bluuebunny/crossref_metadata_2025 huggingface dataset:
The organization of projections from the mediodorsal nucleus of the thalamus to orbital and medial prefrontal cortex in macaque monkeys
Authors: Ray James P. , Price Joseph L.
Published: January 2005

The organization of interconnections between the mediodorsal nucleus of the thalamus (MD) and the orbital and medial prefrontal cortex and the agranular insular cortex in the monkey was studied by retrograde and anterograde tracing techniques. In addition to the magnocellular and parvicellular divisions of MD, three other subdivisions can be recognized on the basis of myeloarchitecture, cytoarchitecture, and connections. The first two of these represent a parcellation of the magnocellular division into a lateral, fiber‐richMD pars fibrosaand a medial, poorly myelinatedMD pars paramedianaadjacent to the midline. The third is a small, poorly myelinated area located at the caudomedial and dorsal edges of MD; it is referred to asMD pars caudodorsalis.

MD pars fibrosa is reciprocally interconnected primarily with areas 11, 12 and 13 in the central and lateral part of the orbital cortex. There is a general organization within this projection, with the rostrocaudal axis of the cortex represented from dorsal to ventral in the pars fibrosa, and the mediolateral cortical axis represented from medial to lateral. Cells that project to area 12 also extend laterally into the adjacent pars parvicellularis. MD pars paramediana is more heavily interconnected with the caudal and medial portions of the orbital region, particularly the agranular insular areas and the caudal parts of areas 13 and 14. Cells that project to two caudal areas, 13a and Iad, do not fit with the general organization, in that they are located in the dorsomedial parts of the pars fibrosa and pars paramediana, where they overlap with cells that project to area 14. The pars fibrosa and pars paramediana receive inputs from areas of the ventral forebrain such as the amygdala, piriform (olfactory) cortex, and entorhinal cortex, which project directly to the orbital and agranular insular cortex, and entorhinal cortex, which project directly to the orbital and agranular insular cortex, as well as from the ventral pallidum.

MD pars caudodorsalis is reciprocally interconnected with areas 14, 24, and 32 on the medial surface of the prefrontal cortex. In this part of the nucleus the dorsoventral axis of the medial prefrontal cortex is represented from caudal to rostral in the thalamus. The amygdala and other ventral forebrain structures do not send fibers into the pars caudodorsalis, even though some of these structures project directly to the medial prefrontal cortex.

Ventral to MD, and separated from it by the internal medullary lamina, a small region was recognized that appears to be comparable to the anteroventral part of the submedial nucleus previously defined in the rat and cat. This region receives input from the piriform cortex and is interconnected with orbital cortical area 13a. © 1993 Wiley‐Liss, Inc.
Ectopic purkinje cells in the adult rat: Olivary innervation and different capabilities of migration and development after grafting
Authors: Rossi Ferdinando , Borsello Tiziana
Published: January 2005

The abnormal location of large numbers of neurones is characteristic of genetic mutations which impair the migratory processes of developing nerve cells. Nevertheless, the presence of small amounts of ectopic neurones is a fairly common finding even in normal adult animals. The first aim of this study was to investigate a series of features of ectopic Purkinje cells in normal adult rats and particularly to assess whether these cells are still capable of interacting with their normal afferents. Several displaced Purkinje cells, identified by anti‐D28K calbindin immunolabelling as well as by typical morphological features, were present in the brainstem and cerebellum of all the examined animals. Two distinct morphological types of such cells could be recognized: (1) noncortical Purkinje cells, located in several areas of the dorsal brainstem and cerebellum, characterised by poorly developed and randomly oriented dendrites; and (2) cortical Purkinje cells, exclusively located in the dorsal cochlear nucleus, characterised by large dendritic trees oriented along parasagittal planes. Tracing experiments, in which Phaseolus vulgaris leucoagglutinin (PHA‐L) was injected into the inferior olive, revealed that several ectopic Purkinje cells, belonging to both types, were contacted by the terminal arbours of olivary axons, structurally similar to cerebellar climbing fibres.

On the basis of the observation that ectopic Purkinje cells were more frequent in the dorsal cochlear nucleus than in any other of the examined regions, we tested the hypothesis that this nucleus might represent a particularly favourable environment for the survival and development of Purkinje cells. By grafting embryonic cerebellar tissue in the fourth ventricle, only minimal migration of Purkinje cells into the recipient parenchyma was observed when the transplant was placed on the brainstem surface caudal to the cochlear nucleus. By contrast, when the graft was apposed to the latter nucleus, large numbers of Purkinje cells migrated and developed in its superficial layers. These Purkinje cells passed through all the different phases which characterise the normal ontogenesis of this neuronal population and finally developed mature structural features similar to those displayed by cortical ectopic Purkinje cells.

