No heroin or morphine 6β-glucuronide analgesia in μ-opioid receptor knockout mice

Abstract

Recent reports suggest that heroin and its metabolite morphine 6beta-glucuronide can produce analgesia independent of the morphine-preferring mu-opioid receptor. We have tested heroin and morphine 6beta-glucuronide analgesia in wild-type, homozygous and heterozygous mu-opioid receptor knockout mice. Homozygotes display no heroin or morphine 6beta-glucuronide analgesia. Heterozygous mice with one mu-opioid receptor gene copy reveal reduced heroin and morphine 6beta-glucuronide analgesia. The mu-opioid receptor-dependence of heroin and morphine 6beta-glucuronide fails to support a requirement for a heroin-specific opiate receptor subtype.