bluuebunny/crossref_metadata_2025 huggingface dataset:
Preoptic projections to Barringon's nucleus and the pericoerulear region: Architecture and terminal organization
Authors: Rizvi Tilat A. , Ennis Matthew , Aston‐Jones Gary , Jiang Maorong , Liu Wei‐Lin , Behbehani Michael M. , Shipley Michael T.
Published: January 2005

The medial preoptic area (MPO), a sexually dimorphic region, plays a pivotal role in neuroendocrine function and reproductive behavior. We recently reported that MPO projects heavily to the midbrain periaqueductal gray (PAG). We also noted that MPO projects to the dorsolateral pontine tegmentum. Here we identified the cells of origin of the MPO→tegmental projection and delineated the terminal organization of MPO projections to Barrington's nucleus, locus coeruleus (LC), and the rostromedial pericoerulear region (pLCrm). Correlative cyto‐ and chemoarchitectonic studies were done to define better the nuclear groups of the dorsolateral pontine tegmentum.

Retrograde tracing revealed that MPO neurons projecting to the dorsolateral pontine tegmentum are preferentially distributed in distinct subregions of MPO, including the sexually dimorphic medial preoptic nucleus (MPN). Anterograde tracing with wheat germ agglutininhorseradish peroxidase or Phaseolus vulgaris leucoagglutinin demonstrated considerable target specificity in projections from MPO to the dorsolateral pontine tegmentum. Barrington's nucleus receives a dense focal input along its entire rostrocaudal axis. In addition, pLCrm is heavily targeted by MPO inputs; pLCrm contains a concentrated plexus of extranuclear dendrites of LC neurons. The lateral dorsal tegmental (LDT) nucleus and LC proper receive only sparse input from MPO.

MPO projections to Barrington's nucleus could regulate micturition reflexes during reproductive behavior. The MPO→pLCrm projection could influence noradrenergic LC neurons in relation to reproductive and/or gonadal steroid function. Given the strong established connections from olfactory structures to MPO, it is possible that the MPO→LC pathway provides an anatomical substrate for olfactory modulation of arousal. © 1994 Wiley‐Liss, Inc.
Ontogeny and effect of activity on proenkephalin mRNA expression during development of the chick spinal cord
Authors: Garner L. K. , Mendelson B. , Albers K. M. , Kindy M. , Overbeck T. L. , David B. M.
Published: January 2005

Numerous studies have shown in the adult nervous system that mRNA expression can be regulated by neuronal activity. To examine the effect of activity during embryogenesis, the ontogeny of proenkephalin mRNA expression and expression following activity blockade was investigated during development of chick spinal cord. A cDNA fragment (ca. 0.5 kb) coding for chick proenkephalin was cloned and sequenced. With this cDNA, a cRNA probe was made to examine proenkephalin mRNA expression in the spinal cord during embryogenesis. Proenkephalin mRNA was expressed in spinal cord in clusters of cells located in the developing dorsal horn and intermediate lamina at the earliest stages examined (stage 22; E4). Proenkephalin‐positive cells in the intermediate lamina were located immediately adjacent to the ventricular zone. At stage 28 (E6) an additional cluster of proenkephalin mRNA‐positive cells was seen at the lateral border of the developing intermediate lamina. At stage 33 (E7. 5–8) the pattern of hybridization positive cells was similar to earlier stages, but individual cells could be identified. At stage 39 (E13) densely labeled cells were seen throughout the dorsal horn and intermediate laminae including the column of Terni. To determine whether neural activity affects proenkephalin mRNA expression, d‐tubocurarine (an inhibitor of neural activity) was injected into developing embryos. Following administration of d‐tubocurarine a dramatic decrease was seen in proenkephalin mRNA hybridization in the dorsal horn and intermediate lamina of the spinal cord. This study demonstrates in vivo that changes in the level of neural activity can alter gene expression during embryogenesis and suggests that activity is required for expression of nervous system‐lspecific genes. © 1994 Wiley‐Liss, Inc.
Distribution of corticospinal motor neurons in the postnatal rat: Quantitative evidence for massive collateral elimination and modest cell death
Authors: Oudega Martin , Varon Silvio , Hagg Theo
Published: January 2005

The postnatal development of rat corticospinal motor neurons (CSMN) was studied by retrograde tracing with cholera toxin B subunit (CTB) injected into the upper cervical dorsal spinal cord on the first postnatal day (P0), P3, P10, P20, and at adulthood. CTB‐labeled neurons were visualized by immunocytochemistry and extensively quantified throughout the cortex. At P0, CSMN were found to an extent similar to that reported in P3 animals with other neuronal tracers, now permitting in vitro studies of neonatal CSMN. Between P0 and P3, the number of labeled neurons increased by 30% to a total maximum of approximately 185,000 in both cortices. The increase occurred throughout the cortex. At P10, the number of labeled CSMN had decreased to 60% of the number at P3. Fewer CSMN were evident particularly in the perirhinal cortex. Between P10 and P20, the number of CSMN decreased further to 52% of the maximal number at P3. This decrease occurred predominantly in the cingulate and parietal cortex. The number of labeled CSMN in rats injected at P0 and analyzed at P20 was 10% lower than the number in P0‐injected littermates that were analyzed at P3, which suggests that only a small portion of the “disappearing” CSMN undergoes developmental neuronal death. Thus, the spinal projection of the remaining 38% is apparently eliminated between P3 and P20. Detailed quantitative analysis of the CSMN distribution demonstrated that neuronal death occurs predominantly in the perirhinal cortex. In contrast, axonal elimination of corticospinal projections occurred throughout the CSMN field, i. e., primarily in the frontal, occipital, and perirhinal cortex between P3–P10 and in the cingulate and parietal cortex between P10–P20. © 1994 Wiley‐Liss, Inc.
Extrasynaptic localization of taurine‐like immunoreactivity in the lamprey spinal cord
Authors: Shupliakov Oleg , Brodin Lennart , Srinivasan Meera , Grillner Sten , Cullheim Staffan , Storm‐Mathisen Jon , Ottersen Ole Petter
Published: January 2005

