The increasing number of opioid users among chronic pain patients, and opioid abusers among the general population, makes perioperative pain management challenging for health care professionals. Anesthesiologists, surgeons, and nurses should be familiar with some pharmacological phenomena which are typical of opioid users and abusers, such as tolerance, physical dependence, hyperalgesia, and ad...

Mechanisms of endogenous pain control are significant. Increasing studies have clearly produced evidence for the clinical usefulness of opioids in peripheral analgesia. The immune system uses mechanisms of cell migration not only to fight pathogens but also to control pain and inflammation within injured tissue. It has been demonstrated that peripheral inflammatory pain can be effectively contr...

In inflammation, leucocytes containing opioid peptides migrate into the tissue. Opioid peptides can be released and bind to opioid receptors on peripheral nerve terminals, which counteracts inflammatory pain. Migration of opioid peptide-containing leucocytes is controlled by chemokines and adhesion molecules. Neurokinins, such as, substance P also contribute to the recruitment of these cells. O...

Although opioid-induced hyperalgesia (OIH) is mentioned as a potential cause of opioid dose escalation without adequate analgesia, true evidence in support of this notion is relatively limited. Most studies conducted in the context of acute and experimental pain, which seemingly demonstrated evidence for OIH, actually might have measured other phenomena such as acute opioid withdrawal or tolera...

with morphine together with subanalgesic doses of a second opiate did not develop tolerance to the morphine even after seven days of treatment. Although morphine is a favored choice for easing pain, a major drawback of its long-term use is the development of tolerance, which results in reduced analgesic effects upon long-term use. Morphine binds the opioid receptor (MOR), one member of the larg...

The opioid abstinence syndrome is associated with spinal excitatory amino acid (EAA) release, hyperalgesia and long-term changes in dorsal horn cellular excitability. N-Methyl-D-aspartate (NMDA) receptor antagonism attenuates opioid tolerance but also blocks EAA release during abstinence. This study examines the effect of repetitive abstinence, and NMDA receptor antagonism during abstinence, on...

A remarkable amount of literature has been generated demonstrating the functional similarities between the endogenous opioid and cannabinoid systems. Anatomical, biochemical and molecular data support the existence of reciprocal interactions between these two systems related to several pharmacological responses including reward, cognitive effects, and the development of tolerance and dependence...

Endomorphins (endomorphin-1, H-Tyr-Pro-Trp-Phe-NH2, endomorphin-2, Tyr-Pro-Phe-Phe-NH2) are potent and selective μ-opioid receptor agonists. In order to improve the affinity and chemical stability of endomorphins, we have designed, synthesized, and characterized novel analogs with unnatural (2′, 6′-dimethyltyrosine, Dmt) and/or β-alicyclic amino acids (ACPC and ACHC). Radioligand binding assay ...

The μ-opioid receptor is the primary site for the action of morphine. In the present study, we investigated the regulation of the μ-opioid receptor mRNA levels in the locus ceruleus, ventral tegmental area, nucleus accumbens and hypothalamus of the rat brain following intracerebroventricular administration of morphine for 7 days. The isolated mRNA from these regions was subjected to real-time q...

Personal social network size exhibits considerable variation in the human population and is associated with both physical and mental health status. Much of this inter-individual variation in human sociality remains unexplained from a biological perspective. According to the brain opioid theory of social attachment, binding of the neuropeptide β-endorphin to μ-opioid receptors in the central ner...