N-Desmethylclozapine (Desmethylclozapine) is an antagonist of serotonin (5-HT) receptor subtype 5-HT2C (IC50: 7.1 nM). It also is an antagonist at dopamine D4 receptors, an agonist at δ-opioid receptors.

N-desmethylclozapine antagonized 5-HT-stimulated phosphoinositide hydrolysis with IC50 values of 29.4 nM [1]. N-desmethylclozapine exhibited slight agonistic effects on the M1 mAChR and agonistic properties at the 5-HT1A receptor in the cerebral cortex and hippocampus. This compound also behaved as an agonist at the δ-opioid receptor in the cerebral cortex and the striatum [2]. Muscarinic agonist activity of N-desmethylclozapine was higher than that of clozapine, higher in excitatory neurons than in inhibitory neurons, sensitive to pirenzepine, and partially masked when co-applied with clozapine [3].

NDMC (3-30mg/kg) decreased exploratory locomotor activity in a dose-dependent manner, and the reduced locomotor activity was significantly antagonized by scopolamine at doses of 0.1 and 0.3mg/kg. NDMC (10-30mg/kg) dose-dependently increased prepulse inhibition (PPI) in DBA/2J mice [4].

Exploratory locomotor activity was monitored as described previously. Animals were habituated to the experimental room for at least 60 min before testing. Oxotremorine (0.01, 0.03, 0.1 mg/kg, s.c.), NDMC (3, 10, 30 mg/kg, s.c.), xanomeline (0.3, 1, 3 mg/kg, s.c.), or scopolamine (0.1, 0.3, 1 mg/kg, s.c.) was administered. Scopolamine (0.1, 0.3 mg/kg, s.c.) was injected 30 min before the administration of test agents in antagonism studies. Animals were placed in plastic cages (22.5D×33.8 W×14.0H cm) immediately after the administration of test agents in the antagonism studies, and exploratory locomotor activity was measured during a 60 min observation period using an infrared motion detector system [4].