The Mitragyna speciosa (kratom) alkaloid mitragynine: Analysis of adrenergic α₂ receptor activity in vitro and in vivo.

ABSTRACT: Mitragynine, an alkaloid present in the leaves of Mitragyna speciosa (kratom), has a complex pharmacology that includes low efficacy agonism at μ-opioid receptors (MORs). This study examined the activity of mitragynine at adrenergic α₂ receptors (Aα₂Rs) in vitro and in vivo. Mitragynine displaced a radiolabeled Aα₂R antagonist ([³H]RX821002) from human Aα_2ARs in vitro with lower affinity (K_i = 1260 nM) than the agonists (-)-epinephrine (K_i = 263 nM) or lofexidine (K_i = 7.42 nM). Mitragynine did not significantly stimulate [³⁵S]GTPγS binding at Aα_2ARs in vitro, but in rats trained to discriminate 32 mg/kg mitragynine from vehicle (intraperitoneally administered; i.p.), mitragynine e

SUBMITTER: Obeng S 

PROVIDER: S-EPMC11556301 | biostudies-literature | 2024 Oct

REPOSITORIES: biostudies-literature