Action Of Morphine Research Articles

A Comparative Study between Ultrasound Guided Pectoral Nerve Block Type II versus Intravenous Patient Controlled Analgesia for Intra-Operative and Post-Operative Analgesia in Patients Undergoing Modified Radical Mastectomy

Abstract Background Breast surgery is becoming more and more common. Patients are often middle-aged women and with high public awareness around issues of breast cancer. The numbers are increasing. Breast surgery is an exceedingly common procedure and associated with an increased incidence of acute and chronic pain. Regional anaesthesia techniques may improve post-operative analgesia for patients undergoing breast surgery. Aim of the Work The primary aim of this study is to compare the efficacy of PECS block versus PCA with iv morphine to provide prolonged post-operative analgesia. The secondary objective is to identify the side effects of both techniques as post-operative analgesic techniques. Patients and Methods This study is a randomized clinical trial study conducted in Ain-shams University Hospitals, Cairo, Egypt for 6 months after medical ethical committee approval. The participants were allocated randomly into two groups of 25 patients each: group A: Patients received general anaesthesia followed by PECS block at the end of the operation before extubation, group B: Patients received general anaesthesia followed by the PCA at the end of surgery after extubation. Results The VAS score in the PECS group was statistically significantly lower at the 1st, 2nd and 4th hours. In this case, the use of PECS for postoperative analgesia is as effective as intravenous Morphine PCA in pain treatment, but with less systemic side effect as the nausea and vomiting is significantly higher in the PCA group than the PECS group at the 6th hour, however, the need of intra operative opioids in PCA group is significant. Conclusion In modified radical mastectomy, PECS block is as effective as intravenous Morphine PCA in pain treatment. Compared with intravenous PCA, PECS block can be considered as a more preferable method because it can avoid the systemic actions of morphine used for PCA, and can decrease the need of analgesia intra-operative, however PCA analgesic effect last longer, less invasive technique and easier to be used while PECS block require hand skills and limited to 24 hours analgesia only.

Additive antinociceptive action of intrathecal anandamide reuptake inhibitor and morphine in the management of post-incisional pain in rats

Spinal opioids have mixed efficacy and their adverse effects force treatment cessation of postoperative pain. Consequently, there is an ongoing search for new therapeutic strategies. Here, we evaluated the analgesic efficacy of intrathecal UCM707, an anandamide reuptake inhibitor, and morphine combination. Firstly, we assessed the effects of morphine (1, 5 and 10 μg), UCM707 (75 μg) and its combination in the hot plate. Then, morphine + UCM707 at sub-effective doses was evaluated in a rat post-incisional pain model. In addition, μ-, CB1r-, CB2r- and TRPV1-antagonists were pre-administered before the combination. Activation of μ-opioid and CB1r, and Cnr1, Cnr2, Oprm1 and TRPV1 expressions were evaluated in the lumbar sacra and periaqueductal grey by [35 S]-GTPγS binding autoradiography and qPCR studies. In the hot plate, morphine (1 μg) and UCM707 (75 μg) induced a more robust analgesic effect than each drug alone. Morphine plus UCM707 did not modify μ-opioid nor CB1 receptor function in the PAG or LS. Cnr1 and TRPV1 expression increased in the lumbar sacra (LS). Morphine plus UCM707 significantly reduced post-incisional pain at 1 and 4 days after surgery. Cnr1, Cnr2 and TRPV1 expressions increased in the LS. Blockade of μ-opioid receptor reduced combination effects on days 1 and 4. CB1r- and CB2r-antagonism reduced morphine + UCM707 effects on days 1 and 4, respectively. CB1r and TRPV1-antagonism improved their antinociceptive effects on day 4. These results revealed a synergistic/additive analgesic effect of UCM707 and morphine combination controlling postincisional pain. CB1r, CB2r and TRPV1 contribute differently as central sensitization occurs.

L-cysteine ethylester reverses the adverse effects of morphine on breathing and arterial blood-gas chemistry while minimally affecting antinociception in unanesthetized rats

