Our recent double blind clinical trials demonstrated that ketamine (an NMDA antagonist) produced rapid onset, robust, and long-pasting antidepressive actions in the patients who are resistant to typical antidepressant treatment. We have hypothesized that targeting AMPA/NMDA receptor throughput is an effective strategy for rapid relief of depression symptoms. To further test the AMPA/NMDA throughput hypothesis and to develop new medication based on this ketamine phenomenon, we conducted a series of animal experiments. We found that Ketamine at a low dose produced rapid onset antidepressant-like effects in two behavioral paradigms, the learned helpless test and the forced swim test. The effects lasted at least more than a week after a single drug administration. These ketamine?s effects can be mimicked by other selective NMDAR antagonists. Animals treated with ketamine in a similar regiment to the learned helpless test performed well on passive avoidance tests, thus the antidepressant-like effects of ketamine in animal is unlikely due to learning and memory deterioration associated with ketamine use. In additional behavioral pharmacological experiments we found that the effects of ketamine were blocked by pretreatment with NBQX, an AMPA receptor antagonist, indicating the antidepressant-like effects require AMPA throughput. Ketamine altered GluR1 phosphorylation in both hippocampal tissues from ketamine treated animals and cultured hippocampal neurons exposed to low-concentration of ketamine. Taken together, our animal findings strongly support the involvement of AMPA receptors in ketamine?s antidepressant-like action and the AMPA/NMDA throughput strategy to develop novel antidepressive agents. Future studies are required to further elucidate the receptor subtype(s) and the brain region(s) involved in this ketamine antidepressant-like action.
| Maeng, Sungho; Zarate Jr, Carlos A; Du, Jing et al. (2008) Cellular mechanisms underlying the antidepressant effects of ketamine: role of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors. Biol Psychiatry 63:349-52 |
