Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0278080 (physical dependence)
 1,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present experiments were performed to investigate the effects of the selective mu opioid receptor antagonist, beta-funaltrexamine (beta-FNA), on the physical dependence liability of butorphanol (a mixed agonist/antagonist opioid analgesic). Butorphanol (26 nmol/microliter/h) was continuously infused via osmotic minipumps into the lateral cerebral ventricle of male Sprague-Dawley rats for 72 h. beta-FNA (12, 24, and 48 nmol/5 microliter/rat) was administered ICV 3 h prior to and 48 h after initiation of the butorphanol infusion. Treatment with beta-FNA significantly diminished naloxone-induced escape behavior, hypothermia, and loss of body weight in a dose-dependent manner, while naloxone-induced teeth-chattering, forepaw tremors, and urination were also reduced, but in a dose-independent manner. These results suggest that the mu opioid receptor is partially involved in the development of physical dependence upon butorphanol.
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PMID:Effects of beta-funaltrexamine on butorphanol dependence. 152 43

Morphine-dependent rats can be trained to discriminate between s.c. injections of saline and 0.1 mg/kg of naltrexone. The discriminative effects of naltrexone, measured by the number of trials completed on the naltrexone-appropriate choice lever in a 20-trial avoidance paradigm, derive from stimuli associated with morphine withdrawal. Opiate and nonopiate drugs were injected s.c. and examined for their ability to block naltrexone-induced discriminative effects and loss of body weight in morphine-dependent rats. Seven opiates blocked dose dependently the discriminative effects of naltrexone and loss of body weight. Potency ranged from fentanyl (330 X morphine) to meperidine (less than 1 X morphine); effects were stereoselective for levorotatory isomers. Loperamide, an opiate that does not readily enter the brain, blocked loss of body weight but not discriminative effects, suggesting that discriminative effects are mediated centrally. Nonopiate behavioral depressants, diazepam, haloperidol and pentobarbital, did not substantially affect either dependent variable, but clonidine (0.01-1.0 mg/kg) blocked discriminative effects of naltrexone partially and weight loss completely. The blockade by morphine (30 mg/kg) of naltrexone-induced discriminative effects and weight loss was surmounted by increasing the dose of naltrexone whereas the blockade by clonidine (0.1 mg/kg) was not. Thus, blockade by opiates of effects of naltrexone appears to be due to a competitive interaction at the mu opioid receptor; clonidine has a different mechanism of action. This discrimination paradigm may afford a specific animal model for studying fundamental processes underlying physical dependence on opiates and for evaluating novel pharmacologic approaches for treating opiate withdrawal in humans.
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PMID:Discriminative stimulus effects of morphine withdrawal in the dependent rat: suppression by opiate and nonopiate drugs. 403 2

U-50,488 (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide) displays analgesic actions in a variety (thermal, pressure and irritant) of assays in mice and rats. Naloxone and MR-2266 block this analgesic effect; thus it is mediated by opioid receptors. However, when compared to morphine analgesia, the naloxone and MR-2266 pA2 values for U-50,488 analgesia were much lower and higher, respectively. Likewise, although tolerance occurs to both morphine and U-50,488 analgesia, there was no cross-tolerance between these drugs, and U-50,488 does not cause morphine-type physical dependence. These observations suggest that different opioid receptors mediate the analgesic effects of morphine and U-50,488. The effects of U-50,488 appear to be mediated by the so-called kappa opioid receptor. In contrast to U-50,488, other reputed kappa opioid agonists displayed varying degrees of mu agonist (ketazocine and ethylketocyclazocine) and narcotic antagonist (bremazocine) activities. Thus U-50,488 is a more selective kappa agonist. This conclusion is further supported by binding studies; of all compounds tested, U-59,488 displacement of [3H]ethylketocyclazocine binding was uniquely not blocked by high concentrations of dihydromorphine. In addition to analgesia, this selective kappa agonist also causes opioid receptor-mediated sedation, diuresis and corticosteroid elevations. U-50,488 is a useful tool for studying contrasting kappa and mu opioid receptor-mediated effects.
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PMID:U-50,488: a selective and structurally novel non-Mu (kappa) opioid agonist. 612 21

