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Meptazinol has a similar agonist action on opioid receptors in field‐stimulated mouse vas deferens and guinea‐pig ileum
Author(s) -
Goodall Jacqueline,
Hughes I.E.,
Mackay D.
Publication year - 1986
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1986.tb10246.x
Subject(s) - vas deferens , agonist , ileum , (+) naloxone , endocrinology , medicine , guinea pig , pharmacology , chemistry , partial agonist , receptor , opioid , biology
1 The effects of the opioid receptor agonist RX783006 and of the opioid receptor partial agonist (+)‐meptazinol have been examined on electrically induced twitch responses of the guinea‐pig isolated ileum and of the mouse isolated vas deferens. 2 Log 10 concentration‐tissue state curves were determined for (+)‐meptazinol and RX783006, alone, in combination and in the presence of naloxone (30 nM). 3 Analysis of these log 10 concentration‐tissue state curves using the null equations derived and tested in the preceding paper indicates that the opioid agonist action of (+)‐meptazinol on mouse vas deferens is quantitatively similar to that on guinea‐pig ileum. 4 The results also suggest that (+)‐meptazinol acts as a functional antagonist on the guinea‐pig ileum as well as on the mouse vas deferens. 5 The potency of (+)‐meptazinol relative to RX783006 has been measured by an indirect method which should eliminate any functional antagonistic action of (+)‐meptazinol. This method gives a relative potency of (+)‐meptazinol in both tissues which is three to six times greater than that measured directly on guinea‐pig ileum. This discrepancy may be due to experimental error but it may also indicate that direct measurements on guinea‐pig ileum underestimate the agonist potency of this compound on opioid receptors.