Opiate Receptor Antagonist Research Articles

The Unrestrained Overeating Behavior and Clinical Perspective.

Obesity-related co-morbidities decrease life quality, reduce working ability, and lead to early death. In the adult population, eating addiction manifests with excessive food consumption and the unrestrained overeating behavior, which is associated with increased risk of morbidity and mortality and defined as the binge eating disorder (BED). This hedonic intake is correlated with fat preference and the total amount of dietary fat consumption is the most potent risk factor for weight gain. Long-term BED leads to greater sensitivity to the rewarding effects of palatable foods and results in obesity fatefully. Increased plasma concentrations of non-esterified free fatty acids and lipid-overloaded hypertrophic adipocytes may cause insulin resistance. In addition to dietary intake of high-fat diet, sedentary lifestyle leads to increased storage of triglycerides not only in adipose tissue but also ectopically in other tissues. Lipid-induced apoptosis, ceramide accumulation, reactive oxygen species overproduction, endoplasmic reticulum stress, and mitochondrial dysfunction play role in the pathogenesis of lipotoxicity. Food addiction and BED originate from complex action of dopaminergic, opioid, and cannabinoid systems. BED may also be associated with both obesity and major depressive disorder. For preventing morbidity and mortality, as well as decreasing the impact of obesity-related comorbidities in appropriately selected patients, opiate receptor antagonists and antidepressant combination are recommended. Pharmacotherapy alongside behavioral management improves quality of life and reduces the obesity risk; however, the number of licensed drugs is very few. Thus, stereotactic treatment is recommended to break down the refractory obesity and binge eating in obese patient. As recent applications in the field of non-invasive neuromodulation, transcranial magnetic stimulation and transcranial direct current stimulation are thought to be important in image-guided deep brain stimulation in humans. Chronic overnutrition most likely provides repetitive and persistent signals that up-regulate inhibitor of nuclear factor kappa B (NF-κB) kinase beta subunit/NF-κB (IKKβ/NF-κB) in the hypothalamus before the onset of obesity. However, how the mechanisms of high-fat diet-induced peripheral signals affect the hypothalamic arcuate nucleus remain largely unknown.

Regulation of the Endogenous Opiate Signaling Pathway against Oxidative Stress and Inflammation: A Considerable Approach for Exploring Preclinical Treatment of Parkinson’s Disease

Introduction: Oxidative stress and inflammation are major factors contributing to the progressive death of dopaminergic neurons in Parkinson’s disease (PD). Recent studies have demonstrated that morphine’s biosynthetic pathway, coupled with nitric oxide (NO) release, is evolutionarily conserved throughout animals and humans. Moreover, dopamine is a key precursor for morphine biosynthesis. Method: The present study evaluated a series of preclinical experiments to evaluate the effects of low-level morphine treatment upon neuro-immune tissues exposed to rotenone and 6-OHDA as models of PD, followed by an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation assay and cell/tissue computer-assisted imaging analyses to assess cell/neuronal viability. Results: Morphine at normal physiological concentrations (i.e., 10−6 M and 10−7 M) provided neuroprotection, as it significantly inhibited rotenone and 6-OHDA dopaminergic insults; thereby, reducing and/or forestalling cell death in invertebrate ganglia and human nerve cells. To ensure that morphine caused this neuroprotective effect, naloxone, a potent opiate receptor antagonist, was employed and the results showed that it blocked morphine’s neuroprotective effects. Additionally, co-incubation of NO synthase inhibitor L-NAME also blocked morphine’s neuroprotective effects against rotenone and 6-OHDA insults. Conclusions: Taken together, the present preclinical study showed that while morphine can attenuate lipopolysaccharide-induced inflammation and cell death, both naloxone and L-NAME can abolish this effect. Preincubation of morphine precursors (i.e., L-3,4-dihydroxyphenylalanine, reticuline, and trihexyphenidyl [THP] at physiological concentrations) mimics the observed morphine effect. However, high concentrations of THP, a precursor of the morphine biosynthetic pathway, induced cell death, indicating the physiological importance of morphine biosynthesis in neural tissues. Thus, understanding the morphine biosynthetic pathway coupled with a NO signaling mechanism as a molecular target for neuroprotection against oxidative stress and inflammation in other preclinical models of PD is warranted.

