Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endogenous peptides (e.g. enkephalins) control many aspects of brain function, cognition, and perception. The use of these neuroactive peptides in diverse studies has led to an increased understanding of brain function. Unfortunately, the use of brain-derived peptides as pharmaceutical agents to alter brain chemistry in vivo has lagged because peptides do not readily penetrate the blood-brain barrier. Attachment of simple sugars to enkephalins increases their penetration of the blood-brain barrier and allows the resulting glycopeptide analogues to function effectively as drugs. The delta-selective glycosylated Leu-enkephalin amide 2, H(2)N-Tyr-D-Thr-Gly-Phe-Leu-Ser(beta-D-Glc)-CONH(2), produces analgesic effects similar to morphine, even when administered peripherally, yet possesses reduced dependence liability as indicated by naloxone-precipitated withdrawal studies. Similar glycopeptide-based pharmaceuticals hold forth the promise of pain relief with improved side-effect profiles over currently available opioid analgesics.
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PMID:Enkephalin glycopeptide analogues produce analgesia with reduced dependence liability. 1089 Nov 18

Many clinical and experimental studies have suggested that diabetes or hyperglycemia alter pain sensitivity, and sensitivity to several drugs. It has been reported that the antinociceptive potency of morphine is decreased in several rodent models of hyperglycemia, including streptozotocin-induced diabetes, an animal models of type I diabetes. The present study was designed to investigate in streptozotocin-induced diabetic mice the effect of the selective micro-opioid agonist [D-Ala(2), NMePhe(4), Gly-ol(5)]enkephalin (DAMGO) on G-protein activation by monitoring guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding to pons/medulla membranes, which contain the key areas for opioid antinociception. In the tail-flick test, DAMGO (1-10 ng, intracerebroventricularly) produced a marked dose-dependent antinociception in non-diabetic mice. In streptozotocin-induced diabetic mice, the effect of DAMGO was significantly attenuated as compared to that in non-diabetic mice. In the [35S]GTPgammaS binding assay, DAMGO (0.1-10 microM) increased the binding of [35S]GTPgammaS to pons/medulla membranes from non-diabetic mice in a concentration-dependent manner, affording approximately 100% maximal stimulation at 10 microM. The maximal stimulation of [35S]GTPgammaS binding by DAMGO (10 microM) in streptozotocin-induced diabetic mice (100.55+/-3.12%), was similar to non-diabetic mice. The present results indicated that the antinociceptive effect of DAMGO given supraspinally was less potent in streptozotocin-induced diabetic mice than that in non-diabetic mice, whereas the mu-opioid receptor-mediated G-protein activation in pons/medulla was unaltered in streptozotocin-induced diabetic mice. Thus, the attenuation of DAMGO-induced antinociception in streptozotocin-induced diabetic mice is probably caused by dysfunction in cellular pathways after the activation of G-proteins.
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PMID:Effects of a mu-opioid receptor agonist on G-protein activation in streptozotocin-induced diabetic mice. 1091 37

The present studies assessed the role of G(zalpha) and G(oalpha) in spinal alpha(2) adrenergic receptor agonist-induced antinociception, as well as in antinociceptive synergism between spinal morphine and clonidine. Mice were pretreated with a single intrathecal (i.t.) injection of artificial cerebrospinal fluid (ACSF), antisense oligodeoxynucleotide(s) (ODN) directed against G(zalpha) or G(oalpha), or nonsense ODN. After 48 h, the antinociceptive effects expressed as per cent maximal possible effect (% MPE) of either i.t. morphine alone, clonidine alone or coadministered morphine plus clonidine, were evaluated in the tail flick test. Antisense ODN to G(zalpha) attenuated clonidine- but not morphine-induced antinociception. The ED(50) (95% confidence interval) value for clonidine in ACSF pretreated mice was 6.3 (4.9-8.1) nmol, and in nonsense ODN pretreated mice, it was 4.2 (2.8-6.3) nmol. However, in the G(zalpha) antisense ODN pretreated mice, the highest dose clonidine tested (50 nmol) produced only 41+/-8.5% MPE. Antisense ODN to G(zalpha) also blocked antinociception produced by i.t. UK14, 304 (alpha(2) adrenergic receptor agonist) and [D-Pen(2), D-Pen(5)] enkephalin (DPDPE) (delta opioid receptor agonist), whereas it failed to attenuate i.t. Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol (DAMGO)- (mu opioid receptor agonist) and U50-488 (kappa opioid receptor agonist) -induced antinociception. Pretreatment with antisense ODN to G(oalpha) attenuated both morphine and clonidine induced antinociception and did not affect synergism between the agonists. These results suggest that spinal G(o)alpha mediates antinociception produced by both clonidine and morphine while G(zalpha) mediates alpha(2) adrenergic and delta opioid receptor mediated antinociception, but not antinociception produced by mu or kappa opioid agonists.
Pain 2000 Aug
PMID:Differential effects of antisense oligodeoxynucleotides directed against g(zalpha) and g(oalpha) on antinociception produced by spinal opioid and alpha(2) adrenergic receptor agonists. 1092 11