This study demonstrates that at least some of the ectopic Purkinje cells receive their physiological olivary input. This fact indicates that Purkinje cells are able to attract olivary axons and establish specific connections, even if they are displaced in an abnormal environment. In addition, we show that the dorsal cochlear nucleus represents a particularly favourable environment for the survival and the development of Purkinje cells. © 1993 Wiley‐Liss,Inc.
Calcium dependence of differentiation of GABA immunoreactivity in spinal neurons
Authors: Spitzer Nicholas C. , Debaca Rosario C. , Allen Keith A. , Holliday Janet
Published: January 2005

The developmental regulation of neurotransmitter synthesis has been extensively studied and appears in many cases to depend on electrical activity. The central nervous system of the Xenopus embryo and young larva is an attractive subject for such studies, since action potentials first elicited from Xenopus spinal neurons at the time of closure of the neural tube are long in duration and calcium‐dependent. Moreover, cells exhibit spontaneous elevations of intracellular calcium during this early period as a consequence of calcium influx through voltage‐dependent channels, which induces calcium release from intracellular stores. Since the early differentiation of Xenopus spinal neurons in dissociated cell culture parallels development in vivo, we have examined the maturation of γ‐aminobutyric acid (GABA) immunoreactivity in cultured neurons and explored its dependence on spontaneous calcium influx at early stages of development. We find that specific GABA immunoreactivity develops in spinal neurons in dissociated cell culture with the same time course previously defined in vivo. Additionally, this process requires calcium influx that occurs spontaneously through voltage‐dependent channels. The appearance of GABA immunoreactivity is blocked by transcriptional inhibitors. The early appearance of GABA raises the possibility that it may play additional roles at early stages of development. © 1993 Wiley‐Liss,Inc.
Distribution of the inositol 1,4,5‐trisphosphate receptor, P400, in adult rat brain
Authors: Rodrigo J. , Suburo A. M. , Bentura M. L. , Fernández T. , Nakade S. , Mikoshiba K. , Martínez‐Murillo R. , Polak J. M.
Published: January 2005

The distribution of the inositol 1,4,5‐trisphosphate receptor protein, P400, was investigated in adult rat brain by immunocytochemistry with the monoclonal antibody 4C11 raised against mouse cerebellar inositol 1,4,5‐trisphosphate receptor protein. Immunoreactive neuronal cell bodies were detected in the cerebral cortex, the claustrum, the endopiriform nucleus, the corpus callosum, the anterior olfactory nuclei, the olfactory tubercle, the nucleus accumbens, the lateral septum, the bed nucleus of the stria terminalis, the hippocampal formation, the dentate gyrus, the caudate‐putamen, the fundus striatum, the amygdaloid complex, the thalamus, the caudolateral part of the hypothalamus, the supramammillary nuclei, the substantia nigra, the pedunculopontine tegmental nucleus, the ventrotegmental area, the Purkinje cells in the cerebellum, the dorsal cochlear nucleus, the subnucleus oralis and caudalis of trigeminal nerve, and the dorsal horn of the spinal cord. Immunoreactive fibres were found in the midial forebrain bundle, the globus pallidus, the stria terminalis, the pyramidal tract, the spinal tract of trigeminal nerve, and the ventral horn of spinal cord. Nerve fibres forming a dense plexus ending in terminal‐like boutons were detected in relation to nonimmunoreactive neurons of the dentate, interpositus, and fastigial nuclei of the cerebellum and around neurons of the vestibular nuclei. This receptor protein binds a specific second messenger, inositol 1,4,5‐trisphosphate, which produces a mobilization of intracellular Ca2+ and a modulation of transmitter release. © 1993 Wiley‐Liss, Inc.
Distribution and characterization of tumor necrosis factor‐α‐like immunoreactivity in the murine central nervous system
Authors: Breder Christopher D. , Tsujimoto Masafumi , Terano Yoshitake , Scott Donald W. , Saper Clifford B.
Published: January 2005

Tumor necrosis factor‐α (TNFα) is a protein released from macrophages during infection and inflammation. Recent studies suggest that it has several effects within the central nervous system, including generation of fever, enhancement of slow wave sleep, and stimulation of pituitary hormone secretion. We have proposed that TNFα may be synthesized by neurons in the CNS and used as a neuromodulator in the pathways involved in the central control of these activities. To test this hypothesis, we have used an antiserum raised against recombinant murine (rm) TNFα with an indirect immunoperoxidase technique to stain the murine CNS immunohistochemically. Western blot analysis of mouse brain homogenates revealed one band with electrophoretic mobility identical to that of rmTNFα. We identified TNFα‐like immunoreactive (ir) neurons in the hypothalamus, in the bed nucleus of the stria terminalis, in the caudal raphe nuclei, and along the ventral pontine and medullary surface. TNFαir innervation was widespread within the CNS, particularly in areas involved in autonomic and endocrine regulation, including the hypothalamus, amygdala, bed nucleus of the stria terminalis, parabrachial nucleus, dorsal vagal complex, nucleus ambiguus, and thoracic sympathetic preganglionic cell column. Our data suggest that TNFα may serve as a neuromodulator in central pathways involved in the regulation of the autonomic, endocrine and behavioral components of the acute‐phase response to inflammation and infection. © 1993 Wiley‐Liss,Inc.
Heterogeneous distribution of glycinergic and GABAergic afferents on an identified central neuron
Authors: Triller Antoine , Sur Cyril , Korn Henri
Published: January 2005