A low dose of naloxone mitigates autoimmune hepatitis by regulating TLR4/NF-κB and Nrf2/HO-1 signaling pathways.

Naloxone is a non-selective opiate receptor antagonist that is mainly used in the management of acute opioid overdose or intoxication. Previously, naloxone has been shown to have anti-inflammatory and antioxidant properties. Concanavalin A (Con A) model is a common and well established animal model of autoimmune hepatitis that closely resembles the pathological alterations that occur in human. The present study demonstrates that a low dose of naloxone (LD NX) has the ability to improve hepatic function and attenuate hepatic damage induced by Con A as indicated by a clear reduction in serum aminotransferase, bilirubin and enhancement of albumin production as well as liver pathological changes. Also, The proinflammatory cytokines, tumor necrosis factor-α (TNF-α), interferon- γ (IFN-γ), interleukin-6 (IL-6) and interleukin-1β (IL-1β) were highly suppressed in animals pretreated with LD NX via interference with TLR4/NF-κB as well as JNK signaling pathways. Furthermore, oxidative stress was highly attenuated in animals pretreated with LD NX as indicated by high reduction in hepatic MDA and an increase in Nrf2, HO-1 expression and subsequent production of the endogenous antioxidants, SOD, CAT and GSH. Collectively, this study demonstrates that LD NX has the ability to mitigate Con A-induced autoimmune hepatitis via modulation of inflammatory cytokines secretion and interference with reactive oxygen species generation.

CARDIOPROTECTIVE EFFECT OF ENKEPHALINS UNDER IMMOBILIZATION STRESS

Objective: The aim of this study was to investigate the cardioprotective effect of dalargin, a synthetic leu-enkephalin. Methods: The induction of myocardial infarction in rats, which were kept on a diet with excess fat and calcium/sodium salts for two months, by the use of immobilization stress. The experimental results indicated that the applied model allowed to induce the development of myocardial infarction within one three days, which was confirmed by electrocardiography, enzyme-linked immunosorbent assay and histological examination. Results: Pre-treatment of rats with dalargin had no prevented myocardial infarction, however, it increased the resistance to immobilization stress and reduced infarction-induced myocardial lesions. Simultaneous administration of naloxone, an opiate receptor antagonist, together with dalargin eliminated its cardioprotective effect in experimental animals. Conclusion: The use of synthetic leu-enkephalin dalargin significantly reduced the risk of myocardial infarction caused by excessive neuromuscular stress. The dalargin effect on the myocardium was mediated by opiate receptors.

Influence of low dose naltrexone on Raman assisted bone quality, skeletal advanced glycation end-products and nano-mechanical properties in type 2 diabetic mice bone

Type 2 diabetes mellitus (T2DM) commonly affects the bone mineral phase and advanced glycation end-products (AGEs) which eventually led to changes in bone material properties on the nano and macro-scale. Several anti-diabetic compounds are widely used to control high blood sugar or glucose caused by T2DM. Low Dose Naltrexone (LDN), an opiate receptor antagonist, and a known TLR4 antagonist, treatment can improve glucose tolerance and insulin sensitivity in high-fat-diet (HFD) induced T2DM mice. However, the influences of LDN on the local bone quality, mineralization of the bone, and the skeletal AGEs levels have not been fully elucidated. The objective of this study is to understand the effect of LDN on Raman assisted bone quality, skeletal AGEs (determined by Raman spectroscopy), and nano-mechanical properties in HFD induced T2DM mice bone. In order to investigate these, mice and corresponding bones were divided into four groups (divided based on diet and treatment), (a) normal control diet treated with saline water, (b) normal control diet treated with LDN, (c) HFD treated with saline water, and (d) HFD treated with LDN. In T2DM condition (HFD treated with saline water), alteration of Raman-based compositional measures in bone quality including mineral-to-matrix ratios, carbonate substitution, mineral crystallinity, and collagen quality was observed. Our data also indicated that T2DM enhances the skeletal AGEs, and impairs the nano-mechanical properties. Interestingly, present results indicated that LDN controls the Raman-based compositional measures in bone quality in HFD induced T2DM mice bone. Additionally, LDN also protects the alteration of the skeletal AGEs levels and nano-mechanical properties in T2DM mice bone. This study concluded that LDN can control the HFD induced T2DM affected bone abnormalities at multiple hierarchical levels.

