(1A) receptor function is enhanced by chronic morphine treatment in the medial prefrontal cortex, and decreased in dorsal raphe nucleus one week later, two regions involved in emotional processing. These molecular adaptations could contribute to the development of emotional disorders experienced by former opiate addicts.

Impaired emotional-like behavior and serotonergic function during protracted abstinence from chronic morphine

BACKGROUND

Opiate abuse is a chronic relapsing disorder, and maintaining prolonged abstinence remains a major challenge. Protracted abstinence is characterized by lowered mood, and clinical studies show elevated comorbidity between addiction and depressive disorders. At present, their relationship remains unclear and has been little studied in animal models. Here we investigated emotional alterations during protracted abstinence, in mice with a history of chronic morphine exposure.

METHODS

C57BL6J mice were exposed to a chronic intermittent escalating morphine regimen (20-100 mg/kg). Physical dependence (naloxone-precipitated withdrawal), despair-related behaviors (tail suspension test), and social behaviors were examined after 1 or 4 weeks of abstinence. Stress hormones and forebrain bioamine levels were analyzed at the end of morphine regimen and after 4 weeks of abstinence. Finally, we examined the effects of chronic fluoxetine during abstinence on morphine-induced behavioral deficits.

RESULTS

Acute naloxone-induced withdrawal was clearly measurable after 1 week, and became undetectable after 4 weeks. In contrast, social and despair-related behaviors were unchanged after 1 week, but low sociability and despair-like behavior became significant after 4 weeks. Chronic morphine regimen increased both corticosterone levels and forebrain serotonin turnover, but only serotonergic activity in the dorsal raphe remained impaired after 4 weeks. Remarkably, chronic fluoxetine prevented depressive-like behavioral deficits in 4-week abstinent mice.

CONCLUSIONS

During protracted abstinence, the immediate consequences of morphine exposure attenuate, whereas fluoxetine-sensitive emotional alterations strengthen with time. Our study establishes a direct link between morphine abstinence and depressive-like symptoms and strongly suggests that serotonin dysfunction represents a main mechanism contributing to mood disorders in opiate abstinence.

Some effects of dopamine transporter and receptor ligands on discriminative stimulus, physiologic, and directly observable indices of opioid withdrawal in rhesus monkeys

RATIONALE

Some monoamine uptake inhibitors (e.g., cocaine) attenuate the subjective and discriminative stimulus effects of opioid withdrawal.

OBJECTIVE

This study examined a role for dopamine transporters and receptors as targets for drugs to modify the discriminative stimulus effects of opioid withdrawal and further examined a subset of these drugs for their capacity to modify some directly observable and physiologic indices of withdrawal.

MATERIALS AND METHODS

Rhesus monkeys receiving 2 mg/kg/day of L: -alpha-acetylmethadol discriminated the opioid antagonist naltrexone (0.0178 mg/kg s.c.).

RESULTS

The naltrexone discriminative stimulus was attenuated not only by the mu agonist morphine but also by the dopamine D(2)-like receptor agonists bromocryptine and quinpirole. In contrast, the naltrexone discriminative stimulus was not consistently modified by the non-selective, D(1)- and D(2)-like agonist apomorphine or by uptake inhibitors with high selectivity for dopamine transporters (GBR 12909, RTI 113, and RTI 177). In the same monkeys, naltrexone dose dependently decreased body temperature, increased breathing frequency, and induced directly observable signs (grimacing, salivation, and unusual posture). Hypothermia, hyperventilation, and signs of withdrawal were significantly attenuated by morphine and not by quinpirole.

CONCLUSIONS

Attenuation of opioid withdrawal by D(2)-like receptor agonists that have lower efficacy than dopamine, and not by uptake inhibitors with selectivity for dopamine transporters, suggests that magnitude of receptor stimulation (e.g., efficacy) and selectivity at dopamine receptors are important factors in the modulation of opioid withdrawal. Attenuation of the naltrexone discriminative stimulus by drugs that inhibit both dopamine and serotonin uptake (e.g., cocaine) could result from an inhibitory effect of serotonin on dopamine. The role of dopamine in opioid withdrawal appears to be restricted to subjective (i.e., not somatic) indices [corrected]

Suppressive effects of dichloromethane fraction from the Areca catechu nut on naloxone-precipitated morphine withdrawal in mice

In the present study, we investigated the effect of the dichloromethane fraction from Areca catechu nut on the severity of naloxone-precipitated morphine withdrawal in morphine-dependent mice. A single intraperitoneal injection of dichloromethane fraction at dose of 125 and 175 mg/kg significantly delayed the onset of withdrawal jumping behavior in a concentration-dependent manner compared to that of saline controls. The dichloromethane fractions also significantly decreased jumping numbers and faecal and urinary excretions during the withdrawal period.

Monoaminergic drugs and directly observable signs of LAAM withdrawal in rhesus monkeys

Monoaminergic ligands modified a naltrexone discriminative stimulus in rhesus monkeys dependent on 2 mg/kg per day of the mu opioid L-alpha-acetylmethadol (LAAM). This study examined a role for monoamines in the directly observable and physiologic manifestations of LAAM withdrawal induced by naltrexone in the same monkeys. The effects of saline, clonidine (0.032 mg/kg), haloperidol (0.032 mg/kg), cocaine (1.0 mg/kg), amphetamine (1.0 mg/kg) and imipramine (10.0 mg/kg) were examined in LAAM-dependent monkeys that subsequently received saline or naltrexone (0.0001-1.0 mg/kg). Naltrexone dose-dependently increased respiration, abdominal rigidity and salivation. Clonidine attenuated each of these withdrawal signs, whereas haloperidol increased some (i.e. respiration) and decreased others (i.e. salivation). When administered alone, cocaine and amphetamine increased respiration and also increased the respiratory stimulant effects of naltrexone; cocaine and amphetamine did not attenuate any measure of withdrawal. With the exception of a decrease in naltrexone-induced salivation, imipramine was without effect. These results are strikingly different from results in these same LAAM-dependent monkeys showing that cocaine and amphetamine, but not clonidine, markedly attenuated a naltrexone discriminative stimulus. That monoaminergic ligands differentially alter the directly observable and discriminative stimulus effects of naltrexone in LAAM-dependent monkeys supports the view that monoamines differentially mediate the physical manifestations (norepinephrine) and subjective experience (dopamine) of opioid withdrawal.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).