Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americanaWatanabe, Hidehiro; Nishino, Hiroshi; Nishikawa, Michiko; Mizunami, Makoto; Yokohari, Fumio
doi: 10.1002/cne.22476pmid: N/A
Glomeruli are structural and functional units in the primary olfactory center in vertebrates and insects. In the cockroach Periplaneta americana, axons of different types of sensory neurons housed in sensilla on antennae form dorsal and ventral antennal nerves and then project to a number of glomeruli. In this study, we identified all antennal lobe (AL) glomeruli based on detailed innervation patterns of sensory tracts in addition to the shape, size, and locations in the cockroach. The number of glomeruli is ∼205, and no sex‐specific difference is observed. Anterograde dye injections into the antennal nerves revealed that axons supplying the AL are divided into 10 sensory tracts (T1–T10). Each of T1–T3 innervates small, oval glomeruli in the anteroventral region of the AL, with sensory afferents invading each glomerulus from multiple directions, whereas each of T4–T10 innervates large glomeruli with various shapes in the posterodorsal region, with a bundle of sensory afferents invading each glomerulus from one direction. The topographic branching patterns of all these tracts are conserved among individuals. Sensory afferents in a sub‐tract of T10 had axon terminals in the dorsal margin of the AL and the protocerebrum, where they form numerous small glomerular structures. Sensory nerve branching pattern should reflect developmental processes to determine spatial arrangement of glomeruli, and thus the complete map of glomeruli based on sensory nerve branching pattern should provide a basis for studying the functional significance of spatial arrangement of glomeruli and its developmental basis. J. Comp. Neurol. 518:3907–3930, 2010. © 2010 Wiley‐Liss, Inc.
Central respiratory chemoreceptionGuyenet, Patrice G.; Stornetta, Ruth L.; Bayliss, Douglas A.
doi: 10.1002/cne.22435pmid: 20737591
By definition central respiratory chemoreceptors (CRCs) are cells that are sensitive to changes in brain PCO2 or pH and contribute to the stimulation of breathing elicited by hypercapnia or metabolic acidosis. CO2 most likely works by lowering pH. The pertinent proton receptors have not been identified and may be ion channels. CRCs are probably neurons but may also include acid‐sensitive glia and vascular cells that communicate with neurons via paracrine mechanisms. Retrotrapezoid nucleus (RTN) neurons are the most completely characterized CRCs. Their high sensitivity to CO2 in vivo presumably relies on their intrinsic acid sensitivity, excitatory inputs from the carotid bodies and brain regions such as raphe and hypothalamus, and facilitating influences from neighboring astrocytes. RTN neurons are necessary for the respiratory network to respond to CO2 during the perinatal period and under anesthesia. In conscious adults, RTN neurons contribute to an unknown degree to the pH‐dependent regulation of breathing rate, inspiratory, and expiratory activity. The abnormal prenatal development of RTN neurons probably contributes to the congenital central hypoventilation syndrome. Other CRCs presumably exist, but the supportive evidence is less complete. The proposed locations of these CRCs are the medullary raphe, the nucleus tractus solitarius, the ventrolateral medulla, the fastigial nucleus, and the hypothalamus. Several wake‐promoting systems (serotonergic and catecholaminergic neurons, orexinergic neurons) are also putative CRCs. Their contribution to central respiratory chemoreception may be behavior dependent or vary according to the state of vigilance. J. Comp. Neurol. 518:3883–3906, 2010. © 2010 Wiley‐Liss, Inc.
Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americanaWatanabe, Hidehiro; Nishino, Hiroshi; Nishikawa, Michiko; Mizunami, Makoto; Yokohari, Fumio
doi: 10.1002/cne.22452pmid: 20737592
Glomeruli are structural and functional units in the primary olfactory center in vertebrates and insects. In the cockroach Periplaneta americana, axons of different types of sensory neurons housed in sensilla on antennae form dorsal and ventral antennal nerves and then project to a number of glomeruli. In this study, we identified all antennal lobe (AL) glomeruli based on detailed innervation patterns of sensory tracts in addition to the shape, size, and locations in the cockroach. The number of glomeruli is ∼205, and no sex‐specific difference is observed. Anterograde dye injections into the antennal nerves revealed that axons supplying the AL are divided into 10 sensory tracts (T1–T10). Each of T1–T3 innervates small, oval glomeruli in the anteroventral region of the AL, with sensory afferents invading each glomerulus from multiple directions, whereas each of T4–T10 innervates large glomeruli with various shapes in the posterodorsal region, with a bundle of sensory afferents invading each glomerulus from one direction. The topographic branching patterns of all these tracts are conserved among individuals. Sensory afferents in a sub‐tract of T10 had axon terminals in the dorsal margin of the AL and the protocerebrum, where they form numerous small glomerular structures. Sensory nerve branching pattern should reflect developmental processes to determine spatial arrangement of glomeruli, and thus the complete map of glomeruli based on sensory nerve branching pattern should provide a basis for studying the functional significance of spatial arrangement of glomeruli and its developmental basis. J. Comp. Neurol. 518:3907–3930, 2010. © 2010 Wiley‐Liss, Inc.
Progranulin expression in the developing and adult murine brainPetkau, Terri L.; Neal, S.J.; Orban, P.C.; MacDonald, J.L.; Hill, A.M.; Lu, G.; Feldman, H.H.; Mackenzie, I.R.A.; Leavitt, B.R.
doi: 10.1002/cne.22430pmid: 20737593
Frontotemporal lobar degeneration (FTLD) is a neurodegenerative condition characterized by focal degeneration of the frontal and temporal lobes of the brain. Autosomal dominantly inherited mutations of the progranulin gene (GRN) have been identified as the cause of a subset of cases of familial FTLD. In order to better understand the function of progranulin in the central nervous system (CNS), we have assessed the spatiotemporal expression pattern of both the murine progranulin gene (Grn) and the protein (Grn) by using transgenic knock‐in mice expressing a reporter gene from the Grn locus and by immunohistochemistry, respectively. We compared Grn expression with a panel of established markers for distinct neuronal developmental stages and specific cell lineages at time points ranging from embryonic day 13.5 through to the mature adult. We find that Grn is expressed in both neurons and microglia within the CNS, but that it shows a different developmental expression pattern in each cell type. Grn expression in neurons increases as the cells mature, whereas expression in microglia varies with the cells' state of activation, being specifically upregulated in microglia in response to excitotoxic injury. Our results suggest that progranulin plays distinct roles in neurons and microglia, both of which likely contribute to overall neuronal health and function. J. Comp. Neurol. 518:3931–3947, 2010. © 2010 Wiley‐Liss, Inc.
How the primate fornix is affected by agePeters, Alan; Sethares, Claire; Moss, Mark B.
doi: 10.1002/cne.22434pmid: 20737595
The effects of age on nerve fibers and neuroglial cells in the fornix were examined in 25 rhesus monkeys between 4 and 33 years of age. There is no age‐related change in the cross‐sectional area of the fornix, but there is a significant loss of myelinated nerve fibers. The loss of myelinated nerve fibers is accompanied by a significant increase in the numbers of nerve fibers that show degeneration of their axons and alterations in myelin sheaths. Aging also brings about an increase in the frequency of profiles of paranodes, indicating that some of the nerve fibers are being remyelinated. Aging also affects neuroglial cells. Each type shows inclusions in their perikarya, and in the case of astrocytes and microglial cells some of these inclusions are phagocytosed myelin. Numbers of astrocytes and microglial cells do not appear to increase with age, but there is a 20% increase in oligodendrocytes. When correlations with cognitive impairments displayed by individual monkeys are examined, the decreased packing density of nerve fibers and the increasing frequency of nerve fibers with degenerating axons and of nerve fibers with altered myelin sheaths all correlate with increasing cognitive impairment. It is suggested that these correlations result from some disconnection of the hippocampus from the thalamus, septal nuclei, and medial frontal cortex and from reductions in the conduction velocity brought about by the shorter internodal lengths of remyelinated nerve fibers in the fornix. J. Comp. Neurol. 518:3962–3980, 2010. © 2010 Wiley‐Liss, Inc.
