Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Differences in binding properties of μ and δ opioid receptors were investigated using DAGO (Tyr-d-Ala-Gly-MePhe-Gly-ol) and DTLET (Tyr-d-Thr-Gly-Phe-Leu-Thr), which occur, respectively, as the most selective μ and δ radioligands available. At high concentration, each agonist is able to interact with its nonspecific sites. Competition experiments indicated that a two-site competitive model was adequate to explain the interactions of DAGO and DTLET with [3H]DTLET and [3H]DAGO binding sites, respectively. The weak cross-reactivity (≃10%) of DTLET for μ sites was taken into account in these experiments. On the other hand, DAGO and DTLET exhibit differential binding kinetics. Thus, at 35°C, the lifetime of DTLET within its receptor site about 14 times longer than that of the μ agonist. Sodium and manganese ions decrease the maximal number of high affinity μ and δ sites, but the sensitivity of μ receptors is three times higher towards Na+ and 20-fold higher towards Mn2+ than that of δ receptors. GTP reduces similarly the μ and δ binding whereas only the DAGO binding was modified by the nonhydrolyzable analogue guanylylimidodiphosphate [GMP-P(NH)P]. However, in the presence of Na+ ions, GMP-P(NH)P inhibits the DTLET binding in a concentration-dependent manner. The effects of Na+ and GMP-P(NH)P could be explained by a sequential transformation of δ receptors to low-affinity states. This model predicts that Na+, by lowering the affinity of a fraction of sites, produces a decrease in the maximal number of high-affinity δ receptors and that GMP-P(NH)P enhances the Na+, effect. Moreover, the binding kinetic to this high-affinity state was also modified by Na+ and nucleotides. All of these data support the existence of two independent μ and δ binding sites, the properties of which are differentially regulated by these endogenous effectors.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A heterogeneity of CCK2 receptors has been reported which could correspond to different states of coupling to G proteins and/or association with different second messenger systems. To investigate these hypotheses, the wild-type CCK2 receptor and three mutants F347A, D100N and K333M/K334T/R335L, expected to modify the coupling of the G protein with the third intracellular loop of the receptor, were transfected into Cos-7 cells and their binding and signalling properties were evaluated using the natural ligand CCK8. Activation of wild-type as well as F347A, D100N or K333M/K334T/R335L CCK2 receptors by this ligand led to a similar arachidonic acid release which was blocked by pertussis toxin and the phospholipase A2 inhibitor, mepacrine. Nevertheless, in contrast to the wild-type CCK2 receptor, addition of CCK8 to cells transfected with the F347A or K333M/K334T/R335L mutants did not result in the production of inositol phosphates while the maximum increase in this second messenger formation was reduced by 30% with the D100N mutant. Taken together, these results suggest that the CCK2 receptor is coupled to two G proteins and that Phe347 and the cluster of basic residues K333/K334/R335 probably play a key role in Gq protein stimulation leading to inositol phosphate production but not in activation of the G protein coupled to phospholipase A2. These data bring additional support at the molecular level to the existence of different affinity states of CCK2 receptors suggested from the results of binding assays and behavioural studies.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The endogenous opioid receptor-like1 (ORL1) ligand, nociceptin/orphanin FQ (FGGFTGARKSARKLANQ), a heptadecapeptide structurally resembling dynorphin A, has recently been identified. The wide distribution of ORL1 mRNA and nociceptin/orphanin FQ precursor in the CNS, particularly in the limbic system regions and in several areas known to be involved in pain perception, suggests that nociceptin/orphanin FQ is potentially endowed with various central functions. In general, activation and/or inactivation of regulatory peptides occur through the action of cell surface peptidases. The physiological mechanisms under which nociceptin/orphanin FQ is metabolized should lead to a better understanding of its physiological functions. Mouse brain cortical slices were incubated in medium containing the heptadecapeptide in the presence or in the absence of peptidase inhibitors. The critical sites of enzymatic cleavage are Phe1-Gly2, Ala7-Arg8, Ala11-Arg12, and Arg12-Lys13 bonds. The major role played by metallopeptidases was confirmed by the complete protection of metabolism in the presence of EDTA. Aminopeptidase N and endopeptidase 24.15 are the two main enzymes involved in nociceptin/orphanin FQ metabolism, whereas endopeptidase 24.11 (involved in enkephalin [YGGFM(L)] catabolism) does not appear critically involved in nociceptin/orphanin FQ metabolism. The physiological relevance of aminopeptidase N and endopeptidase 24.15 in the heptadecapeptide metabolism remains to be determined.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The activation of dopamine (DA) neurotransmission plays a crucial role in the behavioural responses to drugs of abuse. In particular, increased extracellular levels of DA within the mesolimbic pathway have been implicated in the rewarding and locomotor stimulatory properties of morphine. We investigated the behavioural responses to morphine in mice with a genetic disruption of the DA transporter (DAT), resulting in a constitutively high level of extrasynaptic DA. In the conditioned place preference test, DAT–/– mice exhibited a stronger rewarding response to morphine (5 mg/kg, s.c.) compared with control littermates. However, the same dose of morphine failed to increase locomotor activity in DAT–/– mice, whilst enhancing locomotion in DAT+/– and DAT+/+ animals. Morphine-induced analgesia was unaffected in mutant mice, but the behavioural expression of naloxone-induced withdrawal signs was blunted. In vivo voltammetry in the shell of the nucleus accumbens revealed that morphine was able to stimulate DA neurons in DAT–/– mice, resulting in the accumulation of higher extracellular DA levels compared with control animals. Morphine also induced a higher rate of c-fos transcription in the shell of the nucleus accumbens in mutant mice. We conclude that morphine-induced rewarding responses are firmly established in DAT mutant mice despite a DA transmission that is already tonically activated, and independently of any effect on locomotion. These particular behavioural responses to morphine may be associated with the action of the drug on DA release and c-fos expression in the shell of the nucleus accumbens of DAT–/– mice.