L-cysteine ethylester (L-CYSee) is a membrane-permeable analogue of L-cysteine with a variety of pharmacological effects. The purpose of this study was to determine the effects of L-CYSee on morphine-induced changes in ventilation, arterial-blood gas (ABG) chemistry, Alveolar-arterial (A-a) gradient (i.e., a measure of the index of alveolar gas-exchange), antinociception and sedation in male Sprague Dawley rats. An injection of morphine (10 mg/kg, IV) produced adverse effects on breathing, including sustained decreases in minute ventilation. L-CYSee (500 μmol/kg, IV) given 15 min later immediately reversed the actions of morphine. Another injection of L-CYSee (500 μmol/kg, IV) after 15 min elicited more pronounced excitatory ventilatory responses. L-CYSee (250 or 500 μmol/kg, IV) elicited a rapid and prolonged reversal of the actions of morphine (10 mg/kg, IV) on ABG chemistry (pH, pCO2, pO2, sO2) and A-a gradient. L-serine ethylester (an oxygen atom replaces the sulfur; 500 μmol/kg, IV), was ineffective in all studies. L-CYSee (500 μmol/kg, IV) did not alter morphine (10 mg/kg, IV)-induced sedation, but slightly reduced the overall duration of morphine (5 or 10 mg/kg, IV)-induced analgesia. In summary, L-CYSee rapidly overcame the effects of morphine on breathing and alveolar gas-exchange, while not affecting morphine sedation or early-stage analgesia. The mechanisms by which L-CYSee modulates morphine depression of breathing are unknown, but appear to require thiol-dependent processes.

The Effect of Prenatal and Neonatal Fluoride Exposure to Morphine-Induced Neuroinflammation.

Physical dependence is associated with the formation of neuroadaptive changes in the central nervous system (CNS), both at the molecular and cellular levels. Various studies have demonstrated the immunomodulatory and proinflammatory properties of morphine. The resulting neuroinflammation in drug dependence exacerbates substance abuse-related behaviors and increases morphine tolerance. Studies prove that fluoride exposure may also contribute to the development of neuroinflammation and neurodegenerative changes. Morphine addiction is a major social problem. Neuroinflammation increases tolerance to morphine, and neurodegenerative effects caused by fluoride in structures related to the development of dependence may impair the functioning of neuronal pathways, change the concentration of neurotransmitters, and cause memory and learning disorders, which implies this element influences the development of dependence. Therefore, our study aimed to evaluate the inflammatory state of selected brain structures in morphine-dependent rats pre-exposed to fluoride, including changes in cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) expression as well as microglial and astroglial activity via the evaluation of Iba1 and GFAP expression. We provide evidence that both morphine administration and fluoride exposure have an impact on the inflammatory response by altering the expression of COX-1, COX-2, ionized calcium-binding adapter molecule (Iba1), and glial fibrillary acidic protein (GFAP) in brain structures involved in dependence development, such as the prefrontal cortex, striatum, hippocampus, and cerebellum. We observed that the expression of COX-1 and COX-2 in morphine-dependent rats is influenced by prior fluoride exposure, and these changes vary depending on the specific brain region. Additionally, we observed active astrogliosis, as indicated by increased GFAP expression, in all brain structures of morphine-dependent rats, regardless of fluoride exposure. Furthermore, the effect of morphine on Iba1 expression varied across different brain regions, and fluoride pre-exposure may influence microglial activation. However, it remains unclear whether these changes are a result of the direct or indirect actions of morphine and fluoride on the factors analyzed.

Cell Type-Specific Expression of Molecular Players in Morphine Action

Hidden drug abuse has become a concerning issue in Hong Kong, despite an overall decrease in reported cases. The opioid epidemic, fueled by substances like heroin and fentanyl, continues to be a global problem. Understanding the molecular mechanisms of morphine addiction is crucial for developing effective treatments to combat this problem. This study investigates the gene expression patterns of key players in morphine addiction in the Nucleus Accumbens (NAc) region of the mesolimbic dopamine system, a key area in drug-associated reward. The RNA transcripts produced in mice NAc under acute morphine treatment can reveal transcriptional changes that alter the regulation of gene expression related to its molecular mechanisms. By analyzing publicly available single-cell RNA sequencing data, we identified gene expression patterns in specific cell types for genes like BDNF, ΔFosB, CREB, and Npy, all of which were previously studied to be relevant to morphine addiction. The study also highlights novel differentially expressed genes in response to morphine treatment. These findings provide insight into new and relevant genes as well as their cell type-specific expression patterns to glean the pathways that they influence. Understanding these molecular processes can inform personalized pharmaceutical approaches and aid in the development of new therapies.

