Characterization of the opioid receptor type mediating inhibition of rat gastric somatostatin secretion

1990 ◽  
Vol 259 (6) ◽  
pp. G922-G927
Author(s):  
C. H. McIntosh ◽  
X. Jia ◽  
Y. N. Kowk
Keyword(s):  
Opioid Receptor ◽  
Opioid Peptides ◽  
Physiological Role ◽  
Gastric Inhibitory Polypeptide ◽  
Opioid Peptide ◽  
Major Effect ◽  
Rat Stomach ◽  
Dependent Inhibition ◽  
High Concentrations ◽  
Mu Receptors

The opioid peptides are potent inhibitors of gastric somatostatin-like immunoreactivity (SLI) secretion from the isolated perfused rat stomach. In addition, inhibition of SLI secretion induced by vagal stimulation is partially blocked by naloxone, indicating that endogenously released opioid peptides probably play a physiological role in the regulation of SLI release. The opioid peptides exert their effects by interacting with a number of different receptor types. In the present study, the effect of the selective delta-opioid receptor agonists [D-Pen2.5]enkephalin and [D-Pen2,L-Pen5]enkephalin and the mu-receptor agonist [D-Ala2, N-methyl (NMe)-Phe4,Gly5-ol]enkephalin on gastric inhibitory polypeptide (GIP)-stimulated SLI secretion from the isolated perfused rat stomach have been studied. Responses to the less selective delta-agonist [D-Ala2,D-Leu5]enkephalin, dynorphins 1-8, 1-13, and 1-17, and the extended enkephalin forms Met-enkephalin-Arg6-Phe7,Met- enkephalin-Arg6-Gly7-Leu8, and Met-enkephalin-Arg6-Arg7-Val8-NH2 (metorphamide), have also been investigated. [D-Ala2,NMe-Phe4,Gly5-ol]enkephalin induced a concentration-dependent inhibition of GIP-stimulated SLI secretion, with 50% of maximal inhibition at 10 nM. Neither [D-Pen2.5]enkephalin nor [D-Pen2,L-Pen6]enkephalin (10 nM to 1 microM) had any effect on SLI release, and [D-Ala2,D-Leu5] enkephalin inhibited SLI release only at high concentrations. Met-enkephalin-Arg6-Phe7 and metorphamide both inhibited SLI release, whereas Met-enkephalin-Arg6-Gly7-Leu8 and the dynorphins had little or no effect. In conclusion, the strong inhibition of SLI secretion produced by [D-Ala2,NMe-Phe4,Gly5-ol] enkephalin and lack of major effect of [D-Pen2.5]-enkephalin, [D-Pen2,L-Pen5]enkephalin, and the dynorphins indicate that opioid peptide-induced inhibition was mediated by interaction with mu-receptors and that neither delta or kappa-receptors play a significant role.

Enkephalinergic control of somatostatin secretion from the perfused rat stomach

1983 ◽  
Vol 61 (7) ◽  
pp. 657-663 ◽  
Author(s):  
C. H. S. McIntosh ◽  
Y. N. Kwok ◽  
T. Mordhorst ◽  
E. Nishimura ◽  
R. A. Pederson ◽  
...  
Keyword(s):  
Vagal Stimulation ◽  
Gastric Inhibitory Polypeptide ◽  
Endogenous Opioids ◽  
Rat Stomach ◽  
Basal Secretion ◽  
Dependent Inhibition ◽  
Order Of Magnitude ◽  
Endogenous Enkephalins ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

A role for the enkephalins in the regulation of gastric somatostatin (SLI) secretion has been investigated in an isolated perfused rat stomach model. Both methionine- and leucine-enkephalins caused a dose-dependent inhibition of gastric inhibitory polypeptide (GIP) stimulated SLI secretion. Leu-enkephalin was one order of magnitude less potent than met-enkephalin: 50% inhibition by met-enkephalin was at 4 × 10−9 M and with leu-enkephalin 3.5 × 10−8 M. Naloxone (100 nM) had no effect on basal secretion but blocked the inhibitory action of met-enkephalin (1 nM or 1 μM). Vagal stimulation (7 V, 10 Hz, 5 ms) inhibited GIP-stimulated SLI release. Administration of naloxone partially reversed this inhibition, suggesting that endogenous opioids were at least partially responsible for vagally induced inhibition. A number of possible pathways by which endogenous enkephalins may modulate SLI release have been proposed.

