Opioid Compounds Research Articles

Rates of Fetal Polydrug Exposures in Methadone-Maintained Pregnancies from a High-Risk Population

Methadone maintenance treatment (MMT) is the standard of care during pregnancy for opioid-dependency, showing efficacy in improving prenatal care and reducing risk of relapse. By design, however, MMT is only intended to prevent withdrawal thus facilitating cognitive behavioural interventions. In order to maximize the benefits of MMT, it is essential that methadone is both properly prescribed and that additional addiction treatment is concurrently administered. This study aims to determine the effectiveness of MMT engagement in high-risk pregnant women in reducing polydrug use by objective laboratory examination of neonatal meconium. Patients and MethodsOver a 29-month period, the Motherisk Laboratory at the Hospital for Sick Children in Toronto analyzed meconium samples as per request by social services and hospitals for drugs of abuse.ResultsOf the 904 meconium samples received, 273 were tested for methadone with 164 positive and 109 negative for methadone. Almost half of the methadone positive samples (46.34%) were also positive for at least one other opioid compound, which did not differ statistically from the methadone-negative control samples (46.79%; Chi square test, p=0.94). No differences were found between the methadone positive and negative groups in rates of concurrent amphetamines, cocaine, cannabis, and alcohol use indicating a similar risk of polydrug use between pregnant women taking or not taking methadone in this population. DiscussionThe high rates of additional opioid and other drug use in the MMT group, suggest that MMT is failing this population of patients. It is possible that methadone doses during pregnancy are not appropriately adjusted for changes in pharmacokinetic parameters (e.g. blood volume, renal function) during the second and third trimesters. This may result in sub-therapeutic dosing creating withdrawal symptoms leading to additional substance use. Alternatively, these results may be demonstrating a substantial lack in delivery of addiction support services in this vulnerable population.

New Opioid Compound Shows Similar Analgesia Effects and Less Tolerance Liability Than Morphine

Topics in Pain Management: December 2013 - Volume 29 - Issue 5 - p 8-9 doi: 10.1097/01.TPM.0000438612.95352.e5

Effects of opioid therapy on human natural killer cells

Opioid compounds, such as morphine, induce powerful analgesic effects and are extensively used clinically to treat a wide variety of pain. The aim of our study was to evaluate the impact of opioid therapy on phenotype and function peripheral blood NK cells. The patients were referred to three Italian pain therapy centers (Milan, Pavia, Piacenza) for chronic pain in neuropathic or mixed somatic components. The patients were between 18 and 75 years old and were of Caucasian ethnicity. We studied the expression of activating and inhibitory NK receptors to discriminate NK subsets with different CD56 surface expression intensities (CD56(bright) and CD56(dull) NK cells). The flow cytometry analysis of the NK cells was at normal levels in peripheral blood lymphocytes with fewer CD56(bright) compared to the CD56(dull) NK cell subset when compared to blood from drug free donors. Furthermore, the cytolytic activity of in vitro patient NK cells analyzed was not lower, as would be expected from the regular expression of activating NK receptors for both subsets. Taken together, these data indicate that NK cells from opioid treated patients do not show any signs of NK cell immune-suppression.

Endogenous opioids regulate alveolar bone loss in a periodontal disease model

AimThe anti-inflammatory effects of exogenous opioid compounds have been demonstrated in several conditions. Nevertheless, the function of endogenous opioid peptides released by the host during inflammatory processes deserves further characterization. The aim of this study was to verify whether endogenous opioids are involved in the progression of the inflammatory alveolar bone loss induced by ligature in rats. Main methodsThe experimental model of periodontal disease (PD) induced by ligature in rats was used throughout the study. A silk ligature was placed around the 2nd upper molar of male Holtzman rats, for 7days. Rats received different doses of either the non-selective opioid antagonist naloxone or vehicle, locally into the afflicted gingival tissue, from the 3rd to the 5th day after ligature placement. In the 7th experimental day, rats were euthanized and their maxillae were collected for evaluation of alveolar bone and fiber attachment loss, presence of neutrophils (myeloperoxidase assay), osteoclast amount, and levels of cytokines IL-6, TNF-α, IL-8 and IL-10 in periodontal tissues. Key findingsNaloxone increased alveolar bone loss significantly, in a dose-dependent manner, in relation to vehicle-treated rats. In contrast, the opioid antagonist did not affect the loss of fiber attachment. The treatment with naloxone also induced a significant increase in myeloperoxidase levels, osteoclast number and cytokines in periodontal tissues of rats with ligature-induced PD. SignificanceEndogenous opioids protect the host from the progression of inflammatory alveolar bone loss that occurs in chronic periodontitis.

