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...

We have investigated the heterodimerization of ORL1 receptors and classical members of the opioid receptor family. All three classes of opioid receptors could be co-immunoprecipitated with ORL1 receptors from both transfected tsA-201 cell lysate and rat dorsal root ganglia lysate, suggesting that these receptors can form heterodimers. Consistent with this hypothesis, in cells expressing either ...

The endogenous opioid system plays a significant role in the modulation of distress in many psychiatric, neurologic, and neurodevelopmental disorders. Many clinical distress symptoms show similarities to the excitatory autonomic withdrawal effects in chronic opioid-dependent animals and humans, as well as to the “quasi-morphine withdrawal syndrome” evoked in naïve rodents shortly after acute sy...

sigma Ligands modulate opioid actions in vivo, with agonists diminishing morphine analgesia and antagonists enhancing the response. Using human BE(2)-C neuroblastoma cells that natively express opioid receptors and human embryonic kidney (HEK) cells transfected with a cloned mu opioid receptor, we now demonstrate a similar modulation of opioid function, as assessed by guanosine 5'-O-(3-[(35)S]t...

The rostral nucleus of the solitary tract (NST) is the first central relay in the gustatory pathway and plays a key role in processing and modulation of gustatory information. Here, we investigated the effects of opioid receptor agonists and antagonists on synaptic responses of the gustatory parabrachial nuclei (PbN)-projecting neurons in the rostral NST to electrical stimulation of the solitar...

The presence of endogenous opioid peptides in different testicular cell types has been extensively characterized and provides evidence for the participation of the opioid system in the regulation of testicular function. However, the exact role of the opioid system during the spermatogenesis has remained controversial since the presence of the mu-, delta- and kappa-opioid receptors in spermatoge...

Background Opioid receptors belong to the rhodopsin subclass within the superfamily of G protein-coupled receptors (GPCR), which are characterized by the presence of seven transmembrane (7TM) helices. They interact with morphine and related opioid alkaloids as well as with endogenous opioid peptides. There are three main types of opioid receptors (μ, δ, ), which are differently implicated in op...

Opioid abuse and misuse in the USA is a public health crisis. The use of prescription opioid analgesics increased substantially from 2002 through 2010, then plateaued and began to decrease in 2011. This study examined prescriptions of branded and generic immediate- and extended-release opioid analgesics from 1992 to 2016. This was juxtaposed against state and federal policies designed to decrea...

Respiratory depression limits the use of opioid analgesia. Although well described clinically, the specific mechanisms of opioid action on respiratory control centres in the brain have, until recently, been less well understood. This article reviews the mechanisms of opioid-induced respiratory depression, from the cellular to the systems level, to highlight gaps in our current understanding, an...

A previous study has implicated central mu opioid receptors in the preference for salt solutions. Because mu, kappa and delta receptors are all thought to play a role in food intake and/or the mediation of palatability, we performed a series of experiments to determine whether preferential agonists at kappa and delta receptors might also stimulate the intake of salt solutions. When injected cen...