Effect of β-funaltrexamine on opioid side-effects produced by morphine and U-50, 488H

Publisher Website
Google Scholar
Abstract
Pretreatment of rats with the irreversible μ-opioid receptor antagonist, β-funaltrexamine (β-FNA), 20–40 mg kg−1 s.c., produced a dose-related antagonism of the reduction in respiratory rate, gastrointestinal (GI) propulsion, rotarod reaction latencies and body temperature produced by morphine administration 24 h later, suggesting that these effects are mediated via μ-opioid receptors. The k-receptor agonist, U-50,488H, was without effect on respiratory rate at the doses tested, but produced hypothermia, sedation and low maximum inhibition of GI propulsion. These effects of U-50, 488H were not blocked by β-FNA suggesting that they are mediated via k-receptors.