Peripheral antinociceptive efficacy and potency of a novel opioid compound 14-O-MeM6SU in comparison to known peptide and non-peptide opioid agonists in a rat model of inflammatory pain

This study compared the peripheral analgesic effects of a novel opioid agonist 14-O-methylmorphine-6-O-sulfate (14-O-MeM6SU), to that of non-peptide (morphine, fentanyl) and peptide opioid agonists (Met-enkephalin; met-ENK and β-endorphin; β-END) in a model of localized inflammatory pain evoked by intraplantar (i.pl.) Freund's complete adjuvant (FCA). Nociceptive responses to local opioid agonists were measured by pressure paw-withdrawal procedures. In addition, the antinociceptive efficacy and potency of these test compounds in vivo was compared to that in vitro using the rat vas deferens (RVD) bioassay. Intraplantar 14-O-MeM6SU (0.32–2.53nmol/rat), morphine (14.95–112.15nmol/rat), fentanyl (0.19–2.36nmol/rat), met-ENK (0.10–10nmol/rat) and β-END (0.77–5.00nmol/rat) dose dependently increased paw pressure thresholds exclusively in inflamed hindpaws. At higher doses analgesic effects were also seen in noninflamed paws for 14-O-MeM6SU, morphine and fentanyl but not for met-ENK or β-END. The maximal possible local analgesic effect (%) measured in inflamed paws was 50.6±2.7, 18.23±1.78, 37.44±2.17, 36.00±1.43, and 40.69±0.91 for 14-O-MeM6SU, morphine, fentanyl, met-ENK and β-END, respectively. Interestingly, i.pl. administered opioid peptides met-ENK and β-END displayed a peripheral analgesic ceiling effect. This local antinociception was antagonized by co-administered opioid antagonist naloxone-methiodide (NAL-M). Similar to the analgesic testing, the RVD showed the following efficacy order of the test compounds: 14-O-MeM6SU>β-END>fentanyl>met-ENK⪢morphine. Taken together, 14-O-MeM6SU was more potent than morphine, fentanyl and met-ENK and β-END and displayed superiority in the maximum antinociceptive effects. The superiority of local antinociceptive effects of 14-O-MeM6SU might be due to both pharmacodynamic and pharmacokinetic factors.

Orally Active Opioid Compounds from a Non-Poppy Source

The basic science and clinical use of morphine and other "opioid" drugs are based almost exclusively on the extracts or analogues of compounds isolated from a single source, the opium poppy (Papaver somniferum). However, it now appears that biological diversity has evolved an alternative source. Specifically, at least two alkaloids isolated from the plant Mitragyna speciosa, mitragynine ((E)-2-[(2S,3S)-3-ethyl-8-methoxy-1,2,3,4,6,7,12,12b-octahydroindolo[3,2-h]quinolizin-2-yl]-3-methoxyprop-2-enoic acid methyl ester; 9-methoxy coryantheidine; MG) and 7-hydroxymitragynine (7-OH-MG), and several synthetic analogues of these natural products display centrally mediated (supraspinal and spinal) antinociceptive (analgesic) activity in various pain models. Several characteristics of these compounds suggest a classic "opioid" mechanism of action: nanomolar affinity for opioid receptors, competitive interaction with the opioid receptor antagonist naloxone, and two-way analgesic cross-tolerance with morphine. However, other characteristics of the compounds suggest novelty, particularly chemical structure and possible greater separation from side effects. We review the chemical and pharmacological properties of these compounds.

