Lithium treatment attenuates muscarinic M(1) receptor dysfunction.

OBJECTIVE: Altered muscarinic acetylcholine receptor levels and receptor-coupled signaling processes have been reported in mood disorders. M(1) , one of five muscarinic receptor subtypes, couples to the phospholipase C/protein kinase C and extracellular signal-regulated kinase (ERK) pathways. Mood stabilizers regulate these pathways. MicroRNAs (miRNAs) are small noncoding RNAs that suppress translation in a sequence-selective manner. Lithium downregulates several miRNAs, including let-7b and let-7c. One predicted target of let-7b and let-7c is the M(1) receptor. We hypothesized that miRNAs regulate M(1) receptor translation, and that disrupted M(1) expression leads to aberrant behaviors and disrupted downstream signaling pathways that are rescued by lithium treatment. METHODS: The effects of miRNAs and chronic treatment with mood stabilizers on M(1) levels were tested in primary cultures and in rat frontal cortex. Effects of M(1) ablation and chronic treatment with mood stabilizers on several signaling cascades and M(1) -modulated behaviors were examined in wild-type and M(1) knockout mice. RESULTS: Let-7b, but not let-7c, negatively regulated M(1) levels. Chronic treatment with lithium, but not valproate, increased M(1) levels in the rat cortex. M(1) knockout mice exhibit ERK pathway deficits and behavioral hyperactivity; chronic treatment with lithium attenuated these deficits and hyperactivity. CONCLUSIONS: Lithium treatment can affect M(1) receptor function through intracellular signaling enhancement and, in situations without M(1) ablation, concomitant receptor upregulation via mechanisms involving miRNAs. Muscarinic dysfunction may contribute to mood disorders, while M(1) receptors and the downstream ERK pathway may serve as potential therapeutic targets for alleviating manic symptoms such as psychomotor hyperactivity.

Mecanismos celulares que son la base de los efectos antidepresivos de la ketamina: papel de los receptores del ácido alfa-amino-3-hidroximetilisoxazol-4-propiónico / Cellular mechanisms forming the basis of the antidepressant effects of ketamine: role of alpha-amino-3-hydroxymethylisoxazol-4- propionic acid receptors

Fundamento: La ketamina tiene efectos antidepresivos potentes, rápidos y relativamente sostenidos en pacientes con depresión mayor. La comprensión de los mecanismos que son la base de los efectos fascinantes de los antagonistas de la N-metil-D-aspartato (NMDA) podría dar lugar a nuevos fármacos con un inicio rápido de acción. Métodos: Para investigar los efectos conductuales de la ketamina en ratones se usaron los exámenes de indefensión aprendida, natación forzada y evitación pasiva. Se efectuaron experimentos bioquímicos y conductuales adicionales para determinar si en las propiedades de tipo antidepresivo de la ketamina y otros antagonistas de la NMDA participa la producción del receptor del ácido alfa-amino-3-hidroxi-5-metilisoxazol-4-propiónico (AMPA). Resultados: El tratamiento con dosis de ketamina inferiores a las anestésicas dio lugar a efectos agudos y sostenidos de tipo antidepresivo. En estas dosis, la ketamina no deterioró la retención de los recuerdos relacionados con el miedo. MK-801 (dizocilpina) y RO25-6981, un antagonista NR2B selectivo, también tuvieron efectos de tipo antidepresivo; sin embargo, éstos no fueron tan sostenidos como los de ketamina. El pretratamiento con NBQX, un antagonista del receptor de AMPA, atenuó tanto la conducta de tipo antidepresivo inducida por la ketamina como la regulación de los receptores AMPA hipocámpicos Glu1R1 fosforilados. Conclusiones: Los antagonistas de la NMDA pueden producir efectos rápidos de tipo antidepresivo aumentando el AMPA en relación con la producción de NMDA en circuitos neuronales decisivos (AU)