Investigation of Origanum compactum essential oil for analgesic and anti-inflammatory activities

Origanum compactum Benth. has been widely used in moroccan traditional medicine for various therapeutic treatments. Belonging to the same genus, O. onites was found to have marked analgesic and anti-inflammatory activities. The aim of this work is to evaluate theses pharmacological properties of the essential oil of O. compactum in order to provide a basis for the folkloric use of the plant. Aerial parts of plant were subjected to steam distillation, according to the French Pharmacopoeia. Male OF1 mice and male Wistar rats were used for these studies. The analgesic effect was done using Writhing test in mice and Tail-Flick test in rats. The mechanism investigation was evaluated employing an antagonism assay using naloxone, a specific antagonist of opiate receptors. Anti- inflammatory property has been studied using carrageenin and experimental trauma induced edema in rats. The essential oil of the aerial parts of Origanum compactum was found to exert central analgesic properties. Such a dose-dependent action was obtained against chemical and thermic stimuli, respectively, from the doses of 6.25 and 12.5 mg/kg and it was inhibited by a naloxone pretreatment, a specific morphinic antagonist compound. Significant and dose-dependent anti-inflammatory effects were observed on an acute inflammatory process from the dose of 100 mg/kg.

Prospective of low dose naltrexone use in treatment of autoimmune pathology and endometriosis

There are still many complex issues in the management of autoimmune pathologies in gynecology and reproductology, endometriosis in particular. Naltrexone, a competitive antagonist of opiate receptors in the central and peripheral nervous systems, reveals new qualities such as effects on autoimmune processes. Naltrexone in low doses of 1.7–5 mg (Low Dose Naltrexone, LDN) revealed the opposite effect on opiate receptors in the form of a rebound effect and, as a consequence, a strong increase in endogenous endorphins and enkephalins. Studies of elevated levels of these neurotransmitters have provided evidence of a multidisciplinary beneficial effect on the immune system of people with endorphin and enkephalin deficiency, an association between the endogenous opiate system and cells and tissue growth in general and healthy immune function was confirmed. The most explored effects of them are such as blocking the synthesis ofpro inflammatory cytokines IL-6, IL-12, tumor necrosis factor, the effect on neuroglia through toll-like receptors, the effect on the cycle cells growth, especially malignant tumor cells, through interaction with opiate growth factor, modulation synthesis of T- and B-lymphocytes. Growing evidence of LDN efficacy is becoming a potentially effective clinical practice in autoimmune pathologies, but still off-label used.Some data of clinical trials is presented. Four studies with Crohn's disease with results of relief of symptoms and remission, including experience in pediatrics. Three clinical trials with LDN results in multiple sclerosis with improved quality of life and improved symptoms. The scientific hypothesis suggests the success of LDN due to the reduction of induced nitric oxide synthase activity. The success of management of patients with malignant tumors is also presented. The article contains the latest data from clinical trials on reported serious and non-serious side effects of naltrexone at various doses, including data confirming the safety of taking mid-therapeutic naltrexone doses throughout pregnancy. These effects of LDN may prove to be effective in management patients with endometriosis.