Active behaviours produced by antidepressants and opioids in the mouse tail suspension test

Most classical preclinical tests to predict antidepressant activity were initially developed to detect compounds that influenced noradrenergic and/or serotonergic activity, in accordance with the monoaminergic hypothesis of depression. However, central opioid systems are also known to influence the pathophysiology of depression. While the tail suspension test (TST) is very sensitive to several types of antidepressant, the traditional form of scoring the TST does not distinguish between different modes of action. The present study was designed to compare the behavioural effects of classical noradrenergic and/or serotonergic antidepressants in the TST with those of opioids. We developed a sampling technique to differentiate between behaviours in the TST, namely, curling, swinging and immobility. Antidepressants that inhibit noradrenaline and/or serotonin re-uptake (imipramine, venlafaxine, duloxetine, desipramine and citalopram) decreased the immobility of mice, increasing their swinging but with no effect on their curling behaviour. No differences were observed between antidepressants that act on noradrenergic or serotoninergic transmission. While opioid compounds also decreased the immobility of the mice [morphine, codeine, levorphanol, (-)-methadone, (±)-tramadol and (+)-tramadol], they selectively increased curling behaviour. Blocking opioid receptors with naloxone prevented the antidepressant-like effect of codeine, and μ-opioid receptor knockout decreased normal curling behaviour and blocked (±)-tramadol-induced curling, further demonstrating the reliability and validity of this approach. These results show that at least two behaviourally distinct processes occur in the TST, highlighting the antidepressant-like effects of opioids evident in this test. Furthermore, our data suggest that swinging and curling behaviours are mediated by enhanced monoamine and opioid neurotransmission, respectively.

A homogeneous single-label quenching resonance energy transfer assay for a δ-opioid receptor–ligand using intact cells

This study, a homogeneous assay system for delta opioid receptor binding ligands has been developed using Quenching Resonance Energy Transfer (QRET). The QRET system allows receptor-ligand binding assays on intact cells using a single-label approach and a nonspecific quenching mechanism. Binding of antagonists or agonists to the receptor can be defined using a europium(III) labeled ligand. In the presence of the unlabeled ligand the labeled ligand is displaced and remains in solution. The non-bound labeled ligand is not protected by the target receptor, and the luminescence signal is quenched. For this objective, a Eu(III) labeled peptide molecule with three different linkers (AX0, AX1 and AX2) was designed. Peptides were evaluated using the homogeneous QRET technique, radioligand binding assays and the heterogeneous time-resolved luminescence (TRL) technique. Using the Eu-AX0 peptide and the QRET method, a panel of opioid compounds (naltrexone, naltrindole, SCN-80, DPDPE and DAMGO) was tested to prove the assay performance. The signal-to-background ratio for the tested opioid ligand ranged from 3.3 to 12.0. The QRET method showed prominent performance also in high DMSO concentrations. QRET is a homogenous and a non-radioactive detection system for screening and this is the first attempt to utilize peptide ligands in the QRET concept.

Intranasal oxycodone self-administration in non-dependent opioid abusers.

Oxycodone, an opioid with known abuse liability, is misused by the intranasal route. Our objective was to develop a model of intranasal oxycodone self-administration useful for assessing the relative reinforcing effects of opioids and potential pharmacotherapies for opioid use disorders. Healthy, sporadic intranasal opioid abusers (n = 8; 7 M, 1 F) completed this inpatient 2.5-week, randomized, double-blind, placebo-controlled, crossover study. Each intranasal oxycodone dose (0, 14 & 28 mg) was tested in a separate 3-day block of sessions. The first day of each block was a sample session in which the test dose was given. Two randomized progressive ratio sessions were conducted on the next 2 days: (1) subjects could work for the test dose over 7 trials (1/7th of total dose/trial), and (2) subjects could work for either a portion of the dose (1/7th) or money ($3) over 7 trials. Physiological and subjective measures were collected before and after drug administration for all sessions. Subjects never worked to self-administer placebo regardless of whether money was available. In both self-administration sessions, oxycodone self-administration was dose-dependent. Subjects worked less for drug (28 mg oxycodone) when money was available but only modestly so. Oxycodone dose-dependently increased VAS ratings of positive drug effects (e.g., "like") during sample sessions (p < .05). These reports were positively correlated with self-administration behavior (e.g., "like," r = .65). These data suggest that both procedures are sensitive for detecting the reinforcing properties of intranasal oxycodone and may be used to further explore the characteristics of opioid compounds and potential pharmacotherapies for treatment.

