The opioid peptides and receptors have prominent roles in pain transmission and reward mechanisms in mammals. The evolution of the opioid receptors has so far been little studied, with only a few reports on species other than tetrapods. We have investigated species representing a broader range of vertebrates and found that the four opioid receptor types (delta, kappa, mu, and NOP) are present i...

The role of central mu- and kappa-opioid receptors in the regulation of itch sensation was examined using pruritogen-induced mouse scratching behavior model. Intracerebroventricular administration of beta-funaltrexamine, a selective mu-opioid receptor antagonist, inhibited the scratching behavior induced by intradermal substance P, but subcutaneous administration of beta-funaltrexamine did not....

Roles of endogenous opioid peptides and their receptors in modulation of the nocifensive responses to formalin in mice were studied. Mice were pretreated i.c.v. or intrathecally (i.t.) with selective opioid receptor antagonists or intrathecally with antisera against endogenous opioid peptides and the nocifensive licking responses to intraplantar injection of formalin (0.5%, 25 microl) were then...

Opioid analgesics remain the choice for the treatment of moderate to severe pain. Recent research has established that the -opioid receptor is predominantly responsible for mediating many opioid actions, including analgesia and opioid tolerance. However, the function of -opioid receptors is rather puzzling at present, with inconsistent reports of system effects by agonists of -opioid receptors....

In order to investigate the dynamic processes of mRNA levels of proenkephalin, proopiomelanocortin, prodynorphin, and opioid receptors (δ-, μ-, and κ-receptor) induced by electroacupuncture (EA) in the central nerve system, goats were stimulated by EA of 60 Hz for 0.5 h at a set of Baihui, Santai, Ergen, and Sanyangluo points. The pain threshold was measured using the method of potassium iontop...

Biogenesis of various endogenous opioid peptides, anatomical distribution and the characteristics of multiple receptors with which they interact provides an opportunity for understanding the role of opioid systems and mechanism of opioid tolerance. Cellular and anatomical distribution of opioid receptor and their function is important for identification of neuronal systems and local network inv...

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 ...

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...