AMPA Receptor Activation-Independent Antidepressant Actions of Ketamine Metabolite (S)-
Norketamine.
Biol Psychiatry 2018;
84:591-600. [PMID:
29945718 DOI:
10.1016/j.biopsych.2018.05.007]
[Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 04/13/2018] [Accepted: 05/02/2018] [Indexed: 12/28/2022]
Abstract
BACKGROUND
Ketamine, an N-methyl-D-aspartate receptor antagonist, exerts robust antidepressant effects in patients with treatment-resistant depression. The precise mechanisms underlying ketamine's antidepressant actions remain unclear, although previous research suggests that alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) activation plays a role. We investigated whether (S)-norketamine and (R)-norketamine, the two main metabolites of (R,S)-ketamine, also play a significant role in ketamine's antidepressant effects and whether the effects are mediated by AMPAR.
METHODS
Cellular mechanisms of antidepressant action of norketamine enantiomers were examined in mice.
RESULTS
(S)-Norketamine had more potent antidepressant effects than (R)-norketamine in inflammation and chronic social defeat stress models. Furthermore, (S)-norketamine induced more beneficial effects on decreased dendritic spine density and synaptogenesis in the prefrontal cortex and hippocampus compared with (R)-norketamine. Unexpectedly, AMPAR antagonists did not block the antidepressant effects of (S)-norketamine. The electrophysiological data showed that, although (S)-norketamine inhibited N-methyl-D-aspartate receptor-mediated synaptic currents, (S)-norketamine did not enhance AMPAR-mediated neurotransmission in hippocampal neurons. Furthermore, (S)-norketamine improved reductions in brain-derived neurotrophic factor-tropomyosin receptor kinase B signaling in the prefrontal cortex of mice susceptible to chronic social defeat stress, whereas the tropomyosin receptor kinase B antagonist and a mechanistic target of rapamycin inhibitor blocked the antidepressant effects of (S)-norketamine. In contrast to (S)-ketamine, (S)-norketamine did not cause behavioral abnormalities, such as prepulse inhibition deficits, reward effects, loss of parvalbumin immunoreactivity in the medial prefrontal cortex, or baseline gamma-band oscillation increase.
CONCLUSIONS
Our data identified a novel AMPAR activation-independent mechanism underlying the antidepressant effects of (S)-norketamine. (S)-Norketamine and its prodrugs could be novel antidepressants without the detrimental side effects of (S)-ketamine.
Collapse