Morphine was administered intracerebroventricularly to normal or recombinant inbred CXBK (mu-opioid receptor deficient) mice and antinociception was determined against two different stimuli. Morphine-induced antinociception against acetylcholine was strain-dependent, whereas against endothelin-1 it was not. The antinociception was mediated via opioid mu receptors (blocked by beta-FNA, but not naltrindole, ICI 174,864 or nor-BNI) through separate pathways, one naloxonazine-sensitive and the other naloxonazine-insensitive. Taken together, these results appear to demonstrate supraspinal morphine-induced antinociception through distinct subtypes of the mu opioid receptor, supporting the possibility of novel subtype-selective therapeutic agents with greater separation between analgesia and side-effects or physical dependence. Furthermore, the methodology described herein provides model systems for the in vivo screening of such agents.
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PMID:Opioid mu receptor subtypes (possibly mu 1 and mu 2) revealed by morphine-induced antinociception vs endothelin-1 in recombinant inbred CXBK mice. 828 81

Previous studies measuring opioid inhibition of cyclic adenosine monophosphate in SH-SY5Y cells supported the hypothesis that continuous agonist stimulation causes a gradual conversion of the mu opioid receptor to a sensitized or constitutively active state termed mu*. Conversion to mu* was prevented by the kinase inhibitor H7, but not its close analog H8. Naloxone was proposed to act as a negative antagonist (inverse agonist) blocking mu* activity, whereas D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP) appeared to act as a neutral antagonist having no effect on mu* activity. Initial in vivo results indicated that mu* activity may play a role in narcotic tolerance and dependence (Wang et al., Life Sci. 54: PL339-PL350 1994). Our study explores the pharmacology of H7 and H8, naloxone and CTAP in mice after induction of acute tolerance and dependence induced by a single s.c. dose of morphine (100 mg/kg). Physical dependence was defined by withdrawal jumping induced by i.p. naloxone injections 4 hr after the morphine dose, the time of maximal physical dependence. Neither H7 nor H8 (50 nmol or less) induced jumping, affected morphine antinociception or produced significant behavioral effects, when injected by the intracerebroventricular (i.c.v.) or intrathecal (i.th.) routes. When given 30 min before the naloxone challenge, H7, but not H8, significantly reduced naloxone jumping by i.c.v. injection. Administration of naloxone into the central nervous system, rather than by i.p. administration, required coinjection by both i.c.v. and i.th. routes to elicit full withdrawal jumping (30 nmol at each site). In contrast, the putative neutral antagonist CTAP caused little withdrawal jumping when coinjected i.c.v. and i.th., as expected if modulation of mu* activity played a role in dependence. However, CTAP was capable of partially reversing naloxone (i.p.) induced jumping when given either i.c.v. or i.th., indicating that CTAP competes with naloxone at mu*. Moreover, these results demonstrate that both spinal and supraspinal sites are required for full opioid withdrawal jumping in mice. Antinociceptive tolerance was also evaluated by determining the response to morphine in the 55 degrees C warm-water tail-flick test. Morphine pretreatment (100 mg/kg, s.c., -5 hr) produced antinociceptive tolerance as shown by a 2.7-fold increase in the calculated morphine A50 value. Tolerance was reversed by H7, but not H8, treatment (50 nmol, i.c.v., -30 min). These results are consistent with the hypothesis that a sensitized or constitutively active mu* state plays a role in narcotic tolerance and dependence.
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PMID:Effects of naloxone and D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 and the protein kinase inhibitors H7 and H8 on acute morphine dependence and antinociceptive tolerance in mice. 861 58

