Meperidine exerts agonist activity at the alpha(2B)-adrenoceptor subtype

Area of Science:

• Pharmacology
• Neuroscience
• Molecular Biology

Background:

• Meperidine, an opioid agonist, exhibits pronounced antishivering effects not fully explained by opioid receptor interactions.
• Alpha(2) adrenoceptor agonists like clonidine are effective antishivering agents.
• Preliminary data suggest meperidine interacts with alpha(2) adrenoceptors.

Purpose of the Study:

• To investigate the binding and activation capabilities of meperidine across different alpha(2)-adrenoceptor subtypes.
• To determine the role of alpha(2)-adrenoceptor activation in meperidine's analgesic and antishivering effects.

Main Methods:

• Assessed meperidine's binding affinity and inhibitory effects on cyclic adenosine monophosphate (cAMP) formation mediated by transiently transfected alpha(2)-adrenoceptor subtypes (alpha(2A), alpha(2B), alpha(2C)) in COS-7 cells.
• Evaluated the blockade of meperidine's analgesic action in the hot-plate test using opioid (naloxone) and alpha(2)-adrenoceptor (yohimbine, RX821002) antagonists.
• Employed molecular modeling to assess meperidine's fit within the alpha(2B)-adrenoceptor.

Main Results:

• Meperidine demonstrated binding affinity for all alpha(2)-adrenoceptor subtypes, with the highest affinity for alpha(2B).
• Meperidine effectively inhibited cAMP production mediated by all subtypes, most potently at alpha(2B), comparable to dexmedetomidine.
• Naloxone blocked meperidine's analgesia, while alpha(2)-adrenoceptor antagonists did not; molecular modeling confirmed meperidine fits the alpha(2B) receptor.

Conclusions:

• Meperidine functions as a potent agonist at alpha(2)-adrenoceptors, especially alpha(2B), at clinically relevant concentrations.
• Alpha(2B) receptor activation does not significantly contribute to meperidine's analgesic effects.
• The alpha(2)-adrenoceptor mechanism, particularly via alpha(2B), may underlie meperidine's non-analgesic actions like antishivering.