Interdependence of learning and paradoxical sleep in the cat

The effect of learning sessions on the structure of the sleep-wakefulness cycle, as well as the effect of paradoxical sleep (PS) deprivation (PSD) following learning sessions, on the acquisition and extinction of instrumental alimentary reflexes to two feeders with sound discrimination, were studied on cats. The analysis of the data obtained led to following conclusions: The above learning sessions have no marked effect on the structure of the sleep-wakefulness cycle in the post-learning period, i.e. the percentage ratio of its phases is not altered by the increase of one of them. When PSD by non-emotional awakening is used, the number of PS onsets is not affected by learning sessions. This indicates that learning does not produce any considerable effect on the formation of PS need. PSD by non-emotional awakening following learning sessions does not retard the acquisition and extinction of the instrumental alimentary reflexes. The above data are interpreted as indicating that PS has no specific significance in memory trace consolidation during formation of long-term memory.     

Cellular and systems reconsolidation in the hippocampus

Cellular theories of memory consolidation posit that new memories require new protein synthesis in order to be stored. Systems consolidation theories posit that the hippocampus has a time-limited role in memory storage, after which the memory is independent of the hippocampus. Here, we show that intra-hippocampal infusions of the protein synthesis inhibitor anisomycin caused amnesia for a consolidated hippocampal-dependent contextual fear memory, but only if the memory was reactivated prior to infusion. The effect occurred even if reactivation was delayed for 45 days after training, a time when contextual memory is independent of the hippocampus. Indeed, reactivation of a hippocampus-independent memory caused the trace to again become hippocampus dependent, but only for 2 days rather than for weeks. Thus, hippocampal memories can undergo reconsolidation at both the cellular and systems levels.     

Transport mechanisms in acetylcholine and monoamine storage.

Sequence-related vesicular acetylcholine transporter (VAChT) and vesicular monoamine transporter (VMAT) transport neurotransmitter substrates into secretory vesicles. This review seeks to identify shared and differentiated aspects of the transport mechanisms. VAChT and VMAT exchange two protons per substrate molecule with very similar initial velocity kinetics and pH dependencies. However, vesicular gradients of ACh in vivo are much smaller than the driving force for uptake and vesicular gradients of monoamines, suggesting the existence of a regulatory mechanism in ACh storage not found in monoamine storage. The importance of microscopic rather than macroscopic kinetics in structure-function analysis is described. Transporter regions affecting binding or translocation of substrates, inhibitors, and protons have been found with photoaffinity labeling, chimeras, and single-site mutations. VAChT and VMAT exhibit partial structural and mechanistic homology with lactose permease, which belongs to the same sequence-defined superfamily, despite opposite directions of substrate transport. The vesicular transporters translocate the first proton using homologous aspartates in putative transmembrane domain X (ten), but they translocate the second proton using unknown residues that might not be conserved between them. Comparative analysis of the VAChT and VMAT transport mechanisms will aid understanding of regulation in neurotransmitter storage.     

Serotoninergic mechanisms and sleep

Serotoninergic neurons play a critical role in the sleep mechanism. This is supported by a lot of converging experiments and has provided the basis for a great deal of research. A critical analysis is first developed, supported by more recent data which are not in complete agreement with the theory that raphe nuclei are actively implied in slow wave sleep. On the other hand, numerous experimental evidences were collected during the sixties on the EEG synchronizing influence of the lower brain stem and preoptic area. Recent data showed that serotonin could also play here a crucial role in the induction of sleep. Nevertheless, at the moment, it is difficult to make a critical examination of the interaction and regulation of these putative 5-HT-related areas of the brain, but we can postulate that the occurrence of true physiological sleep-waking continuum necessitates their successive or conjoint activation.     

Functional differentiation of the theta-rhythm of the hippocampus in the cat

On the model of discriminating alimentary conditioned reflex with spatial separation of the sources of conditioned (CR, light flashes) and unconditioned (feeding trough) stimuli the theta-rhythm of the dorsal hippocampus was evaluated in cats. Two types of the theta-rhythm were observed in the spectrum of the hippocampal electrical activity: low-amplitude, consisting of a slow growing theta-waves (type I) and high-amplitude consisting of rapidly increasing theta-waves (type II). The type I theta-rhythm is sensitive to noradrenaline and correlates with behavioural forms directed immediately to the realization of alimentary motivation, while the type II is sensitive to serotonin and correlates with behavioural forms directed to the source of the conditioned stimulus. Enhancement of the type II theta-rhythm takes place during a delay of the expected conditioned stimulus. It is suggested that type I theta-rhythm reflects a level of activity of the brain structures connected with unconditioned mechanisms, with realization of biological motivations, while type II theta-rhythm is connected with conditioned reinforcing stimuli; it correlates with various forms of conditioned orienting reflexes and reflects the work of the "nervous model of reinforcing stimulus".     