Taurine is an endogenous amino acid that can occur in nerve terminals in the central nervous system and that can produce inhibitory neuronal responses. It is unclear, however, whether this amino acid can function as a synaptic transmitter. To examine the distribution of taurine at high anatomical resolution in a vertebrate, light and electron microscopic immunocytochemical postembedding techniques were applied to the lamprey spinal cord (Ichtyomyzon unicuspis and Lampetra fluviatilis), which contains many large, unmyelinated axons. The most intense immunolabeling occurred in a population of liquor‐contacting cells (tanycytes), located around the central canal, which extended processes to the dorsal, lateral, and ventral margins of the spinal cord. In addition, a proportion of the taurine‐immunoreactive cells contained gamma‐aminobutyric acid (GABA)‐like immunoreactivity. A moderate level of taurine immunoreactivity was also present in ependymal cells, located around the central canal, as well as in astrocytes throughout all regions of the spinal cord. At the ultrastructural level, the taurine immunoreactivity showed an even distribution in the cytoplasm of the labeled cells. In contrast to the glial labeling, neuronal cell bodies and axons exhibited very low levels of taurine labeling, which were similar to the level of background labeling. The synaptic vesicle clusters within the axons did not show any clear accumulation of taurine immunoreactivity.

These results suggest that taurine may have metabolic roles in the lamprey spinal cord, and, as in other systems, it may take part in osmoregulation. However, the lack of immunolabeling in presynaptic elements is not consistent with a role of taurine as a synaptic transmitter. © 1994 Wiley‐Liss, Inc.
Complexity and scaling properties of amacrine, ganglion, horizontal, and bipolar cells in the turtle retina
Authors: Fernandez Eduardo , Eldred William D. , Ammermüller Josef , Block Arthur , Von Bloh Werner , Kolb Helga
Published: January 2005

In the present studies we have evaluated the complexity and scaling properties of the morphology of retinal neurons using fractal dimension as a quantitative parameter. We examined a large number of cells from Pseudemys scripta and Mauremys caspica turtles that had been labeled using Golgi‐impregnation techniques, intracellular injection of Lucifer Yellow followed by photooxidation, intracellular injection of rhodamine conjugated horseradish peroxidase, or intracellular injection of Lucifer Yellow or horseradish peroxidase alone. The fractal dimensions of two dimensional projections of the cells were calculated using a box counting method. Discriminant analysis revealed fractal dimension to be a significant classification parameter among several other parameters typically used for placing turtle retinal neurons in different cell classes. The fractal dimension of amacrine cells was significantly correlated with dendritic field diameters, while the fractal dimensions of ganglion cells did not vary with dendritic field span. There were no significant differences between the same cell types in two different turtle species, or between the same types of neurons in the same species after labeling with different techniques. The application of fractal dimension, as a quantitative measure of complexity and scaling properties and as a classification criterion of neuronal types, appears to be useful and may have wide applicability to other parts of the central nervous system. © 1994 Wiley‐Liss, Inc.
Two major types of premotoneurons in the feline trigeminal nucleus oralis as demonstrated by intracellular staining with horseradish peroxidase
Authors: Yoshida Atsushi , Yasuda Kouichi , Dostrovsky Jonathan O. , Bae Yong Chul , Takemura Motohide , Shigenaga Yoshio , Sessle Barry J.
Published: January 2005

Previous studies suggest that neurons in the dorsomedial subdivisions of trigeminal nucleus oralis (Vo) may contribute, to reflex control of jaw movements and to modulation of sensory information. The present study has addressed this possibility by the use of intracellular staining with horseradish peroxidase of physiologically identified neurons in Vo to examine functional and morphological properties of these neurons. Of 14 labeled neurons, eight had axon collaterals terminating exclusively in the dorsolateral subdivision of the trigeminal motor nucleus (DL neurons) and four in its ventromedial subdivision (VM neurons); axon collaterals of two neurons were not traced. Both groups of neurons sent terminal arbors into other nuclei of the lower brainstem. The DL neurons were distinguishable from the VM neurons in their receptive field (RF) location, neuronal position, somadendritic architecture, and projections to other brainstem nuclei. All neurons, except for two that were exclusively activated by noxious stimuli applied to the tongue, were responsive to light mechanical stimulation of peri‐ and intraoral structures. The RFs of the DL neurons were located in more posterior oral structures than those of the VM neurons. The RF of nearly all low‐threshold DL neurons was located in the maxillary region, and that of the VM neurons, in contrast, involved the mandibular region. The VM neurons were located medial or ventral to the DL neurons. The soma size of the VM neurons was significantly higher than that of the DL neurons. Dendritic arbors of both groups could be separated into medial and lateral components. The ratio of the dendritic transverse areas in the medial vs. later component was significantly higher in the VM neurons than in the DL neurons. The DL neurons also issued collaterals that terminated in larger brainstem areas than those of the VIM neurons. These observations provide new evidence on the morphological and functional properties of Vo neurons that contribute to reflex control of jaw and facial movements and modulation of sensory information. © 1994 Wiley‐Liss, Inc.
Ultrastructural and morphometric features of the acetylcholine innervation in adult rat parietal cortex: An electron microscopic study in serial sections
Authors: Umbriaco Denis , Watkins Kenneth C. , Descarries Laurent , Cozzari Costantino , Hartman Boyd K.
Published: January 2005