Neuronal DNA content variation (DCV) with regional and individual differences in the human brainWestra, Jurjen W.; Rivera, Richard R.; Bushman, Diane M.; Yung, Yun C.; Peterson, Suzanne E.; Barral, Serena; Chun, Jerold
doi: 10.1002/cne.22436pmid: 20737596
It is widely assumed that the human brain contains genetically identical cells through which postgenomic mechanisms contribute to its enormous diversity and complexity. The relatively recent identification of neural cells throughout the neuraxis showing somatically generated mosaic aneuploidy indicates that the vertebrate brain can be genomically heterogeneous (Rehen et al. [2001] Proc. Natl. Acad. Sci. U. S. A. 98:13361–13366; Rehen et al. [2005] J. Neurosci. 25:2176–2180; Yurov et al. [2007] PLoS ONE:e558; Westra et al. [2008] J. Comp. Neurol. 507:1944–1951). The extent of human neural aneuploidy is currently unknown because of technically limited sample sizes, but is reported to be small (Iourov et al. [2006] Int. Rev. Cytol. 249:143–191). During efforts to interrogate larger cell populations by using DNA content analyses, a surprising result was obtained: human frontal cortex brain cells were found to display “DNA content variation (DCV)” characterized by an increased range of DNA content both in cell populations and within single cells. On average, DNA content increased by ∼250 megabases, often representing a substantial fraction of cells within a given sample. DCV within individual human brains showed regional variation, with increased prevalence in the frontal cortex and less variation in the cerebellum. Further, DCV varied between individual brains. These results identify DCV as a new feature of the human brain, encompassing and further extending genomic alterations produced by aneuploidy, which may contribute to neural diversity in normal and pathophysiological states, altered functions of normal and disease‐linked genes, and differences among individuals. J. Comp. Neurol. 518:3981–4000, 2010. © 2010 Wiley‐Liss, Inc.
Retinal photoreceptors of two subterranean tuco‐tuco species (Rodentia, Ctenomys): Morphology, topography, and spectral sensitivitySchleich, Cristian E.; Vielma, Alex; Glösmann, Martin; Palacios, Adrian G.; Peichl, Leo
doi: 10.1002/cne.22440pmid: 20737597
Traditionally, vision was thought to be useless for animals living in dark underground habitats, but recent studies in a range of subterranean rodent species have shown a large diversity of eye features, from small subcutaneous eyes to normal‐sized functional eyes. We analyzed the retinal photoreceptors in the subterranean hystricomorph rodents Ctenomys talarum and Ctenomys magellanicus to elucidate whether adaptation was to their near‐lightless burrows or rather to their occasional diurnal surface activity. Both species had normally developed eyes. Overall photoreceptor densities were comparatively low (95,000–150,000/mm2 in C. magellanicus, 110,000–200,000/mm2 in C. talarum), and cone proportions were rather high (10–31% and 14–31%, respectively). The majority of cones expressed the middle‐to‐longwave‐sensitive (L) opsin, and a 6–16% minority expressed the shortwave‐sensitive (S) opsin. In both species the densities of L and S cones were higher in ventral than in dorsal retina. In both species the tuning‐relevant amino acids of the S opsin indicate sensitivity in the near UV rather than the blue/violet range. Photopic spectral electroretinograms were recorded. Unexpectedly, their sensitivity profiles were best fitted by the linear summation of three visual pigment templates with λmax at 370 nm (S pigment, UV), at 510 nm (L pigment), and at 450 nm (an as‐yet unexplained mechanism). Avoiding predators and selecting food during the brief aboveground excursions may have exerted pressure to retain robust cone‐based vision in Ctenomys. UV tuning of the S cone pigment is shared with a number of other hystricomorphs. J. Comp. Neurol. 518:4001–4015, 2010. © 2010 Wiley‐Liss, Inc.
