S. Kishioka et al., QUANTITATIVE PROPERTIES OF PLASMA-CORTICOSTERONE ELEVATION INDUCED BYNALOXONE-PRECIPITATED WITHDRAWAL IN MORPHINE-DEPENDENT RATS, Japanese Journal of Pharmacology, 66(2), 1994, pp. 257-263
Elevation of plasma corticosterone (PCS) has been used as an indicator
of morphine withdrawal, but it is not clear whether the magnitude of
elevation is related to the intensity of the dependence. The dose-depe
ndent effects of naloxone on PCS and body weight were studied in male
Sprague-Dawley rats rendered physically dependent on morphine by injec
ting increasing doses of 40-120 mg/kg/day, s.c. twice daily for 1-6 da
ys. Naloxone (0.01-2.0 mg/kg, s.c.) was administered 3 hr after the la
st morphine administration. Naloxone elevated PCS levels in a dose-dep
endent manner in all groups treated with morphine, and the elevation w
as correlated with the number of days of morphine treatment. Naloxone
also reduced dose-dependently the body weight in all groups treated wi
th morphine; in this case, a reverse correlation was obtained between
the body weight changes and the PCS levels. It was confirmed that PCS
elevation is a quantitative sign of naloxone-precipitated morphine wit
hdrawal and that the elevation is indicative of the degree of morphine
physical dependence.