bluuebunny/crossref_metadata_2025 huggingface dataset:
Nerve growth factor mRNA‐containing cells are distributed within regions of cholinergic neurons in the rat basal forebrain
Authors: Lauterborn Julie C. , Isackson Paul J. , Gall Christine M.
Published: January 2005

It has been proposed that nerve growth factor (NGF) provides critical trophic support for the cholinergic neurons of the basal forebrain and that it becomes available to these neurons by retrograde transport from distant forebrain targets. However, neurochemical studies have detected low levels of NGF mRNA within basal forebrain areas of normal and experimental animals, thus suggesting that some NGF synthesis may actually occur within the region of the responsive cholinergic cells. In the present study with in situ hybridization and immunohistochemical techniques, the distribution of cells containing NGF mRNA within basal forebrain was compared with the distribution of cholinergic perikarya. The localization of NGF mRNA was examined by using a 35S‐labeled RNA probe complementary to rat preproNGF mRNA and emulsion autoradiography. Hybridization of the NGF cRNA labeled a large number of cells within the anterior olfactory nucleus and the piriform cortex as well as neurons in a continuous zone spanning the lateral aspects of both the horizontal limb of the diagonal band of Broca and the magnocellular preoptic nucleus. In the latter regions, large autoradiographic grain clusters labeled relatively large Nissl‐pale nuclei; it did not appear that glial cells were autoradiographically labeled. Comparison of adjacent tissue sections processed for in situ hybridization to NGF mRNA and immunohistochemical localization of choline acetyltransferase (ChAT) demonstrated overlapping fields of cRNA‐labeled neurons and ChAT‐immunoreactive perikarya in both the horizontal limb of the diagonal band and magnocellular preoptic regions. However, no hybridization of the cRNA probe was observed in other principal cholinergic regions including the medial septum, the vertical limb of the diagonal band, or the nucleus basalis of Meynert. These results provide evidence for the synthesis of NGF mRNA by neurons within select fields of NGF‐responsive cholinergic cells and suggest that the generally accepted view of “distant” target‐derived neurotrophic support should be reconsidered and broadened.
Organization of midbrain catecholamine‐containing nuclei and their projections to the striatum in the North American opossum, Didelphis virginiana
Authors: Hazlett James C. , Ho Raymond H. , Martin George F.
Published: January 2005

Presumptive catecholamine (CA) neurons in the opossum midbrain were identified by tyrosine hydroxylase immunohistochemistry. In the midline, small to moderate numbers of CA cells were present in the rostral third of the nucleus raphe dorsalis and throughout the nucleus linearis. Ventrolaterally, such cells were observed in the deep tegmental reticular formation, in all subnuclei of the ventral tegmental area, and in the three subdivisions of the substantia nigra. The CA cells in these areas conform to the dopamine cell groups, A8, A9, and A10 as described in the rat. In several areas there appeared to be no separation between the CA neurons belonging to cytoarchitecturally different nuclei. In order to determine which CA neurons gave rise to striatal projections, the neostriatum was injected with True Blue (TB), and sections through the midbrain were processed for tyrosine hydroxylase (TH) and visualized by immunofluoroscence. Neurons containing both TB and TH were observed in each of the CA cell groups mentioned above. The distribution of these cells confirmed organizational features that may be unique to the opossum's substantia nigra. In addition, different patterns of labeling resulted from caudate versus putamen injections, suggesting a rudimentary medial to lateral topography in the organization of nigrostriatal projections. Although our results suggest that the organization of midbrain CA neurons in the opossum is similar to that in placental mammals, it is clear that differences exist.
Mapping study of the parabrachial taste‐responsive area for the anterior tongue in the golden hamster
Authors: Halsell Christopher B. , Frank Marion E.
Published: January 2005

