bluuebunny/crossref_metadata_2025 huggingface dataset:
Hair and supporting‐cell differentiation during the development of the avian inner ear
Authors: Goodyear Richard , Holley Matthew , Richardson Guy
Published: January 2005

Two monoclonal antibodies and serial section analysis have been used to compare the sites and times at which hair and supporting‐cells differentiate in various sensory regions of the chick inner ear during its development. A monoclonal antibody recognising the 275 kD hair‐cell antigen, a protein that is specifically associated with the apical surface of hair cells, was used to identify immature hair cells. Another monoclonal antibody, gm‐2, which stains the gelatinous membranes of the cochlear duct, sacculus, and utriculus and the epithelial supporting cells of all vestibular structures in the inner ears of early posthatch chicks, was used to detect the onset of supporting‐cell differentiation. Although the antigens recognised by the two antibodies are first detected almost simultaneously during the development of each sensory region, their appearance is not always exactly temporally coincident, and their order of appearance, when not coincident, varies between the epithelia but is always the same within any one organ. Also, when the two antigens are first present in any one region, there is not always a very precise overlap in their spatial distribution. These results cannot be explained entirely by a previously proposed model for hair and supporting‐cell development in which hair cells differentiate first and prevent undetermined, surrounding cells from becoming hair cells via lateral inhibition. Modified forms of the original model that can accommodate some of these observations are considered and discussed. © 1995 Willy‐Liss, Inc.
Innervation of the hard palate in the rat studied by anterograde transport of horseradish peroxidase conjugates
Authors: Arvidsson J. , Fundin B. T. , Pfaller K.
Published: January 2005

The innervation of the rat hard palate and the bordering part of the soft palate was studied after anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP) and to choleragenoid (B‐HRP) in separate experiments. WGA‐HRP labeling showed leakage from several types of nerve endings, whereas B‐HRP did not. Both conjugates gave rise to heavy labeling of a variety of nerve endings. Intragemmal and, especially, perigemmal fibers were labeled in chemosensory corpuscles, which were most common in the medial wall of the incisive canal and in the most anterior part of the soft palate. Ruffini endings of different sizes were labeled in the incisive papilla. Other subepithelial endings forming elongated expanded profiles with medium‐to large‐caliber source fibers were most common in protruding parts of the palate. Labeled intraepithelial endings included Merkel endings, which were most frequent in the incisive papilla and the rugae. Other labeled profiles were medium‐caliber afferents giving rise to irregular, beaded, and sometimes branched endings often located far superficially in the epithelium. Such endings were present both within and between protruding parts of the palate. Fine‐caliber intraepithelial endings were labeled almost exclusively in WGA‐HRP experiments. © 1995 Willy‐Liss, Inc.
Distribution of four types of synapse on physiologically identified relay neurons in the ventral posterior thalamic nucleus of the cat
Authors: Liu X.‐B. , Honda C.N. , Jones E.G.
Published: January 2005

This study was aimed at providing quantitative data on the thalamic circuitry that underlies the central processing of somatosensory information. Four physiologically identified thalamocortical relay neurons in the ventral posterior lateral nucleus (VPL) of the cat thalamus were injected with horseradish peroxidase and subjected to quantitative electron microscopy after pre‐ or postembedding immunostaining for γ‐aminobutyric acid to reveal synaptic terminals of thalamic inhibitory neurons.

The four cells all had rapidly adapting responses to light mechanical stimuli applied to their receptive fields, which were situated on hairy or glabrous skin or related to a joint. Their dendritic architecture was typical of cells previously described as type I relay cells in VPL, and they lacked dendritic appendages.

Terminals ending in synapses on the injected cells were categorized as RL (ascending afferent), F (inhibitory), PSD (presynaptic dendrite), and RS (mainly corticothalamic) types and were quantified in reconstructions of serial thin sections. RL and F terminals formed the majority of the synapses on proximal dendrites (approximately 50% each). The number of synapses formed by RL terminals declined on intermediate dendrites, but those formed by F terminals remained relatively high, declining to moderate levels (20–30%) on distal dendrites. RS terminals formed moderate numbers of the synapses on intermediate dendrites and the majority (< 60%) of the synapses on distal dendrites. Synapses formed by PSDs were concentrated on intermediate dendrites and were few in number (∼6%). They formed synaptic triads with F terminals and rarely with RL terminals. On somata, only a few synapses were found, all made by F terminals.

The total number of synapses per cell was calculated to be 5,584–8,797, with a density of 0.6–0.9 per micrometer of dendritic length. Of the total, RL terminals constituted approximately 15%, F terminals approximately 35%, PSD terminals approximately 5%, and RS terminals approximately 50%. These results provide the first quantitative assessment of the synaptic architecture of thalamic somatic sensory relay neurons and show the basic organizational pattern exhibited by representatives of the physiological type of relay neuron most commonly encountered in the VPL nucleus. © 1995 Wiley‐Liss, Inc.
Immunohistochemical identification of neurons in ganglia of the guinea pig sphincter of oddi
Authors: Wells David G. , Talmage Erin K. , Mawe Gary M.
Published: January 2005

