Antagonism of UMB 425 antinociception using various opioid antagonists.
Male, Swiss Webster mice received a pretreatment of the nonselective
opioid antagonist, naloxone (1 mg/kg, i.p. t = −30
min) or the κ-selective antagonist, nor-BNI (30 mg/kg, i.p. t = −24 h) prior to a s.c. injection with an ED90 dose of UMB 425 (15 mg/kg). Latencies were determined 30
min after UMB 425 administration. (a) Antagonism of UMB 425 antinociception
in the hot plate assay by naloxone, but not nor-BNI. *p < 0.05. (b) Antagonism of UMB 425 antinociception in the tail-flick
assay by naloxone, but not nor-BNI. ***p < 0.001.