Measuring online endorsement of prescription opioids abuse: an integrative methodology

The ability to track prescription opioid abusers' endorsement of compounds may be valuable in forecasting abuser's preferences. We developed a metric, referred to as the Endorsement Ratio (ERo), to explore the feasibility of quantifying the sentiment expressed by opioid abusers who post online about prescription opioid products. Internet posts written between April 1, 2010 and March 31, 2011 and related to six prescription opioid compounds (oxycodone ER, hydrocodone, hydromorphone, oxymorphone, morphine ER, and tramadol) were identified and qualitatively coded. A mixed effects multinomial logistic regression was employed to model the probability of observing endorsing, discouraging, mixed, or unclear messages per compound. Endorsement-to-discouragement ratio (ERo) and ratio of endorsement-to-discouragement ratios (RERo) were estimated for each compound. In the study sample of 12 838 Internet posts, a ranking of endorsement could be established, with oxymorphone as most endorsed (ERo = 7.39), followed by hydromorphone (ERo = 5.02), hydrocodone (ERo = 3.53), oxycodone ER (ERo = 3.23), morphine ER (ERo = 2.71), and tramadol (ERo = 1.76). Relative rankings of products required that route of administration be considered. This study expands existing Internet monitoring approaches by developing a metric to estimate the endorsement of specific prescription opioid compounds as viewed through the lens of Internet communities. Route of administration must be taken into account when examining preferences of drug abusers for various products. This study did not assess whether the novel metric is valid with respect to classification of abuse rates of different drugs. Further studies examining external validation studies are warranted.

Opioid receptor characterisation of neuronally stimulated isolated human vas deferens

Rodent vas deferens is routinely used as a native tissue preparation to assess opioid pharmacology of new compounds. The aim of this study was to investigate the effects of a selected number of opioid compounds in the human vas deferens. Stable contractions to electrical field stimulation (EFS) were inhibited by guanethidine (1μM) and tetrodotoxin (TTX, 1μΜ), confirming neuronally induced contractions. Contractile responses to EFS were inhibited by the selective δ-opioid agonists (DPDPE ([D-Pen2,5]enkephalin), PF-391459 (3-{4-[(R)-[(2S,5R)-4-benzyl-2,5-dimethylpiperazin-1-yl](3-hydroxyphenyl)methyl]phenyl}propanoic acid) and SNC-80 ((+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide)) (tested from 1ρM to 10μM or maximum), and the μ-opioid agonists DAMGO ([D-Ala(2), NMe-Phe(4), Gly-ol(5)]-enkephalin), loperamide and SC-50484 (N-{2-[(N-acetyl-L-phenylalanyl)amino]-1,1-dimethylethyl}-L-tyrosinamide). There was no effect using the selective κ agonist U50488 (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide) (tested from 1ρM to 10μM). The selective δ-opioid antagonist naltrindole (10nM) surmountably antagonised the responses to DPDPE, but not to PF-3911459. Responses to DAMGO were completely abolished in the presence of the μ-opioid antagonist CTAP (3μM), which only weakly antagonised responses to SC-50484. We conclude that under these conditions, δ and μ-opioid receptors, but not κ-opioid receptors, are functional in the neuronally stimulated longitudinal human vas deferens. Additionally, the human vas deferens preparation can be used as part of a drug discovery screening project to assess opioid potency, efficacy and selectivity at native human tissues, thus providing more confidence in translation.