The sphincter of Oddi is a smooth muscle sphincter that regulates the flow of bile into the duodenum. To identify potential chemical coding in sphincter of Oddi neurons, immunohistochemistry and histochemistry were employed to assay for putative neurotransmitters and related synthetic enzymes in wholemount preparations, with and without colchicine treatment. Immunoreactivities for enkephalin‐endorphin (ENK‐END), substance P (SP), nitric oxide synthase, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin generelated peptide (CGRP) were demonstrated within the ganglionated plexus. Roughly half of the neurons in the sphincter of Oddi expressed immunoreactivity for both SP and ENK‐END, but not for nitric oxide synthase. About 25% of the neurons expressed nitric oxide synthase immunoreactivity as well as NADPH‐diaphorase activity. This contingent of neurons was made up of two subgroups: one that expressed immunoreactivity for VIP, the other for NPY. Neurons that expressed CGRP immunoreactivity were sparse in sphincter of Oddi ganglia; however, many axons immunoreactive for both CGRP and SP were present in the ganglionated plexus. The CGRP/SP fibers are probably visceral afferents that may influence ganglionic output through axon reflex circuits. These results, along with studies of the actions of these neuroactive compounds on sphincter tone, support the view that ganglia of the sphincter of Oddi are largely comprised of excitatory (SP/ENK‐END‐immunoreactive) and inhibitory (nitric oxide synthase/VIP‐ or NPY‐immunoreactive) neurons, and that sphincter of Oddi tone is controlled by the regulation of the outputs of these two groups of cells. © 1995 Wiley‐Liss, Inc.
Insulin‐like growth factor‐1 mRNA is increased in deafferented hippocampus: Spatiotemporal correspondence of a trophic event with axon sprouting
Authors: Guthrie Kathleen M. , Nguyen Thomas , Gall Christine M.
Published: January 2005

Deafferentation is known to induce axonal sprouting in adult brain, but the signals that direct this response are not understood. To evaluate the possible roles of insulin‐like growth factor‐1 (IGF‐1) and basic fibroblast growth factor (bFGF) in central axonal sprouting, the present study used in situ hybridization to evaluate IGF‐1 and bFGF mRNA expression in entorhinal deafferented rat hippocampus. Alternate tissue sections were processed for Fink‐Heimer impregnation of axonal degeneration, Bandeiraea simplicifolia (BS‐1) labeling of microglia, and glial fibrillary acidic protein immunocytochemistry. In control hippocampus, IGF‐1 mRNA was localized to a few neurons, with no labeled cells in the dentate gyrus molecular layer; bFGF cRNA hybridization was diffuse in dendritic fields but was dense in CA2 stratum pyramidale. Both mRNA species were increased by deafferentation. The distribution of elevated IGF‐1 mRNA corresponded precisely to fields of axonal degeneration and was greatest in the dentate gyrus outer molecular layer and stratum lacunosum moleculare. In these fields, IGF‐1 mRNA was elevated by 2 days, reached maximal levels at 4 days, and declined by 10 days postlesion. Double labeling revealed that the majority of IGF‐1 cRNA‐labeled cells were microglia. In deafferented hippocampus, bFGF mRNA was broadly increased across fields both containing and lacking axonal degeneration. In the dentate, bFGF mRNA levels peaked at 5 days postlesion and remained elevated through 14 days. These results demonstrate that reactive microglia within deafferented hippocampal. Laminae express IGF‐1 mRNA just prior to and during the period of reactive axonal growth and suggest that IGF‐1 plays a role in directing the sprouting of spared afferents into these fields. © 1995 Wiley‐Liss, Inc.
Barrelfield of the prenatally X‐irradiated rat somatosensory cortex: A histochemical and electrophysiological study
Authors: Ito Muneyuki
Published: January 2005

The effect of prenatal X‐irradiation on the vibrissal cortical barrelfield of the brain of rats exposed to 200 R on the embryonic day 17 was studied morphologically and electrophysiologically. Cytoarchitectural barrels fail to appear in adult rats that have been subjected to this in utero treatment. However, sections cut in a plane tangential to the vibrissal cortex and examined for cytochrome oxidase (CO), a mitochondrial enzyme, contained a matrix of patterned CO activity which, albeit smaller and weaker in intensity, is similar to CO barrels in normal controls. Current source density analysis of cortical field potentials indicated that, as in the normal cortex, the earliest sink following peripheral stimulation appears in association with this high CO activity. These results suggest that the specific vibrissal thalamocortical pathway sets up an excitatory synaptic activity in the cortex of the irradiated animal. Efficacy of this route in eliciting postsynaptic spikes in the cortical output neurons was confirmed by recording extracellular spike responses to vibrissa displacements from layer Vb pyramidal neurons that were then injected intracellularly with horseradish peroxidase for later anatomical identification. © 1995 Wiley‐Liss, Inc.
Efferent connections of the lateral cortex of the lizard gekko gecko: Evidence for separate origins of medial and lateral pathways from the lateral cortex to the hypothalamus
Authors: Hoogland Piet V. , Vermeulen‐Vanderzee Eefke
Published: January 2005

The lateral cortex of the lizard Gekko gecko is composed of three parts: a dorsal and ventral part located rostrally and a posterior part located caudally. In order to obtain detailed information about the efferent connections of these lateral cortex subdivisions, iontophoretic injections of the anterograde tracers Phaseolus vulgaris leucoagglutinin and biotinylated dextran were made in the various parts. The main projection from the dorsal part terminates in the caudal part of the medial cortex. Other cortical projections were noted to the ipsi‐ and contralateral lateral cortex, the large‐celled part of the medial cortex, and the dorsal cortex. Additional fibers were found bilaterally in the anterior olfactory nucleus and the external amygdaloid nucleus. The ventral part of the lateral cortex projects mainly to the ipsilateral, posterior part of the dorsal ventricular ridge and the external amygdaloid nucleus. Minor contralateral projections to these nuclei were also found. Other projections were observed to travel to the caudal part of the medial cortex, to the nucleus sphericus, and bilaterally to the lateral cortex and the anterior olfactory nucleus.