This study was aimed at characterizing the ultrastructural morphology of the normal acetylcholine (ACh) innervation in adult rat parietal cortex. After immunostaining with a monoclonal antibody against purified rat brain choline acetyltransferase (ChAT), more than 100 immunoreactive axonal varicosities (terminals) from each layer of the Par 1 area were photographed and examined in serial thin sections across their entire volume. These varicosities were relatively small, averaging 0.6 μm in diameter, 1.6 μM2 in surface, and 0.12 μM3 in volume. In every layer, a relatively low proportion exhibited a synaptic membrane differentiation (10% in layer I, 14% in II–III, 11% in IV, 21% in V, 14% in VI), for a I–VI average of 14%. These synaptic junctions were usually single, symmetrical (>99%), and occupied a small portion of the surface of varicosities (<3%). A majority were found on dendritic branches (76%), some on spines (24%), and none on cell bodies. On the whole, the ACh junctional varicosities were significantly larger than their nonjunctional counterparts, and both synaptic and nonsynaptic varicosities could be observed on the same fiber.

A subsample of randomized single thin sections from these whole varicosities Yielded similar values for size and synaptic frequency as the result of a stereological extrapolation. Also analyzed in single sections, the microenvironment of the ChAT‐immunostained varicosities appeared markedly different from that of unlabeled varicosity profiles randomly selected from their vicinity, mainly due to a lower incidence of synaptically targeted dendritic spines. Thus, the normal ACh innervation of adult rat parietal cortex is predominantly nonjunctional (>85% of its varicosities), and the composition of the microenvironment of its varicosities suggests some randomness in their distribution at the microscopic level. It is unlikely that these ultrastructural characteristics are exclusive to the parietal region. Among other functional implications, they suggest that this system depends predominantly on volume transmission to exert its modulatory effects on cortical activity. © 1994 Wiley‐Liss, Inc.
Glomus cell differentiation in the carotid body region of chick embryos studied by neuron‐specific class III β‐tubulin isotype and leu‐7 monoclonal antibodies
Authors: Kameda Yoko , Yamatsu Yoshiyasu , Kameya Toru , Frankfurter Anthony
Published: January 2005

Development of the carotid body and the glomus cell groups in the wall of the common carotid artery and its branches was examined in chickens at various developmental stages by immunohistochemistry using three different monoclonal antibodies, i. e., anti‐neuron‐specific class III β‐tubulin isotype (TuJ1), anti‐rat brain β‐tubulin, and anti‐Leu‐7 (HNK‐1) antibodies. All the antibodies reacted with neurons. The carotid body anlage was first discerned at 6 days of incubation at the lateral portion of the third branchial artery. The cells and nerve fibers immunoreactive for TuJ1, brain β‐tubulin and Leu‐7, which were connected with the distal ganglion of the vagus nerve, were found around the carotid body anlage at this stage. Within the carotid body anlage, no immunoreactivity yet appeared. The immunoreactive cells were accumulated around the carotid body anlage until 8 days of incubation. From 9 days of incubation, the immunoreactive cells continuing with the distal vagal ganglion began to enter into the carotid body anlage and also dispersed widely along the common carotid artery and its branches, giving rise to the glomus cells. At 12 days of incubation, a large portion of the carotid body was occupied by the immunoreactive cells. Thus, the present study evidences that the glomus cells in the carotid body and around the arteries are emigrés that arrive in each residential place from the distal vagal ganglion. Immunoreactivity for TuJ1, brain β‐tubulin, and Leu‐7 in the glomus cells started to decrease at late stages of embryonic development. After hatching, no TuJ1‐immunoreactive cells were detected in the carotid body region. © 1994 Wiley‐Liss, Inc.
Electron microscopic study on the development of the carotid body and glomus cell groups distributed in the wall of the common carotid artery and its branches in the chicken
Authors: Kameda Yoko
Published: January 2005