The locations of taste‐responsive areas within the brainstem parabrachial nucleus (PBN), an obligatory taste relay in the golden hamster (Mesocricetus auratus), were mapped in relation to cytoarchitectural boundaries. The PBN was systematically searched for multiunit neural activity in response to a taste mixture composed of 0.1 M sucrose, 0.03 M NaCl, and 0.1 MKCl applied to the anterior tongue. Taste responses were located exclusively in one of three subdivisions of the medial PBN, which is thought to be specialized for gustatory processing, and in one of six subdivisions of the lateral PBN, which is thought to be specialized for general visceral processing. Based on Nissl‐stained material, both the medial and lateral PBN subdivisions in the hamster were similar to those reported for the rat PBN. The largest group of taste‐responsive cells encompassed two‐thirds of the central medial subdivision, while a smaller group of taste cells was exclusively located within the ventral lateral subdivision. The two taste‐responsive subdivisions are separated by the superior cerebellar peduncle and contain diverse cell types. The finding that anterior tongue taste may be exclusively represented in circumscribed cy to architecturally defined parts of two PBN divisions suggests that taste information from the anterior tongue is required for both specific gustatory and general visceral functions.
Planar differences in nuclear area and orientation in the subventricular and intermediate zones of the rat embryonic neocortex
Authors: Bayer Shirley A. , Altman Joseph , Dai Xiaofeng , Humphreys Laura
Published: January 2005

Nuclear area and orientation in the subventricular and intermediate zones was studied quantitatively in coronal vs. sagittal sections of the dorsomedial neocortex. Nissl‐stained methacrylate‐embedded normal rat embryos were studied between embryonic days (E) 13 and E22. The area of nuclear profiles and the degrees their long axes (defined as a straight line through the two most distant points in the nuclear profile) deviated from the horizontal (denned as parallel to the pial membrane) were determined with a computer‐graphics program. Because the nucleus is the most clearly outlined structure in embryonic cells, the area and orientation of the nucleus was taken to reflect the overall size and orientation of the cell body. Nuclear area is larger in the coronal plane than it is in the sagittal plane, especially between E17 and E20. Cell body orientation in the subventricular and lower intermediate zones is predominantly horizontal in the coronal plane and predominantly vertical in the sagittal plane. In the upper intermediate zone, cell body orientation is predominantly vertical in both planes, but more so in the sagittal plane. These data indicate that the majority of cell bodies in the subventricular and lower intermediate zones have a horizontally oriented, flattened elliptical shape with their larger diameters lying within the coronal plane and their smaller diameters in the sagittal plane. Because of the flattening, the cell bodies falsely appear to be vertically oriented in the sagittal plane. Qualitative observations in horizontal sections confirmed the quantitative computer analysis. These results are related to other findings with [3H]thymidine autoradiography concerning cell migration and the sojourn of cells in the subventricular and intermediate zones.
Hypophysiotrophic TRH‐producing neurons identified by combining immunohistochemistry for pro‐TRH and retrograde tracing
Authors: Kawano Hitoshi , Tsuruo Yoshihiro , Bando Hiroshi , Daikoku Shigeo
Published: January 2005

To determine hypophysiotrophic thyrotropin‐releasing hormone (TRH)‐producing neurons in the rat hypothalamus, we employed a combination of the immunohistochemistry for TRH prohormone (pro‐TRH) and the retrograde tracing of neurons that project to the median eminence (ME) by injecting biotinylated wheat germ agglutinin (WGA) into the ME. In intact rats, immunoreactive pro‐TRH‐positive neurons occurred in the parvicellular paraventricular nucleus (parvi‐PVN), basal part of the anterior and lateral hypothalamus, perifornical area and dorsomedial nucleus, especially accumulating in the parvi‐PVN. Twenty‐four hours after injection of the WGA into the middle portion of the ME., we found neurons that incorporated the lectin in the anterior periventricular area, the PVN, and the arcuate nucleus. When we examined serial sections consecutively stained. with anti‐WGA, anti‐pro‐TRH, and anti‐WGA, most of the pro‐TRH‐labeled neurons in the medial parvi‐PVN and a part of the neurons in the anterior periventricular area and in the anterior, lateral, and dorsal parvi‐PVN appeared to incorporate WGA. These neurons may correspond with the hypophysiotrophic TRH‐synthesizing neurons in the rat hypothalamus.
GABA‐immunoreactive neurons in the nematode Ascaris
Authors: Guastella John , Johnson Carl D. , Stretton Antony O. W.
Published: January 2005

γ‐Aminobutyric acid (GABA) immunoreactive neurons in the cephalic, somatic, and caudal regions of the Ascaris nervous system were visualized with serial section and whole‐mount GABA immunocytochemistry. In the ventral and dorsal nerve cords, GABA‐ like immunoreactivity (GLIR) is localized to the neurites and cell bodies of identified inhibitory motor neurons and to two fibers, one in each cord, that arise from neurons in the nerve ring. GLIR is absent from identified excitatory motor neurons and from ventral cord interneurons. In neurons containing GLIR, immunoreactivity was present throughout the cell, which argues against an exclusive localization of GABA at conventional synapses.