The posterior part of the lateral cortex has similar efferent connections as the dorsal part and should be regarded as the caudal continuation of the dorsal part.

Because previous studies have shown that the medial cortex and the amygdaloid complex project to different hypothalamic areas, we conclude that the dorsal and ventral parts of the lateral cortex transmit olfactory information to separate hypothalamic areas that are probably involved with different types of behavior. © 1995 Wiley‐Liss, Inc.
Secretory pathways of neuropeptides in rat lumbar dorsal root ganglion neurons and effects of peripheral axotomy
Authors: Zhang Xu , Åman Katarina , Hökfelt Tomas
Published: January 2005

Using immunocytochemistry combined with confocal and electron microscopy, the secretory pathways related to substance P (SP), calcitonin gene‐related peptide (CGRP), galanin (GAL), and neuropeptide Y (NPY) were investigated in neurons in rat lumbar (L) 4 and L5 dorsal root ganglia (DRGs) before and after peripheral axotomy. All four peptides were processed through the regulated secretory pathway in many small neurons in normal DRGs, and CGRP through this pathway also in some large neurons. In many small neurons, two neuropeptides could be sorted into the same or separate large dense‐core vesicles (LDCVs). The LDCVs had a significantly larger diameter in small as compared to large DRG neurons. Fourteen days after sciatic nerve cut, the levels of SP‐ and CGRP‐like immunoreactivities (‐LIs) and the number of LDCVs containing these peptides were markedly reduced, but SP‐ and CGRP‐LIs were still seen in the regulated pathway. GAL‐LI was markedly increased in many small neurons and some large neurons and NPY‐LI mainly in large neurons. Both peptides were particularly abundant in the Golgi region. In small neurons, the number of LDCVs containing GAL‐ or NPY‐LI was increased, but did not appear to reach the numbers containing SP‐ or CGRP‐LI in normal DRG neurons. After axotomy, CGRP‐LI and GAL‐LI were often in separate LDCVs. One type of NPY‐positive large neurons showed budding off of LDCVs after axotomy, but also some “scattered” labeling in the cytoplasm. In the second type, NPY‐LI was mainly found in multivesicular bodies. In several myelinated nerve fibers a “diffuse” distribution of NPY was seen together with some LDCVs containing NPY‐LI. In contrast, in unmyelinated nerve fibers, NPY‐, GAL‐, SP‐, and CGRP‐LIs were always observed in LDCVs. Thus, both in normal and axotomized DRG neurons, peptides are processed through the regulated pathway. However, in some large neurons, NPY is, in addition, secreted through the constitutive pathway, perhaps as a consequence of limited sorting mechanisms for NPY, i.e., the plasticity of the secretory mechanisms does not match the rate of peptide synthesis after axotomy. © 1995 Wiley‐Liss, Inc.
Afferent reorganisation within the superior olivary complex of the gerbil: Development and induction by neonatal, unilateral cochlear removal
Authors: Russell F. Anne , Moore David R.
Published: January 2005

Cochlear removal in young animals has been shown to produce a variety of degenerative and generative effects within the auditory brainstem. A primary target for axons of neurons in the anteroventral cochlear nucleus (AVCN) is the superior olivary complex (SOC). Following unilateral cochlear removal in neonatal gerbils, AVCN neurons on the side of the removal die, and axons deriving from the AVCN on the unlesioned side produce new endings that innervate previously inappropriate target zones within the ipsilateral medial nucleus of the trapezoid body, both medial superior olives, and the contralateral lateral superior olive. In this study, we have used the anterograde transport of Dil and HRP from the AVCN to relate the formation of these endings to the time course of normal development in the gerbil brainstem. We have also examined the effects of cochlear removal at different ages, and survival to various ages after the removal, to define the time course for these generative phenomena. The results show that, while the major projection pathways from the AVCN to the SOC are in place at the time of birth, further and subtle development of AVCN terminal arbors occurs during the first postnatal week. This overlaps with the time during which cochlear removal produces the formation of exuberant afferents to the SOC from the intact AVCN. The exuberant afferents form through axon sprouting rather than through a suppression of normal, developmental regression. They appear to innervate tonotopically appropriate target regions within the SOC. The formation of the novel afferents begins within 3 days of the removal and appears to be complete within a further 5–7 days. By postnatal day (P) 10, both the normal development of the AVCN to SOC projection and the potential for alteration of that projection by removal of the contralateral. Cochlea appear to be over. These results suggest that the potential for forming novel projections in the gerbil auditory brainstem is lost before the onset of functional hearing (at P12) and is, therefore, unlikely to result from changes in auditory experience. © 1995 Wiley‐Liss, Inc.
Subcompartmental organization of the ventral (protrusor) compartment in the hypoglossal nucleus of the rat
Authors: Aldes Leonard D.
Published: January 2005

The extent and myotopic organization of the ventral (protrusor) compartment of the hypoglossal nucleus (nXII) in the rat is controversial. Of particular concern is the location of motoneurons that innervate the intrinsic (verticalis, transversus) as compared to extrinsic (genioglossus) tongue protrusor muscles. These issues were investigated with retrograde transport, lesion /degeneration /immunocytochemical, and classic Golgi staining techniques.