Development of the carotid body and the glomus cell groups in the wall of the common carotid artery and its branches was studied in chickens at various developmental stages by electron microscopy. At 8 days of incubation, the carotid body anlage consisted of mesenchyme‐like cells, whereas the clusters of epithelial cells, which occasionally contained a few dense‐cored vesicles and were accompanied by unmyelinated nerve fibers, were located in the region surrounding the carotid body anlage and in the wall of the common carotid artery. Subsequently, the granule‐containing cells together with nerve fibers were detected in the periphery of the carotid body anlage. At 12 days of incubation, a large number of granule‐containing cells (glomus cells) were dispersed throughout the carotid body parenchyma and were also widely distributed along the common carotid artery and its branches. The cells frequently extended long cytoplasmic processes that made contact with other glomus cells and nerve fibers. Synaptic junctions which showed desmosome‐like thickening of pre‐ and postsynaptic membranes and accumulations of small clear vesicles (around 50 nm in diameter) were first detected along the contact between the long axons and glomus cells at 12 days of incubation. In the wall of the common carotid artery, interdigitations between the cytoplasmic processes of glomus cells and smooth muscle cells began to form. Sustentacular cells investing partly the glomus cells were also discerned both in the carotid body and around the arteries at this stage. At 14 days of incubation, the glomus cells expressed most of the characteristics of the mature cells, and the synaptic junctions displaying afferent morphology appeared; the secretory granules of glomus cells were accumulated near and attached to the desmosome‐like thickening of apposed membranes. © 1994 Wiley‐Liss, Inc.
Localization and developmental expression of the NMDA receptor subunit NR2A in the mammalian retina
Authors: Hartveit E. , Brandstätter J. H. , Sassoè‐Pognetto M. , Laurie D. J. , Seeburg P. H. , Wässle H.
Published: January 2005

The localization of the N‐methyl‐D‐aspartate receptor subunit NR2A was studied, by using light microscopic immunocytochemistry, in the retina of adult rat, rabbit, cat, and monkey. Strong, punctate immunolabeling was observed in the inner plexiform layer indicating a synaptic localization of the NR2A subunit. The punctate labeling was concentrated in two bands corresponding to the on‐ and off‐sublaminae of the inner plexiform layer.

The punctate character of immunofluorescence suggested a synaptic localization of the receptor. This was confirmed by electron microscopy of immunostained adult rat retina. The staining was localized postsynaptic to cone bipolar cells, and only one of the two postsynaptic elements of the dyad was labeled. Staining was not observed at extrasynaptic plasma membranes.

In situ hybridization of adult rat retina showed expression of the NR2A subunit in virtually all ganglion cells and displaced amacrine cells in the ganglion cell layer and in a subset of amacrine cells in the inner nuclear layer.

The postnatal developmental expression of the NR2A subunit was studied in rat retina by light microscopic immunocytochemistry. Punctate immunolabeling appeared prior to eye opening, and the developmental profile of NR2A could be compatible with a role in development of circuitry in the inner plexiform layer. © 1994 Wiley‐Liss, Inc.
Restricted expression of a new paired‐class homeobox gene in normal and regenerating adult goldfish retina
Authors: Levine Edward M. , Hitchcock Peter F. , Glasgow Eric , Schechter Nisson
Published: January 2005

We describe the cloning and expression pattern of a new paired‐class homeobox gene, Vsx‐1, in the continuously growing retina of the goldfish. Vsx‐1 belongs to a subset of paired‐class homeobox genes that lack a second DNA binding domain, the paired‐domain, and is closely related to the C. elegans ceh‐10 gene. In the adult goldfish, Vsx‐1 expression is restricted to the neural retina. In the central, mature retina, Vsx‐1 mRNA is synthesized in a subset of differentiated cells in the inner nuclear layer in a pattern suggestive of bipolar cells. In immature retina, adjacent to the retinal margin, Vsx‐1 is expressed in a relatively broader subset of newly postmitotic cells but is downregulated in some of these cells to form the mature expression pattern. Following retinal injury, during the early phase of regeneration, Vsx‐1 mRNA synthesis appears tp be upregulated in cells in the inner nuclear layer and is expressed de novo in cells outside this layer. By virtue of its identity as a transcriptional regulatory gene and its patterns of expression, we speculate that Vsx‐1 may stabilize the differentiated state of a subset of cells in the inner nuclear layer and may be involved in cellular differentiation during retinal development and regeneration. © 1994 Wiley‐Liss, Inc.
Immunocytochemical localization of the α7 subunit of the nicotinic acetylcholine receptor in the rat central nervous system
Authors: del Toro Eduardo Dominguez , Juiz Jose M. , Peng Xiao , Lindstrom Jon , Criado Manuel
Published: January 2005

Previous molecular cloning studies have revealed that α‐bungarotoxin binding proteins present in the brain are members of the neuronal nicotinic acetylcholine receptor gene family. The α7 subunit is structurally related to the agonist binding subunits present in the central and peripheral nervous systems and, when expressed in Xenopus oocytes, forms functional channels blockable by α‐bungarotoxin. In the present study, three different monoclonal antibodies raised against the α7 subunit were used to map its distribution throughout the central nervous system of the rat.

Immunohistochemical localization revealed that the α7 subunit is expressed in most regions of the brain, being, overall, well correlated with previous “in situ” localization of α7 transcripts and α‐bungarotoxin autoradiographic binding studies. Particularly strong immuno‐reactivity was observed in several sensory and motor nuclei of the brainstem as well as the red nucleus. At the cellular level, α7 immunostaining was usually found both in somata and dendrites, whereas axonal and terminal labeling was not observed.