In whole mounts, ten GABA‐immunoreactive neurons were present in the cephalic region. These include four nerve ring‐associated cells (the RME‐like cells), two bilaterally symmetrical pairs of lateral ganglia neurons (the amphid‐GABA and deirid‐GABA cells) and one bilaterally symmetrical pair of ventral ganglion cells (the VG‐GABA cells). In sections, the RME‐like cells and the VG‐GABA cells were consistently stained through the cephalic region. However, anti‐GABA staining of the lateral ganglia cells in sections was light, thus suggesting that they contain less GLIR than the other more intensely stained GABA‐immunoreactive neurons. In the caudal region, a single GABA‐immunoreactive neuron was present in the dorsal rectal ganglion. Our data suggest that these ten cephalic neurons, and a single dorsal rectal ganglion neuron, use GABA as a neurotransmitter.
Parabrachial nucleus projection towards the hypothalamic supraoptic nucleus: Electrophysiological and anatomical observations in the rat
Authors: Jhamandas Jack H. , Harris Kim H. , Krukoff Teresa L.
Published: January 2005

It has been proposed that the pontine parabrachial nucleus (PBN) participates in the regulation of body fluid balance and the release of vasopressin from the neurohypophysis, although the pathways mediating the latter response are uncertain. This study in the rat, utilizing anatomical and electrophysiological methods, describes a projection from the lateral PBN towards the hypothalamic supraoptic nucleus (SON). Rats received iontophoretic injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA‐L, 2% solution). After 14–17 days, rats were sacrificed and their brains prepared for immunofluorescent visualization of projections to the SON region. PHA‐L‐labelled terminals were found primarily in perinuclear regions immediately dorsal to the SON. In contrast, injections within the medial PBN and the nearby Kölliker‐Fuse nucleus did not reveal labelling in or around the SON. Extracellular recordings from 86 of 118 antidromically identified neurons in anaesthetized rats revealed a set of complex synaptic responses after stimulation in the PBN. Excitatory responses (in 82 of 86 cells) of short (< 100 msec, 39/82 cells) and long (> 100 msec, 43/82) duration were observed in both vasopressin‐ and oxytocin‐secreting cells of the SON, while 4/86 cells displayed a depressant response to PBN stimulation. In the adjacent perinuclear zone, 22/39 nonneurosecretory cells responded with an increase in their excitability consequent to an identical stimulus. These data suggest a predominantly facilitatory influence of lateral PBN neurons on SON neurosecretory cells in the rat, and that the PBN‐SON projection is an indirect one that utilizes an interneuronal network located in the perinuclear zone adjacent to the SON.
From embryo to adult: Anatomy and development of a leg sensory organ in Phormia regina meigen (Insecta: Diptera). I. Anatomy and physiology of a larval “Leg” sensory organ
Authors: Lakes‐Harlan R. , Pollack G. S. , Merritt D. J.
Published: January 2005

Neurons within the precursor of the adult leg, the imaginal disc, innervate a larval sense organ, Keilin's organ. Electron microscopical investigations of first instar larvae show that five dendrites end at the organ: three insert at the bases of the three hairs of the organ and two end against the cuticle, without any apparent cuticular specialization. In third instar larvae, the imaginal leg discs invaginate into the body cavity, and only four of the dendrites (the outer segments of which become greatly elongated) remain in contact with Keilin's organ. The axons of the neurons that supply Keilin's organ project into a ventral neuropile region of the central nervous system, with a pattern that resembles the projections of other larval sensilla. Electrical activity can be recorded from neurons of the imaginal disc in response to mechanical stimulation.
Unmyelinated axons of the auditory nerve in cats
Authors: Ryugo D. K. , Dodds L. W. , Benson T. E. , Kiang N. Y. S.
Published: January 2005

