Naltrexone is an opioid receptor antagonist used primarily in the management of alcohol dependence and opioid dependence.
IC50 Value:
Target: Opioid Receptor
Naltrexone is competitive antagonist for μ, κ, δ, and σ-opioid receptors, Naltrexone has greater oral efficacy and longer duration of action than naloxone. Naltrexone treatment caused a doubling in the density of [3H]DAMGO binding sites in both whole brain membranes and the 7315c cell membranes. Naltrexone treatment may have slightly diminished the affinity of mu opioid receptors for [3H]DAMGO (by 1.5- to 2-fold), but the precision of the assay was inadequate to determine whether this difference was significant. Naltrexone treatment also had no effect on the potency or efficacy of guanosine 5'-O-(3-thiotriphosphate) in diminishing [3H]DAMGO binding to either whole brain or 7315c cell membranes.  Naltrexone which has no SP receptor antagonistic action, not only indirectly acts on SP-ergic neurons but also causes a change in the apparent affinity of NK-1 receptor (as reflected by changes in IC50 values) in the striatum. Cellular inositol-1,4,5-trisphosphate [Ins(1,4,5)P3], quantified by a highly sensitive and selective radioreceptor mass assay, was increased in the striatum by 28% relative to control levels.