Esketamine enhances memory reconsolidation in the novel object recognition task

Abstract

Esketamine, the right-handed optical isomer of racemic ketamine, is a rapidly acting antidepressant approved by the FDA for treatment-resistant depression in 2019. However, few studies have investigated esketamine's role in learning and memory, particularly in the context of memory reconsolidation. Herein, we evaluated esketamine's role in memory reconsolidation in 7-week-old male Institute of Cancer Research mice subjected to the novel object recognition (NOR) memory task. The NOR reconsolidation procedure comprised three phases: sampling, reactivation, and testing. Esketamine-enhanced NOR memory performance when injected into mice 0 h after reactivation rather than following a 6 h delay. Conversely, administering esketamine 24 h after sampling without reactivation did not enhance NOR memory performance. Notably, esketamine exhibited no discernible effects on nonspecific responses, such as locomotor activity and exploratory behavior. Furthermore, the α-amino-3‑hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type receptor antagonist NBQX effectively blocked the esketamine-induced enhancement of memory reconsolidation. In conclusion, esketamine treatment markedly improves memory reconsolidation in NOR tasks, and this effect is linked to AMPA receptor activity.