3,5-Dinitrocatechol is a potent catechol O-methyltransferase (COMT) inhibitor (IC = 12 nM). It is selective for COMT over tyrosine hydroxylase, dopamine β-hydroxylase, dopamine decarboxylase, monoamine oxidase A (MAO-A), and MAO-B (ICs = >14 μM for all). 3,5-Dintrocatechol (30 mg/kg), in combination with L-DOPA and carbidopa , reduces 3-O-methyldopa (3-OMD) levels in rat serum, compared with control animals receiving only L-DOPA and carbidopa. Chronic administration of 3,5-dinitrocatechol (15 mg/kg per day for seven days) induces COMT-dependent thermal hyperalgesia and increases preference for dark in a light/dark preference test, indicating anxiety-like behavior, in rats, effects that can be prevented by the β-adrenergic receptor antagonist propranolol .