Glutamate neurotransmission plays an important role in the processing of pain and in chronic opioid-induced neural and behavioral plasticity, such as opioid withdrawal and opioid dependence. -Opioid receptors also have been implicated in acute opioid modulation of pain and chronic opioid-induced plasticity, both of which are primarily mediated by -opioid receptors. Using whole-cell patch clamp ...

Chronic treatment with opioid receptor antagonists has been shown to increase the density of micro-, delta- and kappa-opioid receptors in cell culture and in the intact animal. Although opioid receptor antagonist-induced up-regulation is a robust phenomenon, the mechanisms responsible for the increase in receptor density remain unclear. In the present study, changes in a kinase and a GTPase tha...

It has been shown previously that sigma receptor agonists reveal potential antidepressant activity in experimental models. Moreover, some data indicate sigma receptor contribution to stress-induced responses (e.g., conditioned fear stress in mice), though the mechanism by which sigma ligands can exert their effects, remains unclear. Recent studies have indicated that antidepressant drugs (ADs) ...

Three types of opioid receptors exist in the animals, each is encoded by a single gene, i.e., the mu opioid receptor gene, the delta opioid receptor gene, and the kappa opioid receptor gene. However, each opioid receptor gene produces multiple mRNA variants as a result of alternative promoter usages, splicing and/or polyadenylation. As such, a large reservoir of regulatory events has evolved fo...

Sigma receptors are unique endoplasmic reticulum proteins that mediate signaling for a variety of drugs. We determined the effect of sigma(1) receptor agonists on immune responses in a syngeneic lung cancer model. Sigma(1) receptor agonists, including cocaine, up-regulated splenocyte IL-10 mRNA and protein production in vitro in a sigma receptor-dependent, pertussis toxin-sensitive manner. In v...

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...

Mu-opioid receptor activation underpins clinical analgesia and is the central event in the abuse of narcotics. Continued opioid use produces tolerance to the acute effects of the drug and adaptations that lead to physical and psychological dependence. Continued mu-receptor signaling provides the engine for these adaptations, with most evidence suggesting that chronic agonist treatment produces ...

BACKGROUND A difficult problem in treating opioid addicts is the maintenance of a drug-free state because of the negative emotional symptoms associated with withdrawal, which may trigger relapse. Several lines of evidence suggest a role for the metabotropic glutamate receptor 5 in opioid addiction; however, its involvement during opioid withdrawal is not clear. METHODS Mice were treated with ...

In contrast to endogenous opioids, the highly addictive drug morphine activates the mu-opioid receptor without causing its rapid endocytosis. It has recently been reported that coapplication of low concentrations of [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) facilitates the ability of morphine to stimulate mu-opioid receptor endocytosis and prevents the development of morphine toleranc...

The purpose of this study was to evaluate the effects of the gonadal hormones on the opioid receptor protein levels of Freund's adjuvant-treated (arthritic) male and female Lewis rats. Following a paw pressure nociception assay, the midbrain and spinal cord tissues were collected for comparison of mu, delta, and kappa opioid receptor protein levels. The effects of Freund's adjuvant-induced hype...