Since beta-endorphins can bind both mu opioid and kappa-opioid receptors we investigated the effect of a mu specific receptor agonist, D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and a mu specific antagonist, D-Phe-Cys-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP) on cardiovascular responses in conscious control and obese rats. (nih.gov)
The mu agonist, DAMGO, increased blood pressure (BP) in control rats. (nih.gov)
We investigated the mechanisms underlying MOR desensitization, in adult mammalian neurons, caused by morphine (a partial agonist in this system) and DAMGO (a high-efficacy agonist). (bath.ac.uk)
CONCLUSIONS AND IMPLICATIONS: In mature mammalian neurons, different MOR agonists can induce MOR desensitization by different mechanisms, morphine by a PKCalpha-mediated, heterologous mechanism and DAMGO by a GRK-mediated, homologous mechanism. (bath.ac.uk)
Neither the δ-opioid agonist, DPDPE ([D-Pen 2,5 ]-enkephalin) nor the μ-opioid agonist, DAMGO (Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol enkephalin) elevated [Ca 2+ ](i) when applied alone. (edu.au)
However, when either DPDPE or DAMGO was applied in the presence of the cholinoceptor agonist, carbachol (100 nM-1 mM) they evoked an elevation of [Ca 2+ ](i) above that caused by carbachol alone. (edu.au)
4. The δ-receptor antagonist, naltrindole (30 nM), blocked the elevations of [Ca 2+ ](i) by DPDPE (100 nM) without affecting those caused by DAMGO while the μ-receptor antagonist, CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Pen-Thr-NH 2 ) (100 nM-1 μM) blocked the elevations of [Ca 2+ ](i) caused by DAMGO (1 μM) without affecting those caused by DPDPE. (edu.au)
Intrathecal (i.t.) administration of peptidic MOR agonist [D-Ala 2 , N-Me-Phe 4 ,Gly 5 -ol]-enkephalin (DAMGO, 0.00032-0.01 mg) evoked scratching, but i.v, DAMGO (0.01-1 mg/kg) did not increase scratching. (ewha.ac.kr)
DAMGO ([D-Ala2, N-MePhe4, Gly-ol]-enkephalin) is a synthetic opioid peptide with high μ-opioid receptor specificity. (wikipedia.org)
Structures of DAMGO bound to the µ opioid receptor reveal a very similar binding pose to morphinans. (wikipedia.org)
Our results show a rise in basal intracellular calcium ([Ca(2+)]i) in response to application of [D-Ala(2)-N-Me-Phe(4),Gly5-ol]-Enkephalin (DAMGO), a MOR agonist, that is blocked by D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), a MOR antagonist. (umassmed.edu)
Buffering DAMGO-induced changes in [Ca(2+)]i with BAPTA-AM completely blocked the inhibition of both I(Ca) and high-K(+)-induced rises in [Ca(2+)]i due to MOR activation, but had no effect on kappa-opioid receptor (KOR)-mediated inhibition. (umassmed.edu)
Deletion of the dopamine D(3) receptor gene resulted in a remarkable enhancement of the morphine-induced rewarding effect. (opioids.wiki)
Furthermore, knock-out mice with deletions of the dopamine D(3) receptor revealed a dramatic potentiation of morphine-induced hyperlocomotion. (opioids.wiki)
Under these conditions, a loss of the dopamine D(3) receptor gene had no effect on the basal levels of dopamine and the increased dopamine turnover by morphine in the limbic forebrain. (opioids.wiki)
Intravenous (i.v.) administration of μ opioid receptor (MOR) agonists (fentanyl, alfentanil, remifentanil, and morphine) evoked scratching in a dose- and time-dependent manner. (ewha.ac.kr)
Antagonist studies revealed that i.v. administration of an opioid receptor antagonist (naltrexone, 0.0032-0.1 mg/kg) dose dependently attenuated scratching induced by i.v. fentanyl (0.018 mg/kg) or morphine (1 mg/kg). (ewha.ac.kr)
In slices from morphine-dependent rats maintained in morphine (5 μ m ) in vitro , action potential frequencies of opioid-sensitive neurons did not differ from untreated control neurons but were greater than in control neurons maintained in morphine in vitro , indicating development of tolerance. (jneurosci.org)
Antagonist3
The responsiveness to the mu agonist and antagonist was greater in controls. (nih.gov)
The nicotinic receptor antagonist, mecamylamine (10 μM), did not affect the elevations of [Ca 2+ ](i) caused by opioids in the presence of carbachol. (edu.au)