Comparison of Ultrasound Guided Transversus Abdominis Plane Block versus Intravenous Patient Controlled Analgesia for Post Operative Analgesia in Parturients Undergoing Cesarean Delivery under General Anesthesia

Abstract Background Cesarean delivery rates are rising, and efficient postoperative pain management is a key priority of women undergoing cesarean delivery. Inadequate pain management in the acute postoperative period is associated with persistent pain, greater opioid use, delayed functional recovery, and increased postpartum depression. In addition to pain relief, optimal management of patients after cesarean delivery should address the goals of unrestricted maternal mobility, minimal maternal and neonatal side effects, rapid recovery to baseline functionality, and early discharge home. Aim of the Work The Primary aim is to compare the efficacy of TAP block versus PCA with IV morphine to Provide Prolonged Post-operative analgesia. Secondary objective is to identify the side effects of both techniques as post operative analgesia. Patients and Methods 74 patients were randomly allocated to one of 2 groups (n=37; each); group A received general anesthesia followed by US-guided TAB block at the end of the operation before extubation using 20 ml bupivacaine 0.25% bilaterally. Group B: received general anesthesia followed by PCA at the end of operation after extubation via dedicated 20 G canula woth disposable PCA pump of 100 ml volume, through continuous infusion of 2 ml/hr & bolus application of 1 ml with 15 min lock time using 50 mg morphine, 60 mg ketorolac, 2 mg granisetrone & filled with 0.9% normal saline. Conclusion when TAP block is given in the volume of 20 mL bilaterally, it is as effective as intravenous Morphine PCA in pain treatment. Compared with intravenous PCA, TAP block can be considered as a more preferable method because it can avoid the systemic actions of morphine used for PCA, and its analgesic effect begins earlier.

Morphine-mediated release of astrocyte-derived extracellular vesicle miR-23a induces loss of pericyte coverage at the blood-brain barrier: Implications for neuroinflammation.

Opioids such as morphine are the most potent and efficacious drugs currently available for pain management. Paradoxically, opioids have also been implicated in inducing neuroinflammation and associated neurocognitive decline. Pericytes, a critical component of the neurovascular unit (NVU), are centrally positioned between endothelial cells and astrocytes, maintaining function of the blood-brain barrier (BBB) nd regulating neuroinflammation by controlling monocyte influx under various pathological conditions. The role of pericytes in morphine-mediated neuroinflammation however, has received less attention, especially in the context of how pericytes crosstalk with other central nervous system (CNS) cells. The current study was undertaken to examine the effect of miRNAs released from morphine-stimulated human primary astrocyte-derived extracellular vesicles (morphine-ADEVs) in mediating pericyte loss at the blood-brain barrier, leading, in turn, to increased influx of peripheral monocytes. Our findings suggest that the heterogeneous nuclear ribonucleoprotein complex A2/B1 (hnRNP A2/B1) plays role in morphine-mediated upregulation and release of miR-23a in ADEVs, and through action of morphine via mu opioid receptor.We further demonstrated that miR-23a in morphine-ADEVs could be taken up by pericytes, resulting in downregulation of PTEN expression, ultimately leading to increased pericyte migration. Furthermore, both overexpression of PTEN and blocking the miR-23a target site at PTEN 3UTR (by transfecting miR-23a-PTEN target protector), attenuated morphine-ADEV-mediated pericyte migration. We also demonstrated that in the microvessels isolated from morphine-administered mice, there were fewer PDGFβR + pericytes co-localizing with CD31+ brain endothelial cells compared with those from saline mice. In line with these findings, we also observed increased loss of pericytes and a concomitantly increased influx of monocytes in the brains of morphine-administered pericyte-labeled NG2-DsRed mice compared with saline mice. In conclusion, our findings indicate morphine-ADEVs mediated loss of pericyte coverage at the brain endothelium, thereby increasing the influx of peripheral monocytes in the central nervous system, leading to neuroinflammation.

Differential Patterns of Synaptic Plasticity in the Nucleus Accumbens Caused by Continuous and Interrupted Morphine Exposure.

Opioid exposure and withdrawal both cause adaptations in brain circuits that may contribute to abuse liability. These adaptations vary in magnitude and direction following different patterns of opioid exposure, but few studies have systematically manipulated the pattern of opioid administration while measuring neurobiological impact. In this study, we compared cellular and synaptic adaptations in the nucleus accumbens shell caused by morphine exposure that was either continuous or interrupted by daily bouts of naloxone-precipitated withdrawal. At the behavioral level, continuous morphine administration caused psychomotor tolerance, which was reversed when the continuity of morphine action was interrupted by naloxone-precipitated withdrawal. Using ex vivo slice electrophysiology in female and male mice, we investigated how these patterns of morphine administration altered intrinsic excitability and synaptic plasticity of medium spiny neurons (MSNs) expressing the D1 or D2 dopamine receptor. We found that morphine-evoked adaptations at excitatory synapses were predominately conserved between patterns of administration, but there were divergent effects on inhibitory synapses and the subsequent balance between excitatory and inhibitory synaptic input. Overall, our data suggest that continuous morphine administration produces adaptations that dampen the output of D1-MSNs, which are canonically thought to promote reward-related behaviors. Interruption of otherwise continuous morphine exposure does not dampen D1-MSN functional output to the same extent, which may enhance behavioral responses to subsequent opioid exposure. Our findings support the hypothesis that maintaining continuity of opioid administration could be an effective therapeutic strategy to minimize the vulnerability to opioid use disorders.SIGNIFICANCE STATEMENT Withdrawal plays a key role in the cycle of addiction to opioids like morphine. We studied how repeated cycles of naloxone-precipitated withdrawal from otherwise continuous opioid exposure can change brain function of the nucleus accumbens, which is an important brain region for reward and addiction. Different patterns of opioid exposure caused unique changes in communication between neurons in the nucleus accumbens, and the nature of these changes depended on the type of neuron being studied. The specific changes in communication between neurons caused by repeated cycles of withdrawal may increase vulnerability to opioid use disorders. This highlights the importance of reducing or preventing the experience of withdrawal during opioid treatment.