Previously, it was determined that microinjection of morphine into the caudal portion of subnucleus caudalis mimicked the facilitatory effects of intravenous morphine on cornea-responsive neurons recorded at the subnucleus interpolaris/caudalis (Vi/Vc) transition region. The aim of the present study was to determine the opioid receptor subtype(s) that mediate modulation of corneal units and to determine whether opioid drugs affected unique classes of units. Pulses of CO(2) gas applied to the cornea were used to excite neurons at the Vi/Vc ("rostral" neurons) and the caudalis/upper cervical spinal cord transition region (Vc/C1, "caudal" neurons) in barbiturate-anesthetized male rats. Microinjection of morphine sulfate (2.9-4.8 nmol) or the selective mu receptor agonist D-Ala, N-Me-Phe, Gly-ol-enkephalin (DAMGO; 1.8-15.0 pmol) into the caudal transition region enhanced the response in 7 of 27 (26%) rostral units to CO(2) pulses and depressed that of 10 units (37%). Microinjection of a selective delta ([D-Pen(2,5)] (DPDPE); 24-30 pmol) or kappa receptor agonist (U50488; 1.8-30.0 pmol) into the caudal transition region did not affect the CO(2)-evoked responses of rostral units. Caudal units were inhibited by local DAMGO or DPDPE but were not affected by U50,488H. The effects of DAMGO and DPDPE were reversed by naloxone (0.2 mg/kg iv). Intravenous morphine altered the CO(2)-evoked activity in a direction opposite to that of local DAMGO in 3 of 15 units, in the same direction as local DAMGO but with greater magnitude in 4 units, and in the same direction with equal magnitude as local DAMGO in 8 units. CO(2)-responsive rostral and caudal units projected to either the thalamic posterior nucleus/zona incerta region (PO/ZI) or the superior salivatory/facial nucleus region (SSN/VII). However, rostral units not responsive to CO(2) pulses projected only to SSN/VII and caudal units not responsive to CO(2) projected only to PO/ZI. It was concluded that the circuitry for opioid analgesia in corneal pain involves multiple sites of action: inhibition of neurons at the caudal transition region, by intersubnuclear connections to modulate rostral units, and by supraspinal sites. Local administration of opioid agonists modulated all classes of corneal units. Corneal stimulus modality was predictive of efferent projection status for rostral and caudal units to sensory thalamus and reflex areas of the brain stem.
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PMID:Cornea-responsive medullary dorsal horn neurons: modulation by local opioids and projections to thalamus and brain stem. 1093 27

We have previously demonstrated that both endomorphin-1 and endomorphin-2 produce their antinociception by the stimulation of mu-opioid receptors. However, the antinociception induced by endomorphin-2 contains an additional component, which is mediated by the release of dynorphin A (1-17) acting on kappa-opioid receptors. These studies were done to determine whether the antinociception induced by endomorphin-1 and endomorphin-2 given supraspinally was mediated by the activation of different descending pain control pathways in the mouse. Specific receptor antagonists or antisera against endogenous opioid peptides were injected intrathecally to block the receptors or bind the released endogenous opioid peptides, and endomorphin-1 or endomorphin-2 was then administered i.c.v. to activate the descending pain control systems to produce antinociception. The tail-flick response was used as antinociceptive test. The blockade of the alpha(2)-adrenoceptors and 5-hydroxytryptamine receptors in the spinal cord by i.t. injection of yohimbine and methysergide, respectively, inhibited the antinociception induced by i.c.v.-administered endomorphin-1 and endomorphin-2. However, the antinociception induced by endomorphin-2 was inhibited by i.t. pretreatment with delta(2)-opioid receptor antagonist naltriben or kappa-opioid receptor antagonist nor-binaltorphimine, but not by the mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Try-Orn-Thr-Pen-Thr-NH(2) or the delta(1)-opioid receptor antagonist 7-benzylidene naltrexamine. Intrathecal pretreatment with antiserum against Met-enkephalin attenuated the antinociception induced by i.c.v.-administered endomorphin-2, but not endomorphin-1. Furthermore, i.t. pretreatment with antiserum against dynorphin A (1-17) also inhibited the antinociception induced by i.c.v.-administered endomorphin-2, but not endomorphin-1. Intrathecal pretreatment with antiserum against Leu-enkephalin or beta-endorphin did not inhibit i.c.v.-administered endomorphin-1- or endomorphin-2-induced antinociception. The results indicate that, like other opioid micro-receptor agonists, morphine, and [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin, endomorphin-1 and endomorphin-2 given i.c.v. produce antinociception by activating spinipetal noradrenergic and serotonergic pathways for producing antinociception. However, the antinociception induced by endomorphin-2 given i.c.v. also contains other components, which are mediated by the release of Met-enkephalin and dynorphin A (1-17) acting on opioid delta(2)- and kappa-receptors, respectively, in the spinal cord.
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PMID:Differential mechanisms mediating descending pain controls for antinociception induced by supraspinally administered endomorphin-1 and endomorphin-2 in the mouse. 1094 66

