Moxonidine hydrochloride is a mixed agonist of α2-adrenergic receptor (α2AR) and imidazoline-1 receptor(I1R) with Ki values of 4.2±3.2 nmol/L, 13.0±4.2 nmol/L, 9.5±4.1 nmol/L and 15.6±9.8 nmol/L for I1R, α2AAR, α2BAR andα2CAR, respectively [1].
In multiple acute pain assays, moxonidine has been reported to produce dose-dependent analgesia.In both the α2AAR-dysfunctional and α2CAR-KO experimentsin mice, the rest analgesia function of moxonidine has been revealed to be mediated by α2ARs but not I1Rs [1]. In addition, Moxonidine has been reported to potently inhibit the binding of [3H]-clonidine to VLM (ventrolateral medulla) membranes in a dose-dependent manner with the IC50 value of 53 ± 10nM. In bovine adrenal medullary cells, Moxonidine has shown low affinity for I2-relative to I1R sites [2].
References:
[1]Stone LS1, Fairbanks CA, Wilcox GL. Moxonidine, a mixed alpha(2)-adrenergic and imidazoline receptor agonist, identifies a novel adrenergic target for spinal analgesia. Ann N Y Acad Sci. 2003 Dec;1009:378-85.
[2]Ernsberger P1, Damon TH, Graff LM, Schäfer SG, Christen MO.Moxonidine, a centrally acting antihypertensive agent, is a selective ligand for I1-imidazoline sites. J Pharmacol Exp Ther. 1993 Jan;264(1):172-82.