Drugs affecting obstructive sleep apnea syndrome

Sleep-disordered breathing is one of the most common sleep-associated disorders. At the same time, their prevalence tends to increase with age. One of the most common forms of respiratory failure during sleep is obstructive sleep apnea syndrome (OSA), which is characterized by repeated episodes of cessation of breathing or a significant decrease in respiratory flow while maintaining respiratory effort as a result of obstruction of the upper respiratory tract. Drugs have different effects on OSA. There are drugs that worsen OSA, drugs that do not affect OSA, and drugs that improve OSA. Benzodiazepines, opioids, muscle relaxants, and male hormones adversely affect OSA. Also of clinical interest are drugs that do not affect OSA and can even potentially improve respiratory function during sleep. These include anti-inflammatory drugs, diuretics, bronchodilators, acetylcholinesterase inhibitors, antiparkinsonian, decongestant drugs, drugs for intranasal use, topical soft tissue lubricant, female sex hormones. Finally, the effect of a number of drugs on OSA is not definitively established and requires further study (benzodiazepine receptor agonist hypnotics, angiotensin-converting enzyme inhibitors, opiate receptor antagonists, antidepressants, proton-pump inhibitors, TNF-α antagonists, glutamate receptor antagonists, drugs for the treatment of acromegaly, drugs for the treatment of narcolepsy). Raising awareness of doctors of different specialties about the impact of various drugs on OSA can not only prevent the deterioration of respiratory distress during sleep, but also, with a rational individual approach, makes it possible to even improve the quality of sleep and blood saturation, thereby contributing to a more favorable course of OSA and the underlying disease.

Вивчення захисної дії синтетичного нейропептиду даларгіну в умовах холодового стресу

The effect of the neuropeptide dalargin, which is a synthetic analogue of leu-enkephalins, on the negative processes caused by cold stress, which occur when artificial hypothermia is used in vivo, was studyd. It was shown that dalargin prevents the development of apoptotic processes in the cells of homeothermic animals after cold stress, which manifested itself in a decrease in the degree of DNA fragmentation. In the kidneys and liver of experimental animals subjected to cooling, this attribute of apoptosis and cell necrosis was not detected, and in the intestinal mucosa and spleen the level of DNA fragmentation as a result of cold stress is statistically significant. The preliminary injection of dalargin to rats reduces the degree of DNA fragmentation to values that occurred in animals that were not exposed to cold stress. It is also shown that dalargin prevents the development of adrenal hypertrophy in experimental animals, reduces the degree of involution of the thymus and spleen, and reduces the severity of cold stress-induced ulcerogenesis. The simultaneous injection to animals of an opiate receptor antagonist naloxone eliminated the protective effect of an opiate receptor agonist dalargin.Probl Cryobiol Cryomed 2019; 29(3): 246–254.

Involvement of central opiate receptors in modulation of centrally administered oxytocin-induced antinociception.

Objective(s):Oxytocin is involved in modulation of many brain-mediated functions. In the present study, we investigated the central effects of oxytocin and its receptor antagonist, atosiban on inflammatory pain. The contribution of opiate receptors was explored using non-selective and selective antagonists. Materials and Methods:The fourth ventricle of the brain of anesthetized rats was implanted with a guide cannula. Inflammatory pain in the orofacial region was induced by subcutaneous (SC) injection of formalin into the vibrissa pad, and time duration of face rubbing behavior was measured for 45 min. Results:A typical biphasic pain was observed after formalin injection. This biphasic pain behavior was attenuated by intra-fourth ventricle administration of oxytocin (12.5, 50, and 200 ng/rat). Central prior administration of 400 ng/rat atosiban (an oxytocin receptor antagonist), naloxone (a non-selective opiate receptor antagonist), naloxonazine (a selective µ-opiate receptor antagonist), and nor-binaltorphimine (a selective κ-opiate receptor antagonist), but not naltrindole (a δ-opiate receptor antagonist), prevented oxytocin-induced (200 ng/rat) antinociception. Except for naltrindole, other antagonists increased pain intensity when used alone. Above-mentioned drugs did not alter locomotor activity. Conclusion:Oxytocin, as a neuropeptide neurotransmitter, may be involved in the supraspinal modulation of inflammatory pain through µ- and κ-, but not δ-opiate receptors.

Abuse liability and therapeutic potential of the Mitragyna speciosa (kratom) alkaloids mitragynine and 7-hydroxymitragynine.