Results from these experiments demonstrate the following: (1) the ventral compartment extends the entire rostrocaudal length of nXII and is organized into three longitudinally oriented subcompartments, one medial and one lateral within the boundaries of nXII, and one outside the confines of nXIL defined as the lateral accessory subcompartment; (2) the medial and lateral subcompartments contain motoneurons that innervate the intrinsic (verticalis, transversus) and extrinsic (genioglossus) tongue protrusor muscles, respectively, while the lateral accessory subcompartment innervates the geniohyoid muscle; (3) ventral subcompartments are unequal in size and vary along the rostrocaudal dimension of nXII. The medial subcompartment is largest caudally and smallest rostrally, while the converse is true for the lateral subcompartment. By contrast, the lateral accessory subcompartment is present only along the caudal one‐half of nXII; (4) medial and lateral subcompartments are further organized into smaller subgroups. Medial and centromedial subgroups are discernible within the medial subcompartment, lateral and centrolateral subgroups within the lateral subcompartment. Both medial and lateral subgroups extend throughout the rostrocaudal length of nXII, whereas the centromedial and centrolateral subgroups are present only along the middle two‐thirds of nXII where they form a central motoneuron band; (5) there is an inverse myotopic organization within the medial and lateral subcompartments such that proximal and distal portions of intrinsic and extrinsic protrusor muscles receive innervation from rostral and caudal motoneurons, respectively; and (6) there is a correlation between motoneuron morphology (size, shape and dendritic field domains), subcompartment localization, and myotopic specificity. Motoneurons in the medial subcompartment are small (X̄ = 23. 08 μm), round to globular, with dendrites oriented medially, dorsomedially, dorsolaterally, and caudally, whereas lateral subcompartment motoneurons are large (X̄ = 29. 49 μm), round to triangular, with dendrites directed mainly mediolaterally and dorsally.

These data are relevant to understanding the functional organization of nXII and the motor control of the tongue. Results are further discussed relative to the convergence of multifunctional afferent systems in the ventromedial subcompartment of nXII. © 1995 Wiley‐Liss, Inc.
Morphology of developing rat genioglossal motoneurons studied in vitro: Relative changes in diameter and surface area of somata and dendrites
Authors: Núñez‐Abades P. A. , Cameron W. E.
Published: January 2005

This study describes the postnatal change in size of motoneurons in the hypoglossal nucleus that innervate the genioglossus muscle. Such anatomical information is essential for determining the cellular mechanisms responsible for the changes observed in the electrical properties of these motoneurons during postnatal development. The cells analyzed here are part of an earlier study (Núñez‐Abades et al. [1994] J. Comp. Neurol. 339:401–420) where 40 genioglossal (GG) motoneurons from four age groups (1–2, 5–6, 13–15, and 19–30 postnatal days) were labeled by intracellular injection of neurobiotin in an in vitro slice preparation of the rat brainstem and their cellular morphology was reconstructed in three‐dimensional space.

The sequence of postnatal dendritic growth can be described in two phases. The first phase, between birth (1–2 days) and 13–15 days, was characterized by no change in either dendritic, diameter (any branch order) or dendritic surface area of GG motoneurons. However, maturation of the dendritic tree produced more surface area at greater distances from the soma by redistributing existing membrane (retracting some terminal branches). During the second phase, between 13–15 days and 19–30 days, the dendritic surface area doubled as a result of an increase in the dendritic diameter across all branch orders and a generation of new terminal branches. In contrast to the growth exhibited by the dendrites, there was little discernible postnatal growth of somata.

At all ages, dendrites of GG motoneurons show the largest amount of tapering in the firstand second‐order dendrites. The calculated dendritic trunk parameter deviated from a value 1.0, indicating that the dendritic tree of developing GG motoneurons cannot be modeled accurately as an equivalent cylinder. However, the value of this parameter increased with age. Strong correlations were found between the diameter of the first‐order dendrite and the dendritic surface area, dendritic volume, combined dendritic length, and, to a lesser extent, the number of terminal dendrites in GG motoneurons. Correlations were also found between somal and dendritic geometry but only when data were pooled across all age groups.

These data support earlier studies on kitten phrenic motoneurons, which concluded that postnatal growth of motoneurons was not a continuous process. Based on the fact that there was no growth in the first 2 weeks, the changes in the membrane properties described during this phase of postnatal development (e.g., decrease in input resistance) cannot be attributed to increases in the total membrane surface area of these motoneurons. It is proposed that these changes result from changes in the specific membrane resistance of these neurons. © 1995 Wiley‐Liss, Inc.
Non‐NMDA glutamate receptors are present throughout the primate hypothalamus
Authors: Ginsberg Stephen D. , Price Donald L. , Blackstone Craig D. , Huganir Richard L. , Martin Lee J.
Published: January 2005