Chronic opiate administration results in the development of tolerance and dependence, but the regulation of mu opioid receptor function during this process is not clearly understood. To localize changes in mu opioid receptor-coupled G-protein activity in various brain regions after chronic morphine treatment, the present study examined mu opioid agonist-stimulated [35S]GTPgammaS binding to brain sections by in vitro autoradiography. Rats were treated for 12 d with increasing doses (10-320mg . kg-1 . d-1) of morphine. Control rats were injected with either saline or a single acute injection of morphine (20 mg/kg). mu opioid-stimulated [35S]GTPgammaS binding was measured by autoradiography of brain sections in the presence and absence of the mu opioid-selective agonist DAMGO. In rats injected with a single acute dose of morphine, no significant changes were detected in basal or agonist-stimulated [35S]GTPgammaS binding in any region. In sections from chronic morphine-treated rats, however, DAMGO-stimulated [35S]GTPgammaS binding was reduced significantly compared with control rats in the following brain-stem nuclei: dorsal raphe nucleus, locus coeruleus, lateral and medial parabrachial nuclei, and commissural nucleus tractus solitarius. No significant changes were observed in several other brain regions, including the nucleus accumbens, amygdala, thalamus, and substantia nigra. These data indicate that chronic morphine administration results in reductions in mu opioid activation of G-proteins in specific brainstem nuclei involved in physiological homeostasis and autonomic function, which may have implications in the development of opiate tolerance and physical dependence.
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PMID:Effects of chronic morphine administration on mu opioid receptor-stimulated [35S]GTPgammaS autoradiography in rat brain. 878 44

The existence of mu, delta and kappa opioid receptors in the central nervous system is well documented. The present review focuses on the relationships between opioid receptor types and physical and psychic dependences. Mu and delta, but not kappa opioid receptor agonists produce physical dependence. From behavioral, biochemical and molecular biological studies, it is suggested so far that development of physical dependence on morphine results predominantly from an activation of mu 1 and mu 2 opioid receptors which causes functional changes in Gi/o, adenylate cyclase, protein kinases A and C, beta-adrenoceptor and NMDA receptor in the locus coeruleus. Recently, there have been significant advances in studies on psychic dependence. Mu and delta opioid receptor agonists produce psychic dependence, but kappa opioid receptor agonists rather produce an aversive effect. Activation of the mesolimbic dopamine system may lead to psychic dependence on opioids. Mu and delta 1 opioid receptor agonists activate the mesolimbic dopamine system to induce a rewarding effect, whereas the rewarding effect of delta 2 opioid receptor agonists may be produced through a non-dopaminergic system. There are complicated interactions among opioid receptor types. The activation of kappa opioid receptor suppresses physical and psychic dependences on mu and delta opioid receptor agonists, but the activation of delta opioid receptor potentiates the dependence on mu opioid receptor agonists. The clinical use of morphine in patients with cancer pain won't develop dependence probably due to the balance of the opioid system coming from these interactions.
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PMID:[Opioid receptor types and dependence]. 916 Mar 46