This paper describes some central terminations of type II spiral ganglion neurons as labeled by extracellular injections of horseradish peroxidase (HRP) into the auditory nerve of cats. After histological processing with diaminobenzidine, both thick (2–4 μm) and thin (0.5 μm) fibers of the auditory nerve were stained. Whenever traced, thick fibers always originated from type I spiral ganglion neurons and thin fibers always from type II ganglion neurons. Because the labeling of type II axons faded as fibers projected into the cochlear nucleus, this report is limited to regions of the ventral cochlear nucleus near the auditory nerve root. The central axons of type II neurons are unmyelinated, have simple yet variable branching patterns in the cochlear nucleus, and form both en passant and terminal swellings. Under the light microscope, most swellings are located in the neuropil but they are also found in the vicinity of cell bodies, nodes of Ranvier of type I axons, and blood vessels. Eighteen en passant swellings in the neuropil were located by light microscopy and resectioned for electron microscopy; two of these swellings exhibited ultrastructural features characteristic of chemical synapses. The data indicate that inputs from outer hair cells might be able to influence auditory processing in the cochlear nucleus through type II primary neurons.
Different postnatal development profiles of neurons containing distinct GABAA receptor β subunit mRNAs (β1, β2, and β3) in the rat forebrain
Authors: Zhang Jian‐Hua , Sato Makoto , Tohyama Masaya
Published: January 2005

The expression of three β subunit (β1, β2, and β3) mRNAs for γ‐aminobutyric acidA receptor in the postnatal rat forebrain was examined by in situ hybridization h istochemistry with probes synthesized for the respective subunit mRNAs. The developmental expression of these subunit mRNAs conformed to one of three patterns. Pattern I was high expression of the mRNA at birth and a constant or increasing expression thereafter. In contrast, pattern II was no or very low expression of the mRNA at birth, with expression quickly increasing to reach the adult level in the early postnatal period. Pattern III was the transient expression of the subunit mRNA or else a marked decrease of its expression after a peak in the early postnatal period.

On the basis of this classification, the expression of β3 subunit mRNA followed pattern I in most regions of the forebrain, such as the isocortex, the olfactory bulb and some of its related areas, the hippocampal formation, the amygdala, the septum, the bed nucleus of the stria terminalis, the caudate‐putamen, the nucleus accumbens, the globus pallidus, the ventral pallidum, and the hypothalamus. In some areas, such as the magnocellular preoptic nucleus, the thalamus, and the subthalamic nucleus, pattern III was seen for this subunit. However, none of the regions of the brain showed pattern II expression of β3 subunit mRNA. In contrast, the expression of β1 and β2 subunit mRNAs followed pattern II in most regions of the forebrain. These included the expression of β1 subunit mRNA in the isocortex, the olfactory bulb, the hippocampal formation, the amygdala, the septum, the bed nucleus of the stria terminalis, the thalamus, and the hypothalamus, and the expression of β2 subunit mRNA in the isocortex, the olfactory bulb and some of its related areas, the amygdala, the nucleus of the diagonal band, the caudate‐putamen, the thalamus, and the hyothalamus. Pattern I was not found for β1 subunit mRNA, although it was seen in some areas for β2 subunit mRNA, such as the ventral pallidum, the globus pallidus, and the magnocellular preoptic nucleus. On the other hand, pattern III was followed by β1 subunit mRNA in the anterior olfactory nucleus, the olfactory tubercle, and the piriform cortex, and the same pattern for the β2 subunit was also found in the olfactory tubercle, the hippocampal formation, the septum, the bed nucleus of the stria terminalis, and the nucleus accumbens.

These results indicate that all three β subunit mRNAs are under developmental regulation, and that the different mRNAs are differentially regulated in various regions of the forebrain. In addition, the present study also showed that β3 subunit mRNA is highly expressed in both the neonatal and adult stages, indicating an important role for this subunit in brain development.
Identification of a retinal protein in Drosophila with antibody to the α subunit of bovine brain Go protein
Authors: Garen‐Fazio Suzanne , Neer Eva J. , Schmidt Carl J.
Published: January 2005

An antibody directed against the αo subunit of bovine brain Go (R4) was used to identify a Drosophila retinal protein which may be the analogue of vertebrate transducin. The immunoreactivity appears predominantly in the retinal and occellar rhabdomeres. On a Western blot, the antibody recognizes a 41 kDa protein that is present in the heads of yellow white flies, but not in the heads of eyeless mutant flies, eyes absent. This protein is not recognized by an antibody raised against Drosophila αo.

Antibody R4 intensely stains rhabdomeres and, to a lesser extent, the neuropil of the central nervous system in tissue sections of adult flies. Antibody to Drosophila αo stains the neuropil of the central nervous system, but does not stain rhabdomeres. In developing flies, faint immunoreactivity appears in the retinal rhabdomeres at about 70% of the time through pupal development and increases to its apparent adult maximal level about 1 day after eclosion. Tissue sections from a phototransduction mutant, norp A, have retinal immunoreactivity at normal levels up to about 1 week after eclosion, but by 2 weeks, immunoreactivity has largely disappeared. This disappearance parallels the degeneration of the retina in norp A mutants.

