Clinical and experimental pharmacology & physiology
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Clin. Exp. Pharmacol. Physiol. · Apr 2009
Antinociceptive interactions between anandamide and endomorphin-1 at the spinal level.
1. Although it is well known that the combined administration of synthetic or plant-originated opioids with cannabinoids (CB) results in synergistic antinociception, the effects of combined administration of endogenous ligands acting at micro-opioid and CB receptors are not known. The aim of the present study was to determine the interaction between anandamide (AEA; a CB(1) receptor agonist) and endomorphin-1 (EM-1; a micro-opioid receptor agonist) after intrathecal administration. 2. ⋯ The results of the present study indicate that the coadministration of AEA and EM-1 results in potentiated antihyperalgesia only for a combination of specific doses. Because AEA activates other receptor types (e.g. TRPV1) in addition to CB(1) receptors, the results of the present suggest that, after the coadministration of EM-1 and AEA, complex interactions ensue that may lead to different outcomes compared with those seen following the injection of exogenous ligands.