Subanesthetic doses of ketamine, a non-competitive N-methyl-D-aspartate receptor (NMDAR) antagonist, produce rapid and robust antidepressant effects in patients with treatment-resistant depression (TRD). However, after a single administration, the therapeutic benefit is short-lived, and strategies to maintain its efficacy remain unclear. This study focused on the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), whose activation is known to be a key effector for the action of ketamine. Thus, we developed a novel positive allosteric modulator of AMPAR (K-4) with potential antidepressant-like effects. In Wistar Kyoto rats, a model of TRD, K-4 produced a more sustained antidepressant-like effect than ketamine. Bulk RNA sequencing analysis revealed that K-4-treated rats showed lower expression of NADPH-oxidase-1 (NOX-1) in the medial prefrontal cortex (mPFC) than in ketamine-treated rats. Furthermore, simultaneous administration of a NOX-1 inhibitor with ketamine prolonged the antidepressant-like effect and reduced burst firing in the lateral habenula (LHb). Similarly, short hairpin RNA knockdown of NOX-1 in the mPFC sustained the antidepressant-like effects of ketamine and suppressed LHb bursting activity. These results indicate that NOX-1 suppression prolongs the antidepressant-like effect of ketamine and represents a promising target for maintenance strategies in TRD.
Nakajima et al. (2026) studied this question.