Publications (34) View all
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Article: Serotonin 1A receptor (5-HT1A) of the sea lamprey: cDNA cloning and expression in the central nervous system.
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ABSTRACT: Serotonergic cells are among the earliest neurons to be born in the developing central nervous system and serotonin is known to regulate the development of the nervous system. One of the major targets of the activity of serotonergic cells is the serotonin 1A receptor (5-HT1A), an ancestral archetypical serotonin receptor. In this study, we cloned and characterized the 3D structure of the sea lamprey 5-HT1A, and studied the expression of its transcript in the central nervous system by means of in situ hybridization. In phylogenetic analyses, the sea lamprey 5-HT1A sequence clustered together with 5-HT1A sequences of vertebrates and emerged as an outgroup to all gnathostome sequences. In situ hybridization analysis during prolarval, larval and adult stages showed a widespread expression of the lamprey 5-ht1a transcript. In P1 prolarvae 5-ht1a mRNA expression was observed in diencephalic nuclei, the rhombencephalon and rostral spinal cord. At P2 prolarval stage the 5-ht1a expression extended to other brain areas including telencephalic regions. 5-ht1a expression in larvae was observed throughout almost all the main brain regions with the strongest expression in the olfactory bulbs, lateral pallium, striatum, preoptic region, habenula, prethalamus, thalamus, pretectum, hypothalamus, rhombencephalic reticular area, dorsal column nucleus and rostral spinal cord. In adults, the 5-ht1a transcript was also observed in cells of the subcommissural organ. Comparison of the expression of 5-ht1a between the sea lamprey and other vertebrates reveals a conserved pattern in most of the brain regions, likely reflecting the ancestral vertebrate condition.Brain Structure and Function 10/2012; · 5.63 Impact Factor -
Article: Glutamatergic neuronal populations in the brainstem of the sea lamprey, Petromyzon marinus: An In situ hybridization and immunocytochemical study.
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ABSTRACT: Glutamate is the major excitatory neurotransmitter in vertebrates, and glutamatergic cells probably represent a majority of neurons in the brain. Physiological studies have demonstrated a wide presence of excitatory (glutamatergic) neurons in lampreys. The present in situ hybridization study with probes for the lamprey vesicular glutamate transporter (VGLUT) provides an anatomical basis for the general distribution and precise localization of glutamatergic neurons in the sea lamprey brainstem. Most glutamatergic neurons were found within the periventricular gray layer throughout the brainstem, with the following regions being of particular interest: the optic tectum, torus semicircularis, isthmus, dorsal and medial nuclei of the octavolateral area, dorsal column nucleus, solitary tract nucleus, motoneurons and the reticular formation. The reticular population revealed a high degree of cellular heterogeneity including small, medium-sized, large and giant glutamatergic neurons. We also combined glutamate immunohistochemistry with neuronal tract-tracing methods or GABA immunohistochemistry to better characterize the glutamatergic populations. Injection of neurobiotin into the spinal cord revealed that retrogradely labeled small and medium-sized cells of some reticulospinal-projecting groups were often glutamate-ir, mostly in the hindbrain. Instead, the large and giant glutamatergic reticulospinal perikarya mostly lacked glutamate immunoreactivity. These results indicate that glutamate immunoreactivity did not reveal the entire set of glutamatergic populations. Some spinal-projecting octaval populations lacked both VGLUT and glutamate. As regards GABA and glutamate, their distribution was largely complementary but colocalization of glutamate and GABA was observed in some small neurons, suggesting that glutamate immunohistochemistry might also detect non-glutamatergic cells or neurons that co-release both GABA and glutamate. J. Comp. Neurol., 2012. © 2012 Wiley Periodicals, Inc.The Journal of Comparative Neurology 07/2012; · 3.81 Impact Factor -
Article: Distribution of glycinergic neurons in the brain of glycine transporter-2 Tg(glyt2:gfp) transgenic adult zebrafish: Relation with brain-spinal descending systems.
