Search results for "Endogenous opioid"
showing 10 items of 21 documents
Lack of plasmic beta-endorphin response to a gastronomic meal in healthy humans.
1991
Abstract In order to study the relationship between the endogenous opiate system and food intake in man, plasma concentrations of beta-endorphin were measured in ten healthy subjects. Time course of beta-endorphinemia was compared under the following conditions: basal (fasting), after an injection of pentagastrin (6 μg/kg), or after a gastronomic meal. No changes in plasma beta-endorphin or ACTH concentrations were observed with pentagastrin nor after the meal, despite the combination of very high sensory pleasure with intake of a very large amount of food. It is concluded that blood beta-endorphin concentration is not a sensitive index of the effects of food intake on the endogenous opioid…
The Endogenous Opioid System Is Not Involved in Modulation of Opioid-Induced Hyperalgesia
2009
Abstract Some recent studies suggested a role of the endogenous opioid system in modulating opioid-induced hyperalgesia (OIH). In order to test this hypothesis, we conducted a prospective randomized, placebo-controlled, 2-way crossover study in healthy human volunteers. We utilized a well-established model of inducing OIH after a brief exposure to the μ-opioid agonist remifentanil using intradermal electrical stimulation. Patients were exposed to a randomized 90-minute infusion of remifentanil or saline placebo during 2 separate occasions. Development of OIH was quantified using changes in the average radius of the area of secondary hyperalgesia generated by electrical pain stimulation. A 2…
Basal opioid receptor binding is associated with differences in sensory perception in healthy human subjects: a [18F]diprenorphine PET study.
2009
The endogenous opioid system is involved in many body functions including pain processing and analgesia. To determine the role of basal opioid receptor availability in the brain in pain perception, twenty-three healthy subjects underwent positron emission tomography (PET) utilizing the subtype-nonselective opioid antagonist [(18)F]diprenorphine, quantitative sensory testing (QST) and the cold pressor test. Binding potentials (BPs) were calculated using a non-invasive reference tissue model and statistical parametric mapping was applied for t-statistical analysis on a voxelwise basis. We found that cold pain-sensitive subjects present a significantly lower BP in regions including the bilater…
Regional distribution of opioidergic nerves in human and canine prostates
1989
The regional distribution of opioidergic nerves in the juvenile and adult human prostate and in the adult canine prostate has been studied immunohistochemically using well-characterized polyclonal antisera against multiple opioid peptides. Nerves displaying immunoreactivity (ir) for the proenkephalin (PRO-ENK) derivatives met-enkephalin (ME), leuenkephalin (LE), octapeptide, and heptapeptide (ordered in decreasing frequency) were present in the dorsolateral stroma of human prostate. In canine prostate, the situation was similar, but the number of opioid-ir nerve fibers was lower than in human prostate. In both species, staining for the prodynorphin (PRO-DYN) derivatives dynorphin A and alph…
Endogenous opioid peptide responses to opioid and anti-inflammatory medications following eccentric exercise-induced muscle damage.
2009
To determine the effects of Vicoprofen, Ibuprofen, and a placebo on the responses of endogenous opioid peptides following eccentric exercise-induced muscle damage 36 healthy men (age: 22.8 years; height: 178.8+/-6.2cm; body mass: 78.9+/-13.7kg; body fat: 15.8+/-6.5%) volunteered to participate in the study. Each participant was evaluated for pain 24h post and randomly assigned to an experimental group: VIC (Vicoprofen), IBU (Ibuprofen), or P (placebo). Medication was given four times daily (i.e., VIC (hydrocodone bitartrate 7.5mg with Ibuprofen 200mg) and IBU 200mg). Blood was obtained at rest and at 0, 24, 48, 72, 96 and 120h following the eccentric exercise damage protocol. No significant…
Intraventricular insulin decreases kappa opioid-mediated sucrose intake in rats.
2002
The hormone insulin acts in the central nervous system (CNS) as a regulator of body adiposity and food intake. Recent work from our laboratory has provided evidence that one way by which insulin may decrease food intake is by decreasing the rewarding properties of food. Evidence from others suggests that endogenous opioids may mediate the palatable properties of foods, and insulin may decrease nonfood-related reward via interaction with some CNS kappa opioid systems. In the present study we examined the ability of insulin to interact with exogenous or endogenous kappa opioids to modulate feeding of palatable sucrose pellets by nondeprived rats. Insulin (5 mU intracerebroventricular (i.c.v.)…
On the opioid receptor subtype inhibiting the evoked release of 3H-noradrenaline from guinea-pig atria in vitro
1986
1. Guinea-pig isolated atria were incubated and loaded with 3H-(−)-noradrenaline. The intrinsic nerves were stimulated with trains of 5 or 35 field pulses (4 Hz), and the evoked efflux of 3H-noradrenaline and of total tritium was determined in the presence of atropine, corticosterone, desipramine, and phentolamine by liquid scintillation spectrometry. 2. Ethylketocyclazocine (1.4 nmol/l, IC50), MR 2033 (9.1 nmol/l), dynorphin A (1–13) (25 nmol/l, peptidase inhibitors present), etorphine (71 nmol/l), and [d-Ala2, d-Leu5]-enkephalin (>10 μmol/l, peptidase inhibitors present) inhibited the stimulation-evoked efflux of 3H-noradrenaline in a concentration-dependent manner, but not morphine up to…
Hunting for the high-affinity state of G-protein-coupled receptors with agonist tracers: Theoretical and practical considerations for positron emissi…
2019
Abstract The concept of the high‐affinity state postulates that a certain subset of G‐protein‐coupled receptors is primarily responsible for receptor signaling in the living brain. Assessing the abundance of this subset is thus potentially highly relevant for studies concerning the responses of neurotransmission to pharmacological or physiological stimuli and the dysregulation of neurotransmission in neurological or psychiatric disorders. The high‐affinity state is preferentially recognized by agonists in vitro. For this reason, agonist tracers have been developed as tools for the noninvasive imaging of the high‐affinity state with positron emission tomography (PET). This review provides an…
Role of Levo-tetrahydropalmatine and its metabolites for management of chronic pain and opioid use disorders.
2021
Abstract Background Opioids have been prescribed to reduce suffering from pain and to enhance quality of life. Due to the addictive potential and the lack of other effective alternatives to treat severe acute and chronic pains, opioids remain a serious public health issue. While, opioids directly influence the drug-seeking behavior, tolerance and withdrawal processes, through neuroadaptation, the brain's endogenous opioid system also adapts in the presence of chronic pain and could contribute to the difficulty of treatment. Despite the seemingly obvious interaction between the presence of pain and opioid-abuse, little is known about the underlying mechanisms in the brain. Purpose To review …
GHB differentially affects morphine actions on motor activity and social behaviours in male mice
2003
There are several reports suggesting that gamma-hydroxybutyric acid (GHB) influences the endogenous opioid system. The present study aimed to investigate the effects of GHB on motor and social activities and to examine its influence on morphine's actions on these behaviours. In a first experiment, several doses of GHB were studied but only the highest (200 and 400 mg/kg) produced a decrease in spontaneous motor activity measured in an actimeter cage. When hyperactivity induced by injecting 50 mg/kg of morphine was evaluated, all the GHB doses efficiently counteracted this morphine action. Using the paradigm of isolation-induced aggression, administration of 200 mg/kg of GHB significantly de…