The purpose of the present investigation was to examine the development of tolerance to the rate-suppressing effects of mu and kappa opioids in rats administered either 3.0 (low) or 30 (high) mg/kg per day of butorphanol, an opioid with low relative efficacy at the mu receptor. The mu opioids butorphanol, buprenorphine, morphine, fentanyl and sufentanil, and the kappa opioid U50,488 dose-dependently suppressed responding under all conditions examined. In rats administered the low maintenance dose of butorphanol, tolerance developed to the effects of butorphanol, buprenorphine and morphine, but not to fentanyl and sufentanil. In rats administered the high maintenance dose, tolerance developed to all of the mu opioids examined. In both treatment groups, the degree to which tolerance developed was greater for butorphanol and buprenorphine than for morphine, fentanyl and sufentanil; and the degree to which tolerance developed to these mu opioids was greater in rats administered the high maintenance dose of butorphanol. The tolerance that developed to morphine, fentanyl and sufentanil was not altered when tested at both 23 and 47 h following the previous maintenance dose of butorphanol, suggesting that these changes were not due to any acute pharmacological interactions between butorphanol and the test compound (i.e., antagonism). Tolerance was also conferred to the kappa opioid U50,488 in both groups of rats, and in rats administered the high maintenance dose, this effect was obtained when tested 23 and 47 h following the previous maintenance dose of butorphanol. Physical dependence developed in rats administered the high maintenance dose of butorphanol, as evidenced by the development of enhanced sensitivity to the rate-suppressing effects of naloxone, and the finding that 30 mg/kg naloxone decreased body weight in a time-dependent manner. No physical dependence was apparent in rats administered the low maintenance dose of butorphanol. These data suggest that during chronic treatment with butorphanol, (1) greater degrees of tolerance are conferred to drugs possessing low efficacy at the mu opioid receptor, (2) tolerance is enhanced as the maintenance dose of the toleragen is increased, and (3) mu-opioid tolerance may be observed under conditions that do not produce mu-opioid dependence.
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PMID:Tolerance and cross-tolerance to the rate-suppressing effects of opioids in butorphanol-treated rats: influence of maintenance dose and relative efficacy at the mu receptor. 986 3

This report reviews the causes of ocular pain and discusses the pharmacology, pharmacokinetics, efficacy, adverse effects, and dosage of tramadol, a novel non-narcotic oral analgesic. Tramadol is a synthetic analog of codeine with a dual mechanism of action that involves agonist activity at the mu opioid receptor, as well as inhibition of monoaminergic (norepinephrine and serotonin) re-uptake. Unlike opiate analgesics, tramadol has very low propensity toward physical dependence. Common dose-related adverse effects of tramadol include dizziness, nausea, vomiting, dry mouth, and/or drowsiness. Clinically, tramadol has been shown to be equivalent to acetaminophen (325 mg)-codeine (30 mg) combinations for the treatment of moderate or severe nonocular pain. Tramadol appears to be an effective analgesic agent for pain control due to postoperative surgical trauma, as well as in various chronic malignant and nonmalignant disease states. Tramadol has shown variable effectiveness in the control of pain related to dental procedures. The usefulness of tramadol in pain states from ophthalmic origin has yet to be clinically established.
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PMID:Analgesics in ophthalmic practice: a review of the oral non-narcotic agent tramadol. 1044 36

Long-term administration of opiates leads to changes in the effects of these drugs, including tolerance, sensitization and physical dependence. There is, as yet, incomplete understanding of the neural mechanisms that underlie these phenomena. Tolerance, sensitization and physical dependence can be considered adaptive processes similar to other experience-dependent changes in the brain, such as learning and neural development. There is considerable evidence demonstrating that N-methyl-D-aspartate (NMDA) receptors and downstream signaling cascades may have an important role in different forms of experience-dependent changes in the brain and behavior. This review will explore evidence indicating that NMDA receptors and downstream messengers may be involved in opiate tolerance, sensitization and physical dependence. This evidence has been used to develop a cellular model of NMDA receptor/opiate interactions. According to this model, mu opioid receptor stimulation leads to a protein kinase C-mediated activation of NMDA receptors. Activation of NMDA receptors leads to influx of calcium and activation of calcium-dependent processes. These calcium-dependent processes have the ability to produce critical changes in opioid-responsive neurons, including inhibition of opioid receptor/second messenger coupling. This model is similar to cellular models of learning and neural development in which NMDA receptors have a central role. Together, the evidence suggests that the mechanisms that underlie changes in the brain and behavior produced by long-term opiate use may be similar to other central nervous system adaptations. The experimental findings and the resulting model may have implications for the treatment of pain and addiction.
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PMID:The neurobiology of opiate tolerance, dependence and sensitization: mechanisms of NMDA receptor-dependent synaptic plasticity. 1282 26


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