The widespread distribution of the α7 subunit polypeptide is consistent with immunoprecipitation data demonstrating that it is a component of the predominant subtype of brain α‐bungarotoxin‐sensitive nicotinic receptors. © 1994 Wiley‐Liss, Inc.
Morphology of retinal axon arbors induced to arborize in a novel target, the medial geniculate nucleus. II. Comparison with axons from the inferior colliculus
Authors: Pallas S. L. , Sur M.
Published: January 2005

Specific neonatal lesions in ferrets can induce retinal axons to project into the medial geniculate nucleus (MGN). In the accompanying paper (Pallas et al., this issue), we described the morphology of these retinal ganglion cell axons. Those results and others (Roe et al. [1993] J. Comp. Neurol. 334:263) suggest that these axons belong to the W class of retinal axons.

In this paper, the retino‐MGN axons are compared with the normal inputs to the MGN from the brachium of the inferior colliculus (BIC). We first sought to determine further the extent to which a novel target might influence retinal axon arbor morphology. The second issue concerns retinal topography. Ferrets with retinal projections to the MGN have a two‐dimensional retinotopic map in the MGN and the primary auditory cortex rather than the one‐dimensional tonotopic map normally present (Roe et al. [1990] Science 250:818). To investigate whether there might be an anatomical substrate for a two‐dimensional retinotopic map in the MGN, we compared the space‐filling characteristics of the retino‐MGN axons with the IC‐MGN axons.

Our results show that the branched retino‐MGN axons resemble normal retinal W axons much more closely than they resemble the normal inputs to MGN. In addition, most of the axon arbors from the BIC are elongated along the rostrocaudal (isofrequency) axis, whereas the branched retino‐MGN axons are more spatially restricted, suggesting an anatomical substrate for a retinotopic map in the MGN of the rewired ferrets. © 1994 Wiley‐Liss, Inc.
Cytoarchitecture and responsiveness of the medial ansate region of the cat primary somatosensory cortex
Authors: Myasnikov Alexandre A. , Dykes Robert W. , Avendano Carlos
Published: January 2005

To understand its relationship to somatosensory areas in other species, we studied the rostral bank of the medial ansate sulcus in adult cats. Neurons in the shoulder and upper part of the sulcal wall responded to low‐threshold cutaneous stimuli much like neurons on the crown of the gyrus, whereas neurons in some deeper portions of the sulcus required more intense but innocuous somatic stimuli. Because we found much of the body surface re‐represented in this area, we suggest that, besides the representation in area 3b, there is another cutaneous representation of the hindlimb and trunk located on the gyral crown near the medial end of the medial ansate sulcus and of the forelimb and trunk within the medial ansate sulcus. Posterior to this second cutaneous representation, many parts of the body were also represented in regions activated by more intense stimuli and having a different cytoarchitecture, suggesting that they were part of another body representation.

Area 3b and the shoulder of the gyrus were distinguished by relatively intense acetylcholinesterase staining of layers III and IV. In the wall of the sulcus, all layers except layer I were uniformly stained to a point where electrophysiological recordings showed the cortex to be unresponsive, whereupon the outer two‐thirds of layer I became very pale. Neurons activated by afferents from knee joints were found only in a small area; we did not find a mediolateral band serving joint afferents as is reported in primates. These data suggest that cat somatosensory cortex differs in some ways from primates but that it contains multiple representations of the body, as do most other mammals. © 1994 Wiley‐Liss, Inc.
Metabotropic glutamate receptor mGluR1 distribution and ultrastructural localization in hypothalamus
Authors: van den Pol Anthony N.
Published: January 2005

The metabotropic glutamate receptor mGluR1 is a G‐protein‐coupled glutamate receptor whose activation induces phosphotidylinositol hydrolysis and increases diacylglycerol and cytoplasmic calcium. By using affinity‐purified antisera against a partial amino acid sequence of mGluR1α, deduced from the nucleotide sequence of the cloned gene, the heterogeneous expression of this glutamate receptor was studied immunocytochemically with light and electron microscopy in the rat hypothalamus. Immunoreactivity was restricted to cell bodies and dendrites throughout many regions of the adult hypothalamus, including the preoptic area, anterior hypothalamus, suprachiasmatic nucleus, dorsomedial hypothalamus, and periventricular region. Strong immunolabeling was found in the lateral hypothalamus where immunoreactivity could be detected as early as embryonic day 18. Intense immunoreactivity was also found in the medial mammillary nuclei. In contrast to the strong labeling in many other regions, the neuroendocrine neurons of the arcuate, supraoptic, and paraventricular nuclei showed relatively little staining in adults.

With light microscopy, immunoperoxidase labeling was found distributed in patches on the cytoplasmic side of the plasma membrane of immunoreactive neurons. When the same tissue was examined ultrastructurally, the patches were not restricted to synaptic specializations but were also found distributed on perikaryal and dendritic membranes sometimes associated with synapses and sometimes not. Some immunoreactive membranes showed no immunolabeling at the synaptic junction. When the tissue was strongly stained, labeling could be found in the cytoplasm of immunoreactive cells. No immunostaining was found on axons or presynaptic boutons.