Kratom, derived from the plant Mitragyna speciosa, is receiving increased attention as an alternative to traditional opiates and as a replacement therapy for opiate dependence. Mitragynine (MG) and 7-hydroxymitragynine (7-HMG) are major psychoactive constituents of kratom. While MG and 7-HMG share behavioral and analgesic properties with morphine, their reinforcing effects have not been examined to date. 7-HMG, but not MG, substituted for morphine self-administration in a dose-dependent manner in the rat self-administration paradigm. Following the substitution procedure, re-assessment of morphine self-administration revealed a significant increase following 7-HMG and a significant decrease following MG substitution. In a separate cohort, 7-HMG, but not MG, engendered and maintained intravenous self-administration in a dose-dependent manner. The effects of pretreatment with nalxonaxine (NLXZ), a μ1 opiate receptor antagonist, and naltrindole (NTI), a δ opiate receptor antagonist, on 7-HMG and morphine self-administration were also examined. Both NLXZ and NTI reduced 7-HMG self-administration, whereas only NLXZ decreased morphine intake. The present results are the first to demonstrate that 7-HMG is readily self-administered, and the reinforcing effects of 7-HMG are mediated in part by μ and δ opiate receptors. In addition, prior exposure to 7-HMG increased subsequent morphine intake whereas prior exposure to MG decreased morphine intake. The present findings indicate that MG does not have abuse potential and reduces morphine intake, desired characteristics of candidate pharmacotherapies for opiate addiction and withdrawal, whereas 7-HMG should be considered a kratom constituent with high abuse potential that may also increase the intake of other opiates.

Naloxone’s Effect on Activity-Induced Phase Shifts of Circadian Rhythms

Vigorous running in a novel exercise wheel by hamsters during the subjective day results in large (about 3 hr) phase advances of their circadian rhythms. We administered the opiate receptor antagonist naloxone at 10 mg/kg and 20 mg/kg (i.p.) and found that at 20 mg/kg it significantly reduced phase shifts. This dose of naloxone also reduced the amount of running shown by hamsters in the novel wheel. At the 20 mg/kg dose, the reduced amount of running resulted in smaller phase shifts. The results are consistent with the hypothesis that nonphotic phase shifts are linked to exercise and arousal in hamsters. However, because high amounts of running were accompanied by phase shifting in animals whose opiate receptors were blocked, the results provide no evidence that the rewarding nature of running in rodents is an important causal factor in nonphotic phase shifting beyond its role in promoting running.

Cannabinoid reward and aversion effects in the posterior ventral tegmental area are mediated through dissociable opiate receptor subtypes and separate amygdalar and accumbal dopamine receptor substrates.

The ventral tegmental area (VTA) and its projections to the basolateral amygdala (BLA) and nucleus accumbens (NAc) are critical for cannabinoid-related motivational effects. Cannabinoid CB1 receptor (CB1R) transmission modulates VTA dopamine (DA) neuron activity and previous reports demonstrate anatomically segregated effects of CB1R transmission in the VTA. However, the underlying pharmacological and anatomical regions responsible for these effects are currently unknown. The objective of the study is to characterize the motivational effects of localized anterior vs. posterior intra-VTA activation vs. blockade of CB1R transmission and the potential role of intra-BLA and intra-NAc DA transmission in these phenomena. Using a conditioned place preference (CPP) procedure, we administered a CB1 agonist (WIN-55,212-2) or antagonist (AM 251) into the posterior VTA (pVTA) or anterior VTA (aVTA) of rats, combined with intra-BLA or intra-NAc DA receptor blockade and intra-VTA co-administration of selective mu vs. kappa opiate-receptor antagonists. Intra-pVTA CB1R activation produced robust rewarding effects through a mu-opiate receptor mechanism whereas CB1R blockade produced conditioned place aversions (CPA) through a kappa-opiate receptor substrate. In contrast, modulation of aVTA CB1R transmission produced no observable effects. Intra-BLA DA receptor blockade prevented the rewarding effects of pVTA CB1R activation, but had no effects on CB1R blockade-induced aversions. In contrast, intra-NAc DA receptor blockade selectively blocked the aversive effects of pVTA CB1R antagonism. Activation vs. blockade of CB1R transmission in the posterior VTA produces bivalent rewarding or aversive effects through separate mu vs. kappa-opiate receptor substrates. These dissociable effects depend on separate DA receptor transmission substrates in the BLA or NAc, respectively.

