Morphine induces peripherally μ-opioid-mediated antinociception to heat but not to mechanical stimulation. Peripheral sigma-1 receptors tonically inhibit μ-opioid antinociception to mechanical stimuli, but it is unknown whether they modulate μ-opioid heat antinociception. We hypothesized that sigma-1 receptors might play a role in the modality-specific peripheral antinociceptive effects of morp...

abstractprevious studies have shown the role of opioid receptors located in the nucleus cuneiformis (cnf) in acute pain, but not in chronic pain models. in the present study, we have determined that possible effects of these receptors at the cnf on both early and late phases of formalin test following local and systemic morphine administration. each rat was given a subcutaneous 50-μl injection ...

Scientists have endeavored to understand sigma receptors for over 40 y. Althoughmost agree that they are important, there is little agreement on anything else. In their behavioral classification of opioid receptors in 1976, Martin et al. (1) proposed three groups of compounds illustrating three distinct opioid receptor classes (mu, kappa, and sigma) based upon morphine, ketocyclazocine, and SKF...

the µ (mu) opioid receptors, which mediate the effects of morphine, are widely distributed in brain. the purpose of this study was to design a simple expression system for rat µ-receptor in escherichia coli (bl21). in this laboratory study, rat µ-receptor cdna was isolated from pcdna3 vector using xba1 and hind3 restriction enzymes. pet-15b was digested by nco1 restriction enzyme. µ-receptor cd...

centuries, both in amedicinal and ‘recreational’ manner. Indeed, findings of fossilized opium poppy seeds dating as far back as 30 000 yr ago suggest the use of opium by Neanderthal man. In 1799, Friedrich Serturner discovered the major active ingredient of opium, which he named morphine and opioid pharmacology was born. Morphine and its derivates are used today for the treatment of acute and c...

BACKGROUND The opioid receptor antagonists naloxone and naltrexone are competitive antagonists at the mu, kappa, and sigma receptors with a higher affinity for the mu receptor and lacking any mu receptor efficacy. Buprenorphine is classified as a partial agonist. It has a high affinity, but low efficacy at the mu receptor where it yields a partial effect upon binding. It also, however, possesse...

The cloning of a fourth member of the opioid receptor family has led to the discovery of a new neuropeptide termed orphanin FQ or nociceptin (OFQ/N). Studies in CD-1 mice confirm the ability of OFQ/N to rapidly induce hyperalgesia within 15 min which is insensitive to opioid antagonists. This is followed in the next 30 min by loss of hyperalgesia and the appearance of analgesia in the tailflick...

introduction: association between single-nucleotide polymorphisms (snps) in mu opioid receptor gene and drug addiction has been shown in various studies. here, we have evaluated the existence of polymorphisms in exon 3 of this gene in iranian population and investigated the possible association between these mutations and opioid addiction.  methods: 79 opioid-dependent subjects (55 males, 24 fe...

Sigma (sigma) receptors, initially described as a subtype of opioid receptors, are now considered unique receptors. Pharmacological studies have distinguished two types of sigma receptors, termed sigma(1) and sigma(2). Of these two subtypes, the sigma(1) receptor has been cloned in humans and rodents, and its amino acid sequence shows no homology with other mammalian proteins. Several psychoact...

This article provides an overview of present knowledge regarding the relationship between the cholinergic system and sigma-1 receptors, and discusses potential applications of sigma-1 receptor agonists in the treatment of memory deficits and cognitive disorders. Sigma-1 receptors, initially considered as a subtype of the opioid family, are unique ligand-regulated molecular chaperones in the end...