Immunocytochemical methods were used on serial sections to study the glycine‐ and gamma‐amino butyric acid (GABA)ergic innervations of the teleost Mauthner (M) cell. We found different distributions for the boutons containing the two amino acids. Endings filled with GABA predominate on the distal portion of the lateral dendrite (LD) while glycine‐positive profiles are more abundant on the soma and within the axon cap (AC), a specialized neuropil surrounding the M‐cell initial segment. A few endings containing both transmitters are present on the soma and on the small dendrites issuing ventrally from it. At this level some glutamic acid decarboxylase (GAD) containing boutons face glycine receptor‐93 kD‐associated protein, an observation suggesting that the associated glycine functions as a neurotransmitter. Elsewhere on the M‐cell, where glycine and GABA are not colocalized, GAD‐positive profiles were never observed in front of postsynaptic differentiations with 93 kD labelling. GABA was detected in the small vesicle boutons (SVBs), most of them, following the classification of Tuttle et al., J. Comp. Neurol. 265:254–274, 1987, belonging to the A‐type, while glycine was found in the unmyelinated club endings in the AC, and in C‐ and B‐type SVBs, outside this region. All terminals established symmetrical synapses and were filled with a population of pleiomorphic vesicles. Boutons with GABA also contained numerous dense‐core vesicles suggesting the presence of an associated peptide(s). A quantitative study of the transmitter content based on the number of the gold particles revealed a variable intensity of the labelling over certain profiles. For GABA, it was maximum at the tip of the LD and it decreased proximally. In contrast, the staining density was constant for glycine along all parts of the cell, except for the ventral dendrite (VD) where it decreased progressively. Taken together, these data suggest that the amino acid content varies, depending upon the location of the synapses on their target neuron. 1993 Wiley‐Liss, Inc. © 1993 Wiley‐Liss, Inc.
Development of the hamster serotoninergic system: Cell groups and diencephalic projections
Authors: Botchkina G. I. , Morin Lawrence P.
Published: January 2005

Nuclei of the circadian visual system are extensively innervated by serotoninergic neurons and rhythmicity is modulated by the serotoninergic system. This study investigated the temporal relationships between prenatal origins of serotoninergic cell groups and perinatal innervation of structures in the hamster circadian visual system as well as in the remaining diencephalon. Serotonin‐immunoreactive (5‐HT‐IR) neurons of the B4‐B9 complex were first seen on embryonic day 8 (E8). The number of neurons increases sharply by E10 when the first 5‐HT‐IR cells are evident in the medulla (B1–B3 complex). The distribution of serotoninergic neurons in the hamster brainstem is generally adult‐like by E14. Thick 5‐HT‐IR fibers arch around the mesencephalic flexure at E10 and reach more rostral mesencephalic areas at E11.A branch of the medial forebrain bundle (MFB) projects ventrally toward the retrochiasmatic area; a second branch ascends along the fasciculus retroflexus. Fibers cross the midline in the supraoptic commissure by E12, others arrive in the lateral geniculate region, and a branch of the MFB extends toward the mammillary area. At E13, a periventricular medial thalamic branch of the MFB is seen, axons appear in the supramammillary commissure, and a fine fasciculus between the medial thalamus and intergeniculate leaflet is visible. Lateral, paraventricular, and retrochiasmatic hypothalamic areas and centro‐ and dorsomedial thalamus are densely innervated at E14. The mammillary area and lateral geniculate body are moderately innervated, and the first fibers appear in the deep laminae of the superior colliculus. The innervation of the suprachiasmatic nuclei, periventricular hypothalamus, and superficial layers of the superior colliculus occurs postnatally. The results are consistent with serotoninergic system development in other species. © 1993 Wiley‐Liss, Inc.
Efferent projections of the sexually dimorphic area of the gerbil hypothalamus: Anterograde identification and retrograde verification in males and females
Authors: Finn Patricia D. , De Vries Geert J. , Yahr Pauline
Published: January 2005

Outputs of the sexually dimorphic area (SDA) of the gerbil hypothalamus were identified by injecting Phaseolus vulgaris‐leucoagglutinin into the medial or lateral SDA (mSDA, ISDA) in males and females. They were verified by injecting Fluoro‐Gold or rhodamine‐labeled beads into over half the areas that contained labeled fibers. Both anterograde and retrograde tracing showed that the mSDA and ISDA project to many of the same sites but often to differing degrees. The mSDA projects more heavily than the ISDA to many of their forebrain targets including the ventral part of the lateral septal nucleus, the bed nucleus of the stria terminalis, the medial tuberal area, and the anteroventral periventricular, arcuate, ventromedial and ventral premammillary nuclei of the hypothalamus. The ISDA projects more heavily than the mSDA to many of their mid‐ and hindbrain targets including the caudal, ventrolateral part of the periaqueductal gray, the retrorubral field, the pedunculopontine tegmental nucleus, and the locus coeruleus. In many other areas of the brain, the projections of the mSDA and ISDA are similar in size. These areas include the substantia innominata, the vascular organ of the lamina terminalis, the anterior amygdela, the posterior hypothalamus, the reuniens and paraventricular nuclei of the thalamus, and the pontine periaqueductal gray lateral to the fourth ventricle. The SDA pars compacta (SDApc), a small cell group embedded in the mSDA of males, projects to many fewer areas than the surrounding mSDA. It was strongly labeled when retrograde tracers were injected into the encapsulated part of the bed nucleus of the stria terminalis, the anteroventral periventricular nucleus, or the mSDA. It was also labeled from the vascular organ of the lamina terminalis, the caudal part of the lateral bed nucleus of the stria terminalis, the ISDA, the area lateral to the mSDA, the arcuate nucleus, the ventral premammillary nucleus, and the ventrolateral part of the ventromedial nucleus of the hypothalamus. Nothing resembling an SDApc was identified during retrograde tracing in females. © 1993 Wiley‐Liss, Inc.
Spinal cord and trigeminal projections to the pontine parabrachial region in the rat as demonstrated with Phaseolus vulgaris leucoagglutinin
Authors: Slugg Robert M. , Light Alan R.
Published: January 2005