Opioid extended-release tablets with improved tamper-resistant properties

Objective: To prepare a polyethylene oxide-based tablet with high mechanical strength that would release an opioid for once- or twice-daily administration. This tablet would also create barriers against crushing and subsequent preparation steps for abuse and misuse that are not present in conventional opioid formulations.Research design & methods: Innovative manufacturing processes were created by applying heat and force simultaneously, using tramadol HCl as model compound; production scale testing used oxymorphone HCl. Standardized in vitro crush force and extraction tests were performed.Results & discussion: A production scale manufacturing process using hot melt extrusion of a strand, cooling, slicing and shaping the slices into tablet form produced stable oxymorphone extended-release (ER) tablets with in vitro dissolution characteristics similar to commercial oxymorphone ER. The tablets resisted crushing by spoons, pill crushers and a hammer and resisted extraction in a test battery of solvents. The standardized tampering methods used here do not include all methods an abuser might employ. Postmarketing data will be needed to determine the actual impact of tamper resistance mechanisms on opioid abuse rates.Conclusions: This purely mechanical approach to tamper resistance may make a tablet less attractive for abuse without exposing compliant patients to new risks associated with opioid antagonists or aversive compounds. A compliant patient's risk of adverse events may be reduced by the tablet's resistance to accidental crushing.

The analgesic activity of biphalin and its analog AM 94 in rats

Biphalin is an opioid linear octapeptide, which displays a broad affinity for all opioid receptors (μ, δ and κ), as well as exceptionally high antinociceptive activity. AM 94 is a biphalin analog and a selective agonist at μ and δ opioid receptors. This study investigated the antinociceptive profile of AM 94. All antinociception evaluations were made in adult male rats using the hot-plate test. AM 94 proved to induce greater and longer antinociception compared to biphalin following intracebroventricular (1nmol/kg) and intravenous administration (1200nmol/kg) as evaluated by % maximum possible effect (M.P.E.), when administered intracerebroventricularly and intravenously and sustained analgesia up to 210min. The antinociceptive activities of biphalin and AM 94 were antagonized by naloxone (10mg/kg intraperitoneally). Our data suggest that AM 94 could be regarded as a novel pharmacologically active opioid compound for eliciting potent and sustained analgesia after central and peripheral administration.

A Group III mGluR agonist potentiates morphine's anti-hyperalgesic effect on sensitized nociceptors

Opioid compounds (i.e. morphine) are used extensively to treat pain in acute and chronic settings. Unfortunately, opioids induce many burdensome side effects encompassing itching, nausea, constipation, difficulty breathing, addiction, tolerance, and dependence. In order to reduce side effects, current studies focus on using low doses of morphine in combination with other drugs such as Group III metabotropic glutamate receptor (mGluR) agonists. We demonstrated previously that combining low doses of a Group III mGluR agonist (L-AP4) and morphine increase morphine's potency in the periphery and that the low dose combination possesses a synergistic relationship.

A comparison of the analgesic effects of H-Dmt-D-Arg-Phe-Lys-NH2, a synthetic opioid peptide, and morphine in experimental neuropathic pain

