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Enkephalinase Inhibition Prevented Tolerance to Nitrous Oxide Analgesia in Rats
Author(s) -
Rupreht J.,
Ukponmwan O. E.,
Dworacek B.,
Admiraal P. V.,
Dzoljic M. R.
Publication year - 1984
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1984.tb02132.x
Subject(s) - enkephalinase , phosphoramidon , thiorphan , nitrous oxide , medicine , nociception , analgesic , drug tolerance , anesthesia , pharmacology , neprilysin , enkephalin , opioid , biochemistry , receptor , enzyme , chemistry , endothelin receptor
Tolerance to nitrous oxide (N 2 O) antinociception was studied in rats in accordance with the Randall‐Selitto pressure nociception test. Both N 2 O (70% in 30% O 2 ) and the relatively selective enkephalinase inhibitor phosphoramidon (350 μg i.c.v.), which blocks the biotransformation of enkephalins, were administered. They both induced a significant analgesic effect which vanished within 45 min. The rapidly developed tolerance to N 2 O analgesia does not affect the anaesthetic state since the animals remained motionless for the duration of exposure lasting 3 h. In the animals treated with the enkephalinase inhibitor phosphoramidon, no development of tolerance to N 2 O‐antinociception occurred during the exposure lasting 3 h. The results indicate that tolerance to N 2 O analgesia can be abolished by activation of the enkephalinergic system, which might suggest a possible insufficiency of this system during tolerance to N 2 O.