To determine the distributions of glutamate receptors throughout the macaque hypothalamus, we utilized highly specific antipeptide antibodies to visualize α‐amino‐3‐hydroxy‐5‐methyl4‐isoxazole propionate receptor subunits (GluRl, GluR2 and GluR3 {designated as GluR2/3}, and GluR4); kainate receptor subunits (GluR6 and GluR7, {Idesignated as GluR6/7}), and a metabotropic receptor (mGluRlα). The results indicate that these glutamate receptors are distributed differentially throughout the monkey hypothalamus. α‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate receptors are the dominant non‐N‐methyl‐D‐aspartate glutamate receptors within the monkey hypothalamus, and the GluR2 subunit is most abundant. GluR1‐immunoreactive neurons and neuropil are observed predominantly in the tuberal and mammillary nuclei. GluR2/3‐immunoreactive neurons and neuropil have a broader distribution within preoptic, anterior, tuberal, and caudal regions. Separate (but partially overlapping) distributions of GluRl‐ and GluR2/3‐immunoreactive neurons were found, suggesting that the GluR1, GluR2, and/or GluR3 subunits may be coexpressed in subsets of hypothalamic neurons. In contrast, GluR4 immunoreactivity was expressed minimally within monkey hypothalamus. GluR6/7 immunoreactivity was enriched selectively within the suprachiasmatic nucleus. mGluRlα immunoreactivity was present in the mammillary complex. The localization of non‐N‐methyl‐D‐aspartate glutamate receptor subunits to neurons throughout the macaque hypothalamus provides further evidence for the glutamatergic regulation of neuroendocrine, autonomic, and limbic circuits. Differential distributions of glutaniate receptor subunits may increase the dynamic range of the effects of presynaptic glutamate, allowing for the regulation of several distinct functions subserved by hypothalamic neurons. © 1995 Wiley‐Liss, Inc.
Fibroblast growth factor‐2‐like immunoreactivity in auditory brainstem nuclei of the developing and adult rat: Correlation with onset and loss of hearing
Authors: Riedel Bettina , Friauf Eckhard , Grothe Claudia , Unsicker Klaus
Published: January 2005

Fibroblast growth factor‐2 (FGF‐2; basic FGF) is widely distributed in the developing and adult brain and has numerous effects on cultured and lesioned neural cells. The physiological role of FGF‐2 in the unlesioned nervous system, however, is still not understood. We have studied the distribution of FGF‐2 in the developing, adult, and functionally impaired central auditory system of the rat using specific antibodies and peroxidase‐antiperoxidase immunocytochemistry. FGF‐2‐like immunoreactivity (FGF‐2‐IR) occurred in neuronal cell bodies and/or nerve fibers but was very rarely observed in glial cells. Several auditory brainstem nuclei, including the superior paraolivary nucleus, the medial superior olive, the lateral and ventral trapezoid nuclei, and the central nucleus, as well as the external cortex of the inferior colliculus, were entirely devoid of FGF‐2‐IR. In the dorsal cochlear nucleus, the lateral superior olive, and the nuclei of the lateral lemniscus, FGF‐2‐IR was not detectable in nerve cell bodies prior to adult age. Neurons in the medial geniculate body exhibited FGF‐2‐IR only transiently, from postnatal day (P) 5 until P16. Neurons in the medial nucleus of the trapezoid body were immunoreactive from P8 onwards. FGF‐2‐IR in anteroventral and posteroventral cochlear neurons disappeared at P14, i. e., at the onset of hearing, but immunoreactivity returned after P21. A transient expression of FGF‐2 around the time when hearing function commences was observed in the dorsal cortex of the inferior colliculus. Thus, regulation of neuronal FGF‐2‐IR in several, but not all, auditory, nuclei is related to the onset of hearing, in that IR disappears at that time or transiently appears. This suggests a causal link between the onset of hearing and FGF‐2 expression. In support of this notion, ototoxic treatment with gentamycin abolished FGF‐2‐IR in the P16 medial geniculate body but not in other auditory brainstem centers. Thus, FGF‐2 may be considered a regulator or indicator of the acquisition of functional activity and responsiveness to sensory stimuli in several areas of the auditory system. © 1995 Wiley‐Liss, Inc.
Morphology and dendritic domains of neurons in the lateral parabrachial nucleus of the rat
Authors: Herbert Horst , Bellintani‐Guardia Breno
Published: January 2005

The present study provides a description of the dendritic morphology and the dendritic domains of neurons in the lateral parabrachial nucleus (PB) of the rat. The cells were intracellularly stained in vitro with Lucifer yellow. A subpopulation of these cells was characterized beforehand as neurons projecting to the amygdaloid complex by retrograde transport with rhodamine beads.

With respect to their dendritic arborization, different types of “spatially” organized PB neurons were discriminated. One major cell type in the external lateral PB (PBel) is characterized by long, elongated dendritic trees that are preferentially oriented parallel to the superior cerebellar peduncle. The majority of their dendrites appears to respect subnuclear boundaries, yet their distal dendrites often exceed the limits of the PBel to encroach upon adjacent subnuclei located dorsally and ventrolaterally to the PBel. Another prominent cell type in the PBel has fairly small and locally restricted dendritic trees that are also elongated, running with their main axis from ventrolateral to dorsomedial. The dendrites of the majority of these neurons apparently stay within the confines of the PBel. A distinct group of neurons is found in the ventral portion of the PBel. The majority of their dendrites is mediolaterally oriented and not confined to the PBelsubnucleus. In addition, we found a smaller number of neurons scattered within the lateral PB whose dendrites do not show a preferential orientation but travel across subnuclear boundaries into several different PB subnuclei.