In order to determine the regions within the parabrachial nucleus that receive synaptic input from nociceptive regions of the spinal cord and medulla in the rat, we analyzed the “Golgi‐like” labeling produced by anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA‐L) from discrete iontophoretic injections confined to either the superficial dorsal horn of the lumbar spinal cord or to the superficial dorsal horn of the trigeminal nucleus at the level of the obex. Labeled fibers from both the spinal cord and the medulla ascended through the ventral lateral pons and coursed with the ventral spinocerebellar tract toward the parabrachial nuclei. Spinal cord injections led to labeling of fine caliber fibers and en passant and terminal enlargements in the rostral part of the contralateral lateral parabrachial nucleus (PBL), mostly in the central lateral and dorsal lateral subnuclei. Medullary injections revealed fiber and enlargement labeling primarily in the ipsilateral caudal PBL, mostly in the central lateral, external lateral, and medial subnuclei. Injections in both regions resulted in labeled terminations in the Kö;lliker‐Fuse nucleus. These results indicate that the nociceptive regions of the spinal cord and medulla terminate in regions of the parabrachial nucleus that have been associated with autonomic functions because of their interconnections with the hypothalamus, brainstem cardiovascular and respiratory control centers, and the amygdala. © 1994 Wiley‐Liss, Inc.
Development of the dendritic fields of layer 3 pyramidal cells in the kitten's visual cortex
Authors: Zec Nataša , Tieman Suzannah Bliss
Published: January 2005

The cat's visual cortex is immature at birth and undergoes extensive postnatal development. For example, cells of layers 2 and 3 do not complete migration until about 3 weeks after birth. Despite the importance of dendritic growth for synaptic and functional development, there have been few studies of dendritic development in the cat's visual cortex to correlate with numerous studies of functional and synaptic development. Accordingly, we used the Golgi method to study the development of the dendrites of layer 3 pyramidal cells in the visual cortex of a series of cats ranging in age from 2 days to 3 years. Blocks of visual cortex were impregnated by the Golgi‐Kopsch method and sectioned in the tangential plane. Layer 3 pyramidal cells were drawn with a camera lucida and analyzed by Sholl diagrams and vector addition. In kittens < 1 week old, these cells were very immature, with only an apical dendrite and no basal dendrites. Basal dendrites appeared during the second week. By 2 weeks, all of the basal dendrites had emerged from the soma, but they had few branches and were tipped with growth cones. By 4 weeks, they had finished branching but continued to grow in length until, by 5 weeks, they reached their adult size. Examination of the basal dendritic fields in the tangential plane revealed that the dendritic fields were more elongated at 2 weeks than at later ages, perhaps because of their smaller size. The distribution of dendritic field orientations was uniform at all ages except 3 and 4 weeks, when there was a preponderance of fields oriented in the rostrocaudal direction. Because dendritic growth and branching occurred very rapidly over a period that precedes and overlaps with the peak periods of synaptogenesis and of sensitivity to the effects of early visual experience, they may depend on afferent visual activity. The early emergence of primary dendrites, however, suggests that this process is independent of afferent activity. The coincident timing of dendritic branching with the presence of dendritic growth cones suggests that branching may occur at growth cones. © 1994 Wiley‐Liss, Inc.
Pyramidal neurons in layer 5 of the rat visual cortex. III. Differential maturation of axon targeting, dendritic morphology, and electrophysiological properties
Authors: Kasper Ekkehard M. , Lübke Joachim , Larkman Alan U. , Blakemore Colin
Published: January 2005

This paper describes the early morphological and physiological development of pyramidal neurons in layer 5 of the rat visual cortex in relation to the targets chosen by their axons. Cells were prelabeled by retrograde transport from the superior colliculus or the contralateral visual cortex and intracellularly injected either in fixed slices or after recording in living slices. In the adult, corticotectal cells have thick apical dendrites with an extensive terminal arborization extending into layer 1, and fire characteristic bursts of action potentials when injected with a depolarizing current; interhemispheric cells have slender apical dendrites that terminate without a terminal tuft, usually in layer 2/3, and they display a more regular firing pattern (Kasper et al.: J Comp Neurol, this issue, 339:459–474). At embryonic day E18 (when axons of the two classes of cells are already taking different routes towards their targets) and E21, pyramidal‐like cells throughout the cortical plate all have similar soma‐dendritic morphology, with spindle‐shaped cell bodies and few, short basal dendrites but apical dendrites that all end in distinct tufts in the marginal zone. At postnatal day P3, after the axons of both cell classes have reached their targets, all pyramidal neurons in layer 5 still have distinct terminal in distinct tufts in the marginal zone. At postnatal day P3, after the axons of both cell classes have reached their targets, all pyramidal neurons in layer 5 still have distinct terminal arborizations in layer 1, though they vary in complexity and extent. The somata are now more mature (round to ovoid in shape), and the basal dendritic tree has extended. As early as P5, all cells studied could be clearly classified as tufted or untufted (considerably earlier than previously reported; Koester and O'Leary: J Neurosci 12:1382, '92), and these features correlated precisely with the projection target, as in the adult. Measurement showed that although interhemispheric cells lose their terminal tufts, in general the trunks of their apical dendrites do not withdraw but continue to grow, at roughly the same rate as those of corticotectal cells. The two classes of layer 5 pyramidal neurons differentiate from each other in three distinct phases: pathway selection by axons precedes the loss of the apical tuft by interhemispheric cells, and these morphological characteristics are established 10 days before the onset of burst‐firing in corticotectal cells. These three steps may be guided by different molecular signals. © 1994 Wiley‐Liss, Inc.
Distribution of cytochrome oxidase and parvalbumin in the primary visual cortex of the adult and neonate monkey, Callithrix jacchus
Authors: Spatz W. B. , Illing R.‐B. , Weisenhorn D. M. Vogt
Published: January 2005

