Neuronal 5-hydroxytryptamine receptors outside the central nervous system

5-HT receptors are present on many types of neurone in the peripheral nervous system (PNS), e.g. sympathetic, parasympathetic, enteric and sensory cells, and mediate complex effects. These include depolarization, cell discharge and facilitation or depression of transmission. If 5-HT receptors can be classified according to the membrane mechanism associated with them, following the system adopted for mollusc neurones, such a classification would have to take into account two kinds of presynaptic and at least four kinds of postsynaptic action. Recent work suggests that a small number of analogues of 5-HT (tryptamine, 5-MOT, LSD) and antagonists (cocaine, methysergide, quipazine) may be useful in differentiating the various kinds of 5-HT receptor in the PNS. It is suggested that no single feature should be relied upon to characterize the receptors; classification might be based on consideration of function, evidence of tachyphylaxis, sensitivity to methysergide, cocaine, etc. On this basis, it is tentatively concluded that there are two kinds of 5-HT receptor mediating excitation in the PNS, neither of which can sensibly be termed an ‘M’ receptor. An interim form of terminology is proposed which makes use of an acronym of the distinctive features. A receptor mediating (E)xcitation, which shows (T)achyphylaxis, is (M)ethysergide (I)nsensitive but is blocked by (C)ocaine might be designated a 5-HT_ETMIC receptor, while a second which differs because it is insensitive to cocaine but activated by (F)ive-methoxytryptamine might be designated a 5-HT_ETMIF receptor. Amongst receptors mediating (I)nhibition, the best characterized is one mediating decreased transmitter release and activated by (L)SD. The term 5-HT_IL receptor is proposed. A second, post-synaptic inhibitory receptor is likely, but has not been adequately characterized at present.     

Sox neuro, a new Drosophila Sox gene expressed in the developing central nervous system

We describe the identification and detailed expression pattern of a second Drosophila Sox gene, SoxNeuro (SoxN), highly related to mammalian group B Sox1, 2, 3 genes. SoxN is expressed in a highly dynamic pattern during embyogenesis, being associated with the development of the central nervous system (CNS), from the early steps onwards. We present strong evidence that the early SoxN neuroectoderm expression is controlled by the zygotic dorso-ventral patterning genes (dpp, sog, brk, twi).     

Acetylcholine receptors in the central nervous system of Drosophila melanogaster.

Mating between gametes of the biflagellated unicellular green alga Chlamydomonas reinhardi consists of several events culminating in zygote formation. Initially, the cells agglutinate by their flagellar tips. This is followed by pairing, cell wall loss, and cell fusion. Here we report on the relationship between the length of the flagellum, and the cells' ability to agglutinate, undergo cell wall loss (as measured by medium carbohydrate accumulation), and to form zygotes. We found that deflagellated gametes regained the potential for sexual agglutination when the flagella had regenerated to less than 3 μm (compared to the full length flagella of approx. 11 μm), while medium carbohydrate appeared only after the flagella had reached an average length greater than 5 μm. By inhibiting flagellar regeneration with cycloheximide or colchicine, we determined that carbohydrate release is related to the length of the flagellum and not to the time after deflagellation. A flagellar length dependence similar to that of carbohydrate release was also observed when we measured the relationship between the gametes' ability to fuse and flagellar length.     

中枢神经系统内神经元信号处理(英文)

一种新颖的轴突断端(axon bleb)膜片钳记录方法大力促进了中枢神经系统轴突功能的研究。我们的工作应用这一方法揭示了大脑皮层锥体神经元的数码信号(具全或无特性的动作电位)的爆发和传播机制。在轴突始段(axon initial segment,AIS)远端高密度聚集的低阈值Na+通道亚型Nav1.6决定动作电位的爆发;而在AIS近端高密度聚集的高阈值Na+通道亚型Nav1.2促进动作电位向胞体和树突的反向传播。应用胞体和轴突的同时记录,我们发现胞体阈下膜电位的变化可以在轴突上传播较长的距离并可到达那些离胞体较近的突触前终末。进一步的研究证明了胞体膜电位的变化调控动作电位触发的突触传递,该膜电位依赖的突触传递是一种模拟式的信号传递。轴突上一类特殊K+通道(Kv1)的活动调制动作电位的波形,特别是其波宽,从而调控各种突触前膜电位水平下突触强度的变化。突触前终末的背景Ca2+浓度也可能参与模拟信号的传递。这些发现深化了我们对中枢神经系统内神经信号处理基本原理的认识,进而帮助我们理解脑如何工作。     

中枢神经系统烟碱受体：性质的多样性，功能的求知性

中枢神经系统烟碱受体其药理学和生理学性质表面为多样性特点。位于突触前的烟碱受体具有调节突触传递的作用。中枢由烟碱受体介导的功能性快突触传递,长期以来（自1966年）认为只存在于脊髓前角运动神经元与闰绍细胞间,只是到最近（1998年）才在脑中发现。尽管如此,中枢神经系统尤其是脑内的烟碱受体,其生理功能目前仍然是个谜。     

GLIA: A reassessment based on novel data on the developing and mature central nervous system

Several studies on neurobiology have contributed to our understanding of the genesis, survival and death of neurons, unquestionably the stars of the Central Nervous System (CNS). However, they would not be so famous without their close associates: the glial cells. Since novel studies have demonstrated new and important functions for glial cells, they are beginning to gain significant importance in brain research to allow us to reinterpret long known functions on the basis of new concepts. Here, we review recent progress in our understanding of the role of glial cells in the biology of tissue development and maturation.     