Our data show that the dendrites of a large proportion of neurons in the lateral PB either stay within the confines of a particular subnucleus or slightly extend across subnuclear limits. In any case, they appear to match with terminal territories of afferent axons and, thus, maintain the functional specificity of inputs by their relay through the PB. In contrast, PB neurons that extend their dendrites across subnuclear boundaries or known terminal territories are likely to receive inputs of different qualities from a variety of sources and therefore transmit a more general, integrated signal to the forebrain. © 1995 Wiley‐Liss, Inc.
Commissural fibers may guide cholinergic neuronal migration in developing rat cervical spinal cord
Authors: Phelps Patricia E. , Vaughn James E.
Published: January 2005

The present investigation examines the role of intercellular, relationships in the guidance of neuronal migration in embryonic rat cervical spinal cord. A “U‐shaped” group of cholinergic neurons, was first detected on embryonic days (E) 15. 5–16 surrounding the ventral proliferative zone. At these stages, no cholinergic cells were observed in the dorsal spinal cord, but by E17, many of the “U‐shaped” group of cholinergic cells appeared to have translocated dorsally, to become the cholinergic dorsal horn cells seen in older animals. Between E16 and E17, these choline acetyltransferase (ChAT)‐immunoreactive cells displayed primitive processes oriented dorsoventrally, suggesting migration along that axis. Two early forming substrates present in embryonic spinal cord have been implicated in the guidance of other populations of migrating neurons: glial cells organized in radial arrays and commissural axons aligned along the dorsoventral axis. Involvement of the commissural fibers with cholinergic cell migration seems more likely because the fibers and the translocation pathway have similar orientations. In double‐labeling immunocytochemical studies of E15. 5–17 spinal cord, some immature ChATcontaining neurons were directly adjacent to commissural fibers, as identified by SNAP/TAG‐1 immunoreactivity. The temporal and spatial coincidence of developing cholinergic neurons and commissural axons is consistent with the hypothesis that these neurons could use commissural fibers as migratory guides. In addition, conventional electron micrographs were examined to determine if immature neuronal profiles were physically apposed to commissural axons. Immature neurons with leading and trailing processes oriented dorsally and ventrally, respectively, were embedded within and aligned along bundles of commissural fibers or along other similarly oriented neurons. This direct apposition of immature cells to the surfaces of commissural axons and other bipolar neurons is consistent with the hypothesis that the “U‐shaped” group of cholinergic neurons may use commissural axons and other cohort neurons for guidance during their dorsal migration.
Synaptic organization of the interstitial subdivision of the nucleus tractus solitarii and of its laryngeal afferents in the rat
Authors: Mrini Abdelghani , Jean André
Published: January 2005

The nucleus tractus solitarii, the first central relay for gustatory and a variety of visceral afferents, is also an integrative center for numerous functions. Its interstitial subdivision is involved in swallowing and respiratory reflexes. The ultrastructural characteristics of this subdivision and of its laryngeal afferents were investigated in adult rat by a serial‐section study and by application of wheat germ agglutinin‐horseradish peroxidase conjugate to the peripheral afferent fibers. The interstitial subnucleus contained scattered small neuronal cell bodies with such ultrastructural features as a large nucleus with deep indentations and an organellepoor cytoplasm. On the basis of their size and vesicular content, the axon terminals were classified into three categories. Group I and group II terminals were small or large, respectively, and contained mainly small, round, and clear synaptic vesicles. Group III terminals were also small but contained small, pleomorphic, and clear vesicles. Axodendritic synapses were the most numerous. They were either asymmetrical, comprised of group I and II terminals, or symmetrical, comprised of group III terminals. More than 50% were part of complex synaptic arrangements in the form of rosettes or glomeruli. Axosomatic contacts involved both group I and group III terminals and were always symmetrical. A high frequency of axoaxonic synapses was found. They were symmetrical, comprised of group III terminals on group I or II terminals. Different types of symmetrical synaptic contacts made by dendrites were also found. This study indicates also that the ipsilateral interstitial subdivision constitutes the preferential site of termination for superior laryngeal afferents. The labeled axon terminals belonged exclusively to groups I and II and were involved in both axodendritic and axodxonic synapses. Some of the axodendritic synapses were part of rosettes or glomeruli. All these synaptic arrangements may be considered a morphological substrate for important processing of afferent information in the nucleus tractus solitarii. They may account for some of the integrative functions of the interstitial subnucleus such as physiological processes triggered from the superior laryngeal nerve.
Model of forebrain regionalization based on spatiotemporal patterns of POU‐III homeobox gene expression, birthdates, and morphological features
Authors: Alvarez‐Bolado G. , Rosenfeld M. G. , Swanson L. W.
Published: January 2005