In Drosophila and other invertebrates, light activates a phospholipase C in the retina. The identification of a protein in Drosophila rhabdomeres with an antibody raised against a mammalian G protein α subunit thought to be involved in phospholipase C activation suggests that there may be common structural features between the putative Drosophila transducin and α0, The identification of regions common to mammalian α0 and Drosophila transducin may then provide clues to the structural requirements for PLC activation.
Postnatal development of thalamic recipient neurons in the monkey striate cortex: Somatic inhibitory synapse acquisition by spiny stellate neurons of layer 4C
Authors: Lund Jennifer S. , Harper Thomas R.
Published: January 2005

The development of type 2 (Colonnier,1981) synapses on the cell bodies of thalamic recipient spiny stellate neurons in layers 4C alpha and 4C beta of primary visual cortex neurons was examined over the first 36 postnatal weeks and in the adult monkey. The type 2 synapses, known to be GABAergic (Ribak, 1978) and therefore presumed to be inhibitory, developed faster on the alpha neurons than the beta neurons. Both neuron groups show a marked increase and then decline in the percentage of the somatic membrane covered by type 2 synaptic appositions during this 36‐week time period. The time course of the type 2 synapses development is compared to that of the spine synapse development described in previous studies (Lund and Holbach, 1991; Lund et al., 1991), and it is clear that on both neuron groups this inhibitory synapse population is put in place and refined later than the spine synapses. These findings suggest that each cortical neural circuit has a unique time course for its early development within an overall time window (Rakic et al., 1986), or sensitive period (Hubel and Wiesel, 1970). Visual deprivation, although causing the alpha and beta neurons to adopt a more similar temporal and numerical developmental pattern than normal, did not prevent acquisition and loss phases of type 2 synapses or the assumption of a normal numerical loading by 36 weeks of age.
Neurogenesis in the brain auditory pathway of a marsupial, the northern native cat (dasyurus hallucatus)
Authors: Aitkin Lindsay , Nelson John , Farrington Moyra , Swann Sue
Published: January 2005

Neurogenesis in the auditory pathway of the marsupial Dasyurus hallucatus was studied. Intraperitoneal injections of tritiated thymidine (20–40 m̈Ci) were made into pouch‐young varying from 1 to 56 days pouch‐life. Animals were killed as adults and brain sections were prepared for autoradiography and counterstained with a Nissl stain.

Neurons in the ventral cochlear nucleus were generated prior to 3 days pouch‐life, in the superior olive at 5–7 days, and in the dorsal cochlear nucleus over a prolonged period. Inferior collicular neurogenesis lagged behind that in the medial geniculate, the latter taking place between days 3 and 9 and the former between days 7 and 22. Neurogenesis began in the auditory cortex on day 9 and was completed by about day 42. Thus neurogenesis was complete in the medullary auditory nuclei before that in the midbrain commenced, and in the medial geniculate before that in the auditory cortex commenced.

The time course of neurogenesis in the auditory pathway of the native cat was very similar to that in another marsupial, the brushtail possum. For both, neurogenesis occurred earlier than in eutherian mammals of a similar size but was more protracted.
Position‐ and fibre type‐dependent selectivity by regenerating motor axons in reformation of the topographical projection to the glutaeus muscle in the adult toad (bufo marinus)
Authors: Brown David R. , Everett Alan W.
Published: January 2005