The ventilatory depressant actions but not the antinociceptive effects of morphine are blunted in rats receiving intravenous infusion of L-cysteine ethyl ester

This study demonstrates that intravenous infusion of the cell-penetrant thiol ester, L-cysteine ethyl ester (L-CYSee), to adult male Sprague-Dawley rats elicited (a) minor alterations in frequency of breathing, expiratory time, tidal volume, minute ventilation, or expiratory drive but pronounced changes in inspiratory time, end-inspiratory and expiratory pauses, peak inspiratory and expiratory flows, EF50, relaxation time, apneic pause, inspiratory drive and non-eupneic breathing index, (b) minimal changes in arterial blood-gas (ABG) chemistry (pH, pCO2, pO2, SO2) and Alveolar-arterial (A-a) gradient (index of alveolar gas exchange), and (c) minimal changes in antinociception (tail-flick latency). Subsequent injection of morphine (10 mg/kg, IV) elicited markedly smaller effects on the above parameters, ABG chemistry, and A-a gradient in rats receiving L-CYSee, whereas morphine antinociception was not impaired. Infusions of L-cysteine or L-serine ethyl ester (oxygen rather than sulfur moiety), did not affect morphine actions on ABG chemistry or A-a gradient. L-CYSee (250 μmol/kg, IV) injection elicited dramatic changes in ventilatory parameters given 15 min after injection of morphine in rats receiving L-CYSee. Our findings suggest that (a) L-CYSee acts in neurons that drive ventilation, (b) L-CYSee reversal of the adverse actions of morphine on ventilation, ABG chemistry and A-a gradient may be via modulation of intracellular signaling pathways activated by morphine rather than by direct antagonism of opioid receptors since morphine antinociception was not diminished by L-CYSee, and (c) the thiol moiety of L-CYSee is vital to efficacy, (d) intracellular conversion of L-CYSee to an S-nitrosylated form may be part of its mechanism of action.

Morphine stimulates cervical cancer cells and alleviates cytotoxicity of chemotherapeutic drugs via opioid receptor-dependent and -independent mechanisms.

Morphine is frequently applied in cancer patients for pain management. However, its effects on cancer are not well understood but observed to be specific to certain cancer types. We previously revealed the stimulatory properties of morphine in esophageal carcinoma. This work addressed the effects of morphine and its underlying mechanisms in cervical cancer. Proliferation, apoptosis, and migration assays were performed to examine the effects of morphine alone and its combinatory effects with chemotherapeutic drugs. Immunoblotting and biochemical analysis were performed to determine the underlying mechanisms of morphine's action. Morphine promoted proliferation in opioid receptor‐dependent manner and stimulated migration in opioid receptor‐independent manner. However, morphine did not affect cervical cancer cell survival. Morphine also interfered with all tested chemotherapeutic drugs (e.g., cisplatin, 5‐FU, and paclitaxel) and alleviates their efficacy. Mechanistically, morphine‐stimulated growth via activating EGFR‐mediated signaling pathways and is opioid‐receptor‐dependent; morphine‐stimulated migration via activating RhoA‐mediated signaling pathways and this is opioid receptor‐independent. Our work suggests a strong correlation of this opioid receptor on growth factor signaling to stimulate growth and opioid receptor‐independent activation of RhoA and consequent migration. Our findings have the potential to guide the clinical use of morphine for patients with cervical cancer.

L-cysteine methyl ester overcomes the deleterious effects of morphine on ventilatory parameters and arterial blood-gas chemistry in unanesthetized rats.