In situ hybridization was used to map spatiotemporal expression patterns of the four known intronless POU‐III transcription factor genes Brn‐1, Brn‐2, Brn‐4, and Tst‐1 in the developing rat forebrain vesicle, beginning on embryonic day 10. The results indicate that the proliferation layers (ventricular and subventricular) and mantle layer of the forebrain neural tube each display a strikingly unique pattern of regionalized POU‐III expression. Within a particular region, or layer within a region, none to all four of the mRNAs may be detected, and during development a particular mRNA in a particular region displays one of five expression patterns, or a combination of these patterns, which may be described as conserved, lost, transient, acquired, or redeployed expression. In the developing brain as a whole, Brn‐1 and Brn‐2 early on display somewhat different spatial expression patterns that converge to essential identity in the adult, whereas Brn‐4 expression is initially broad and becomes much more restricted in the adult, and Tst‐1 expression expands greatly through development. Usually, though not always, expression patterns tend to correlate with major histological features in the forebrain (often internal or external sulci associated with proliferation zones), and little evidence for waves of expression moving through the whole forebrain over time was obtained. Thus, clear differences in hybridization intensity often are observed between the cerebral cortex, basal telencephalic nuclei, hypothalamus, ventral thalamus, dorsal thalamus, and pretectal region. In contrast, transverse bands of hybridization extending from the roof to the floor of the forebrain, corresponding to proposed neuromeres, were not observed with these probes. The results suggest that POU‐III transcription factors help define specific regions in the early neuroepithelium as well as different cellular phenotypes in the ventricular, subventricular, and mantle layers of specific regions later in development. Thus, the functions of these regulatory proteins may be different in proliferating neuroepithelial cells, young neurons, and mature neurons and appear to be region‐specific.
D1 and D2 dopamine receptor gene expression in the rat striatum: Sensitive cRNA probes demonstrate prominent segregation of D1 and D2 mRNAS in distinct neuronal populations of the dorsal and ventral striatum
Authors: Le Moine Catherine , Bloch Bertrand
Published: January 2005

The postsynaptic effects of dopamine in the striatum are mediated mainly by receptors encoded by D1, D2, and D3 dopamine receptor genes. The D1 and D2 genes are the most widely expressed in the caudate‐putamen, the accumbens nucleus, and the olfactory tubercle. Several anatomical studies, including studies using in situ hybridization with oligonucleotide and cDNA probes, have suggested that D1 and D2 receptors are segregated into distinct efferent neuronal populations of the striatum: D1 in substance P striatonigral neurons and D2 in enkephalin striatopallidal neurons. In contrast, on the basis of several in vivo and in vitro studies, other authors have suggested the existence of an extensive colocalization of D1 and D2 in the same striatal neurons. Our study was undertaken in order to analyze in detail the expression of the D1 and D2 receptor genes in the efferent striatal populations, with special reference to the various striatal areas, and to yield insights into the question about D1 and D2 mRNA localization in the striatum. We have, therefore, used highly sensitive digoxigenin‐and 35S‐labeled cRNA probes to address this question. The present results demonstrate that the D1 and D2 receptor mRNAs are segregated, respectively, in substance P and enkephalin neurons in the caudate‐putamen and accumbens nucleus (shell and core) and in the olfactory tubercle (for their largest part). A very small percentage of neurons may coexpress both genes. These results confirm that the D1 and D2 receptor genes are expressed in distinct populations of striatal efferent neurons in the normal adult rat. © 1995 Wiley‐Liss, Inc.
Distribution of natriuretic peptide precursor mRNAs in the rat brain
Authors: Langub Moises C. , Watson Robert E. , Herman James P.
Published: January 2005

Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C‐type natriuretic peptide (CNP) represent members of a recently discovered neuropeptide family involved in central regulation of endocrine and autonomic functions. The present study employed an in situ hybridization approach to provide the first detailed comparative mapping of ANP, BNP, and CNP mRNAs in brain. Results indicate that ANP mRNA is highly expressed in anterior olfactory nuclei, limbic cortices, dorsal endopiriform nucleus, hippocampal subfield CA1, cortical amygdaloid nuclei, medial habenula, anteroventral periventricular and arcuate nuclei, periventricular stratum, zona incerta, mammillary nuclei, inferior olive, nucleus ambiguus, and pontine paragigantocellular nuclei. CNP mRNA is expressed at highest levels in olfactory nuclei, limbic cortices, dorsal endopiriform nucleus, hippocampal subfields CA1–3, anteroventral periventricular and arcuate nuclei, and numerous brainstem regions (including the pontine, lateral reticular, solitary tract, prepositus hypoglossal, and spinal trigeminal nuclei). Positive labeling for BNP mRNA was not observed in brain. The presence of both ANP and CNP mRNA in the same regions of distinct nuclei (e.g., the anteroventral periventricular and arcuate nuclei) suggests the potential for coexpression. Overall, the present data are consistent with a prominent role for both ANP and CNP in neuroendocrine regulation and central cardiovascular integration. The extensive localization of ANP and/or CNP mRNA in olfactory nuclei, limbic cortex, hippocampus, amygdala and diencephalic limbic relays further indicate a putative role for ANP and CNP as neuromodulators of olfactory/limbic information processing. © 1995 Wiley‐Liss, Inc.
Molecular compartmentation expressed in cerebellar cultures in the absence of neuronal activity and neuron‐glia interactions
Authors: Seil Fredrick J. , Johnson Marilyn L. , Hawkes Richard
Published: January 2005