The toad glutaeus magnus muscle receives a topographical innervation dependent on the rostrocaudal origins of glutaeus motor axons on the spinal cord. The same projection is re‐established in adult animals after cutting the glutaeus muscle nerve and allowing regenerating axons to reinnervate the muscle (Brown and Everett (1990) J. Comp. Neurol. 292:363–372). To determine whether the topographically selective reinnervation of the glutaeus muscle comes about because of genuine positional qualities associated with the pre‐ and post‐synaptic tissues, we undertook two different experimental procedures: first, the nerve supply to the muscle was cut and redirected to ensure that regenerating axons entered the muscle via entirely novel pathways; and second, the triceps femoris nerve was cut so that the glutaeus muscle was reinnervated from a large pool of motor axons which were mostly foreign but segmentally appropriate. The motor projection to the muscle was determined by the glycogen depletion procedure; single glutaeus motor axons were repetitively stimulated in vitro to deplete muscle fibres of their stores of glycogen. The spatial location of fibres belonging to single motor units could then be determined by staining sections of the muscle histochemically for glycogen. A similar to normal projection was re‐established after both experiments in that rostrally located motor axons innervated mostly the ventral portion of the muscle and caudal axons mostly the dorsal portion of the muscle. “Intermediate” axons synapsed predominantly with fibres in the middle of the muscle. Furthermore, the arrangement of fibre types in the muscle could not fully account for the reformation of the topographical projection by a type matching mechanism, although a secondary role for fibre types in the subsequent refinement of the projection was clearly suggested by our findings. Our results provide evidence for a distinction between at least two determinants that influence the reinnervation of muscle: positional cues and fibre types, with the former taking precedence over the latter.
Glycinergic interplexiform cells make synaptic contact with amacrine cell bodies in goldfish retina
Authors: Yazulla Stephen , Studholme Keith M.
Published: January 2005

Recent works utilizing glycine‐immunoreactivity (IR) and combined Golgi impregnation and 3H‐glycine uptake autoradiography indicate that glycinergic interplexiform cells (IPC) may synapse upon cell bodies in the inner nuclear and ganglion cell layers in fish retina. This possibility was investigated with immunocytochemical techniques using presynaptic and postsynaptic markers for glycinergic neurons: a monoclonal antibody (mAb 7A) against the 93 kDa subunit of the strychnine‐sensitive glycine receptor and a polyclonal antiserum against a glycine/BSA conjugate. Synaptic contacts onto the lateral and proximal surfaces of amacrine cell bodies and onto the distal surface of cells in the ganglion cell layer were identified with both probes. The contacts were rare with one contacted amacrine cell/section of 500 linear μm. Serial 1‐μm sections were processed alternately for glycine and GABA antisera using postembedding techniques at the light microscopic level. Glycine‐IR processes + boutons were apposed to GABA‐IR cell bodies in 16 of 17 examples, indicating that the dendro‐somatic contacts were onto GABA‐immunoreactive amacrine cell bodies. In context of other published morphological data, we suggest that the dendro‐somatic synapses were derived from glycinergic IPCs. Glycinergic IPCs receive input from GABAergic horizontal cells and, via a shunt conductance produced by the dendro‐somatic contacts, may be involved in controlling the sensitivity, temporal, or spatial properties of amacrine cell responses to large field illuminatio.
Immunohistochemical localization of calretinin in the rat hindbrain
Authors: Arai Ryohachi , Winsky Lois , Arai Mari , Jacobowitz David M.
Published: January 2005

The localization of calretinin in the rat hindbrain was examined immunohistochemically with an antiserum against calretinin purified from the guinea pig brain. Calretinin immunoreactivity was found within neuronal elements. The distribution of calretinin‐immunoreactive cell bodies and fibers is presented in schematic drawings and summarized in a table. Major calretinin immunoreactive neurons were found in the lateral and medial geniculate nuclei, substantia nigra, ventral tegmental area, interpeduncular nucleus, periaqueductal gray, mesencephalic trigeminal nucleus, superior and inferior colliculi, pontine nuclei, parabrachial nucleus, dorsal and laterodorsal tegmental nuclei, cochlear nuclei, vestibular nuclei, medullary reticular nuclei, nucleus of the solitary tract, area postrema, substantia gelatinosa of the spinal trigeminal nucleus, and cerebellum. These results show that distinct calretinin‐immunoreactive neurons are widely distributed in the rat hindbrai.
Synaptic organization of cortico‐cortical connections from the primary visual cortex to the posteromedial lateral suprasylvian visual area in the cat
Authors: Lowenstein Pedro R. , Somogyi Peter
Published: January 2005

The synaptic organization of the projection from the cat striate visual cortex to the posteromedial lateral suprasylvian cortical area (PMLS) was examined. The anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA‐L) was iontophoretically delivered into area 17, and anterogradely labeled fibers were revealed in PMLS by means of an immunocytochemical detection method. Most axons and presumptive terminal swellings were found in layers III and IV. The neuronal elements (n = 190) that were postsynaptic to anterogradely labeled boutons were quantitatively analyzed. All anterogradely labeled cortico‐cortical boutons (n = 182) established type 1 synapses. The results show that 83% of the postsynaptic targets were dendritic spines, probably belonging to pyramidal cells. Dendritic shafts constituted 17% of the targets. The dendritic shafts postsynaptic to cortico‐cortical boutons were studied for the presence of gamma‐aminobutyric acid (GABA) with a postembedding immunogold method. Most dendritic shafts (85%) that were tested were found to be GABA‐positive, demonstrating that they originate from local inhibitory neurons. Taking into account that most postsynaptic targets were spines and extending the results of the immunocytochemical testing to the total population of postsynaptic dendrites, it was calculated that at least 14% of targets originated from GABA‐positive cell.

