(+)-Dihydrexidine hydrochloride is an agonist of dopamine D1 receptor(EC50 of 72± 21 nM).

(+)-Dihydrexidine hydrochloride (DHX) is a high-potency, bioavailable agonist of D1 dopamine receptor. (+)-Dihydrexidine is screened for activity against 40 other binding sites, and is inactive (IC50 > 10 microM) against all except D2 dopamine receptors with IC50 of 130 nM and alpha 2 adrenoreceptors (IC50=230 nM). Dihydrexidine competes stereoselectively and potently for D1 binding sites in rat striatal membranes labeled with [3H]SCH23390 with an IC50 of about 10 nM compared to about 30 nM for the prototypical D1 agonist SKF38393[2].

To check the functional status of striatum neurons in response to D1 receptor activation, AC5+/+ and AC5-/- mice are injected with the D1 agonist (+)-Dihydrexidine (30 mg/kg, i.p.) and obtained the dorso-lateral striatum and NAc, separately, 45 min later for RT-PCR analysis. These experiments reveal that (+)-Dihydrexidine -triggered induction of the immediate early genes, c-fos, egr-1, and junB, in the NAc is markedly enhanced in AC5-/- mice compared with that in AC5+/+ mice, while the induction in the dorso-lateral striatum is suppressed in AC5-/- mice[3].