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The specific participation of protein kinases in the expression of the somatic signs of morphine withdrawal has been previously demonstrated, suggesting that changes in intracellular signalling systems are involved in opioid addiction. In the present study, the involvement of protein kinases in the aversive/dysphoric effects of morphine abstinence has been investigated in the nucleus accumbens, because of the critical role played by the mesolimbic system in the rewarding effects of opioids. Rats were chronically treated with morphine, twice a day for 5 days, with doses progressively increased from 5 to 30 mg/kg (i-p.). In addition, microinjections into the nucleus accumbens of the serine-threonine kinase inhibitors H7 or H8 (1 or 10 nmol per side) or saline once daily were also given, both in control and in morphine-treated animals. After these chronic treatments, withdrawal syndrome was induced by naloxone administration (0.1 mg/kg, s. c.), and the motivational component of morphine abstinence was studied using the place aversion paradigm. When administered at the highest dose (10 nmol), H7 and H8 strongly reduced the place aversion induced by naloxone in morphine dependent animals. Protein kinase inhibitors did not induce significant behavioural responses in non-dependent animals. Chronic morphine treatment induced a selective up-regulation of adenylate cyclase activity in the amygdala, without affecting other brain regions. The morphine-increased adenylate cyclase activity in amygdala was reversed by the chronic intra-accumbens microinjection of H7 or H8. These results suggest that serine-threonine kinases in the nucleus accumbens play an important role in the emotional/dysphoric properties which characterize opiate withdrawal.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Given the high resistance of the cholecystokinin octapeptide (CCK8) to in vivo peptidase degradation, the possible existence of a reuptake system for this peptide was investigated. Efficient accumulation of intact, tritiated propionyl CCK8 ([3H]pCC8) was observed following its incubation with rat cortical synaptosomes but not with cerebellar synaptosomes, where no cholecystokinin immunoreactivity was found. This uptake process appeared to be dependent on temperature, duration of incubation, concentration of radioligand, the presence of glucose and the integrity of the synaptosomes. A Lineweaver-Bürk analysis indicated that the putative uptake process is characterized by a single Km value of 10.7 nM and a Vmax of 8.5 fmol/min/mg of protein. Carbonyl cyanide-m-chlorophenyl hydrazone, an uncoupler of oxidative phosphorylation, blocked accumulation of [3H]pCCK8, whereas ouabain did not. The uptake was found to be highly specific since, among all the cholecystokinin analogues tested, only CCb and, to a lesser extent, CCK7, were able to inhibit [3H]pCCK8 uptake. The rate of [3H]pCCK8, uptake was not affected by CCK4, CCK5, D-Trp CCK8, BC 264, a potent and selective CCK-B agonist, and L-365,260, a selective CCK-B antagonist. In addition, no accumulation of radioactivity was observed using [3H]pBC 264, a result which is not in favour of a cholecystokinin receptor-induced internalization mechanism. The potent and selective uptake mechanism characterized in this study could participate, in conjunction with extra and intracellular degradation of CCK8 by peptidases, in the interruption of cholecystokinin-conveyed messages in the brain.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: CB1 cannabinoid receptors are widely distributed in the central nervous system where they mediate most of the cannabinoid-induced responses. Here we have evaluated the interactions between the CB1 cannabinoid receptors and the endogenous opioid system by assaying a number of well-characterized opioid responses, e.g. antinociception and stress-mediated effects, on mutant mice in which the CB1 receptor gene was invalidated. The spontaneous responses to various nociceptive stimuli (thermal, mechanical and visceral pain) were not changed in mutant CB1 mice. Furthermore, the absence of the CB1 cannabinoid receptor did not modify the antinociceptive effects induced by different opioid agonists: morphine (preferential mu opioid agonist), d-Pen2- d-Pen5-enkephalin (DPDPE) and deltorphin II (selective delta opioid agonists), and U-50,488H (selective kappa opioid agonist) in the hot-plate and tail-immersion tests. In contrast, the stress-induced opioid mediated responses were modified in CB1 mutants. Indeed, these mutants did not exhibit antinociception following a forced swim in water at 34 °C and presented a decrease in the immobility induced by the previous exposure to electric footshock. However, the antinociception induced by a forced swim in water at 10 °C was preserved in CB1 mutants. These results indicate that CB1 receptors are not involved in the antinociceptive responses to exogenous opioids, but that a physiological interaction between the opioid and cannabinoid systems is necessary to allow the development of opioid-mediated responses to stress.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Regulatory factor X (RFX) proteins are transcriptional activators that recognize X-boxes (DNA of the sequence 5′-GTNRCC(0–3N)RGYAAC-3′, where N is any nucleotide, R is a purine and Y is a pyrimidine) using a highly conserved 76-residue DNA-binding domain (DBD). ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The u,-opioid-receptor (MOR) gene was inactivated in PI embryonic stem (ES) cells from the 129/Sv mouse line by insertion of a neomycin-resistance (neor) cassette in the gene coding region (Fig. la). Gene targeting was identified by Southern blotting using a 5' probe (Fig. Ib), giving 7 positives ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Dopamine receptors have been implicated in the behavioural response to drugs of abuse. These responses are mediated particularly by the mesolimbic dopaminergic pathway arising in the ventral tegmental area and projecting to the limbic system. The rewarding properties of opiates and the somatic ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...