In vivo functional imaging by means of positron emission tomography (PET) is the sole method for providing a quantitative measurement of mu-, kappa and delta-opioid receptor-mediated signalling in the central nervous system. During the last two decades, measurements of changes to the regional brain opioidergic neuronal activation--mediated by endogenously produced opioid peptides, or exogenousl...

BACKGROUND AND PURPOSE In addition to its analgesic functions, the peripheral opioid receptor system affects skin homeostasis by influencing cell differentiation, migration and adhesion; also, wound healing is altered in δ-opioid receptor knockout mice (DOPr(-/-) ). Hence, we investigated δ-opioid receptor effects on the expression of several proteins of the desmosomal junction complex and on t...

in this study, the effects of subcutaneous (sc) injection of pilocarpine (a cholinomimetic agent) and atropine (a muscarinic receptors antagonist) were investigated on a tonic model of orofacial pain in rats. the contribution of the endogenous analgesic opioid system was assessed using naloxone (an opioid receptors antagonist). tonic orofacial pain was induced by sc injection of a diluted forma...

The authors estimated the prevalence of lifetime prescription opioid-use disorder among outpatients on opioid therapy using criteria from both versions 4 and 5 of the Diagnostic and Statistical Manual of Mental Disorders (DSM). Using electronic records from a large health care system, a random sample of outpatients undergoing long-term opioid therapy for non-cancer pain was identified and 705 p...

Opium is one of the oldest herbal medicines currently used as an analgesic, sedative and antidiarrheal treatment. The effects of opium are principally mediated by the μ-, κ- and δ-opioid receptors. Opioid substances consist of all natural and synthetic alkaloids that are derived from opium. Most of their effects on gastrointestinal motility and secretion result from suppression of neural activi...

Opioid receptors are widely expressed in the central and peripheral nervous system as well as in numerous nonneuronal tissues. Both animal models and human clinical data support the involvement of peripheral opioid receptors in analgesia, particularly in inflammation where both opioid receptor expression and efficacy are increased. Immune cells have been shown to contain numerous opioid peptide...

Nicotine (NIC) is an exogenous ligand of the nicotinic acetylcholine receptor (nAChR), and it influences various functions in the central nervous system. Systemic administration of NIC elicits the release of endogenous opioids (endorphins, enkephalins, and dynorphins) in the supraspinal cord. Additionally, systemic NIC administration induces the release of methionine-enkephalin in the spinal do...

The central opioid system is involved in a broadly distributed neural network that regulates food intake. Here, we show that activation of central δ-opioid receptor not only stimulated normal diet intake but conversely suppressed high-fat diet intake as well. [D-Pen(2,5)]-enkephalin (DPDPE), an agonist selective for the δ-receptor, increased normal diet intake after central administration to no...

The Tyr-MIF-1 family of neuropeptides (Tyr-MIF-1’s) includes MIF-1, Tyr-MIF-1, Tyr-W-MIF-1 and Tyr-K-MIF-1. Nowadays it is certain that they can modulate pain and some forms of stress-induced analgesia (SIA) by antiopiate and μ-specific processes. The objectives of the present study were twofold: 1) to determine the involvement of opioid system in analgesia induced by immobilization, cold and h...

The endogenous opioid system, comprised of multiple opioid neuropeptide and receptor gene families, is highly expressed by developing neural cells and can significantly influence neuronal and glial maturation. In many central nervous system (CNS) regions, the expression of opioid peptides and receptors occurs only transiently during development, effectively disappearing with subsequent maturati...