RESUMEN
Cognitive performance in people varies according to time-of-day, with memory retrieval declining in the late afternoon-early evening. However, functional roles of local brain circadian clocks in memory performance remains unclear. Here, we show that hippocampal clock controlled by the circadian-dependent transcription factor BMAL1 regulates time-of-day retrieval profile. Inducible transgenic dominant negative BMAL1 (dnBMAL1) expression in mouse forebrain or hippocampus disrupted retrieval of hippocampal memories at Zeitgeber Time 8-12, independently of retention delay, encoding time and Zeitgeber entrainment cue. This altered retrieval profile was associated with downregulation of hippocampal Dopamine-cAMP signaling in dnBMAL1 mice. These changes included decreases in Dopamine Receptors (D1-R and D5-R) and GluA1-S845 phosphorylation by PKA. Consistently, pharmacological activation of cAMP-signals or D1/5Rs rescued impaired retrieval in dnBMAL1 mice. Importantly, GluA1 S845A knock-in mice showed similar retrieval deficits with dnBMAL1 mice. Our findings suggest mechanisms underlying regulation of retrieval by hippocampal clock through D1/5R-cAMP-PKA-mediated GluA1 phosphorylation.
Asunto(s)
Relojes Circadianos/fisiología , Hipocampo/metabolismo , Recuerdo Mental/fisiología , Receptores AMPA/metabolismo , Factores de Transcripción ARNTL/genética , Factores de Transcripción ARNTL/metabolismo , Animales , AMP Cíclico/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/genética , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Dopamina/metabolismo , Femenino , Técnicas de Sustitución del Gen , Masculino , Aprendizaje por Laberinto , Ratones , Ratones Transgénicos , Modelos Animales , Fosforilación/fisiologíaRESUMEN
Magnesium (Mg2+) is an essential mineral for maintaining biological functions. One major action of Mg2+ in the brain is modulating the voltage-dependent blockade of N-methyl-d-aspartate type glutamate receptors, thereby controlling their opening, which is crucial for synaptic plasticity. Therefore, Mg2+ has been shown to play critical roles in learning and memory, and synaptic plasticity. However, the effects of dietary Mg2+ deficiency (MgD) on learning and memory and the morphology of neurons contributing to memory performance have not been examined in depth. Here, we show that MgD impairs hippocampus-dependent memories in mice. Mice fed an MgD diet showed deficits in hippocampus-dependent contextual fear, spatial and social recognition memories, although they showed normal amygdala- and insular cortex-dependent conditioned taste aversion memory, locomotor activity, and emotional behaviors such as anxiety-related and social behaviors. However, MgD mice showed normal spine density and morphology of hippocampal neurons. These findings suggest that MgD impairs hippocampus-dependent memory without affecting the morphology of hippocampal neurons.
Asunto(s)
Deficiencia de Magnesio/metabolismo , Memoria/efectos de los fármacos , Memoria/fisiología , Animales , Ansiedad/fisiopatología , Condicionamiento Clásico/fisiología , Espinas Dendríticas , Suplementos Dietéticos , Miedo/fisiología , Ácido Glutámico/farmacología , Hipocampo/efectos de los fármacos , Aprendizaje/fisiología , Magnesio/metabolismo , Deficiencia de Magnesio/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Plasticidad Neuronal/fisiología , Neuronas/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Reconocimiento en Psicología , Transmisión Sináptica/fisiologíaRESUMEN
Transcription factor CREB is believed to play essential roles in the formation of long-term memory (LTM), but not in learning and short-term memory (STM). Surprisingly, we previously showed that transgenic mice expressing a dominant active mutant of CREB (DIEDML) in the forebrain (DIEDML mice) demonstrated enhanced STM and LTM in hippocampal-dependent, rapid, one-trial learning tasks. Here we show that constitutive activation of CREB enhances hippocampal-dependent learning of temporal association in trace fear conditioning and delayed matching-to-place tasks. We then show that in DIEDML mice the apical tuft dendrites of hippocampal CA1 pyramidal neurons, required for temporal association learning, display increased spine density, especially of thin spines and of Homer1-negative spines. In contrast, the basal and apical oblique dendrites of CA1 neurons, required for rapid one-trial learning, show increased density of thin, stubby, and mushroom spines and of Homer1-positive spines. Furthermore, DIEDML mice showed increased dendritic complexity in the proximal portion of apical CA1 dendrites to the soma. In contrast, forebrain overexpression of CaMKIV, leading to enhanced LTM but not STM, show normal learning and CA1 neuron morphology. These findings suggest that dendritic region-specific morphological changes in CA1 neurons by constitutive activation of CREB may contribute to improved learning and STM.
Asunto(s)
Aprendizaje por Asociación , Región CA1 Hipocampal/citología , Región CA1 Hipocampal/fisiología , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/genética , Espinas Dendríticas , Células Piramidales/citología , Células Piramidales/metabolismo , Activación Transcripcional , Animales , Condicionamiento Clásico , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Miedo , Femenino , Masculino , Aprendizaje por Laberinto , Memoria a Corto Plazo , RatonesRESUMEN
cAMP response element-binding (CREB) has been known to be an essential transcription factor that activates gene expression required for the formation of long-term memory (LTM) in a wide range of animal models, from nematodes to higher animals such as Aplysia, Drosophila, and rodents. In mammals, various CREB mutant mice have been developed and analyzed. These studies have shown that gain or loss of CREB function improves and impairs, respectively, the formation of LTMs, enabling us to understand the roles of CREB in the formation and enhancement of memory. In this article, the analyses conducted on CREB mutant mice are reviewed with a particular focus on learning and memory formation. This article is part of a Special Issue entitled 'Memory enhancement'.