The anatomical distributions of the mitochondrial enzyme cytochrome oxidase (CO) and of the calcium binding protein parvalbumin (PV) were studied in the striate cortex of adult and neonate New World monkeys (Callithrix jacchus). In the adult marmoset, both proteins were found in laminar arrangements similar to those described for the macaque monkey, with prominent bands of PV‐like immunoreactive (PV‐LI) puncta in layers IV and IIIb, and fairly evenly distributed PV‐LI nonpyramidal neurons. Furthermore, the pattern of CO activity in area 17 of the neonate marmoset was almost identical to the CO pattern described in neonate macaque and squirrel monkeys. It came, therefore, as a surprise to find that the adult pattern of PV‐like immunoreactivity (PV‐LI) in the marmoset striate cortex arises from a neonatal pattern strikingly different from that seen in any developmental stage of the macaque, or in any other mammal studied so far. In the deep layers IV through VI of the neonate marmoset, a large number of PV‐LI neurons was stained in bandlike patterns, their number in layers IV and V exceeding the number of PV‐LI neurons present in these layers of the adult marmoset area 17. Staining of layers IV and VI was restricted to area 17 and involved nonpyramidal cells and their exceeding the number of PV‐LI neurons present in these layers of the adult marmoset area 17. Staining of layers IV and VI was restricted to area 17 and involved nonpyramidal cells and their processes. The stained band of layer V, in contrast, continued throughout most of the neocortex. In area 17, an estimated 10 to 20% of the stained cells in layer V exhibited pyramidal shapes. The findings show that the expression of PV by visual cortical cells occurs before birth and suggest that the comparatively early onset of PV expression is not dependent on the onset of textured vision. The exuberant number of stained cells in some layers, and particularly the staining of pyramidal cells, in the neonate marmoset, suggest that a considerable number of cells possesses the stainability for PV‐LI only transiently, i.e., in the marmoset, these cells have a specific demand for parvalbumin during this phase of their development. © 1994 Wiley‐Liss, Inc.
Morphology of GABAergic neurons in the inferior colliculus of the cat
Authors: Oliver Douglas L. , Winer Jeffery A. , Beckius Gretchen E. , Marie Richard L. Saint
Published: January 2005

The goal of the present study was to provide a comprehensive and quantitative description of neurons immunoreactive for γ‐aminobutyric acid (GABA) in the inferior colliculus (IC) of the cat. Neurons were investigated with two different antisera and two different incubation methods. Free‐floating frozen or vibratome‐cut sections were incubated either with an antiserum to glutamic acid decarboxylase (GAD) or to GABA conjugated to protein with glutaraldehyde. Additional 1.5‐μm‐thick sections were incubated with the GABA antiserum after embedding and removal of the plastic. Quantitative data were obtained from much of this material. Despite the use of these different antisera and reaction methods, the results obtained were remarkably similar.

The results show that GAD‐ or GABA‐positive neurons represent a significant population of cells in the central nucleus of the IC, up to 20% of the neurons. Most of these neurons have large or medium‐sized perikarya. In contrast, immunonegative neurons are medium‐sized or small. Many GABA‐positive neurons had proximal dendrites or somata oriented in parallel to the fibrodendritic laminae of the central nucleus and are presumed to be disc‐shaped neurons. Others have an orthogonal orientation and are presumed to be stellate cells. Large GABA‐positive neurons form two groups, those with many axosomatic endings and those with few. Collectively, these observations suggest that there are several types of GABAergic neuron in the central nucleus and, by extension, that these may participate in many types of inhibitory circuits. © Wiley‐Liss, Inc.
The ontogeny of GAP‐43 (neuromodulin) mRNA in postnatal rat brain: Evidence for a sex dimorphism
Authors: Shughrue Paul J. , Dorsa Daniel M.
Published: January 2005

GAP‐43 is a membrane‐bound protein selectively concentrated in axonal growth cones during brain development and implicated in axonal outgrowth and elongation. A sex dimorphism in the number of synapses in certain regions of the adult rat brain has been attributed to differences in gonadal steroid hormone action during early postnatal life. The results of recent studies have demonstrated that gonadal steroids modulate GAP‐43 mRNA in regions of the postnatal and adult brain where steroid hormone receptors are concentrated. Since gonadal steroids influence the development of the sexually undifferentiated brain during the first few weeks of postnatal life, the present study investigated the ontogeny of GAP‐43 mRNA in the male and female rat brain between postnatal days 1 and 25. On postnatal days 1, 3, 6, 12, 18, and 25, brains were collected from male and female postnates and frozen, and 16 μm cryostat sections were processed and hybridized with a 35S‐labeled antisense riboprobe complementary to GAP‐43 mRNA. Evaluation of film autoradiograms demonstrated a widespread distribution of GAP‐43 mRNA in postnatal brain regions, including the cerebral cortex; bed nucleus of the stria terminalis; and medial preoptic area, ventromedial nucleus, and arcuate nucleus of the hypothalamus. Densitometric measurements revealed that GAP‐43 mRNA was transiently elevated during early postnatal life, with a subsequent decrease during brain maturation, although the pattern of change varied among the brain regions investigated. In addition, the level of GAP‐43 hybridization signal was significantly higher in the male cortex, bed nucleus, and medial preoptic nucleus, but not the ventromedial and arcuate nuclei, than in postnatal females. Analysis of slide autoradiograms demonstrated that the change in GAP‐43 mRNA during postnatal development was due to changes at the cellular level. The present results indicate that expression of GAP‐43 mRNA is transiently elevated and sexually dimorphic in certain regions of the early postnatal rat brain. The results further suggest that the differential expression of GAP‐43 in the male and female postnatal brain may be related to sex differences in neuronal outgrowth and connectivity resulting in a dimorphism in the pattern of adult neuronal circuitry. © Wiley‐Liss, Inc.
Pattern formation in the developing superior colliculus: Ontogeny of the periodic architecture in the intermediate layers
Authors: Illing R.‐B. , Graybiel A. M.
Published: January 2005