We are developing a series of thiolesters that produce an immediate and sustained reversal of the deleterious effects of opioids, such as morphine and fentanyl, on ventilation without diminishing the antinociceptive effects of these opioids. We report here the effects of systemic injections of L-cysteine methyl ester (L-CYSme) on morphine-induced changes in ventilatory parameters, arterial-blood gas (ABG) chemistry (pH, pCO2, pO2, sO2), Alveolar-arterial (A-a) gradient (i.e., the index of alveolar gas-exchange within the lungs), and antinociception in unanesthetized Sprague Dawley rats. The administration of morphine (10 mg/kg, IV) produced a series of deleterious effects on ventilatory parameters, including sustained decreases in tidal volume, minute ventilation, inspiratory drive and peak inspiratory flow that were accompanied by a sustained increase in end inspiratory pause. A single injection of L-CYSme (500 μmol/kg, IV) produced a rapid and long-lasting reversal of the deleterious effects of morphine on ventilatory parameters, and a second injection of L-CYSme (500 μmol/kg, IV) elicited pronounced increases in ventilatory parameters, such as minute ventilation, to values well above pre-morphine levels. L-CYSme (250 or 500 μmol/kg, IV) also produced an immediate and sustained reversal of the deleterious effects of morphine (10 mg/kg, IV) on arterial blood pH, pCO2, pO2, sO2 and A-a gradient, whereas L-cysteine (500 μmol/kg, IV) itself was inactive. L-CYSme (500 μmol/kg, IV) did not appear to modulate the sedative effects of morphine as measured by righting reflex times, but did diminish the duration, however, not the magnitude of the antinociceptive actions of morphine (5 or 10 mg/kg, IV) as determined in tail-flick latency and hindpaw-withdrawal latency assays. These findings provide evidence that L-CYSme can powerfully overcome the deleterious effects of morphine on breathing and gas-exchange in Sprague Dawley rats while not affecting the sedative or early stage antinociceptive effects of the opioid. The mechanisms by which L-CYSme interferes with the OR-induced signaling pathways that mediate the deleterious effects of morphine on ventilatory performance, and by which L-CYSme diminishes the late stage antinociceptive action of morphine remain to be determined.

Detection of Mu‐Opioid Receptors in SH‐SY5Y Human Neuroblastoma Cells by Flow Cytometry

PurposePharmacological actions of morphine are mediated through G‐protein‐coupled receptors (GPCRs), specifically mu‐opioid receptors (MORs). Morphine‐induced activation of GPCRs inhibits adenylyl cyclase and decreases 3’,5’‐cyclic adenosine monophosphate (cAMP). Neuroblastoma SH‐SY5Y cell lines endogenously express MORs. Our aim was to develop a flow cytometry (FC) assay for MORs on the surface of SH‐SY5Y cells. This assay will provide in‐depth understanding of opioid‐induced downstream cAMP signaling.MethodsSH‐SY5Y human neuroblastoma cells (ATCC® CRL2266™) were grown in DMEM/10% FBS and maintained in a humidified incubator at 37ºC/5%CO2. Cells were seeded in 96‐well white, opaque‐bottom plates (5×104cells/well). Transfection conditions were optimized using ViaFect™ (Promega™) and a stably transfected SH‐SY5Y cell line was established using GloSensor™ ‐23F cAMP plasmid (Promega™) containing hygromycin‐resistance gene. Cells were washed in FACS buffer (PBS + 2% FBS) and incubated for 1h at room temperature with monoclonal rabbit anti‐MOR antibody (Ab) (Novus Biologicals). Following the wash, cells were incubated with donkey anti‐rabbit secondary Ab (Abcam). We used monoclonal mouse anti‐muscarinic Ab (Novus Biologicals) and donkey anti‐mouse secondary Ab (Jackson Labs). Both secondary Abs are bound to a fluorophore (Alexa Fluor® 488) which emits light when excited by FITC channel frequency (excitation/emission: 495nm/519nm). A Cytoflex flow cytometer (Beckman Coulter) analyzes cells for FITC fluorescence emission. Multiple primary and secondary concentrations were tested; Human TruStain Fc blocker (BioLegend) was used to prevent nonspecific tagging.ResultsRelative fluorescence emission was measured as percent shift increase from the untagged control group. Because MOR Abs have been tested in a limited capacity, we tested for presence of muscarinic receptors (another endogenously expressed GPCR in these cells) to establish the FC assay. Initial trials with low primary and secondary MOR Ab concentrations showed limited shifts (~1‐2%), however, muscarinic receptor Abs bound to their receptors at lower concentrations compared to MOR Abs. Testing muscarinic receptors showed secondary Ab concentration‐dependent fluorescence shifts indicating that the technique was viable. Studies with increased concentration ratios of primary and secondary MOR Abs showed secondary Ab concentration‐dependent response with maximum % shifts reaching up to 16%. Use of Fc blocker eliminated nonspecific binding, increasing the percent shift.ConclusionCompared to untagged controls, antibody‐tagging on SH‐SY5Y cell surface produced greater immunofluorescence indicating presence of MORs in both non‐transfected and 23F cAMP plasmid transfected cells. Direct binding of receptor modulators leads to altered downstream cAMP signaling as shown in previous in vitro signaling studies and behavioral mouse models. Detection of the MOR is essential to ensure that cAMP signaling is regulated by MOR agonists. In future studies, we plan to investigate the expression of endothelin‐A receptor (ETAR) and explore potential interactions between MOR and ETAR in SH‐SY5Y cells.