The nonopioid actions of spinal dynorphin may promote aspects of abnormal pain after nerve injury. Mechanistic similarities have been suggested between opioid tolerance and neuropathic pain. Here, the hypothesis that spinal dynorphin might mediate effects of sustained spinal opioids was explored. Possible abnormal pain and spinal antinociceptive tolerance were evaluated after intrathecal administration of [D-Ala(2), N-Me-Phe(4), Gly-ol(5)]enkephalin (DAMGO), an opioid mu agonist. Rats infused with DAMGO, but not saline, demonstrated tactile allodynia and thermal hyperalgesia of the hindpaws (during the DAMGO infusion) and a decrease in antinociceptive potency and efficacy of spinal opioids (tolerance), signs also characteristic of nerve injury. Spinal DAMGO elicited an increase in lumbar dynorphin content and a decrease in the mu receptor immunoreactivity in the spinal dorsal horn, signs also seen in the postnerve-injury state. Intrathecal administration of dynorphin A(1-17) antiserum blocked tactile allodynia and reversed thermal hyperalgesia to above baseline levels (i.e., antinociception). Spinal dynorphin antiserum, but not control serum, also reestablished the antinociceptive potency and efficacy of spinal morphine. Neither dynorphin antiserum nor control serum administration altered baseline non-noxious or noxious thresholds or affected the intrathecal morphine antinociceptive response in saline-infused rats. These data suggest that spinal dynorphin promotes abnormal pain and acts to reduce the antinociceptive efficacy of spinal opioids (i.e., tolerance). The data also identify a possible mechanism for previously unexplained clinical observations and offer a novel approach for the development of strategies that could improve the long-term use of opioids for pain.
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PMID:Dynorphin promotes abnormal pain and spinal opioid antinociceptive tolerance. 1099 54

The role of endogenous opioid systems in the analgesic response to exogenous opiates remains controversial. We previously reported that mice lacking the peptide neurotransmitter beta-endorphin, although unable to produce opioid-mediated stress-induced antinociception, nevertheless displayed intact antinociception after systemic administration of the exogenous opiate morphine. Morphine administered by a peripheral route can activate opioid receptors in both the spinal cord and brain. However, beta-endorphin neuronal projections are confined predominantly to supraspinal nociceptive nuclei. Therefore, we questioned whether the absence of beta-endorphin would differentially affect antinociceptive responses depending on the route of opiate administration. Time- and dose-response curves were obtained in beta-endorphin-deficient and matched wild-type C57BL/6 congenic control mice using the tail-immersion/withdrawal assay. Null mutant mice were found to be more sensitive to supraspinal (i.c.v.) injection of the micro-opioid receptor-selective agonists, morphine and D-Ala(2)-MePhe(4)-Gly-ol(5) enkephalin. In contrast, the mutant mice were less sensitive to spinal (i.t.) injection of these same drugs. Quantitative receptor autoradiography revealed no differences between genotypes in the density of mu, delta, or kappa opioid receptor binding sites in either the spinal cord or pain-relevant supraspinal areas. Thus we report that the absence of a putative endogenous ligand for the mu-opioid receptor results in opposite changes in morphine sensitivity between discrete areas of the nervous system, which are not simply caused by changes in opioid receptor expression.
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PMID:Disparate spinal and supraspinal opioid antinociceptive responses in beta-endorphin-deficient mutant mice. 1111 19