H-Dmt-D-Arg-Phe-Lys-NH2 ([Dmt1]DALDA) is a synthetic tetrapeptide with extraordinary selectivity for the mu-opioid receptor and has unique characteristics. [Dmt1]DALDA appears to act predominantly in the spinal cord to produce analgesia while morphine, the prototypical mu-opioid agonist, acts both in the brain and the spinal cord (1). Furthermore, [Dmt1]DALDA inhibits norepinephrine re-uptake (2) and it is also a mitochondria-targeted antioxidant (3). With these characteristics, [Dmt1]DALDA may be more effective as an analgesic than morphine especially in the treatment of neuropathic pain. This study was designed to compare the effects of systemic [Dmt1]DALDA and morphine on experimental neuropathic pain in rats. Neuropathic pain in the right hind limb was produced by tight ligation of the L5 spinal nerve and was evaluated by thermal hyperalgesia using the Hargreaves paw withdrawal test. ED30 and ED90 doses of morphine and [Dmt1]DALDA were determined by dose-response assays in naïve rats and their effects on thermal hyperalgesia in neuropathic animals were compared. Both ED30 and ED90 doses of [Dmt1]DALDA were more effective in increasing paw withdrawal latencies in neuropathic rats as compared to ED30 and ED90 doses of morphine, respectively. The results suggest that [Dmt1]DALDA may be a promising opioid compound for the treatment of neuropathic pain. Supported in part by a Grant-in-aid for Cancer Research (Study Group on Palliative Care and Psycho-oncology in Cancer Treatment) from the Ministry of Health and Welfare, Japan (NS). (1. Shimoyama, Pharmacol, 2009; 2.Shimoyama, J Pharmacol Exp Ther, 2001; 3. Szeto and Schiller, Pharm Res, 2011.) H-Dmt-D-Arg-Phe-Lys-NH2 ([Dmt1]DALDA) is a synthetic tetrapeptide with extraordinary selectivity for the mu-opioid receptor and has unique characteristics. [Dmt1]DALDA appears to act predominantly in the spinal cord to produce analgesia while morphine, the prototypical mu-opioid agonist, acts both in the brain and the spinal cord (1). Furthermore, [Dmt1]DALDA inhibits norepinephrine re-uptake (2) and it is also a mitochondria-targeted antioxidant (3). With these characteristics, [Dmt1]DALDA may be more effective as an analgesic than morphine especially in the treatment of neuropathic pain. This study was designed to compare the effects of systemic [Dmt1]DALDA and morphine on experimental neuropathic pain in rats. Neuropathic pain in the right hind limb was produced by tight ligation of the L5 spinal nerve and was evaluated by thermal hyperalgesia using the Hargreaves paw withdrawal test. ED30 and ED90 doses of morphine and [Dmt1]DALDA were determined by dose-response assays in naïve rats and their effects on thermal hyperalgesia in neuropathic animals were compared. Both ED30 and ED90 doses of [Dmt1]DALDA were more effective in increasing paw withdrawal latencies in neuropathic rats as compared to ED30 and ED90 doses of morphine, respectively. The results suggest that [Dmt1]DALDA may be a promising opioid compound for the treatment of neuropathic pain. Supported in part by a Grant-in-aid for Cancer Research (Study Group on Palliative Care and Psycho-oncology in Cancer Treatment) from the Ministry of Health and Welfare, Japan (NS). (1. Shimoyama, Pharmacol, 2009; 2.Shimoyama, J Pharmacol Exp Ther, 2001; 3. Szeto and Schiller, Pharm Res, 2011.)

Bifunctional μ/δ Opioid Peptides: Variation of the Type and Length of the Linker Connecting the Two Components

On the basis of evidence that opioid compounds with a mixed μ agonist/δ antagonist profile may produce an antinociceptive effect with low propensity to induce side effects, bifunctional opioid peptides containing the μ agonist H-Dmt-d-Arg-Phe-Lys-NH(2) ([Dmt(1) ]DALDA; Dmt = 2',6'-dimethyltyrosine) connected tail-to-tail via various α,ω-diaminoalkyl- or diaminocyclohexane linkers to the δ antagonists H-Tyr-TicΨ[CH(2) -NH]Cha-Phe-OH (TICP[Ψ]; Cha = cyclohexylalanine, Tic = 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid), H-Dmt-Tic-OH or H-Bcp-Tic-OH (Bcp = 4'-[N-((4'-phenyl)phenethyl)carboxamido]phenylalanine) were synthesized and pharmacologically characterized in vitro. Bifunctional [Dmt(1) ]DALDA→NH-(CH(2) )(n) -NH←TICP[Ψ] compounds (n = -12) showed decreasing μ and δ receptor binding affinities with increasing linker length. As expected, several of the bifunctional peptides were μ agonist/δ antagonists with low nanomolar μ and δ receptor binding affinities. However, compounds with unexpected opioid activity profiles, including a μ partial agonist/δ partial agonist, μ antagonist/δ antagonists and μ agonist/δ agonists, were also identified. These results indicate that the binding affinities and intrinsic efficacies of these bifunctional compounds at both receptors depend on the length and type of the linker connecting the μ and δ components. An important recommendation emerging from this study is that the in vitro activity profiles of bifunctional compounds containing an agonist and an antagonist component connected via a linker need to be determined prior to their pharmacological evaluation in vivo.

