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Effects of Stress on Physiological Conditions in the Oral Cavity
Published in Eli Ilana, Oral Psychophysiology, 2020
Recent research suggests that the mechanism which mediates stress and pain results from activation of an endogenous opioid peptide system. The evidence that stress induces endogenous opioid activity, which concomitantly leads to stress-induced analgesia, is primarily based on animal studies that use opioid antagonists (especially Naloxone) to block the analgesic effects of the opioid system. Antagonist drugs have been shown to neutralize the analgesia induced by stressful stimuli in animal studies.107,109,122-127
Psychoneuroimmunology, Stress and Infection
Published in Herman Friedman, Thomas W. Klein, Andrea L. Friedman, Psychoneuroimmunology, Stress, and Infection, 2020
Many have challenged the “nonspecific” aspect of Selye’s definition of stress, but the two physiological responses (sympathoadrenal and HPA) occur in most situations regarded as stressful. Thus, most physiological definitions of stress cite the co-activation of the sympathoadrenal and HPA axes, i.e. elevation of plasma concentrations of catecholamines and corticosteroids. Some ethologists do not agree with this hormonal definition of stress, and prefer a poorly defined behavioral definition. A schematic indicating the relationships within and between the sympathoadrenal and HPA systems appears in Figure 2.4 The major known interactions are the regulation of CRF secretion by catecholamines, and the glucocorticoid regulation of a number of facets of catecholamine function, including epinephrine synthesis in the adrenal medulla, and up- and downregulation of receptors for catecholamines. There are also complex effects of the opioid peptides.
Pharmacotherapy of Neurochemical Imbalances
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Rupali Patil, Aman Upaganlawar, Suvarna Ingale
Peptides, which bind to opioid receptors, are called opioid peptides. Opioid peptides are also called opioid neuropeptides or opioid neuromodulators. Opioid receptors are the membrane proteins located in nerve endings in brain and GIT. Opioid receptors are of three types: µ, κ, and δ. These proteins are called opioid receptors because of their affinity toward the opiate or morphine, which are derived from opium. Opiate and morphine act by binding with the receptor proteins (opioid receptors) for the natural neuropeptides. Natural neuropeptides are called endogenous opioid peptides. Endogenous opioid peptides have opiate like activity and inhibit the neurons in the brain involved in pain sensation (Froehlich, 1997). Opioid peptides are of three types:
On the path toward personalized medicine: implications of pharmacogenetic studies of alcohol use disorder medications
Published in Expert Review of Precision Medicine and Drug Development, 2020
Steven J. Nieto, Erica N. Grodin, Lara A. Ray
Several families of endogenous opioid peptides bind to these receptors, but the primary ligands are the endorphins, dynorphins, and enkephalins. These three families of peptides have varying degrees of affinity for each of the opioid receptors and none bind to only one receptor subtype. β-endorphins are derived from pro-opiomelanocortin (POMC) and are the primary ligands for the mu-opioid receptor, dynorphins for the kappa-opioid receptors, enkephalins for the delta-opioid receptors, and the peptides nociceptin and orphanin bind to nociceptin/orphanin receptors. It is currently posited that NTX works by occupying mu-opioid receptors preventing the binding of endogenous opioid peptides (e.g., β-endorphin) that are released upon alcohol intake [35], which in turn prevents GABA-mediated release of dopamine in the ventral tegmental area thereby blocking alcohols reinforcing effects [36,37].
Can therapeutic strategies prevent and manage dyskinesia in Parkinson’s disease? An update
Published in Expert Opinion on Drug Safety, 2019
Valentina Leta, Peter Jenner, K. Ray Chaudhuri, Angelo Antonini
Endogenous opioid peptides and receptors are physiologically localized in the basal ganglia [106]. Alterations of the opioid pathway, including abnormalities in the striatal expression of opioid peptides and opioid receptors, have been reported both in animal models and PD patients with dyskinesia [107]. Thus, several agents acting on different opioid receptors have been investigated in LID and results in non-human primates seem to suggest that mu-antagonism is the most effective [108,109], followed by kappa-agonism [110]. It has been shown that mu‐opioid receptor antagonists may have a dose-dependent effect on LID: Cyprodine ADL5510 can repress LID in primates at low and moderate doses but it loses its efficacy at higher doses probably due to loss of selectivity and the additional antagonization of kappa-opioid receptors as well [109]. Moreover, nalbuphine, a mixed mu-antagonist and kappa-agonist, reduced dyskinesia in non-human primates in a dose-dependent manner [111]. This can explain why clinical trials on unselective opioid antagonists, such as naloxone and naltrexone, have failed in the past [112,113].
Pharmacogenetics and levodopa induced motor complications
Published in International Journal of Neuroscience, 2019
Kallirhoe Kalinderi, Vasileios Papaliagkas, Liana Fidani
Opioid receptors are 7-transmembrane domain receptors that couple to heterotrimeric G proteins. There are three types of opioid receptors (μ receptor, δ receptor and κ receptor). The basal ganglia have one of the highest levels of endogenous opioids and opioid peptide receptors in the brain [63]. All subtypes of opioid peptide receptor are involved in regulating dopamine functions. In animal models of PD, dopamine denervation and repeated L-dopa administration has been associated with an enhancement of opioid transmission in the basal ganglia [64]. It has also been suggested that some of the changes in opioid transmission are directly implicated in LID. Opioids are co-transmitters in both the direct and the indirect basal ganglia pathways. Importantly, in a PET scan study, PD patients with LID had lower opioid binding in striatum and thalamus [65]. The human mu opioid receptor gene has a common genetic variant, the A118G (rs1799971) single nucleotide polymorphism, which has been found to increase binding affinity and functional activity of the endogenous opioid peptide, endorphin [66]. This polymorphism has been associated with earlier development of dyskinesia in L-dopa–treated PD patients [36], probably due to changes in enkephalins and dynorphins. Interestingly, receptor-specific opioid antagonists used in primate models, has been observed to affect LID [64, 67].