D-cysteine ethyl ester and D-cystine dimethyl ester reverse the deleterious effects of morphine on arterial blood-gas chemistry and Alveolar-arterial gradient in anesthetized rats

We determined whether intravenous injections of the membrane-permeable ventilatory stimulants, D-cysteine ethyl ester (ethyl (2 S)− 2-amino-3-sulfanylpropanoate) (D-CYSee) and D-cystine dimethyl ester (methyl (2 S)− 2-amino-3-[[(2 S)− 2-amino-3-methoxy-3-oxopropyl]disulfanyl] propanoate) (D-CYSdime), could overcome the deleterious actions of intravenous morphine on arterial blood pH, pCO2, pO2 and sO2, and Alveolar-arterial (A-a) gradient (i.e., the measure of exchange of gases in the lungs) in Sprague Dawley rats anesthetized with isoflurane. Injection of morphine (2 mg/kg, IV) caused pronounced reductions in pH, pO2 and sO2 accompanied by elevations in pCO2, all which are suggestive of diminished ventilation, and elevations in A-a gradient, which suggests a mismatch of ventilation-perfusion. Subsequent boluses of D-cysteine ethyl ester (2 ×100 μmol/kg, IV) or D-cystine dimethyl ester (2 ×50 μmol/kg, IV) rapidly reversed of the negative actions of morphine on pH, pCO2, pO2 and sO2, and A-a gradient. Similar injections of D-cysteine (2 ×100 μmol/kg, IV) were without effect, whereas injections of D-cystine (2 ×50 μmol/kg, IV) produced a modest reversal. Our data show that D-cysteine ethyl ester and D-cystine dimethyl ester readily overcome the deleterious effects of morphine on arterial blood gas (ABG) chemistry and A-a gradient by mechanisms that may depend upon their ability to rapidly enter cells. As a result of their known ability to enter the brain, lungs, muscles of the chest wall, and most likely the major peripheral chemoreceptors (i.e., carotid bodies), the effects of the thiolesters on changes in ABG chemistry and A-a gradient elicited by morphine likely involve central and peripheral mechanisms. We are employing target prediction methods to identify an array of in vitro and in vivo methods to test potential functional proteins by which D-CYSee and D-CYSdime modulate the effects of morphine on breathing.

Morphine-induced modulation of Nrf2-antioxidant response element signaling pathway in primary human brain microvascular endothelial cells

Morphine is one of the most potent opioid analgesic used for pain treatment. Morphine action in the central nervous system requires crossing the blood–brain barrier. Due to the controversial relationship between morphine and oxidative stress, the potential pro- or antioxidant effects of morphine in the blood–brain barrier is important to be understood, as oxidative stress could cause its disruption and predispose to neurodegenerative diseases. However, investigation is scarce in human brain endothelial cells. Therefore, the present study evaluated the impact of morphine exposure at three different concentrations (1, 10 and 100 µM) for 24 h and 48 h on primary human brain microvascular endothelial cells. A quantitative data-independent acquisition mass spectrometry strategy was used to analyze proteome modulations. Almost 3000 proteins were quantified of which 217 were reported to be significantly regulated in at least one condition versus untreated control. Pathway enrichment analysis unveiled dysregulation of the Nrf2 pathway involved in oxidative stress response. Seahorse assay underlined mitochondria dysfunctions, which were supported by significant expression modulations of relevant mitochondrial proteins. In conclusion, our study revealed the dysregulation of the Nrf2 pathway and mitochondria dysfunctions after morphine exposure, highlighting a potential redox imbalance in human brain endothelial cells.