Thus cortico‐cortical axons establish direct monosynaptic connections mainly with pyramidal and to a lesser extent with GABAergic nonpyramidal neurons in area PMLS, providing both feedforward excitation and feedforward inhibition to a visual associational area known to be involved in the processing of motion information. The results are consistent with previously demonstrated deficits in physiological properties of neurons in PMLS following removal of cortico‐cortical afferent.
Electron‐microscopic analysis of synaptic input from the perigeniculate nucleus to the A‐laminae of the lateral geniculate nucleus in cats
Authors: Cucchiaro Josephine B. , Uhlrich Daniel J. , Sherman S. Murray
Published: January 2005

The perigeniculate nucleus of carnivores is thought to be a part of the thalamic reticular nucleus related to visual centers of the thalamus. Physiological studies show that perigeniculate neurons, which are primarily GABAergic, provide feedback inhibition onto neurons in the lateral geniculate nucleus. However, little is known about the anatomical organization of this feedback pathway. To address this, we used two complementary tracing methods to label perigeniculate axons for electron microscopic study in the geniculate A‐laminae: intracellular injection of horseradish peroxidase (HRP) to fill an individual perigeniculate cell and its axon; and anterograde transport of Phaseolus vulgaris leucoagglutinin to label a population of perigeniculate axons. Labeled perigeniculate terminals display features of F1 terminals in the geniculate neuropil: they are small, contain dark mitochondria, and form symmetric synaptic contacts. We found that most of the perigeniculate terminals (> 90%) contact geniculate cell dendrites in regions that also receive a rich innervation from terminals deriving from visual cortex (e.g., “cortico‐recipient” dendrites). The remainder of the perigeniculate synapses (10%) contacted dendrites in regions that also received direct retinal input (e.g., “retino‐recipient” dendrites). Serial reconstruction of segments of dendrites postsynaptic to perigeniculate terminals suggests that these terminals contact both classes of relay cell in the A‐laminae (X and Y), although our preliminary conclusion is that an individual perigeniculate cell contacts only one class. Finally, our quantitative comparison between labeled perigeniculate terminals and unlabeled Fl terminals indicates that these perigeniculate terminals form a distinct subset of Fl terminals. We quantitatively compared the labeled perigeniculate terminals to unlabeled F1 terminals. Although the parameters of the perigeniculate terminals fell entirely within the range of those for the unlabeled F1 terminals, as populations, we found consistent differences between these two groups. We thus conclude that, as populations, other sources of F1 terminals are morphologically distinct from perigeniculate terminals and innervate different target.
Effects of prenatal protein deprivation on postnatal development of granule cells in the fascia dentata
Authors: Diáz‐Cintra S. , Cintra L. , Galván A. , Aguilar A. , Kemper T. , Morgane P. J.
Published: January 2005

The effect of prenatal protein deprivation on the postnatal development of granule cells in the fascia dentata in the rat was studied at 15, 30, 90, and 220 days of age. The granule cells showed a significant reduction in cell size, decreased number of synaptic spines throughout their dendritic extent, and reduced complexity of dendritic branching in the outer two‐thirds of the molecular layer. All of these deficits were present at 15 days and persisted throughout the study (220 days). The least deficits in synaptic spine density occurred at 90 days and in dendritic branching at 30 days. Partial restitution of earlier, more severe deficits was associated primarily with maturational events occurring in the protein deprived rats, whereas later increases in deficits were related primarily to a failure of the protein deprived rats to keep pace with neuronal development occurring in the controls. The present results are similar to those noted in our previous study in this journal of the effect of a low protein diet (8% casein) on these neurons that extended from pregnancy until the time of sacrifice at 30, 90, and 220 days of age (Cintra et al, 1990; 532:271–277). Taken together, these two studies suggest that the postnatal adaptation of the granule cells to prenatal protein deprivation is primarily due to events that occur during pregnancy and that the site of predilection for the deficit is their dendrites in the outer two‐thirds of the molecular layer of the fascia dentat.
Alterations in afferent pathways from the urinary bladder of the rat in response to partial urethral obstruction
Authors: Steers William D. , Ciambotti Jonathan , Etzel Barbara , Erdman Susan , de Groat William C.
Published: January 2005