A morphine/heroin vaccine with new hapten design attenuates behavioral effects in rats

Heroin use has seriously threatened public heath in many countries, but the existing therapies continue to have many limitations. Recently, immunotherapy has shown efficacy in some clinical studies, including vaccines against nicotine and cocaine, but no opioid vaccines have been introduced in clinical studies. The development of a novel opioid antigen designed specifically for the prevention of heroin addiction is necessary. A morphine-keyhole limpet hemocyanin conjugate was prepared and administered subcutaneously in rats. Antibody titers in plasma were measured using an enzyme-linked immunosorbent assay (ELISA). Competitive ELISA was used to assess the selectivity of the antibodies. Dopamine concentrations in the nucleus accumbens in rats after vaccine administration were determined by high-performance liquid chromatography with electrochemical detection. The effects of the vaccine on the heroin-primed restatement of self-administration and locomotor sensitization were evaluated. A novel hapten, 6-glutarylmorphine, was produced, and the vaccine generated a high antibody titer response. This vaccine displayed specificity for both morphine and heroin, but the anti-morphine antibodies could not recognize dissimilar therapeutic opioid compounds, such as buprenorphine, methadone, naloxone, naltrexone, codeine, and nalorphine. The morphine antibody significantly decreased morphine-induced locomotor activity in rats after immunization. Importantly, rats immunized with this vaccine did not exhibit heroin-primed reinstatement of heroin seeking when antibody levels were sufficiently high. The vaccine reduced dopamine levels in the nucleus accumbens after morphine administration, which is consistent with its behavioral effects. These results suggest that immunization with a novel vaccine is an effective means of inducing a morphine-specific antibody response that is able to attenuate the behavioral and psychoactive effects of heroin.

Effectiveness of electroacupuncture analgesia compared with opioid administration in a dog model: a pilot study

Although opioid analgesics are the usual drugs to treat post-surgical pain, acupuncture has also been demonstrated to relieve various pain syndromes. The present pilot study aims to investigate the efficacy of electroacupuncture compared with a conventional opioid compound, butorphanol, for postoperative pain treatment in dogs undergoing elective ovariohysterectomy. Twelve dogs were randomly allocated into two groups. Dogs received either electroacupuncture stimulation (16 and 43 Hz) at Shen Shu, Chang Shu, He Gu, Tai Yuan, Zu San Li, Yang Ling Quan, and Bai Hui acupoints, while control dogs were treated with butorphanol. Cardiovascular and respiratory parameters were recorded for both groups during operation. Plasma β-endorphin concentrations were evaluated before surgery (baseline) and up to 24 h later. For each dog, pain was measured according to a dedicated subjective pain scoring system. Plasma β-endorphin levels in dogs receiving electroacupuncture increased significantly against baseline values after 1 and 3 h after surgery. Moreover, the end-tidal isoflurane concentration needed for second ovary traction was significantly lower in acupuncture-treated dogs than control animals. All animals having electroacupuncture experienced prolonged analgesia, over 24 h at least, while four out of six dogs treated with butorphanol needed post-surgical ketorolac and tramadol supplementation to their pain relief. The results obtained from the present investigation showed some evidence for electroacupuncture as an alternative technique to provide postoperative analgesia in dogs.

