Elevation of serum corticosterone in rats by bremazocine, a κ-opioid agonist

Abstract
Bremazocine at doses of 0·01 mg kg−1 s.c., and higher, increased serum corticosterone concentration several-fold in rats. The increase occurred within 20 min, was maximum at 40–60 min and subsided after 120 min. Pretreatment with naloxone (1–10 mg kg−1 s.c.) antagonized the corticosterone increase. These data support the view that κ-opioid agonist activity of bremazocine mediated the corticosterone increase.