Alleviation of pain and depression by specific neural transplants: Fine structural correlates

1992 ◽  
Vol 50 (2) ◽  
pp. 1066-1067
Author(s):  
George D. Pappas ◽  
Jacqueline Sagen
Keyword(s):  
Opioid Peptides ◽  
Chromaffin Cells ◽  
Pain Sensitivity ◽  
Opioid Peptide ◽  
Local Source ◽  
Pain Models ◽  
Neural Transplants ◽  
Adrenergic Antagonists ◽  
Csf Levels ◽  
Donor Source

We have been interested in the use of neural transplants mainly as a local source of neuroactive substances, rather than as a replacement for damaged neural circuities. In particular, we have been exploring the possibilities of reducing pain by transplants of opioid peptide producing cells, and reducing depression by transplants of monoamine-producing cells. For the past several years, work in our laboratory has demonstrated in both acute and chronic pain models that transplantation of adrenal medullary tissue or isolated chromaffin cells into CNS pain modulatory regions can reduce pain sensitivity in rodents. Chromaffin cells were chosen as donor source since they produce high levels of both opioid peptides and catecholamines, substances which independently, and probably synergistically, reduce pain sensitivity when injected locally into the spinal cord. The analgesia produced by these transplants most likely results from the release of both opioid peptides and catecholamines, since it can be blocked or attenuated by opiate or adrenergic antagonists, respectively. Furthermore, CSF levels of met-enkephalin and catecholamines are increased by the transplants.

Hepatocyte nitric oxide biosynthesis inhibits glucose output and competes with urea synthesis for L-arginine

1995 ◽  
Vol 268 (1) ◽  
pp. G183-G188 ◽  
Author(s):  
J. Stadler ◽  
D. Barton ◽  
H. Beil-Moeller ◽  
S. Diekmann ◽  
C. Hierholzer ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Hepatic Dysfunction ◽  
Urea Synthesis ◽  
No Donors ◽  
Gapdh Activity ◽  
Urea Production ◽  
Dependent Inhibition ◽  
High Concentrations ◽  
Glucose Output ◽  
Exact Correlation

Inflammatory stimulation of the liver is known to induce nitric oxide (NO) biosynthesis. NO can interfere with the activity of a number of enzymes important to cellular metabolism. This study was carried out to investigate the influence of NO on rat hepatocyte glucose output and urea production. Induction of NO synthesis by incubation with a combination of cytokines and lipopolysaccharide led to a 48.8 +/- 2.4% inhibition of glucose output and to a 45.0 +/- 6.4% suppression of urea production. Inhibition of NO synthesis with NG-monomethyl-L-arginine was able to totally prevent these effects. High concentrations of L-arginine overcame the inhibition of urea production caused by endogenous NO synthesis. Exposure of HC to NO donors resulted in a concentration-dependent inhibition of glucose output, without having any effect on urea production. Hepatocellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity was also found to be inhibited by endogenously produced NO (33.5 +/- 5.2%), as well as by exogenously applied NO. However, an exact correlation between GAPDH activity and glucose output could not be established. These data indicate that NO biosynthesis may contribute to the development of hepatic dysfunction in chronic sepsis.

Opioid receptors in the accessory optic system of the rat: Effects of monocular enucleation

1990 ◽  
Vol 5 (5) ◽  
pp. 497-506 ◽  
Author(s):  
R.A. Giolli ◽  
R.H.I. Blanks ◽  
Y. Torigoe ◽  
R.J. Clarke ◽  
J.H. Fallon ◽  
...  
Keyword(s):  
Opioid Receptor ◽  
Opioid Receptors ◽  
Receptor Binding ◽  
Mu Opioid Receptor ◽  
Mu Opioid Receptors ◽  
Mu Opioid ◽  
Mu Receptor ◽  
Monocular Enucleation ◽  
Mu Receptors ◽  
Opioid Receptor Binding

AbstractThe presence and concentrations of each of the three subtypes of opioid receptors (mu, kappa, and delta) has been studied in the accessory optic nuclei (dorsal, lateral, and medial terminal nuclei and the interstitial nucleus of the superior fasciculus, posterior fibers: DTN, LTN, MTN, and inSFp) in normal young rats with radioligands directed towards each opioid receptor subtype. The changes in mu opioid receptors have also been investigated in monocularly enucleated rats in which one eye was removed and the rats sacrificed at postoperative day (PO) 2, 3, 5, 7, 14, and 30. As the MTN is the only accessory optic nucleus of the rat large enough for semiquantitative evaluation, the mu receptor population of the MTN has been subjected to optical microdensitometric analysis.All four of the accessory optic nuclei (AOS nuclei) are found to contain exceedingly high levels of mu opioid receptor binding with the selective radioligand [3H]-[D-Ala, MePhe4, Gly-ol5] (DAGO), low levels of kappa opioid receptor binding using the radioligand [3H]-[ethylketocyclazocine] (EKC) together with the competing agents [D-Pro4]-morphiceptin and [D-Ser2, Thr6]-Leu-enkephalin, and an absence of delta opioid receptor binding with the radioligand [3H]-[D-A1a2, D-Leu5]-enkephalin (DADLE) combined with the competing agent [D-Pro4]-morphiceptin. Monocular enucleation, as studied on the mu opioid receptor population with this experimental approach, results in virtually a complete loss of mu opioid receptors throughout all four of the contralaterally located AOS nuclei, including both dorsal and ventral subdivisions of the medial terminal nucleus (MTNd, v). Kappa and delta receptors are very few (kappa receptors) or are lacking (delta receptors) in the AOS nuclei, and for this reason, the effects of monocular enucleation on these two opioid receptor subtypes have not been investigated. Monocular enucleation also produces a significant lowering in mu receptor binding in other primary optic nuclei (the lateral geniculate nuclei, nucleus of the optic tract, and superficial layers of the superior colliculus) and in the pars principalis of the medial geniculate nucleus (description of changes in mu receptors in non-accessory optic primary optic nuclei will be considered elsewhere).Microdensitometric study of the MTNd, v shows that the decreased binding of mu receptors in this nucleus is barely detectable (about 6%) at PO2 and rises to 6–15% at PO3. At PO5 receptor loss reaches approximately 62%, whereas at PO7 it is about 81% complete. At PO14 and PO30, the mu receptor loss is nearly complete at around 93%. Mu receptor loss involves all of the AOS nuclei contralateral, but none ipsilateral, to ocular enucleation, an observation entirely consistent with the overwhelmingly crossed (about 97%) nature of the retinofugal projection to the rat accessory optic nuclei. These opioid receptors represent a prominent feature in the AOS and other primary optic nuclei of the rat. Their role in visuomotor control remains uncertain but probably involves the fine-tuning of information concerned with compensatory eye movements.