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ABSTRACT: We used a Tg(glyt2:gfp) transgenic zebrafish expressing the green fluorescent protein (GFP) under control of the glycine transporter 2 (GLYT2) regulatory sequences to study for the first time the glycinergic neurons in the brain of an adult teleost. We also performed in situ hybridization using a GLYT2 probe and glycine immunohistochemistry. This study was combined with biocytin tract tracing from the spinal cord to reveal descending glycinergic pathways. A few groups of GFP-positive/GLYT2 negative cells were observed in the midbrain and forebrain, including numerous pinealocytes. Conversely, a small nucleus of the midbrain tegmentum, was GLYT2 positive but GFP negative. Most of the GFP-positive and GLYT2-positive neurons were observed in the rhombencephalon and spinal cord, and a proportion of these cells showed double GLYT2/GFP labeling. In the hindbrain, GFP/GLYT2-positive populations were observed in the medial octavolateral nucleus, the secondary, magnocellular and descending octaval nuclei, the viscerosensory lobes and reticular populations distributed from trigeminal to vagal levels. No glycinergic cells were observed in the cerebellum. Tract tracing revealed three conspicuous pairs of GFP/GLYT2-positive reticular neurons projecting to the spinal cord. In the spinal cord, GFP/GLYT2-positive cells were observed in the dorsal and ventral horns. GFP-positive fibers were observed from the olfactory bulbs to the spinal cord, although its density varied among regions. The Mauthner neurons received very rich GFP-positive innervation, mainly around the axon cap. Comparison of the zebrafish glycinergic system with those of other adult vertebrates reveals shared patterns but also divergent traits in the evolution of this system. J. Comp. Neurol., 2012. © 2012 Wiley Periodicals, Inc.The Journal of Comparative Neurology 06/2012; · 3.81 Impact Factor -
Article: The sea lamprey UNC5 receptors: cDNA cloning, phylogenetic analysis and expression in reticulospinal neurons at larval and adult stages of development.
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ABSTRACT: UNC5 receptors mediate repulsive signaling of netrin on neurons. Although only one UNC5 receptor has been identified in invertebrates, four members of the UNC5 family have been identified in gnathostomes. Lampreys, together with mixynes, belong to the oldest branch of extant vertebrates, and their phylogenetic position near to the vertebrate root makes them an interesting model for understanding molecular evolution. Here, we cloned three sea lamprey UNC5 (UNC5L) receptors, and phylogenetic analyses indicated that the first two duplications of the ancestral UNC5 gene occurred before the separation of jawless and jawed vertebrates. UNC5 receptors play important roles during early development, but expression studies have also suggested that UNC5 receptors play roles in the mature nervous system. Here, we report the expression of the different UNC5L receptor transcripts in identified reticulospinal neurons of mature larval or adult sea lampreys detected by in situ hybridization in wholemounted brain preparations. In addition, an extensive expression of the UNC5 receptors was also observed in most brain regions of the adult lamprey. An increase in the types of identifiable reticulospinal neurons expressing the UNC5L receptors was observed in adults compared with larvae. Expression of UNC5 receptors at late developmental stages appears to be a shared characteristic of lampreys and mammals. In larvae, expression of UNC5L receptors was observed in reticulospinal neurons that when axotomized are known to be "bad regenerators." Results in lampreys and mammals suggest that the UNC5-Netrin axonal guidance system may play a role in limiting axonal regeneration after spinal cord injury. J. Comp. Neurol. 520:4141-4156, 2012. © 2012 Wiley Periodicals, Inc.The Journal of Comparative Neurology 05/2012; 520(18):4141-56. · 3.81 Impact Factor -
Article: The sea lamprey tryptophan hydroxylase: new insight into the evolution of the serotonergic system of vertebrates.
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ABSTRACT: Recent research has shown that at least two tryptophan hydroxylase (Tph) genes are present in gnathostome vertebrates, but it is not known when the duplication of the ancestral Tph gene took place during evolution. By their position as an out-group of gnathostomes, lampreys (agnathans) are key models to understand molecular evolution in vertebrates. Here, we report the cloning of a Tph cDNA of the sea lamprey and the pattern of Tph mRNA expression in larval and postmetamorphic (young adult) sea lampreys using in situ hybridization. Phylogenetic analysis indicated that the lamprey Tph is an orthologue of Tphs of other vertebrates and suggested that the duplication of the ancestral Tph gene occurred before the separation of agnathans and gnathostomes, although alternative hypothesis are also discussed in the present study. In the sea lamprey brain, the Tph transcript was expressed in perikarya of the pineal organ, the retina, the diencephalic and rhombencephalic nuclei reported previously with serotonin immunohistochemistry and in small cells of the spinal cord, with a pattern similar to that observed with anti-serotonin antibodies. This suggests that expression of this Tph gene is shared by all lamprey serotonergic brain populations, unlike that reported in zebrafish and mammals for their different Tph genes. However, no Tph expression was observed in peripheral serotonergic cells, which, unlike in other vertebrates, are widely distributed in lampreys. Our results suggest that the selection of Tph2 to be expressed in raphe neurons may have occurred along the line leading to gnathostomes.Brain Structure and Function 04/2012; · 5.63 Impact Factor
