ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
The putative regulatory effect of opioids on adenylate cyclase was investigated in two different preparations containing, respectively, two different populations of opioid receptors: the rabbit cerebellum (〉75%μ-opioid receptors) and the guinea pig cerebellum (〉80%K-opioid receptors). In the μ-preparation, but not in the K-preparation, opioids inhibited the basal and the forskolin-stimulated adenylate cyclase activity in a dose-dependent manner and stereospecifically. The inhibition was in the 20–30% range, required the presence in the assay medium of Mg2+ and of GTP, but was independent of the presence of Na+. Pharmacological characterization of the inhibitory response in the rabbit cerebellum clearly showed that it was under the control of a μ-opioid binding site, with the effect being elicited by nonselective (etorphine and morphine) and μ-selective (Tyr-D-Ala-Gly-Me-Phe-Gly-ol) agonists, whereas δ- and K-selective agonists were almost totally ineffective. ADP ribosylation of inhibitory GTP-binding protein by pertussis toxin failed to block the inhibitory effect of opioids, and data presented suggest that this failure is likely to be the consequence of a limited access of the toxin to its substrate in rabbit cerebellum membranes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1990.tb01908.x
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