The superior colliculus of mammals contains a striking neurochemical architecture in which histochemically identifiable compartments are distributed in an iterative arrangement in the intermediate layers. We used stains for acetylcholinesterase activity as a compartment marker to trace ontogenesis of this architecture during pre‐ and postnatal development in the domestic cat. We found that compartmentation in the intermediate collicular layers is virtually absent at birth, and only gradually emerges during the first weeks of postnatal life. Over the same postnatal period, acetylcholinesterase activity shifts from a predominantly perikaryal expression pattern immediately postnatally to a nearly exclusive localization in the neuropil at maturity.

Remarkably, a striking compartmentation of the superior colliculus was readily apparent with acetylcholinesterase histochemistry prenatally. The first appearance of a periodic architecture in the superior colliculus was observed at embryonic day 34, a time at which the collicular plate had not yet become laminated. The compartments characterized by high levels of acetylcholinesterase activity then gained in prominence until late in the prenatal period, when they receded and disappeared. The loss of the acetylcholinesterase‐positive compartments in the perinatal period did not reflect a loss of compartmentation altogether. Neonatally, there was a distinct compartmental architecture visible with enkephalin immunohistochemistry. The virtual absence of acetylcholinesterase‐positive compartments in the superior colliculus at birth therefore reflects developmental regulation of enzyme expression in the compartments, not regulation of the compartments as structural entities. We conclude that the periodic architecture, which characterizes the intermediate collicular layers in the adult cat, arises early in ontogenesis. These observations raise the possibility that the histochemical compartments are ontogenetic units that undergo remodeling as the superior colliculus matures. © Wiley‐Liss, Inc.
Direct projections from the non‐laminated divisions of the medial geniculate nucleus to the temporal polar cortex and amygdala in the cat
Authors: Shinonaga Yasuhide , Takada Masahiko , Mizuno Noboru
Published: January 2005

The medial geniculate nucleus (MG) is well known to send projection fibers not only to the auditory cortex, but also to the limbic structures of the forebrain including the perirhinal cortex and amygdala. In the cat, the non‐laminated portions of the MG are also known to project to the amygdala, as well as to the auditory cortical areas surrounding the primary auditory area. On the other hand, projections from the non‐laminated MG to the limbic cortical areas have not so far been studied systematically. Thus, in the present study, direct projections from the non‐laminated portions of the medial geniculate nucleus to the temporal polar cortex and amygdala were examined in the cat by retrograde and anterograde tract‐tracing techniques. The temporal polar cortex is the ventral polar region of the posterior sylvian and posterior ectosylvian gyri, which is located dorsal to the posterior rhinal sulcus and includes the ectorhinal area. After injection of cholera toxin B subunit into the temporal polar cortex, retrogradely labeled neurons were seen in the caudal two‐thirds of the medial geniculate nucleus ipsilateral to the injection; they were distributed in the non‐laminated portions of the MG (the dorsal and medial divisions and the ventromedial part of the ventral division), but not in the laminated portion (the principal part of the ventral division). These findings were confirmed by injecting Phaseolus vulgaris leucoagglutinin into each division of the MG. After the injection into each non‐laminated division, terminal labeling was observed in the temporal polar cortex. Terminal labeling was further found in the lateral amygdaloid nucleus ipsilateral to the injection. Then, cholera toxin B subunit was injected into the lateral amygdaloid nucleus; retrogradely labeled neurons were observed ipsilaterally in the non‐laminated portions of the MG, as well as in the temporal polar cortex.

The results indicate that the non‐laminated portions of the MG send projection fibers to the temporal polar cortex and lateral amygdaloid nucleus, and that the non‐laminated portions of the MG and temporal polar cortex give rise to overlapping projections to the lateral amygdaloid nucleus. These connections appear to constitute neuronal links in “emotional” and/or “motivational” circuitry in the forebrain. © Wiley‐Liss, Inc.
Development of lateral line organs in the axolotl
Authors: Northcutt R. Glenn , Catania Kenneth C. , Criley Bruce B.
Published: January 2005

Lateral line sensory receptors and their cranial nerves in axolotls arise from a dorsolateral series of placodes, including the octaval placode, that gives rise to the inner ear and the octaval nerve. Anterodorsal and anteroventral placodes occur rostral to the octaval placode and give rise to anterodorsal and anteroventral lateral line nerves and electroreceptors and mechanoreceptors of the snout, cheek, and lower jaw. Middle, supratemporal, and posterior placodes occur caudal to the octaval placode and give rise to similarly named lateral line nerves, electroreceptors and mechanoreceptors of the occipital region of the head, and trunk neuromasts.