However, opioid receptor-effector uncoupling cannot account fully for physical dependence, which is characterized by withdrawal signs, or abnormal rebound responses in single neurons after administration of an opiate antagonist. (jneurosci.org)
Opioid Analgesics1
Together, these data suggest that MOR, not other opioid receptor types or histamine, mediates scratching evoked by opioid analgesics. (ewha.ac.kr)
Pharmacology1
British Journal of Pharmacology , 117 (2), 333-340. (edu.au)
Opioids3
5. Block of carbachol activation of muscarinic receptors with atropine (10 μM) abolished the elevation of [Ca 2+ ](i) by the opioids. (edu.au)
Thus, in SH-SY5Y cells, opioids can mobilize Ca 2+ from intracellular stores but they require ongoing muscarinic receptor activation. (edu.au)
It was synthesized as a biologically stable analog of δ-opioid receptor-preferring endogenous opioids, leu- and met-enkephalin. (wikipedia.org)
Rats4
The expression of mu opioid receptors was increased in obese rats. (nih.gov)
These studies were designed to investigate how the aging process alters the spinal antinociceptive efficacy of mu (mu), delta (delta) and epsilon (epsilon) opioid receptor agonists administered intrathecally (i.t.) in rats. (omeka.net)
Substance P (SP) levels in the spinal cords of very old rats are less than the levels in younger rats (Bergman et al. (omeka.net)
Neurons3
Specific isoforms of PKC were inhibited by using inhibitors of the receptors for activated C-kinase (RACK), and in vivo viral-mediated gene-transfer was used to transfect neurons with dominant negative mutants (DNMs) of specific G-protein-coupled receptor kinases (GRKs). (bath.ac.uk)
In all neurons tested, methionine (Met)-enkephalin (0.003-30 μM) inhibited the peak amplitude of the EPSCs. (psu.edu)
Immunohistochemical studies revealed that nerve terminals apposing DMV neurons showed immunoreactivity to μ-opioid receptors colocalized with glutamate immunoreactivity but not glutamic acid decarboxylase immunoreactivity. (psu.edu)
Dorsal1
The present studies were designed to determine the actions of opioid peptides on synaptic transmission within the dorsal motor nucleus of the vagus (DMV) and the localization of μ-opioid receptors. (psu.edu)
Intracellular2
Furthermore, previous data suggest that the intracellular mechanisms underlying desensitization may be agonist-specific. (bath.ac.uk)
1. In this study we have investigated δ and μ opioid receptor-mediated elevation of intracellular Ca 2+ concentration ([Ca 2+ ](i)) in the human neuroblastoma cell line, SH-SY5Y. (edu.au)
Dopamine2
opioid receptor in the brain determined by the [tylosil-3,5-(3)H(N)]-[d-Ala(2),N-MePhe(4),Gly-ol(5)]enkephalin binding assay was not significantly changed by a deletion of the dopamine D(3) receptor gene. (opioids.wiki)
opioid receptor itself was not affected by a deletion of the dopamine D(3) receptor gene. (opioids.wiki)
Inhibition2
An increase in the ratio of the evoked paired pulses indicated that the inhibition was attributable to actions at presynaptic receptors. (psu.edu)
However, mu-opioid receptor (MOR)-mediated inhibition of I(Ca) is reliably demonstrated using the perforated-patch configuration. (umassmed.edu)
Calcium1
mu-Opioid agonists have no effect on calcium currents (I(Ca)) in neurohypophysial terminals when recorded using the classic whole-cell patch-clamp configuration. (umassmed.edu)
Functional1
These data represent functional selectivity at the level of receptor desensitization. (bath.ac.uk)
Studies1
This ongoing area of research has led to further investigations into the 1,5-hydrogen atom transfer process and in particular, studies into the effectiveness of deuterium as a protecting group for C-H bonds in radical and carbene chemistry. (exeter.ac.uk)
Activation1
6. Muscarinic receptor activation, not a rise in [Ca 2+ ](i), was required to reveal the opioid response. (edu.au)
Suggest1
These results suggest that within the DMV, μ-opioid receptors are present on the nerve terminals of excitatory but not inhibitory inputs to Gl motoneurons. (psu.edu)
Action1
The aim of this study was to elucidate the roles of opioid receptor types and the site of action in opioid-induced itch in monkeys. (ewha.ac.kr)