The purpose of the study was to determine if zebrin compartmentation developed in permanently isolated cerebellar cultures, in the presence of agents that block neuronal activity and in the absence of myelination and astrocytic ensheathment of Purkinje cells. Parasagittally oriented organotypic cultures derived from newborn mice and carefully undercut at explantation to exclude extracerebellar afferents were subjected to three conditions: (1) Some were maintained in standard nutrient medium; (2) some were chronically exposed to tetrodotoxin and elevated levels of magnesium to block neuronal activity; and (3) some were exposed to cytosine arabinoside for the first 5 days in vitro (DIV) to destroy granule cells and oligodendrocytes and functionally compromise astrocytes, so that the astrocytic survivors did not ensheath Purkinje cells. Cultures fixed as whole‐mount preparations were reacted with antibody to zebrin II. Cultures that were cryostat sectioned were dually reacted with antibody to zebrin II and calbindin. Groups of zebrin+ and zebrin− Purkinje cells were evident after 14 DIV in all of the experimental conditions, indicating that zebrin compartmentation developed (1) in isolated cerebellar explants, (2) in the absence of neuronal activity, and (3) in the absence of neuron‐glia interactions such as myelination and glial ensheathment of Purkinje cell somata and dendrites. These results are consistent with the concept that expression of the zebrin+ and zebrin− phenotypes is an intrinsic property of Purkinje cells. The fact that zebrin expression seems to depend on an intrinsic program of differentiation in Purkinje cells suggests some role for zebrin compartmentation in cerebellar function. © 1995 Wiley‐Liss, Inc.
Autoradiographic localization of opioid receptors in vocal control regions of a male passerine bird (Junco hyemalis)
Authors: Gulledge Cynthia C. , Deviche Pierre
Published: January 2005

Previous studies have found opioid peptide‐like immunoreactivity in avian vocal control regions, but whether these regions contain receptors for opioid peptides has not been examined. To address this question, we used quantitative in vitro autoradiography to determine the anatomical distribution and to measure the densities of μ, δ, and κ opioid receptors in vocal control regions (area X higher vocal center, and nucleus intercollicularis) of adult male dark‐eyed juncos (Junco hyemalis). To evaluate whether opioid receptor densities in these regions depend on the activity of the reproductive system, we also measured these densities in birds collected during the spring, summer, and fall. We found area X, the higher vocal center, and nucleus intercollicularis to contain the three receptor types under study, but opioid receptor densities did not vary seasonally in any of these regions. The presence of specific opioid receptors in avian vocal control regions suggests the participation of opioids in the control of vocal behavior. This participation may consist of short‐term (e. g., auditory processing) and/or long‐term (e. g., neuronal plasticity) influences. © 1995 Wiley‐Liss, Inc.
Specificity of rabies virus as a transneuronal tracer of motor networks: Transfer from hypoglossal motoneurons to connected second‐order and higher order central nervous system cell groups
Authors: Ugolini Gabriella
Published: January 2005

The specificity of transneuronal transfer of rabies virus [challenge virus standard (CVS) strain] was evaluated in a well‐characterized neuronal network, i. e., retrograde infection of hypoglossal motoneurons and transneuronal transfer to connected (second‐order) brainstem neurons. The distribution of the virus in the central nervous system was studied immunohistochemically at sequential intervals after unilateral inoculation into the hypoglossal nerve. The extent of transneuronal transfer of rabies virus was strictly time dependent and was distinguished in five stages. At 1 day postinoculation, labelling involved only hypoglossal motoneurons (stage 1). Retrograde transneuronal transfer occurred from 2.0–2.5 days postinoculation (stage 2). In stages 2–4, different groups of second‐order neurons were labelled sequentially, depending on the strength of their input to the hypoglossal nucleus. In stages 4 and 5, labelling extended to several cortical and subcortical cell groups, which can be regarded as higher order because they are known to control tongue movements and/or to provide input to hypoglossal‐projecting cell groups. The pattern of transneuronal transfer of rabies virus resembles that of alpha‐herpesviruses with regard to the nonsynchronous labelling of different groups of second‐order neurons and the transfer to higher order neurons. In striking contrast to alpha‐herpesviruses, the transneuronal transfer of rabies isnotaccompanied by neuronal degeneration. Moreover, local spread of rabies from infected neurons and axons to adjoining glial cells, neurons, or fibers of passage does not occur. The results show that rabies virus is a very efficient transneuronal tracer. Results also provide a new insight into the organization of cortical and subcortical higher order neurons that mediate descending control of tongue movements indirectly via hypoglossal‐projecting neurons. © 1995 Wiley‐Liss, Inc.
Expression of polysialylated N‐CAM in the central nervous system of adult canaries and its possible relation to function
Authors: Rousselot P. , Nottebohm F.
Published: January 2005

Polysialylated neuronal cell adhesion molecule (PSAqN‐CAM) is a cell surface molecule associated with neurons that undergo changes in configuration or spatial translocation. In both cases, this molecule is thought to reduce the adhesivity of these cells or of their processes, which can thereby insinuate themselves into the existing parenchyma. We used a monoclonal antibody specific to PSA to offer what we believe is the first account of the distribution of PSA‐N‐CAM in the adult songbird brain. This antibody stained a diversity of cell classes and processes, as follows: (1) a subset of ventricular zone cells; (2) migrating cells thought to be neuroblasts; (3) a subset of differentiated neurons; (4) some brain surface astrocytes; (5) some tanycytes; (6) the neuropil of some regions; (7) some axonal fibers; and (8) possibly some synapses. Our results demonstrate also, for the first time, the wide distribution of a very numerous population of migrating cells in the telencephalon and the seasonal regulation of PSA‐Nq‐CAM expression in a part of the adult brain known to undergo seasonal changes in cell recruitment and function. However, we did not find PSA‐N‐CAM associated with young migrating cells in the high vocal center (HVC), nor was there PSA‐N‐CAM in the robust nucleus of the archistriatum (RA), which is known to receive new axonal endings from HVC. In these instances spatial translocation may occur with the assistance of other surface molecules. © 1995 Wiley‐Liss, Inc.