6-Iodopravadoline (AM630)

AM630 behaves as a low-potency neutral competitive antagonist in AM630-pre-incubated cells, a low-potency agonist in SR144528-pre-incubated cells, and a much higher-potency inverse agonist/antagonist in vehicle-pre-incubated cells. AM630 is a protean ligand that can target a constitutively active form of the hCB2 receptor with low affinity to produce agonism or neutral antagonism and a constitutively inactive form of this receptor with much higher affinity to produce inverse agonism.^[2]

Binding assays with [3H]-CP55940 or [35S]-GTPγS are performed with hCB2 CHO cell membranes. The hCB2 CHO cells are pre-incubated in complete medium with 10 μM AM630 or vehicle (dimethyl sulphoxide) for up to 24 h and then subjected to intense washing. For membrane preparation, cells are removed from flasks by scraping, centrifuged at 489× g and then frozen as a pellet at −20°C until required. Before use in a radioligand binding assay, cells are defrosted and diluted in Tris binding buffer (radioligand displacement assay) or GTPγS binding buffer ([35S]-GTPγS binding assay).

Chronic AM630 treatment is anxiolytic in light-dark box (LDB) and elevated plus maze (EPM) tests. Chronic AM630 treatment increases gene and reduces protein expression of CB2 receptors, GABAAα2 and GABAAγ2 in cortex and amygdala. In addition, chronic AM630 administration decreases the anxiety of DBA/2 mice in the LDB test. The efficacy of AM630 in reducing the anxiety of the spontaneously anxious DBA/2 strain of mice strengthens the potential of the CB2 receptor as a new target in the treatment of anxiety-related disorders.^[1]