English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The newly discovered endogenous mu-opioid receptor (MOP-R) ligands endomorphin-1 (EM-1) and -2 (EM-2) exhibit the highest specificity and affinity for the MOP-R of any endogenous substance so far described in the mammalian nervous system. This review focuses on differential mechanism of the motivational effects induced by EM-1 and EM-2. In the [35S]GTPgammaS binding assay, either EM-1 or EM-2 causes a concentration-dependent G-protein activation in brain membrane of normal mice, whereas neither EM-1 nor EM-2 produces any activation of G-protein in membranes obtained from the MOP-R knockout mice. These results provide direct evidence at the molecular level that both EMs act on the MOP-R as the endogenous MOP-R agonists. Based on the conditioned place preference paradigm in mice, EM-1 given intracerebroventriculally produced a dose-related place preference. This effect was abolished by pretreatment with the MOP-R antagonist beta-funaltrexamine (FNA) but not the delta-opioid receptor (DOP-R) antagonist naltrindole and the kappa-opioid receptor (KOP-R) antagonist nor-bialtorphimine (BNI). Unlike EM-1, EM-2 exhibited a place aversion. The aversive effect was inhibited by not only beta-FNA but also nor-BNI. Place aversion produced by EM-2 was also attenuated by pretreatment with an antiserum against an endogenous KOP-R ligand dynorphin A(1-17). These findings indicate that EM-1 may produce its rewarding effect via MOP-Rs. Furthermore, the aversive effect induced by EM-2 may be associated with the stimulation of the EM-1-insensitive MOP-R subtype and necessarily activate an endogenous KOPergic system in the mouse brain.

japanese journal of pharmacology/japanese journal of pharmacology

Recent Advances in the Search for the μ-Opioidergic System: Endomorphin-Induced Motivational Effect: Differential Mechanism of Endomorphin-1 and Endomorphin-2