Together with other evidence showing a widespread expression of many different subtypes of both ionotropic and metabotropic receptors, these data support the hypothesis that glutamate may regulate hypothalamic cellular activity with a number of physiologycally different mechanisms, and these mechanisms include second‐messenger systems activated by G proteins. © 1994 Wiley‐Liss, Inc.
Fine structure of rat septohippocampal neurons. III. Recovery of choline acetyltransferase immunoreactivity after fimbria‐fornix transection
Authors: Naumann T. , Kermer P. , Frotscher Michael
Published: January 2005

Most cholinergic projection neurons in the medial septal nucleus (MS) lose their capability to synthesize choline acetyltransferase (ChAT) after axotomy by bilateral fimbria‐fornix transection. We have recently shown that identified septohippocampal neurons survive axotomy up to 10 weeks and display fine‐structural characteristics of cells in control rats. However, the fate and functional role of these neurons remained unclear. Here we describe observations made in rats which survived axotomy for 6 months.

Adult Sprague‐Dawley rats were subjected to bilateral transection of the fimbria‐fornix system. In some animals septochippocampal projection neurons were labeled by the retrograde fluorescent tracer Fluoro‐Gold (FG) prior to axotomy. After varying survival times following fimbria‐fornix transection, the animals were fixed and sections of the septal region immunostained for ChAT.

Three weeks postlesion, the number of ChAT‐positive cells in the MS was reduced to 19% of control, suggesting a severe neuronal loss. However, 10 weeks and 6 months after axotomy this value increased to 28% and 54%, respectively. Fine‐structural analysis of ChAT‐postive neurons after 6 months survial revealed all characteristics of vital cells including normal input synapses. The majority of these cells could be identified as former septohippocampal projection neurons by the presence of FG.

We conclude that many neurons in the MS have the capacity to restore their transmitter synthesis in a long‐lasting process following axotomy. © Wiley‐Liss, Inc.
Serotoninergic and nonserotoninergic neurons in the medullary raphe system have axon collateral projections to autonomic and somatic cell groups in the medulla and spinal cord
Authors: Allen Gary V. , Cechetto David F.
Published: January 2005

Fluorescent double retrograde‐tracing studies combined with fluorescent immunostaining for serotonin were carried out to determine the potential patterns of divergence in axonal projections to autonomic and somatic motor sites from medullary raphe and parapyramidal neurons. Injections (20–60 nl) of combinations of fluorescent retrograde tracers (Fast Blue, fluoro‐gold, green latex microspheres, Diamidino Yellow) were made into the intermediolateral cell column (IML) of the spinal cord and the brainstem lateral tegmental field or ventral horn of the lumbar spinal cord of male Wistar rats. The animals were perfused after a 7–10‐Day survival period, and the brains were removed, sectioned (50μm), and immunostained for serotonin.

Following injections of different retrograde‐tracer substances into the IML of the thoracic cord and the ventral horn of the lumbar cord, 36% of the neurons with axon collateral projections to the IML and the lumbar ventral horn were serotoninergic. Following injections of different retrograde‐tracer substances into the IML and the lateral tegmental field, 26% of the neurons with axon collateral projections to the IML and the lateral tegmental field were serotoninergic. Many of the medullary neurons with projections to the lateral tegmental field and the lumbar cord were located dorsal and lateral to those neurons with projections to the IML. The results indicate that serotoninergic and nonserotoninergic neurons of the midline raphe system and parapyramidal region have axon collateral branches to the IML and the lateral tegmental field or the IML and the lumbar ventral horn. These projection neurons may form the anatomical substrate for the integration of autonomic and somatic motor activity.
Pyramidal and nonpyramidal callosal cells in the striate cortex of the adult rat
Authors: Martínez‐García Fernando , González‐Hernández Tomás , Martínez‐Millán Luis
Published: January 2005

The aim of this study has been to determine the neuronal types (pyramidal and nonpyramidal) within the rat's visual cortex, which project through the corpus callosum. To this end, the morphology and laminar distribution of callosal cells have been investigated by combining Diamidino Yellow retrograde tracing with intracellular injection of Lucifer Yellow in slightly fixed tissue slices.

The visual callosal projection arises from pyramidal cells of diverse morphology in layers II to VIb, as well as from several modified pyramids located mainly in layers II, IV (star pyramids) and VIb (horizontal or inverted pyramids and related forms of spiny stellate cells). Our results indicate that in rats, as in other mammals, several types of nonpyramidal neurons also contribute to the contralateral projection. Bitufted cells in layers II–III and V were found to project contralaterally. Moreover, a spine‐free layer V cell and a sparsely spiny multipolar neuron of layer IV were also labeled. In both stellate cells, partial axonal labeling reveals that these callosal cells display a local axonal arborization. Finally, our results of retrograde transport with Diamidino Yellow and with another sensitive retrograde tracer, the beta subunit of the cholera toxin, demonstrate for the first time that the two main neuronal types of layer I participate in the callosal projection. In layer I, several small horizontal cells of the inner half of layer I and a large subpial cell displaying long radiating dendrites were also injected. The latter cell may correspond to the Cajal‐Retzius cell of the adult rat.

In spite of the important differences in the organization of the visual system between rodents and cats, the callosal projection in both mammals is composed of a large variety of pyramidal cells and several nonpyramidal neurons. This high morphological diversity suggests that the callosal projection is much more physiologically complex than the extracortical efferents of the visual cortex, resembling other cortico‐cortical connections. The roles that the different callosal cells may play in the processing of visual information are discussed in relation to the known functions of the corpus callosum.
NADPH‐diaphorase neurons in the retina of the hamster
Authors: Lau Kam Cheung , So Kwok‐Fai , Tay David , Leung Mason Chin Pang
Published: January 2005

NADPH‐diaphorase‐positive neurons have been demonstrated in the inner nuclear layer and ganglion cell layer of the retina of different mammalian species, but so far no experiments have been conducted to identify whether these cells are amacrine cells and/or retinal ganglion cells. We attempted to solve this problem by studying the NADPH‐diaphorase‐positive neurons in the hamster retina.