Opioid receptors mediate the acquisition, but not the expression of mitragynine-induced conditioned place preference in rats.

Mitragynine is the main psychoactive ingredient of the herbal drug preparation Kratom (Ketum), derived from the plant Mitragyna speciosa. Kratom is a widely abused drug in Southeast Asian and has a psychostimulant profile at low-medium doses, while high doses have opioidergic effects. Mitragynine was shown to possess opiate receptor affinity. However, its role in the behavioural effects of mitragynine is unclear. Here we asked whether the reinforcing effects of mitragynine are mediated by opiate receptors using a conditioned place preference (CPP) paradigm in rats. In the first experiment we tested the effects of the opiate receptor antagonist naloxone (0.1, 0.3 and 1.0mg/kg) on the acquisition of mitragynine (10mg/kg)-induced CPP. In the second experiment, we tested the involvement of opiate receptors in the expression of mitragynine-induced CPP in rats. We found that naloxone suppresses the acquisition of mitragynine-induced CPP. This effect was already evident at a dose of naloxone (0.1mg/kg) which, by itself, had no conditioned place aversion (CPA) effect. Higher doses of naloxone induced a CPA and blocked mitragynine-induced CPP. In contrast, naloxone had no effect on the expression of mitragynine-induced CPP. These findings suggest that the acquisition, but not the expression of the reinforcing effects of mitragynine is mediated by opiate receptors.

Role of thalamic ventral posterolateral nucleus histamine H2 and opiate receptors in modulation of formalin-induced muscle pain in rats.

Histamine and opiate systems contribute to supraspinal processing of pain. In the present study, we investigated the effects of microinjection of histamine and agonists and antagonists of histamine H2 and opiate receptors into the thalamic ventral posterolateral nucleus on muscle pain in rats. The thalamic ventral posterolateral nuclei were bilaterally implanted with two guide cannulas. Muscle pain was induced by intramuscular injection of a diluted formalin solution (2.5%, 50μl) into the belly of gastrocnemius muscle, and pain-related behaviors including paw licking duration and paw flinching number were recorded at five-min blocks for 60min. Formalin produced a biphasic pattern of pain-related behaviors. Ranitidine (a histamine H2 receptor antagonist) alone did not affect pain intensity, whereas it prevented the antinociceptive activities of histamine, dimaprit (a histamine H2 receptor agonist) and morphine (an opiate receptor agonist). Naloxone (an opiate receptor antagonist) alone increased pain, and inhibited histamine-, dimaprit-, and morphine-induced antinociception. Locomotor activity was not changed with these chemicals. Our results showed an interaction between histamine H2 and opiate receptors at the thalamic ventral posterolateral nucleus in modulation of muscle pain.

Critical Review of Alcohol, Alcoholism and the Withdrawal Symptoms. II. Treatment Strategies

Alcoholic beverages, socially accepted drinks around the world, are consumed (legally by adults and illegally by minors) to socialize, celebrate, and relax. However, persistent drinking results in the development of tolerance that necessitates a perpetual increase in alcohol drinking to achieve desired effects. In genetically predisposed subjects and in the presence of certain environmental cue, chronic alcohol drinking induces addiction, characterized by excessive uncontrollable drinking associated with rapid onset of the withdrawal symptoms. Currently there are only three medications approved by the U.S. FDA to treat alcoholism: disulfiram (alcohol metabolizing enzyme inhibitor), naltrexone (opiate receptor antagonist), topiramat and acamprosate (NMDA receptor inhibitor).

