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...

The constrained opioid peptide (2S,3R) -methyl-2 ,6 -dimethyltyrosine-L-tetrahydroisoquinoline-3-carboxylic acid [(2S,3R)TMT-LTic-OH] exhibits high affinity and selectivity for the -opioid receptors (Liao et al., 1997). In the present study, we examined the pharmacological properties of (2S,3R)TMT-L-Tic-OH in mouse brain. A 5 -O-(3-[S]thiotriphosphate) ([S]GTP S) binding assay was used to deter...

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...

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...

Oxidative stress plays a major role in neurodegenerative disease since central nervous system is particularly vulnerable to reactive oxygen species (ROS) due to several reasons: high consumption of O 2 ; high production of ROS and nitrosative species, which originate from specific neurochemical reactions (e.g., dopamine oxidation); high deposition of metal ions in the brain with aging leading t...

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...