N. Pedron et al., EFFECTS OF ADMINISTRATION OF AN OPIOID ANTAGONIST ON SERUM LEVELS OF PROLACTIN AND TESTOSTERONE IN MALE RABBITS, Medical science research, 26(8), 1998, pp. 511-512
The objective of the study was to evaluate the effect of low daily dos
es of naloxone on serum testosterone and prolactin levels in male rabb
its over 10 days of treatment. Six groups of New Zealand white male ra
bbits were used: two for the testosterone assay, two for the prolactin
assay and two control groups. Animals in the testosterone groups were
injected with 10 or 100 mu g/kg/day doses of naloxone, and those in t
he prolactin groups with 12.5 or 100 mu g/kg/day doses of naloxone. Co
ntrol groups were injected with saline. Blood samples were taken from
all rabbits at baseline, 90 minutes after administering naloxone and 1
, 2, 4, 7 and 10 days after starting the study. Blood samples were dra
wn from the main ear artery. Serum testosterone and prolactin levels w
ere measured by radioimmunoassay. The testosterone levels increased si
gnificantly and progressively with both doses. Prolactin levels, at th
e 12.5 mu g dose of naloxone, decreased significantly at 90 min and re
mained stable during the study. Prolactin levels at the 100 mu g dose
decreased progressively. Low doses of naloxone cause important effects
on the opioid endogenous system with a consecutive rise in testostero
ne and a decrease in prolactin serum levels. Med Sci Res 26:511-512 (C
) 1998 Lippincott Williams & Wilkins.