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THE EFFECT OF CHLORPROMAZINE PRETREATMENT ON MORPHINE ANALGESIA AND NALOXONE POTENCY IN ADRENALECTOMIZED MICE
Author(s) -
Wong ChakLam,
Wai ManKeung
Publication year - 1982
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1982.tb00830.x
Subject(s) - potency , (+) naloxone , morphine , chlorpromazine , pharmacology , medicine , narcotic antagonists , anesthesia , opioid , chemistry , receptor , biochemistry , in vitro
SUMMARY Morphine pretreatment (2.0 mg/kg s.c.) induced no overt tolerance to its antinociceptive effect in mice 3 h later, but enhanced the antagonistic potency of naloxone. 2 Pretreatment with chlorpromazine slightly potentiated the antinociceptive effect of morphine measured 3.5 h later. The antagonistic effect of naloxone was also enhanced. 3 The observed effect of chlorpromazine on naloxone potency was augmented when naloxone was administered in the pretreatment regime. 4 The enhanced naloxone potency induced by morphine pretreatment was inhibited by chlorpromazine administered 0.5 h before the morphine pretreatment. 5 Adrenalectomy sensitized the animals to the antinociceptive effect of morphine. However, the naloxone potency was similar to that of the sham‐operated controls. 6 Adrenalectomy greatly attenuated the effect of chlorpromazine pretreatment on naloxone potency. However, the effect of combined pretreatment with either chlorpromazine plus naloxone or morphine remained unaffected. 7 These results indicate that the increased naloxone potency after chlorpromazine pretreatment may be partly mediated through an adrenal‐linked process. However, it appears that this process is not essential for the development of increased naloxone potency induced by morphine pretreatment and for the interaction between chlorpromazine, naloxone and morphine.