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INTERACTIONS BETWEEN MORPHINE AND THE OPIOID‐LIKE PEPTIDES IN THE RAT VAS DEFERENS
Author(s) -
HUIDOBRO F.,
HUIDOBROTORO J. PABLO,
MIRANDA H.
Publication year - 1980
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.1476-5381.1980.tb09770.x
Subject(s) - vas deferens , morphine , levorphanol , chemistry , pethidine , enkephalin , pharmacology , endocrinology , medicine , opioid , contraction (grammar) , analgesic , (+) naloxone , receptor
1 Morphine, methadone, levorphanol, pethidine, etonitazene and related morphine‐like alkaloids produced an increase in the electrically‐evoked muscular contraction of the rat vas deferens. In contrast, the enkephalins and β‐endorphin caused inhibition of the twitching. 2 The concentration of β‐endorphin required to inhibit by 50% the muscular twitch was about 50 to 100 times less than that of the enkephalins. 3 Pretreatment of the vasa with morphine antagonized the inhibition of the neuromuscular transmission caused by either β‐endorphin or enkephalin. 4 Conversely, pretreatment with β‐endorphin sensitized the vasa to the increase in twitch tension caused by morphine. 5 Morphine did not alter the sensitivity to exogenously administered noradrenaline, dopamine or potassium.