Stimulation and transient inactivation of ventral tegmental area modify reinstatement of acquisition phase of morphine-induced conditioned place preference in male rats

For processing the development of psychological dependency, opioid reinforcement, and opiate-related associative reward, learning, and memory in the brain, the ventral tegmental area (VTA) is considered the key zone. As the responsible region for the morphine role in conditioned place preference (CPP), this area has an important role. So, the present research was conducted to investigate the effects of different intensities of electrical stimulation on VTA utilizing CPP, with two morphine doses. Reversible inactivation of VTA was performed via bilateral microinjection of Lidocaine into this area with two implanted separate cannulas. Our findings indicated that 5 mg/kg morphine-induced CPP was suppressed by 150 μA VTA electrical stimulation. The results also showed that bilateral Intra-VTA administration of Lidocaine significantly decreased the 5 mg/kg morphine-induced CPP acquisition phase in comparison with their respective sham group, which reversed in the reinstatement test. It should be concluded that these findings are important for the detection of mesolimbic nervous system ties and could help to find new ways to attenuate the rewarding action of morphine.

Effect of Umbelliprenin on Antinociceptive Activity of Morphine in a Rat Model of Neuropathic Pain Induced by Chronic Constriction Injury of the Sciatic Nerve

Objective: Although morphine is among of the first line medicines for treatment of neuropathic pain, evidence has shown that the morphine efficacy gradually decreases and a tolerance can occur. Rregarding the many reports concerning the antinociceptive and anti-inflammatory properties of umbelliprenin (UMB), this study aimed to investigate the effect of UMB on antinociceptive activity of morphine in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve. Methods: Twenty-four male Wistar rats were randomly divided into sham, CCI and CCI + UMB100 (100 μg UMB per rat) groups. UMB was intrathecally administered once daily for four consecutive days (from the day before surgery until day 2 after surgery). All the animals received a single dose of morphine (5 mg/kg, s.c.) on day 14. To evaluate the effect of UMB on antinociceptive activity of morphine, allodynia and hyperalgesia were measured using the von-Frey and hot plate tests, before and 30 min after morphine injection and the Percentage of Maximum Possible Effect (%MPE) was calculated. Besides, the expression and concentration of tumor necrosis factor-alpha (TNF-α), as a proinflammatory cytokine, was measured in the spinal cord using quantitative real-time PCR (RTPCR) and ELISA, respectively. Results: UMB significantly enhanced anti-allodynic and anti-hyperalgesic effects of morphine in the neuropathic animals. Moreover, UMB considerably downregulated TNF-α expression in the spinal cord of the animals. Conclusion: UMB can enhance the antinociceptive effects of morphine, and this action may be partially due to its anti-inflammatory property.

Modulatory effect of opioid administration on the activity of cholinesterase enzyme: a systematic review of mice/rat models

We aimed to review the literature to find the specific effect of opioids on the activity of cholinesterase (ChE) enzyme which plays a substantial role in the functioning of cholinergic system. Literature search was performed by two independent reviewers in order to find relevant articles about the changes in the activity of ChE in mice or rat following opioid administration. Based on findings from literature review, opioid administration is able to induce cholinergic modulation via decreasing or increasing the activity of ChE enzyme. However, the degree of variation of ChE in various brain regions is different. No gender differences was reported in the effect of opioids on ChE activity. Although chronic opioid administration may decrease enzyme function, ChE activity might be unchanged following opioid withdrawal using naloxone or the development of tolerance. Opioid type affects whether or not naloxone can reverse the changes of ChE. Direct inhibitory action of morphine and the other opioid ligands believed responsible for the decrease in the ChE activity. Moreover, the potency of codeine to induce allosteric enhancement of acetylcholine receptor signaling might be involved in the cholinergic modulation of codeine and other opioids. Animal studies on rat and mice showed that opioids may change the activity of ChE. These changes can pertain an increase or decrease in enzyme activity; as there might be no change. The type of opioid used may have an effect on the cholinergic modulation. It is beneficial to conduct cross-sectional and cohort studies on addicted individuals, especially opium abusers, to find the precise association of opioids with alterations in human acetyl cholinesterase or butyrylcholinesterase. Simulation studies can also examine the structure-function relationships and provide important details to better understand the mechanism of action of opioid compounds on ChE activity. In addition, understanding how opioids impact ChE activity may help perform proper interventions for drug abstinence.

Pain-induced impulsivity is sexually dimorphic and mu-opioid receptor sensitive in rats.