All placodes, except the posterior placode, elongate, forming sensory ridges, following the genesis of sensory ganglia. Primary mechanoreceptor primordia begin to form within the central zone of the sensory ridges at stage 36; primary electroreceptor primordia originate within the lateral zones of these ridges at stage 38. The first primary mechanoreceptors erunt during stage 37; all primary mechanoreceptors have erupted at hatching (stage 41). Primary electroreceptors begin to erupt at stage 43. Secondary mechanoreceptor primordia begin to form in 1‐week‐old larvae and erupt 1–2 weeks later. Secondary electroreceptor primordia also begin to form in 1‐week‐old larvae and continue until clusters of two to five electoreceptors are formed.

The developmental stages thought to characterize lateral line placodes in the earliest gnathostomes suggest that this ancestral ontogeny has been truncated in modern amphibians, and ontogenetic mechanisms underlying placodal differentiation are suggested. © Wiley‐Liss, Inc.
Development of fungiform papillae, taste buds, and their innervation in the hamster
Authors: Whitehead Mark C. , Kachele Diane L.
Published: January 2005

Fungiform taste buds in mature hamsters are less subject to neurotrophic influences than those of other species. This study evaluates taste‐bud neurotrophism during development in hamsters by examining the relation between growing nerves and differentiating fungiform papillae. Chorda tympani (CT) or lingual (trigeminal) nerve (LN) fibers were labelled with Lucifer Yellow as they grew into (CT fibers) or around (LN fibers) developing taste buds. Developing fungiform papillae and taste pores were counted with the aid of a topical tongue stain.

The tongue forms on embryonic days (E) 10.5–11 and contains deeply placed CT and LN fibers but no papillae. By E12, the tongue epithelium develops scattered elevations. These “eminences” selectively become innervated by LN fibers that grow to the epithelium earlier and in larger numbers than CT fibers. Definitive fungiform papillae form rapidly during E13–14 and become heavily innervated by LN fibers. Intraepithelial CT fibers, rare at E13, invariably innervate fungiform papillae containing nascent taste buds at E14. During E14–15 (birth = E15–16), most papillae contain taste buds with pores, extensive perigemmal LN innervation, and extensive intragemmal CT innervation. At birth, numbers of fungiform papillae and taste pores are adultlike.

The results show that fungiform eminences begin forming in the absence of innervation. The subsequent differentiation of definitive fungiform papillae and their innervation by LN fibers occur synchronously, prior to the differentiation of taste buds and their CT innervation. The hamster is precocious (e.g., compared to rat) in terms of LN development and the structural maturity of the anterior tongue at birth. © Wiley‐Liss, Inc.
Blockade of NMDA receptors increases cell death and birth in the developing rat dentate gyrus
Authors: Gould Elizabeth , Cameron Heather A. , McEwen Bruce S.
Published: January 2005

Excitatory input regulates cell birth and survival in many systems. The granule cell population of the rat dentate gyrus is formed primarily during the postnatal period. Excitatory afferents enter the dentate gyrus and begin to form synapses with granule cells during the first postnatal week, the time of maximal cell birth and death. In order to determine whether excitatory input plays a role in the regulation of cell birth and survival in the developing granule cell layers and their germinal regions, the subependymal layer and hilus, we treated rat pups with the N‐methyl D‐aspartate (NMDA) receptor antagonists MK‐801, CGP 37849, or CGP 43487 during the first postnatal week and examined the numbers of 3H‐thymidine‐labeled cells, pyknotic cells, and healthy cells in these regions. In order to determine the cell type that was affected, sections from brains of MK‐801‐treated rats were processed for 3H‐thymidine autoradiography combined with immunohistochemistry for the marker of radial glia, vimentin, and the marker of mature astrocytes, glial fibrillary acidic protein (GFAP).

Within the dentate gyrus, NMDA receptor blockade resulted in the following changes: (1) the density of 3H‐thymidine‐labeled cells was increased, (2) the density of pyknotic cells was increased, (3) the density of 3H‐thymidine‐labeled pyknotic cells was increased, and (4) the density of healthy cells was decreased. The infrapyramidal blade/hilus showed changes throughout its extent, whereas the suprapyramidal blade showed changes only at the rostral level. No change in the numbers of 3H‐thymidine‐labeled vimentin‐immunoreactive or GFAP‐immunoreactive cells was observed in the dentate gyrus with MK‐801 treatment, indicating that glia are not primarily affected by NMDA receptor blockade.

Blockade of NMDA receptors resulted in gross morphologic changes in the dentate gyrus; in most cases, the infrapyramidal blade was indistinguishable from the hilus. Moreover, in several brains of animals treated with CGP 37849 or CGP 43487 on postnatal day (P)5, an abnormal aggregation of cells was observed ventral to the normal location of the infrapyramidal blade. This cellular cluster contained many pyknotic and 3H‐thymidine‐labeled cells and may represent cells that normally comprise the infrapyramidal blade. Dramatic changes to the subependymal layer were also seen following NMDA receptor blockade. The cross‐sectional area of this region was significantly increased with MK‐801, CGP 37849, or CGP 43487 treatment and contained a high density of 3H‐thymidine‐labeled cells and 3H‐thymidine‐labeled pyknotic cells.

