Opioid receptors have been targeted for the treatment of pain and related disorders for thousands of years and remain the most widely used analgesics in the clinic. Mu (μ), kappa (κ), and delta (δ) opioid receptors represent the originally classified receptor subtypes, with opioid receptor like-1 (ORL1) being the least characterized. All four receptors are G-protein coupled and activate inhibit...

Background: Several studies have shown that the ethanol-derived metabolite salsolinol (SAL) can activate the mesolimbic system, suggesting that SAL is the active molecule mediating the rewarding effects of ethanol. In vitro and in vivo studies suggest that SAL exerts its action on neuron excitability through a mechanism involving opioid neurotransmission. However, there is no direct pharmacolog...

In this study, the activity of the delta-opioid receptor subtype-selective agonist, SB 227122, was investigated in a guinea pig model of citric acid-induced cough. Parenteral administration of selective agonists of the delta-opioid receptor (SB 227122), mu-opioid receptor (codeine and hydrocodone), and kappa-opioid receptor (BRL 52974) produced dose-related inhibition of citric acid-induced cou...

introduction: oxytocin is a active neuropeptide of central nervous system. in this study the effects of naloxone (opioid receptor antagonist) and yohimbine (α-2 adrenergic receptor antagonist) on analgesic effect of oxytocin applied into the locus coeruleus (lc) nucleus were investigated. methods: adult male wistar rats were used. animals divided into different groups receiving saline, oxytocin...

Agonist-induced receptor phosphorylation is an initial step in opioid receptor desensitization, a molecular mechanism of opioid tolerance and dependence. Our previous research suggested that agonist-induced d-opioid receptor (DOR) phosphorylation occurs at the receptor carboxyl terminal domain. The current study was carried out to identify the site of DOR phosphorylation during agonist stimulat...

Fear learning depends on prediction error, or the discrepancy between the actual and expected outcome of a conditioning trial. These experiments used blocking and unblocking designs to study the role of opioid receptors in the nucleus accumbens (Acb) in predictive fear learning. Previous fear conditioning to a context blocked later fear conditioning to a conditioned stimulus (CS) in that contex...

Cytochrophin-4 (cyt-4), a tetrapeptide with opioid-like activity, caused amnesia when injected into chick forebrain 5 hr after passive-avoidance training. Bilateral injections of cyt-4 directly into the lobus parolfactorius (LPO) resulted in the chicks being amnesic for the training task 24 hr later, whereas unilateral injections of cyt-4 were effective only when injected into the right LPO. Cy...

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...

Apoptosis of human liver cells is commonly found in liver diseases and liver surgery and directly affects their prognosis. Recent studies have found that δ-opioid receptors, abundant in the membranes of hepatic cells, participate in the oncogenesis and progression of liver tumors, viral hepatitis, liver cirrhosis and other diseases. The purpose of this study was to analyze the effect of the act...

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...