TH-030418: a potent long-acting opioid analgesic with low dependence liability

Numerous efforts have been made on the chemical modification of opioid compounds, with the ultimate goal of developing new opioid analgesics that is highly potent and low/non-addictive. In a search for such compounds, TH-030418 [7α-[(R)-1-hydroxy-1-methyl-3-(thien-3-yl)-propyl]-6,14-endo-ethanotetrahydrooripavine] was synthesized. Here, we evaluated the pharmacological activities of TH-030418, in comparison with morphine, the prototype opioid analgesic. In radioligand binding assays, TH-030418 bound potently and nonselectively to μ-, δ-, κ-, and ORL1 (opioid receptor-like 1) receptors stably expressed in CHO (Chinese hamster ovary) cells with K (i) values of 0.56, 0.73, 0.60, and 1.55nM, respectively. When administered subcutaneously, TH-030418 was much more potent than morphine in analgesia, with the ED(50) values of 1.37μg/kg and 1.70μg/kg in hot plate and acetic acid writhing tests, respectively. The opioid antagonist naloxone blocked the antinociceptive effect of TH-030418, indicating that the action of TH-030418 was mediated by opioid receptors. The antinociceptive effect of s.c. TH-030418 in hot plate test lasted for more than 12h, which is much longer than those of morphine (2.5h) and dihydroetorphine (1.5h). In addition, naloxone did not precipitate withdrawal syndrome in the mice treated with TH-030418 previously. Most importantly, TH-030418 did not induce conditioned place preference in mice after chronic treatment. These results indicate that TH-030418 is a potent long-acting opioid analgesic with low dependence liability and may be of some value in the development of new analgesics.

Abstract 4526: Inhibition of human multiple myeloma proliferation by naltrindole

Abstract The purpose of this study was to test and characterize the antiproliferative activity of naltrindole (Nti), a selective delta opioid receptor antagonist, toward human multiple myeloma (MM) cells. Nti has been shown to inhibit the allogeneic mixed lymphocyte reaction in vitro, and to block graft rejection in vivo, similarly to cyclosporine A. Based on its immunosuppressive properties we decided to test the effects of Nti on proliferation of MM cells. MM is an invasive and incurable plasma cell neoplasm responsible for 10% of all hematological malignancies. We have screened a variety of opioid compounds for activity against MM and we found that Nti inhibited the proliferation of several human MM cell lines (U266, RPMI 8226, ARP1) with an EC50 of approximately 20 μM, whereas a variety of other human cells lines were substantially less sensitive. Co-culture of MM cells with human bone marrow stromal cells did not affect the antiproliferative activity of Nti. A 10-fold molar excess of naltrexone, a non-selective opioid antagonist, did not block the Nti-induced inhibition of U266 cell proliferation. [3H]-Nti exhibits saturable, low affinity binding to intact MM cells and the pharmacological properties of the Nti binding site differ significantly from the properties of the delta opioid receptor, leading us to hypothesize that Nti inhibits proliferation of MM cells through a non-opioid receptor-dependent mechanism. RT-PCR assays confirmed the lack of delta, kappa and mu receptor mRNA in U266 and RPMI 8226 MM cells. The identity of the naltrindole binding site is currently under investigation. Nti does not induce apoptosis in MM cells, based on FACS analysis and caspase cleavage assays. While investigating the mechanism of action of Nti, we have observed that it increases intracellular calcium levels in MM cells, and the calcium appears to be released from the endoplasmic reticulum, based on inhibition of the response following thapsigargin treatment. This effect is specific to Nti as other opioids such as naltrexone and morphine do not affect the levels of calcium in MM cells, nor do they block the activity of Nti. Based on the observed in vitro anti-proliferative activity of Nti toward MM cell lines, an in vivo study was conducted. Nti injected IP daily at 30mg/kg significantly decreased tumor volumes in a murine SCID/human RPMI 8226 xenograft model over a 39-day period compared with saline injected controls. Curcumin, a constituent of turmeric extracted from the rhizomes of the plant Curcuma longa) has been shown to induce apoptosis in MM cells. We have also observed that curcumin inhibits the proliferation of MM cells. Although the chemical structures of Nti and curcumin differ substantially, curcumin inhibits Nti binding with an EC50 of 58 µM in MM cells. It appears that Nti and curcumin warrant further study as potential therapeutic agents for the treatment of human MM. Supported by grants from NIDA, the NJ Commission on Cancer Research, and the Foundation of UMDNJ. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4526. doi:10.1158/1538-7445.AM2011-4526