Background: Ketamine exerts a robust, rapid, and relatively sustained antidepressant effect in patients with major depression. Understanding the mechanisms underlying the intriguing effects of Nmethyl d-aspartate (NMDA) antagonists could lead to novel treatments with a rapid onset of action. Methods: The learned helplessness, forced swim, and passive avoidance tests were used to investigate ketamine’s behavioral effects in mice. Additional biochemical and behavioral experiments were undertaken to determine whether the antidepressant-like properties of ketamine and other NMDA antagonists involve alpha-amino-3-hydroxy-5-methylisoxazole-4- propionic acid (AMPA) receptor throughput. Results: Subanesthetic doses of ketamine treatment caused acute and sustained antidepressantlike effects. At these doses, ketamine did not impair fear memory retention. MK-801 (dizocilpine) and Ro25-6981, an NR2B selective antagonist, also exerted antidepressant-like effects; these effects, however, were not sustained as long as those of ketamine. Pretreatment with NBQX, an AMPA receptor antagonist, attenuated both ketamine-induced antidepressant-like behavior and regulation of hippocampal phosphorylated GluR1 AMPA receptors. Conclusions: NMDA antagonists might exert rapid antidepressant-like effects by enhancing AMPA relative to NMDA throughput in critical neuronal circuits (AU)

BAG1 plays a critical role in regulating recovery from both manic-like and depression-like behavioral impairments.

Recent microarray studies with stringent validating criteria identified Bcl-2-associated athanogene (BAG1) as a target for the actions of medications that are mainstays in the treatment of bipolar disorder (BPD). BAG1 is a Hsp70/Hsc70-regulating cochaperone that also interacts with glucocorticoid receptors (GRs) and attenuates their nuclear trafficking and function. Notably, glucocorticoids are one of the few agents capable of triggering both depressive and manic episodes in patients with BPD. As a nexus for the actions of glucocorticoids and bipolar medications, we hypothesized that the level of BAG1 expression would play a pivotal role in regulating affective-like behaviors. This hypothesis was investigated in neuron-selective BAG1 transgenic (TG) mice and BAG1 heterozygous knockout (+/-) mice. On mania-related tests, BAG1 TG mice recovered much faster than wild-type (WT) mice in the amphetamine-induced hyperlocomotion test and displayed a clear resistance to cocaine-induced behavioral sensitization. In contrast, BAG1+/- mice displayed an enhanced response to cocaine-induced behavioral sensitization. The BAG1 TG mice showed less anxious-like behavior on the elevated plus maze test and had higher spontaneous recovery rates from helplessness behavior compared with WT mice. In contrast, fewer BAG1+/- mice recovered from helplessness behavior compared with their WT controls. BAG1 TG mice also exhibited specific alterations of hippocampal proteins known to regulate GR function, including Hsp70 and FKBP51. These data suggest that BAG1 plays a key role in affective resilience and in regulating recovery from both manic-like and depression-like behavioral impairments.

Cellular mechanisms underlying the antidepressant effects of ketamine: role of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors.

BACKGROUND: Ketamine exerts a robust, rapid, and relatively sustained antidepressant effect in patients with major depression. Understanding the mechanisms underlying the intriguing effects of N-methyl d-aspartate (NMDA) antagonists could lead to novel treatments with a rapid onset of action. METHODS: The learned helplessness, forced swim, and passive avoidance tests were used to investigate ketamine's behavioral effects in mice. Additional biochemical and behavioral experiments were undertaken to determine whether the antidepressant-like properties of ketamine and other NMDA antagonists involve alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor throughput. RESULTS: Subanesthetic doses of ketamine treatment caused acute and sustained antidepressant-like effects. At these doses, ketamine did not impair fear memory retention. MK-801 (dizocilpine) and Ro25-6981, an NR2B selective antagonist, also exerted antidepressant-like effects; these effects, however, were not sustained as long as those of ketamine. Pre-treatment with NBQX, an AMPA receptor antagonist, attenuated both ketamine-induced antidepressant-like behavior and regulation of hippocampal phosphorylated GluR1 AMPA receptors. CONCLUSIONS: NMDA antagonists might exert rapid antidepressant-like effects by enhancing AMPA relative to NMDA throughput in critical neuronal circuits.