From the NADPH‐diaphorase histochemical reaction, two distinct types of neurons in the hamster retina were identified. They were named ND(g) and ND(i) cells. The ND(g) cells were cells with larger somata, ranging from 10 to 21 μm in diameter with a mean of 15.58 μm (S.D.= 2.59). They were found in the ganglion cell layer only. The ND(i) cells were smaller, with the somata ranging from 7 to 11 μm and having the mean diameter of 8.77 μm (S.D. = 1.24). Most of the ND(i) cells were found in the inner nuclear layer, and only very few could be observed in the inner plexiform layer. On average, there were 8,033 ND(g) and 5,051 ND(i) cells in the ganglion cell layer and inner nuclear layer, respectively.

Two experiments were performed to clarify whether any of the NADPH‐diaphorase neurons were retinal ganglion cells. Following unilateral optic nerve section, which leads to the retrograde degeneration of retinal ganglion cells, the numbers of both ND(g) and ND(i) cells did not change significantly for up to 4 months. In addition, when retinal ganglion cells were prelabeled retrogradely (horseradish peroxidase of flurescent microspheres) and retinas were then stained for NADPH diaphorase, no double‐labeled neurons were detected. These results indicated that the NADPH‐diaphorase neurons in the hamster retina were the amacrine cells in the inner nuclear layer and displaced amacrine cells in the ganglion cell layer.

Dendrites of the ND(g) and ND(i) cells were found to stratify in sublaminae 1, 3, and 5 of the inner plexiform layer, with a prominent staining in the sublamina 5. The possible importance of this arrangement in the rod pathway is also discussed. © 1994 Wiley‐Liss, Inc.
Corticorubral synaptic organization in Macaca fascicularis: A study utilizing degeneration, anterograde transport of WGA‐HRP, and combined immuno‐GABA‐gold technique and computer‐assisted reconstruction
Authors: Ralston Diane Daly
Published: January 2005

The macaque red nucleus receives afferents from two major sources, the cerebral cortex and the deep cerebellar nuclei. Approximately 90% of the corticorubral afferent axons project to pars parvicellularis of the red nucleus, the neurons of which transmit information to the cerebellum by way of the inferior olivary nucleus. The remaining 10% project to pars magnocellularis of the red nucleus, the major projection of which is to the spinal cord. In this study, corticorubral terminations labeled following lesions or injections of wheatgerm agglutinin conjugated to horseradish‐peroxidase into the topographically defined hand area of the primary motor cortex were quantitatively studied via electron microscopy. Cortical afferent terminals within pars parvicellularis and pars magnocellularis synapse upon all regions of the dendritic arbors of rubral projection neurons. However, the majority of these labeled afferents synapse upon thin‐diameter shafts or presumed spinous processes of rubral distal dendrites as well as upon vesicle‐containing profiles of presynaptic dendrites of local circuit interneurons that are γ‐aminobutyric acid‐immunoreactive, as identified by postembedding immunohistochemistry. Synaptic contacts formed by the labeled cortical terminal were large in width and extended through several serial sections. Synaptic contacts formed by the presynaptic dendritic profiles, on the other hand, were more punctate and could be seen in only one or two serial sections. These latter synaptic interactions probably provide a modification of the effects of cortical input to rubral projection neurons as suggested by previous physiological studies that indicated the dominance of cortical input onto distal dendrites as well as involvement with inhibitory circuits. An example of the complexities of these synaptic interactions is further demonstrated by a three‐dimensional computer reconstruction. This quantitative study of corticorubral afferents in the macaque monkey provides insight into the interactions of cerebral cortical afferents with rubral projection neurons and their relationship with local circuit inhibitory interneurons to elucidate the role played by the cortex in the activation of rubral neurons. © 1994 Wiley‐Liss, Inc.
Medullary visceral reflex circuits: Local afferents to nucleus tractus solitarii synthesize catecholamines and project to thoracic spinal cord
Authors: Mtui E. P. , Anwar M. , Reis D. J. , Ruggiero D. A.
Published: January 2005