Effects of human opiorphin on food intake and water intake in mice following central administration

Human opiorphin plays an important pharmacological functions in rats or mice. The present study was performed to investigate effects and underlying mechanism of central injected opiorphin on food intake and water intake in mice. Intracerebroventricularly (i.c.v.) administered opiorphin (5–20μg/kg) dose-dependently suppressed food intake in fasted mice, but had no influence on food intake in freely feeding mice. The cumulative food intake was significantly decreased at 60min after injection of 10 and 20μg/kg opiorphin and the food intake was significantly reduced during the 20–60min period after treatment. Non-selected opiate receptor antagonist naloxone could fully block the inhibitory effect induced by opiorphin on cumulative food intake at 60min in fasted mice, suggesting that the anorexic effect of opiorphin was related to the opioid system. Moreover, the anorexic effect induced by opiorphin in fasted mice was also significantly inhibited by pretreatment with captopril or valsartan, which suggested that endogenous angiotensin may be involved in the response to opiorphin. Interestingly, the effect of opiorphin on water intake was increased in both fasted and freely feeding mice, which was completely blocked by captopril and valsartan. Furthermore, naloxone did not modify the effect of opiorphin on water intake. All together, the food and water intake effects of opiorphin may be due to the protection of the endogenous angiotensin and opioid peptides from degradation by NEP or APN.

Morphine Inhibited the Rat Neural Stem Cell Proliferation Rate by Increasing Neuro Steroid Genesis.

Up to present, a large number of reports unveiled exacerbating effects of both long- and short-term administration of morphine, as a potent analgesic agent, on opium-addicted individuals and a plethora of cell kinetics, although contradictory effect of morphine on different cells have been introduced until yet. To address the potent modulatory effect of morphine on neural multipotent precursors with emphasis on endogenous sex-related neurosteroids biosynthesis, we primed the rat neural stem cells isolated from embryonic rat telencephalon to various concentrations of morphine including 10, 20, 50 and 100µM alone or in combination with naloxone (100µM) over period of 72h. Flow cytometric Ki-67 expression and Annexin-V/PI based necrosis and apoptosis of exposed cells were evaluated. The total content of dihydrotestosterone and estradiol in cell supernatant was measured by ELISA. According on obtained data, both concentration- and time-dependent decrement of cell viability were orchestrated thorough down-regulation of ki-67 and simultaneous up-regulation of Annexin-V. On the other hand, the addition of naloxone (100µM), as Mu opiate receptor antagonist, could blunt the morphine-induced adverse effects. It also well established that time-course exposure of rat neural stem cells with morphine potently could accelerate the endogenous dihydrotestosterone and estradiol biosynthesis. Interestingly, naloxone could consequently attenuate the enhanced neurosteroidogenesis time-dependently. It seems that our results discover a biochemical linkage between an accelerated synthesis of sex-related steroids and rat neural stem cells viability.

P10 The Effect Of Naltrexone, An Opioid Receptor Antagonist, On Capsaicin Evoked Cough, In Healthy Male Subjects

Introduction Chronic cough is a troublesome condition that reduces patient quality of life. Recent evidence suggests that healthy females cough more than healthy males but the mechanism underlying this in unclear. 1 We hypothesise that opiate-sensitive inhibitory control mechanisms determine capsaicin-evoked cough responses in healthy subjects. Aim To show that in healthy males the number of capsaicin-evoked coughs is increased following administration of naltrexone, an opiate receptor antagonist, compared with placebo. Method 15 male subjects (median age 30 yrs (21–59)) were recruited in to a randomised double blind cross-over trial of single doses of naltrexone vs. placebo given 1 week apart. A capsaicin inhalational challenge (doubling doses 0.48 to 125[micro]M) was performed 60 min after ingestion of naltrexone/placebo using a dosimeter. Four inhalations 30 seconds apart were performed at each concentration and the total coughs evoked at each dose were recorded and verified using a cough monitor. Results There was a tendency for subjects to cough more when treated with naltrexone (16.7 ± 2.7 (SEM) compared with placebo (13.7 ± 1.6), (p = 0.11, general estimating equations). See Figure 1 Conclusion This small pilot study suggest that opiate sensitive inhibitory mechanisms may have a role in controlling the cough reflex even in healthy subjects. References Hilton EC, Baverel PG, Woodcock A, Van Der Graaf PH, Smith JA. J Allergy Clin Immunol . 2013 Oct;132(4):847–55

Opioid Antagonists

Opioid Antagonists