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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. The functional interaction between -opioid receptors and ␦-opioid receptors is also poorly understood. In this study, we demonstrated that in a brainstem site critically involved in opioid analgesia, agonists of ␦-opioid receptors, ineffective in opioid naive rats, significantly inhibit presynaptic GABA release in the brainstem neurons from morphine-tolerant rats. In membrane preparation from control brainstem tissues, Western blot detected no proteins of ␦-opioid receptors, but consistent ␦-opioid receptor proteins were expressed in membrane preparation from morphine-tolerant rats. Immunohistochemical studies revealed that long-term morphine treatment significantly increases the number of ␦-opioid receptor-immunoreactive varicosities that appose the postsynaptic membrane of these neurons. The colocalization of ␦-opioid receptor-immunoreactive varicosities with the labeling of the GABA-synthesizing enzyme glutamic acid decarboxylase is also significantly increased. From a behavioral perspective, activation of ␦-opioid receptors in the brainstem nucleus, lacking an effect in opioid naive rats, became analgesic in morphine-tolerant rats and significantly reduced morphine tolerance. These findings indicate that long-term morphine treatment induces the emergence of functional ␦-opioid receptors and ␦-opioid receptor-mediated analgesia, probably through receptor translocation to surface membrane in GABAergic terminals. They also suggest that opioid drugs with preference for ␦-opioid receptors may have better therapeutic effect in a -opioid-tolerant state.

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We have examined the potential role of spinal glial cells in the induction of C fiber-evoked long-term potentiation (LTP) in the spinal cord. Tetanic stimulation of the sciatic nerve induced longterm potentiation of C-fiber-evoked field potentials in the spinal dorsal horn in all rats. Following intrathecal fluorocitrate (1 nmol), a glial metabolic inhibitor, tetanic stimulation induced longterm depression (LTD) but not LTP. The effects of fluorocitrate were abolished by kynurenic acid or 2-amino-5-phosphonovaleric acid (AP-5), but not by 6,7-dinitroquinoxaline-2,3-dione (DNQX), picrotoxin or strychnine. These data suggest that spinal glial cells may modulate the central sensitization of nociceptive neurons via NMDA receptors.

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -This research seeks to extend the animosity model of foreign product purchase by examining the direct and moderating effects of cultural similarity in consumers' product judgment and willingness to buy foreign products. Design/methodology/approach -Empirical data were collected from a sample (n ¼ 225) of Taiwanese consumers. The data analysis used bivariate correlations, repeated general linear modeling, and structural equation modeling. Findings -Cultural similarity between consumers' home country (region) and a foreign product's country of origin has: a positive impact on consumers' product evaluation and willingness to buy foreign products; a weakening effect on the negative impact of war and economic animosity on willingness to buy foreign products; and a weakening effect on the negative impact of consumer ethnocentrism on their willingness to buy foreign products.Originality/value -This study not only enriches the animosity model of foreign product purchase, but also offers additional insights for international market entry and international marketing strategies.

The effects of molecular structures on nanostructural morphologies have been studied through the preparation of nanospheres, square nanowires, and nanocubes from three isomeric molecules of bis(iminopyrrole)benzene.

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