Distribution of relaxin‐3 and RXFP3 within arousal, stress, affective, and cognitive circuits of mouse brainSmith, Craig M.; Shen, Pei‐Juan; Banerjee, Avantika; Bonaventure, Pascal; Ma, Sherie; Bathgate, Ross A.D.; Sutton, Steven W.; Gundlach, Andrew L.
doi: 10.1002/cne.22442pmid: 20737598
Relaxin‐3 (RLN3) and its native receptor, relaxin family peptide 3 receptor (RXFP3), constitute a newly identified neuropeptide system enriched in mammalian brain. The distribution of RLN3/RXFP3 networks in rat brain and recent experimental studies suggest a role for this system in modulation of arousal, stress, metabolism, and cognition. In order to facilitate exploration of the biology of RLN3/RXFP3 in complementary murine models, this study mapped the neuroanatomical distribution of the RLN3/RXFP3 system in mouse brain. Adult, male wildtype and RLN3 knock‐out (KO)/LacZ knock‐in (KI) mice were used to map the central distribution of RLN3 gene expression and RLN3‐like immunoreactivity (‐LI). The distribution of RXFP3 mRNA and protein was determined using [35S]‐oligonucleotide probes and a radiolabeled RXFP3‐selective agonist ([125I]‐R3/I5), respectively. High densities of neurons expressing RLN3 mRNA, RLN3‐associated β‐galactosidase activity and RLN3‐LI were detected in the nucleus incertus (or nucleus O), while smaller populations of positive neurons were observed in the pontine raphé, the periaqueductal gray and a region adjacent to the lateral substantia nigra. RLN3‐LI was observed in nerve fibers/terminals in nucleus incertus and broadly throughout the pons, midbrain, hypothalamus, thalamus, septum, hippocampus, and neocortex, but was absent in RLN3 KO/LacZ KI mice. This RLN3 neural network overlapped the regional distribution of RXFP3 mRNA and [125I]‐R3/I5 binding sites in wildtype and RLN3 KO/LacZ KI mice. These findings provide further evidence for the conserved nature of RLN3/RXFP3 systems in mammalian brain and the ability of RLN3/RXFP3 signaling to modulate “behavioral state” and an array of circuits involved in arousal, stress responses, affective state, and cognition. J. Comp. Neurol. 518:4016–4045, 2010. © 2010 Wiley‐Liss, Inc.
Sympathetic innervation of the ileocecal junction in horsesRusso, D.; Bombardi, C.; Grandis, A.; Furness, J.B.; Spadari, A.; Bernardini, C.; Chiocchetti, R.
doi: 10.1002/cne.22443pmid: 20737599
The distribution and chemical phenotypes of sympathetic and dorsal root ganglion (DRG) neurons innervating the equine ileocecal junction (ICJ) were studied by combining retrograde tracing and immunohistochemistry. Immunoreactivity (IR) for tyrosine hydroxylase (TH), dopamine beta‐hydroxylase (DBH), neuronal nitric oxide synthase (nNOS), calcitonin gene‐related peptide (CGRP), substance P (SP), and neuropeptide Y (NPY) was investigated. Sympathetic neurons projecting to the ICJ were distributed within the celiac (CG), cranial mesenteric (CranMG), and caudal mesenteric (CaudMG) ganglia, as well as in the last ganglia of the thoracic sympathetic chain and in the splanchnic ganglia. In the CG and CranMG 91 ± 8% and 93 ± 12% of the neurons innervating the ICJ expressed TH‐ and DBH‐IR, respectively. In the CaudMG 90 ± 15% and 94 ± 5% of ICJ innervating neurons were TH‐ and DBH‐IR, respectively. Sympathetic (TH‐IR) fibers innervated the myenteric and submucosal ganglia, ileal blood vessels, and the muscle layers. They were more concentrated at the ICJ level and were also seen encircling myenteric plexus (MP) and submucosal plexus (SMP) descending neurons that were retrogradely labeled from the ICJ. Among the few retrogradely labeled DRG neurons, nNOS‐, CGRP‐, and SP‐IR nerve cells were observed. Dense networks of CGRP‐, nNOS‐, and SP‐IR varicosities were seen around retrogradely labeled prevertebral ganglia neurons. The CGRP‐IR fibers are probably the endings of neurons projecting from the intestine to the prevertebral ganglia. These findings indicate that this crucial region of the intestinal tract is strongly influenced by the sympathetic system and that sensory information of visceral origin influences the sympathetic control of the ICJ. J. Comp. Neurol. 518:4046–4066, 2010. © 2010 Wiley‐Liss, Inc.