MicroRNAs show a wide diversity of expression profiles in the developing and mature central nervous system

Background  

MicroRNA (miRNA) encoding genes are abundant in vertebrate genomes but very few have been studied in any detail. Bioinformatic tools allow prediction of miRNA targets and this information coupled with knowledge of miRNA expression profiles facilitates formulation of hypotheses of miRNA function. Although the central nervous system (CNS) is a prominent site of miRNA expression, virtually nothing is known about the spatial and temporal expression profiles of miRNAs in the brain. To provide an overview of the breadth of miRNA expression in the CNS, we performed a comprehensive analysis of the neuroanatomical expression profiles of 38 abundant conserved miRNAs in developing and adult zebrafish brain.     

Pax gene expression in the developing central nervous system of Ciona intestinalis

We compare the expression patterns in Ciona intestinalis of three members of the Pax gene family, CiPax3/7, CiPax6 and Cipax2/5/8. All three genes are expressed in restricted patterns in the developing central nervous system. At the tailbud stage, CiPax3/7 is present in three patches in the brain and along the posterior neural tube, CiPax6 throughout the anterior brain and along the posterior neural tube and CiPax2/5/8 in a restricted region of the posterior brain. Double in situ hybridisations were used to identify areas of overlap between the expression of different genes. This showed that CiPax3/7 overlaps with the boundaries of CiPax6 expression in the anterior brain, and with CiPax2/5/8 in the posterior brain. The overlap between CiPax3/7 and CiPax2/5/8 is unlike that described in the ascidian Halocynthia rorezti.     

Corticosteroid receptors and the central nervous system

In mammalian systems, the physiological mineralocorticoid is aldosterone (aldo), and the physiological glucocorticoid cortisol (F), or corticosterone (B) in rats and mice. Receptors (MR) with high affinity for aldo, B and F are found in both epithelia and the central nervous system (CNS); receptors (GR) with lower affinity for F and B, and still lower for aldo, are found in essentially all cells. Both MR and GR bind to and activate canonical pentadecamer response elements in transfected cells and in epithelia, wherein MR aldo, B and F all act as agonists. In vivo, in epithelial cells a low K_m, NAD-dependent, 11β hydroxysteroid dehydrogenase (11βOHSD) converts B and F, but not aldo, to receptor-inactive 11-keto congeners, thus allowing aldo to occupy epithelial MR and produce sodium retention. The CNS differs markedly in terms of MR/GR in a number of ways: (i) most but not all MR in the CNS are functionally unprotected, despite the presence of a low K_m, NADP-preferring 11βOHSD, so that they operate as high-affinity GR; (ii) in such CNS ‘MR’, aldo antagonizes the effects of B, and vice versa, in contrast with epithelia; (iii) also in contrast with epithelia, activated GR in the CNS do not mimic activated MR, suggesting considerable if not total specificity at the response element level. These differences suggest that glucocorticoids have two distinct domains of action in the CNS, mediated by ‘MR’ at low B/F concentrations, and GR at higher concentrations; secondly, they suggest that the nuclear recognition and response elements mediating these effects are other than canonical pentadecamer sequences.     

Analysis of hunger-driven gene expression in the Drosophila melanogaster larval central nervous system

A transposon-inserted mutant of Drosophila melanogaster was recently identified, and the larvae show no food preference (Ryuda and Hayakawa, 2005). To reveal the genetic mechanism underlying the preference change in this mutant, a large-scale oligo-DNA microarray screening was carried out to identify genes whose expression is different in control and mutant strains. We focused especially on hunger-driven changes in gene expression in the larval central nervous system (CNS) of both strains, because the state of food depletion should promote a feeding response due to changed expression of certain genes in the CNS. We identified 22 genes whose expression changed after starvation in either or both of the two strains. Quantitative RT-PCR analyses confirmed the expression changes in four genes, CG6271, CG6277, CG7953, and new glue 3 (ng3, encoding a putative structural molecule). CG6271 and CG6277 encode triacylglycerol lipase, and CG7953 produces a protein homologous to a juvenile hormone (JH) binding protein. The expression of these two groups of genes was enhanced in control strain larvae with a normal food preference but not in GS1189 strain larvae. Given that these genes contribute to mediating hunger-driven changes in food preference and intake in D. melanogaster larvae, the dysfunction of these key genes could cause the defect in food preference observed in GS1189-strain larvae.     

Specific immunolabeling of brain macrophages and microglial cells in the developing and mature chick central nervous system.

The present study showed that the HIS-C7 monoclonal antibody, which recognizes the chick form of CD45, is a specific marker for macrophages/microglial cells in the developing and mature chick central nervous system (CNS). HIS-C7-positive cells were characterized according to their morphological features and chronotopographical distribution patterns within developing and adult CNS, similar to those of macrophages/microglial cells in the quail CNS and confirmed by their histochemical labeling with Ricinus communis agglutinin I, a lectin that recognizes chick microglial cells. Therefore, the HIS-C7 antibody is a valuable tool to identify brain macrophage and microglial cells in studies of the function, development, and pathology of the chick brain. CD45 expression differed between chick microglia (as revealed with HIS-C7 antibody) and mouse microglial cells (as revealed with an antibody against mouse form of CD45). Thus, a discontinuous label was seen on mouse microglial cells with the anti-mouse CD45 immunostaining, whereas the entire surface of chick microglial cells was labeled with the anti-chick CD45 staining. The functional relevance of these differences between species has yet to be determined.     

Segmental determination in Drosophila central nervous system

We have analyzed the control of two segment-specific features in the central nervous system of Drosophila larvae. One of them is present only in the thoracic ganglia of the larva, where it represents the anlage of the adult leg neuromeres; the other is found in the first abdominal, as well as in the thoracic, ganglia. We show that mutations within the bithorax complex have parallel but independent effects on these neural structures and on the larval epidermis. We also show that the central nervous system is very sensitive to mild perturbations of the bithorax complex, and in particular to haploinsufficiency.