Pain sensation can negatively impact cognitive function, including impulsivity. Pain-induced changes in impulsivity can contribute to development of psychiatric comorbidities found in those with chronic pain conditions. The goal of this study was to determine whether complete Freund's adjuvant (CFA)-induced pain manipulation enhances impulsivity in rats. Whether the pain-induced impulsivity is sexually dimorphic, and if mu-opioid receptors play a role in these processes. Male and female rats were screened for trait impulsivity and designated as high or low impulsive using a delay discounting task. Rats then received a hind paw injection of CFA, and their impulsivity was assessed for 16days. The effects of morphine on impulsivity were also examined. In a separate experiment, rats were pretreated with beta-funaltrexamine (β-FNA) to determine the role of mu-opioid receptors on impulsivity. CFA treatment increased impulsivity in males and females. The onset of CFA-induced impulsivity was faster in high impulsive females than males. Morphine blocked CFA-induced impulsivity in both sexes in a dose- and time-dependent manner. β-FNA prevented the actions of morphine on CFA-induced impulsivity in high impulsive males, but not high impulsive females. Moreover, β-FNA increased CFA-induced impulsivity in morphine naïve males, but not females. These findings demonstrate unique sex differences in CFA-induced impulsivity, response to morphine, and the impact of mu-opioid receptors. A better understanding of cognitive deficits and their mechanisms can provide insight into the development of substance abuse and psychiatric comorbidities that occur in people with chronic pain.

Astrocyte-Derived Extracellular Vesicle–Mediated Activation of Primary Ciliary Signaling Contributes to the Development of Morphine Tolerance

BackgroundMorphine is used extensively in the clinical setting owing to its beneficial effects, such as pain relief; its therapeutic utility is limited because the prolonged use of morphine often results in tolerance and addiction. Astrocytes in the brain are a direct target of morphine action and play an essential role in the development of morphine tolerance. Primary cilia and the cilia-mediated sonic hedgehog (SHH) signaling pathways have been shown to play a role in drug resistance and morphine tolerance, respectively. Extracellular vesicles (EVs) play important roles as cargo-carrying vesicles mediating communication among cells and tissues. MethodsC57BL/6N mice were administered morphine for 8 days to develop tolerance, which was determined using the tail-flick and hot plate assays. EVs were separated from astrocyte-conditioned media using either size exclusion chromatography or ultracentrifugation approaches, followed by characterization of EVs using nanoparticle tracking analysis for EV size distribution and number, Western blotting for EV markers, and electron microscopy for EV morphology. Astrocytes were treated with EVs for 24 hours, followed by assessing primary cilia by fluorescent immunostaining for primary cilia markers (ARL13B and acetylated tubulin). ResultsMorphine-tolerant mice exhibited an increase in primary cilia length and percentage of ciliated astrocytes. The levels of SHH protein were upregulated in morphine-stimulated astrocyte-derived EVs. SHH on morphine-stimulated astrocyte-derived EVs activated SHH signaling in astrocytes through primary cilia. Our in vivo study demonstrated that inhibition of either EV release or primary cilia prevents morphine tolerance in mice. ConclusionsEV-mediated primary ciliogenesis contributes to the development of morphine tolerance.

Biased signaling at mu opioid receptor full‐length C‐terminal splice variants

Acting on the samee G-protein coupled receptor, various ligands produce distinct activities by differentially activating downstream signaling pathways, a phenomenon referred to as biased agonism or functional selectivity. The original mu opioid receptor (MOR-1) has largely been studied in biased agonism mainly through G protein and β-arrestin2 signaling pathways. Mu opioid-induced G protein activation is often associated with its analgesic action, while mu opioid-induced β-arrestin recruitment is commonly linked to the side effects related to traditional opiates. However, there exist multiple full-length 7 transmembrane (7TM) C-terminal variants generated by alternative 3′ splicing of the mu opioid receptor gene, OPRM1, which is conserved from rodent to human. These 7TM C-terminal variants have identical receptor structures including the ligand binding pocket except for a variable intracellular C-terminal sequence. Several in vitro studies indicated marked differences among the 7TM C-terminal variants in mu agonist-induced G protein activation, receptor phosphorylation, internalization, desensitization, and post-endocytic sorting. Using a set of gene targeting mouse models in which a specific C-terminus was truncated at translational level, we demonstrated the functional importance of the C-terminal tails in various morphine actions. In the current study, we examined the role of different 7TM C-terminal variants on mu agonist-induced G protein activation and β-arrestin2 recruitment, which were used to determine signaling bias. The results showed that mu agonists induced significant differences in G protein activation and β-arrestin recruitment among various C-terminal variants. Especially, exon 7-associated 7TM variants displayed greater β-arrestin2 bias for most mu agonists compared to exon 4-associated 7TM MOR-1. Our finding provides new insights into mu agonist-induced biased signaling in vivo where these 7TM C-terminal variants are co-expressed.