Central effects of gluten exorphin A5 (Gly-Tyr-Tyr-Pro-Thr), a fragment from wheat gluten, were studied on the pain-inhibitory system, emotionality and learning/memory processes in mice. Orally administered gluten exorphin A5 produced neither an antinociceptive effect nor an effect on morphine analgesia. Intracerebroventricularly (i.c.v.) administered gluten exorphin A5 produced mild but significant antinociception in a dose-depepndent manner, while not affecting the morphine analgesia. On the other hand, oral gluten exorphin A5 suppressed the endogenous pain-inhibitory system, i.e., antinociception induced by socio-psychological- (PSY-) stress (SIA) using a communication box; intraperitoneal gluten exorphin A5 abolished both footshock- (FS-) stress-induced antinociception (SIA) and PSY-SIA; and i.c.v. gluten exorphin A5 suppressed FS-SIA, but rather potentiated PSY-SIA. This peptide given by these routes was without effect on forced swim-SIA. In addition, oral gluten exorphin A5 tended to prolong the retention time on open arms in the elevated plus-maze test. Finally, oral gluten exorphin A5 when given during the post-training period of learning/memory processes significantly increased the latency into the dark compartment in the one-trail step-though type passive avoidance test, indicating that the peptide also facilitates the acquire/consolidation process of learning/memory. Thus, gluten exorphin A5 has been found to produce various effects not only in the peripheral nervous systems but also in the central nervous system.
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PMID:Behavioral and pharmacological studies on gluten exorphin A5, a newly isolated bioactive food protein fragment, in mice. 1113 26

This study examined a mechanism responsible for the enhanced antihyperalgesic and antinociceptive effects of the mu opioid receptor agonist (ORA) [D-Ala(2), NMePhe(4), Gly(5)-ol]enkephalin (DAMGO) microinjected in the rostroventromedial medulla (RVM) of rats with inflammatory injury induced by injection of complete Freund's adjuvant (CFA) in one hindpaw. In rats injected with CFA 4 hr earlier, microinjection of the mu opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP) in the RVM antagonized both the marginal enhancement of the potency of DAMGO and its antinociceptive effect. The delta opioid receptor antagonist naltriben (NTB) was without effect. In rats injected with CFA 2 weeks earlier, CTAP antagonized the effects of DAMGO to a lesser extent. However, NTB completely prevented the enhancement of the potency of DAMGO, whereas it did not antagonize DAMGO's antinociceptive effects. Microinjection of NTB alone, but not CTAP in the RVM of CFA-treated rats, enhanced the hyperalgesia present in the ipsilateral hindpaw and induced hyperalgesia in the contralateral, uninjured hindpaw. These results suggest that persistent inflammatory injury increased the release in the RVM of opioid peptides with preferential affinity for the delta opioid receptor, which can interact in a synergistic or additive manner with an exogenously administered mu opioid receptor agonist. Indeed, the levels of [Met(5)]enkephalin and [Leu(5)]enkephalin were increased in the RVM and in other brainstem nuclei in CFA-treated rats. This increase most likely presents a compensatory neuronal response of the CNS of the injured animal to mitigate the full expression of inflammatory pain and to enhance the antinociceptive and antihyperalgesic effects of exogenously administered mu opioid receptor analgesics.
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PMID:Contribution of endogenous enkephalins to the enhanced analgesic effects of supraspinal mu opioid receptor agonists after inflammatory injury. 1126 27

The protein kinase C (PKC)gamma isoform is a major pool of the PKC family in the mammalian spinal cord. PKCgamma is distributed strategically in the superficial layers of the dorsal horn and, thus, may serve as an important biochemical substrate in sensory signal processing including pain. Here we report that mu-opioid receptor-mediated analgesia/antinociception and activation of G-proteins in the spinal cord are enhanced in PKCgamma knockout mice. In contrast, delta- and kappa-opioidergic and ORL-1 receptor-mediated activation of G-proteins in PKCgamma knockout mice was not altered significantly relative to the wild-type mice. Deletion of PKCgamma had no significant effect on the mRNA product of spinal mu-opioid receptors but caused an increase of maximal binding of the mu-opioid receptor agonist [3H][d-Ala(2),N-Me-Phe(4),Gly(5)-ol]enkephalin in spinal cord membranes obtained from PKCgamma knockout mice. These findings suggest that deletion of PKCgamma genes protects the functional mu-opioid receptors from degradation by phosphorylation. More importantly the present data provide direct evidence that PKCgamma constitutes an essential pathway through which phosphorylation of mu-opioid receptors occurs.
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PMID:Enhanced mu-opioid responses in the spinal cord of mice lacking protein kinase Cgamma isoform. 1127 52


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