ISSN:
1474-8673
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
〈list xml:id="l1" style="custom"〉1To validate the relationship between the dopaminergic, opioidergic and cholinergic nervous systems, we evaluated the effect of domperidone, a dopamine (D2) antagonist, on the opioid system in myenteric plexus-longitudinal muscle preparation isolated from the guinea-pig ileum.2One micromolar of domperidone did not affect the 0.1 Hz-evoked (duration 0.5 ms, maximum intensity) twitch response, but concentration dependently inhibited the twitch response between concentrations of 2 and 20 μm, and the inhibition was maximum after 20–30 min at the highest concentration used (20 μm).3 Acetylcholine-evoked contraction on basal tension was also not inhibited by 1 μm domperidone, but the contraction was concentration dependently inhibited at concentrations of 10–100 μm in a non-competitive manner.4One micromolar of domperidone, however, increased post-tetanic twitch inhibition, an indicator of the release of endogenous opioids. This increase was completely antagonized by 1 μm naloxone.5Twitch inhibition induced by dynorphin 1–13 (0.1–10 nm) was not affected by 1 μm domperidone, but increased the maximum twitch inhibition caused by morphine (0.1–1 μm).6These results might reflect the existence of an interaction between the dopaminergic and opioidergic system without the inhibition of the cholinergic system. Dopamine antagonists increased opioid action, an action that may depend more on the increased release of endogenous opioids than on supersensitivity of the opioid receptor.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1474-8673.2003.00277.x
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