Role of interneuronal systems in the formation of main patterns of field electrical activity in the hippocampus

Studies on the cellular and subcellular levels promote elucidation of the fundamental principles of formation of effective neuronal systems from cell units. To estimate the interrelations between electrical activity of neuronal networks and processes realized on the cellular level, we need to adequately understand the general patterns of behavior of populations of interneurons, which are components of these networks, under different physiological conditions. In this review, we describe and discuss the relations between the electrical activity of single hippocampal neurons and different components of the field electrical activity, as well as modern concepts on the mode of involvement of the system of hippocampal interneurons in the formation of physiologically important patterns of efferent activity of the above-mentioned structure (in particular in encoding of information on the neuronal level). Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 58–68, January–February, 2008.     

脑缺血大鼠海马信号转导与转录激活子-3的激活及其调控

以往的研究表明,在脑缺血/再灌注的皮层和纹状体组织中信号转导与转录激活子-3(STAT3)被激活。本实验旨在研究SD大鼠四动脉结扎诱导的全脑缺血是否引起海马组织STAT3的快速激活及其调控机制。结果表明,脑缺血导致STAT3快速磷酸化激活及DNA结合活性增加。胞浆STAT3的磷酸化水平从缺血5min起就显著增高,10min达高峰(增加约1．7倍),然后开始下降。核内STAT3的磷酸化水平则逐渐增加,缺血30min时达高峰(增加约2．3倍)。电泳迁移率改变分析法显示,STAT3的DNA结合活性从缺血5min起就显著增加,30min达高峰(增加约3．2倍)。进一步的研究表明,缺血前20min腹腔注射给药,然后缺血30min,发现蛋白酪氨酸激酶抑制剂染料木黄酮和抗氧化剂N-乙酞半胱氨酸能显著地抑制核内STAT3的磷酸化水平及DNA结合活性的增加(磷酸化水平从2．3和2．5倍分别降为1．2和1．4倍,DNA结合活性则从2．8和3．7倍分别降为1．1和1．5倍),而蛋白酪氨酸磷酸酶抑制剂矾酸钠则能明显地促进他们的增高(磷酸化水平从2．0倍增到3．4倍,DNA结合活性从3．1倍增为5．1倍)。这些结果提示,蛋白酪氨酸激酶和蛋白酪氨酸磷酸酶可能共同参与了缺血诱导STAT3的激活调控,STAT3的激活可能有助于海马神经元适应氧化应激。     

Role of cholinergic mechanisms of the ventrolateral preoptico-anterior hypothalamic area in regulation of sleep and wakefulness states in pigeons

Maintenance of wakefulness is established to accomplish muscarinic (M-) cholinergic receptor activation in the ventrolateral preoptic area of the hypothalamus. The "muscarinic" wakefulness is characterized by enhancement of electroencephalogram (EEG) power spectra in the 0.75-12 Hz band and by increase in brain temperature. Activation of nicotinic (N-) cholinergic receptors of the area produces an increase in the duration of slow wave sleep, EEG power spectra reduction in the 0.75-7 Hz band, a decrease in brain temperature. And its hyperactivation leads to wakefulness, during its episodes the brain temperature decreases. During M- and N-cholinergic receptor blockade, the sleep-wakefulness and thermoregulation changes opposite to their activation were found. It is suggested that M- and N-cholinergic receptors of the ventrolateral preoptic area in pigeons participate in the sleep-wakefulness regulation and this effect is related to influence of this area on GABA-ergic system.     

Differences of antioxidant systems in the cerebellum and hippocampus

The effect of portacaval shunting on the antioxidant status of the cerebellum and hippocampus has been studied in rats using standard methods of enzymatic analysis. Endogenous ammonia levels and activities of eight antioxidant enzymes were shown to be unequal in these two brain regions and to respond differently to intrahepatic portosystemic shunt surgery.