scholarly journals μ-opioids activate phospholipase C in SH-SY5Y human neuroblastoma cells via calcium-channel opening

1995 ◽  
Vol 305 (2) ◽  
pp. 577-581 ◽  
Author(s):  
D Smart ◽  
G Smith ◽  
D G Lambert
Keyword(s):  
Phospholipase C ◽  
Opioid Receptor ◽  
Neuroblastoma Cells ◽  
Receptor Occupancy ◽  
Mu Opioid Receptor ◽  
Human Neuroblastoma ◽  
Mu Opioid ◽  
Inositol 1,4,5 Trisphosphate ◽  
Dependent Inhibition ◽  
Dose Dependent

We have recently reported that, in SH-SY5Y cells, mu-opioid receptor occupancy activates phospholipase C via a pertussis toxin-sensitive G-protein. In the present study we have further characterized the mechanisms involved in this process. Fentanyl (0.1 microM) caused a monophasic increase in inositol 1,4,5-trisphosphate mass formation, with a peak (20.5 +/- 3.6 pmol/mg of protein) at 15 s. Incubation in Ca(2+)-free buffer abolished this response, while Ca2+ replacement 1 min later restored the stimulation of inositol 1,4,5-trisphosphate formation (20.1 +/- 0.6 pmol/mg of protein). In addition, nifedipine (1 nM-0.1 mM), an L-type Ca(2+)-channel antagonist, caused a dose-dependent inhibition of inositol 1,4,5-trisphosphate formation, with an IC50 of 60.3 +/- 1.1 nM. Elevation of endogenous beta/gamma subunits by selective activation of delta-opioid and alpha 2 adrenoceptors failed to stimulate phospholipase C. Fentanyl also caused a dose-dependent (EC50 of 16.2 +/- 1.0 nM), additive enhancement of carbachol-induced inositol 1,4,5-trisphosphate formation. In summary, we have demonstrated that in SH-SY5Y cells activation of the mu-opioid receptor allows Ca2+ influx to activate phospholipase C. However, the possible role of this mechanism in the process of analgesia remains to be elucidated.

EVIDENCE FOR A CENTRAL OPIOID CONTROL OF RUMINATION

1984 ◽  
Vol 64 (5) ◽  
pp. 13-15 ◽  
Author(s):  
Y. RUCKEBUSCH ◽  
TH. BARDON
Keyword(s):  
Key Words ◽  
Opioid Receptor ◽  
Opioid Receptors ◽  
Opioid Peptides ◽  
Kappa Opioid Receptor ◽  
Kappa Opioid ◽  
Receptor Agonists ◽  
Opioid Agonists ◽  
Reflex Control ◽  
Opioid Receptor Agonists

Intravenous adrenaline induced reticular extracontractions and rumination within 26 sec in hay-fed, and 184 sec in cube-fed sheep. Regardless of diet, pretreatment with cerebroventricular infusion of kappa-opioid-receptor agonists enhanced this reflex. Control of rumination may involve multiple opioid-receptors, since inhibition of the reflex occurred after mu- and delta-opioid-agonists. Key words: Sheep, rumination, opioid-peptides

Opioid peptide receptor studies. 7. The methylfentanyl congener RTI-4614-4 and its four enantiomers bind to different domains of the rat ? opioid receptor

Synapse ◽  
1998 ◽  
Vol 28 (2) ◽  
pp. 117-124 ◽  
Author(s):  
Yi-Feng Lu ◽  
Heng Xu ◽  
Lee-Yuan Liu-Chen ◽  
Chongguang Chen ◽  
John S. Partilla ◽  
...  
Keyword(s):  
Opioid Receptor ◽  
Opioid Peptide ◽  
Peptide Receptor
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