Visceral feedback circuits in lower brainstem were elucidated with retrograde tracers by mapping neurons that issue local projections to the general visceral afferent division of the nucleus tractus solitarii (NTS) and dorsomotor vagal nucleus (DMX) in adult male rats. In study 1, spinal and intramedullary afferents to the visceral‐sensorimotor complex (NTS‐X) were traced to contiguous populations of cell bodies arranged in cylindrical segmental organization. NTS‐X afferents derive from curvilinear arrays of neurons that parallel the efferent radiations of the solitariotegmental tract. Newly discovered afferents arise from circumscribed cell groups in the dorsal reticular formation and periventricular zone. Another source was traced to a paraambigual cell column in the apex of the rostral ventrolateral reticular nucleus (n.RVL). In study 2, catecholaminergic afferents were initially defined with combined retrograde transport‐immunocytochemical methods. Deposits of retrograde tracers into NTS‐X transported to neurons containing tyrosine hydroxylase (TH) in the A1, C1, and C3 areas or phenylethanolamine N‐methyltransferase (PNMT) in the C1 area of the n.RVL and C3 area. In study 3, it was revealed that NTS‐X afferents arise, in part, as collaterals of thoracic reticulospinal neurons. Deposits of the retrograde fluorescent tracer Fluorogold into the upper thoracic cord and rhodamine‐labeled microbeads into NTS‐X transported to the same neurons within a subambigual locus in n.RVL and parts of nucleus raphe magnus. In study 4, dual retrograde tracer‐immunocytochemical analysis demonstrated that catecholamines are synthesized by a subset of neurons in the n.RVL that issue collaterals to the NTS‐X and thoracic cord. Double retrogradely labeled TH‐or PNMT‐immunoreactive cell bodies were restricted to the C1 area within a 450‐μm column bordered rostrally by the facial nucleus and ventrally by the medullary subpial surface. We conclude that visceral reflex arcs are reciprocally organized. Targets of NTS projection are also sources of local NTS‐X afferent innervation. Catecholaminergic and other local afferents from reticular formation, periventricular, and spinal gray may, via collaterals, simultaneously modulate visceral reflex excitability at the level of NTS and the outflow of autonomic and respiratory motoneurons. © 1995 Willy‐Liss, Inc.
Nervus terminalis ganglion of the bonnethead shark (Sphyrna tiburo): Evidence for cholinergic and catecholaminergic influence on two cell types distinguished by peptide immunocytochemistry
Authors: White Joel , Meredith Michael
Published: January 2005

The nervus terminalis is a ganglionated vertebrate cranial nerve of unknown function that connects the brain and the peripheral nasal structures. To investigate its function, we have studied nervus terminalis ganglion morphology and physiology in the bonnethead shark (Sphyrna tiburo), where the nerve is particularly prominent. Immunocytochemistry for gonadotropin‐releasing hormone (GnRH) and Leu‐Pro‐Leu‐Arg‐Phe‐NH2 (LPLRFamide) revealed two distinct populations of cells. Both were acetylcholinesterase positive, but LPLR‐Famide‐immunoreactive cells consistently stained more darkly for acetylcholinesterase activity. Tyrosine hydroxylase immunocytochemistry revealed fibers and terminal‐like puncta in the ganglion, primarily in areas containing GnRH‐immunoreactive cells.

Consistent with the anatomy, in vitro electrophysiological recordings provided evidence for cholinergic and catecholaminergic actions. In extracellular recordings, acetylcholine had a variable effect on baseline ganglion cell activity, whereas norepinephrine consistently reduced activity. Electrical stimulation of the nerve trunks suppressed ganglion activity, as did impulses from the brain in vivo. During electrical suppression, acetylcholine consistently increased activity, and norepinephrine decreased activity. Muscarinic and, to a lesser extent, α‐adrenergic antagoinsts both increased activity during the electrical suppression, suggesting involvement of both systems. Intracellular recordings revealed two types of ganglion cells that were distinguishable pharmacologically and physiologically. Some cells were hyperpolarized by cholinergic agonists and unaffected by norepinephrine; these cells did not depolarize with peripheral nerve trunk stim stimulation. Another. Another group of cells did depolarize with peripheral trunk stimulation; a representative of this group was depolarized by carbachol and hyperpolarized by norepinephrine.

These and other data suggest that the bonnethead nervus terminal is ganglion contains at least two cell populations that respond differently to acetylcholine and norepinephrine. The bonnethead nervus terminals ganglion appears to differ fundamentally from sensory and autonomic ganglia but does share some features with the neural circuits of forebrain GnRH systems. © 1995 Willy‐Liss, Inc.
Analysis of dendritic spines in rat CA1 pyramidal cells intracellularly filled with a fluorescent dye
Authors: Trommald Mart , Jensen Vidar , Andersen Per
Published: January 2005

The dendritic branching pattern and the distribution of dendritic spines were studied in hippocampal neurones with an improved technique. In slices taken from adult Wistar rats, CA1 pyramidal cells were filled with Lucifer yellow and examined under a laser‐scanning confocal microscope.

The basal dendrites were found evenly distributed inside a regular cupola‐shaped volume. Their total length was about 4,500 μm. The branches divided between one and three times, with the initial segments comprising less than 2%, and the long terminal segments (mean length, 119 μm) including more than 80% of the total length of the basal dendrites. The apical dendritic branches emerged obliquely from the main shaft, ran for a distance of 50 to 250 μm, and made up a total length of about 5,100 μm in stratum radiatum and between 1,100 and 3,200 μm in stratum lacunosum‐moleculare. The mean total length of the dendritic tree was 11,900 μm. All values were corrected for shrinkage. Shrinkage was measured in three dimensions and was 20.2% in the horizontal (x/y) plane and 40.9% in the vertical (z) plane.

Both the basal and the apical dendritic branches were covered by regularly spaced spines. When corrected for dehydration‐induced shrinkage and for hidden spines, the density was 1.80 and 2.00 spines/μm dendritic length for the basal and apical dendritic branches, respectively. Apart from the initial parts of the branches, which had few or no spines, the spines were remarkably evenly spaced. In particular, the distance between spine heads was significantly different from a random distribution, suggesting a regulatory process for the spacing of spines. © 1995 Wiley‐Liss, Inc.