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Sleep and oligodendrocyte functions
Full text linkTranscriptomic studies have revealed that the brains of sleeping and awake animals differ significantly at the molecular level, with hundreds of brain transcripts changing their expression across behavioral states. However, it was unclear how sleep affects specific cells types, such as oligodendrocytes, which make myelin in the healthy brain and in response to injury. In this review, I summarize the recent findings showing that several genes expressed at higher levels during sleep are involved in the synthesis/maintenance of all membranes and of myelin in particular. In addition, I will discuss the effect of sleep and wake on oligodendrocyte precursor cells (OPCs), providing a working hypothesis on the function of REM sleep and acetylcholine in OPC proliferation.</p
Reduction of EEG Theta power (4-10 Hz) in rats treated with ceftriaxone
No full textIl trasportatore del glutammato GLT-1 e’ responsabile della ricaptazione di glutammato rilasciato a livello sinaptico. Grazie alla sua azione, il glutammato extracellulare e’ tenuto a bassi livelli di concentrazione, evitando fenomeni patologici di eccitotossicita’. Per questa ragione, GLT-1 e’ coinvolto nella patogenesi di numerose malattie. Recentemente e’ stato dimostrato che e’ possibile incrementare l’espressione di GLT-1 somministrando il ceftriaxone (CEF), un comune antibiotico. Recenti studi hanno rivelato che la somministrazione di CEF e’ in grado di alterare l’elaborazione dell’infromazione nervosa e la plasticita’ sinaptica. Date queste premesse, ipotiziamo che il CEF, aumentando l’espressione di GLT-1, alteri l’attivita’ di ampie popolazioni di neuroni. Per dimostrare questo, ci siamo avvalsi di studi elettroncefalografici (EEG), misurando differenze quantitative della potenza dello spettro del segnale EEG prima e dopo il trattamento con CEF. Inoltre abbiamo valutato se le alterazioni EEG si associavano ad alcuni aspetti comportamentali. Per fare questo, abbiamo registrato l’EEG dale cortecce frontali e parietali di ratto, abbiamo inoltre registrato l’EMG ed abbiamo video registrato gli animali. Infine abbiamo studiato l’andamento nel tempo della potenza dello spettro e dell’ativita’motoria per mezzo dell’analisi EMG e delle registrazioni video.
Abbiamo scoperto che il CEF riduce la potenza del segnale nelle frequenze theta con un picco a 7-9 Hz e che incrmenta l’attivita’ locomotoria degli animali. Queste alterazioni mostravano un andamento temporale sovrapponibile, indicando un possibile legame tra le alterazioni EEG e l’aumento dell’attivita’ locomotoria.
Inoltre, i dati presentati suggeriscono che il CEF e’ in grado di alterare, attraverso la modulazione della trasmissione glutammatergica, l’attivita’ di ampie popolazioni di neuroni
Synaptic plasticity modulates autonomous transitions between waking and sleep states: Insights from a Morris-Lecar model
No full textThe transitions between waking and sleep states are characterized by considerable changes in neuronal firing. During waking, neurons fire tonically at irregular intervals and a desynchronized activity is observed at the electroencephalogram. This activity becomes synchronized with slow wave sleep onset when neurons start to oscillate between periods of firing (up-states) and periods of silence (down-states). Recently, it has been proposed that the connections between neurons undergo potentiation during waking, whereas they weaken during slow wave sleep. Here, we propose a dynamical model to describe basic features of the autonomous transitions between such states. We consider a network of coupled neurons in which the strength of the interactions is modulated by synaptic long term potentiation and depression, according to the spike time-dependent plasticity rule (STDP). The model shows that the enhancement of synaptic strength between neurons occurring in waking increases the propensity of the network to synchronize and, conversely, desynchronization appears when the strength of the connections become weaker. Both transitions appear spontaneously, but the transition from sleep to waking required a slight modification of the STDP rule with the introduction of a mechanism which becomes active during sleep and changes the proportion between potentiation and depression in accordance with biological data. At the neuron level, transitions from desynchronization to synchronization and vice versa can be described as a bifurcation between two different states, whose dynamical regime is modulated by synaptic strengths, thus suggesting that transition from a state to an another can be determined by quantitative differences between potentiation and depression
Diagnostic difficulties with central nervous system actinomycosis
No full textWhen faced with expanding brain lesions of unknown origin showing a ring-shaped enhancement on post-contrast imaging, we use definite criteria to direct further investigation and distinguish among a number of possible diagnostic hypotheses. However, a correct diagnosis may be difficult in some cases, especially when dealing with less frequent conditions. This is the case of actinomycosis, a highly treatable but insidious infection for which nowadays there may be a low level of attention. Brain localization is associated with a significant morbidity and may represent a true diagnostic pitfall. Here we report the difficulties encountered with a case of central nervous system actinomycosis
Sleep quality relates to emotional reactivity via intracortical myelination.
Full text linkA good quality and amount of sleep are fundamental to preserve cognition and affect. New evidence also indicates that poor sleep is detrimental to brain myelination. In this study, we test the hypothesis that sleep quality and/or quantity relate to variability in cognitive and emotional function via the mediating effect of interindividual differences in proxy neuroimaging measures of white matter integrity and intracortical myelination. By employing a demographically and neuropsychologically well-characterized sample of healthy people drawn from the Human Connectome Project (n = 974), we found that quality and amount of sleep were only marginally linked to cognitive performance. In contrast, poor quality and short sleep increased negative affect (i.e. anger, fear, and perceived stress) and reduced life satisfaction and positive emotionality. At the brain level, poorer sleep quality and shorter sleep duration related to lower intracortical myelin in the mid-posterior cingulate cortex (p = 0.038), middle temporal cortex (p = 0.024), and anterior orbitofrontal cortex (OFC, p = 0.034) but did not significantly affect different measures of white matter integrity. Finally, lower intracortical myelin in the OFC mediated the association between poor sleep quality and negative emotionality (p < 0.05). We conclude that intracortical myelination is an important mediator of the negative consequences of poor sleep on affective behavior
Region-Specific Dissociation between Cortical Noradrenaline Levels and the Sleep/ Wake Cycle
Full text linkThe activity of the noradrenergic system of the locus coeruleus (LC) is high in wake and low in sleep. LC promotes arousal and EEG activation, as well as attention, working memory, and cognitive flexibility. These functions rely on prefrontal cortex and are impaired by sleep deprivation, but the extent to which LC activity changes during wake remains unclear. Moreover, it is unknown whether noradrenergic neurons can sustain elevated firing during extended wake. Recent studies show that relative to LC neurons targeting primary motor cortex (M1), those projecting to medial prefrontal cortex (mPFC) have higher spontaneous firing rates and are more excitable. These results suggest that noradrenaline (NA) levels should be higher in mPFC than M1, and that during prolonged wake LC cells targeting mPFC may fatigue more
GLT-1 up-regulation enhances the effect of PCP on prepulse inhibition of the startle reflex in adult rats.
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