These results indicate that NMDA receptor activation is critical for the normal development of the rat dentate gyrus. The finding that blockade of NMDA receptors resulted in increased levels of cell death and birth supports the hypothesis that NMDA receptor activation is a natural signal for the inhibition of these processes in the developing dentate gyrus. © Wiley‐Liss, Inc.
Distribution of primary afferent fibers projecting from hindlimb cutaneous nerves to the medulla oblongata in the cat and rat
Authors: Ueyama Teizo , Houtani Takeshi , Ikeda Michiko , Sato Kazuo , Sugimoto Tetsuo , Mizuno Noboru
Published: January 2005

The dorsal column nuclear complex, one of the most important relays for tactile perception, has well been known to be somatotopically organized. Topographical arrangements of terminal sites of individual cutaneous nerves within the dorsal column nuclei, however, have not been examined systematically, although many studies have been done upon primary afferents to the medulla oblongata, including the dorsal column nuclear complex. Thus, in the present study, distribution of primary afferent fibers projecting from the hindlimb cutaneous nerves to the medulla oblongata was examined in the cat and rat by means of the transganglionic transport method with horseradish peroxidase. Cutaneous primary afferent fibers projecting from the hindlimb to the medulla oblongata were distributed mainly in the ipsilateral gracile nucleus. Terminal labeling in the gracile nucleus was seen at all rostrocaudal levels of the nucleus, occasionally including the nuclear part straddling the midline (the median or accessory nucleus). The labeled axon terminals in the gracile nucleus were more densely distributed in the middle and caudal parts of the nucleus than in the rostral part. Although the fields of termination of the hindlimb cutaneous nerves overlapped in the gracile nucleus, the foci of the terminal labeling of the nerves innervating the distal parts of the hindlimb were located more medially or dorsomedially than those of the nerves innervating the proximal parts. Terminal labeling was further found in a small zone immediately medial to the rostromedial border of the external cuneate nucleus. This hitherto undescribed zone (U zone) contained a small cluster of medium‐sized neurons in the cat. Although no particular cell cluster was found in the U zone of the rat, convergence of the primary afferent fibers of the cutaneous nerve from the hindlimb appeared to occur as in the U zone of the cat.
Neurons of the medial cortex outer plexiform layer of the lizard Podarcis hispanica: Golgi and immunocytochemical studies
Authors: de la Iglesia J. A. Luis , Martinez‐Guijarro F. J. , Lopez‐Garcia C.
Published: January 2005

The study of Golgi‐impregnated lizard brains has revealed a scarce but heterogeneous neuronal population in the outer plexiform layer of the medial cortex. Some of the neuronal types detected here resemble the neurons of the dentate molecular layer of the mammalian hippocampus.

According to their morphology, five intrinsic neuronal types have been clearly identified: short axon aspinous bipolar neuron (type 1, or sarmentous neuron), short axon aspinous juxtasomatic neuron (type 2, or coral neuron), short axon sparsely spinous multipolar neuron (type 3, or stellate neuron), short axon sparsely spinous juxtasomatic multipolar neuron (type 4, or deep stellate neuron, and sparsely spinous juxtasomatic horizontal neuron (type 5, or couchant neuron).

Most neuronal types were identified as γ‐aminobutyric acid (GABA) and parvalbumin immunoreactive, and are thus probably involved in medial cortex inhibition. Moreover, a small fraction of them displayed ß‐endorphin immunoreactivity.

The distribution of these neuronal types is not uniform in the laminae of the outer plexiform layer. Type 1 (sarmentous) and type 3 (stellate) neurons overlap the axonal field projection coming from the dorsal cortex and the thalamus, whereas types 4 (deep stellate) and 5 (couchant) neurons overlap ipsi‐ and contralateral dorsomedial projection fields as well as raphe serotoninergic and opioid immunoreactive axonal plexi. Thus, these neuronal types may be involved in the control of specific inputs to the medial cortex by presumably feed‐forward inhibition; nevertheless, feed‐back inhibition may also occur regarding type 4 (deep stellate) neurons that extend deep dendrites to the zinc‐rich bouton field.
Morphology of two classes of target‐specific bullfrog sympathetic preganglionic neurons
Authors: Peruzzi Daniel , Forehand Cynthia J.
Published: January 2005

These experiments took advantage of the unique ability to define target‐specific sympa‐thetic preganglionic neurons in the bullfrog spinal cord in order to examine the morphologies of different classes of preganglionic neurons. Sympathetic preganglionic neurons were identified by retrograde transport of fast blue from the sympathetic chain. Subsequently, fast blue‐labelled sympathetic preganglionic neurons in fixed spinal cord slices were filled with lucifer yellow and processed for visualization with lucifer yellow antiserum, biotinylated secondary antiserum, and avidin peroxidase. Target specificity of sympathetic preganglionic neurons was determined by anatomical position; sympathetic preganglionic neurons that control the vasculature (C‐type sympathetic preganglionic neurons) lie in a position caudal to those that control nonvascular targets [B‐type sympathetic preganglionic neurons; Horn and Stofer (1988) J. Comp. Neurol. 268:71].

These two classes of sympathetic preganglionic neurons have qualitatively similar morphologies. However, they exhibit significant quantitative differences in total dendritic length and the rostrocaudal extent of dendrites. These differences are likely to be associated with differences in the number of synapses received by these two classes of sympathetic preganglionic neurons. Moreover, the segmental control of sympathetic preganglionic neurons by descending brainstem projections is likely to be finer for those involved in vascular control than for those that influence other targets.