Afferent pathways from the urinary bladder were examined with axonal tracing techniques in normal female Wistar rats and in those with partial urethral ligation. Following injection of wheat germ agglutinin‐horseradish peroxidase (HRP) into the bladder wall, HRP was detected in lumbosacral dorsal root ganglion cells and in afferent projections to the L6–S1 spinal cord at sites in laminae I, II, V–VII, and X known to receive visceral afferent input. Partial urethral ligation (6 weeks) produced a sixfold increase in bladder weight and altered the morphology of bladder afferent pathways. Changes included an increase in the average cross‐sectional area of labelled neuronal profiles in L6 and ST dorsal root ganglia in obstructed (766 ± 378 μm2, P < 0.001) compared to control rats (528 ± 189 μm2). The cross‐sectional area of the largest profiles also increased by approximately 40%. The mean number of labelled dorsal root ganglion cell profiles was similar in ligated (837 ± 198) and control (883 ± 352) groups. When compared to control animals the obstructed animals exhibited a 60% increase in the area of the labelled afferent terminal field in the intermediolateral region of the L6‐S1 spinal cord. This increased labelling was even more remarkable given that the volume of tracer per bladder weight injected into the hypertrophied bladder was 87% less than controls. These results provide evidence that bladder afferents project to regions of the spinal cord known to regulate micturition and that these afferents can undergo morphological alterations and/or changes in axoplasmic transport in response to urethral ligation. Changes may occur in response to increased target organ mass, increased neural activity, or alterations in the levels or activity of neurotrophic factors.
Architectonics of the parietal and temporal association cortex in the strepsirhine primate Galago compared to the anthropoid primate Macaca
Authors: Preuss Todd M. , Goldman‐Rakic Patricia S.
Published: January 2005

A number of higher order association areas have been described in the parietal and temporal cortex of large‐brained anthropoid primates such as Macaca. However, little is known about the evolution of these areas, and the existence of homologous areas has not yet been clearly demonstrated in other mammalian groups. We addressed this issue by comparing the myelo‐ and cytoarchitecture of posterior association cortex in the anthropoid Macaca to that of the small‐brained, strepsirhine (“prosimian”) primate Galag.

Our results suggest that Galago possesses many, if not most, of the areas present in Macaca. We were able to identify regions in Galago which resemble Macaca posterior parietal area 7, superior temporal polysensory cortex (ST), inferotemporal visual cortex (IT), the temporoparietal auditory area (Tpt), and posterior parahippocampal cortex (areas TH and TF). Area 7, ST, and IT can each be subdivided further in Macaca, and for most of these subdivisions we were able to identify counterparts in Galago. However, we could not distinguish as many divisions of ST cortex in Galago as in Macaca, and it is possible that new areas arose in this region during anthropoid evolution. There also appear to be general differences in architectonic organization between these animals, with Macaca exhibiting greater development of pyramidal layer IIIc and of the internal granular layer (IV) across much of the parieto‐temporal corte.

These findings suggest that many, although possibly not all, of the parietal and temporal association areas present in the modern anthropoid Macaca evolved early in primate history, prior to the divergence of the lineages leading to strepsirhines and anthropoids.
Differential effect of functional olfactory bulb deafferentation on tyrosine hydroxylase and glutamic acid decarboxylase messenger RNA levels in rodent juxtaglomerular neurons
Authors: Stone Donna M. , Grillo Mary , Margolis Frank L. , Joh Tong H. , Baker Harriet
Published: January 2005

Expression of the dopaminergic phenotype in olfactory bulb (OB) juxtaglomerular neurons (constituting a population of periglomerular and external tufted cells) is dependent upon functional innervation by peripheral olfactory receptors. Loss of functional input in rodents, by either peripheral deafferentation or deprivation of odorant access, results in a profound decrease in the expression of juxtaglomerular tyrosine hydroxylase (TH). We have examined the effects of such treatments on the expression of the neurotransmitter biosynthetic enzyme glutamic acid decarboxylase (GAD), which is colocalized with TH in the majority of TH‐containing juxtaglomerular neurons. Following either chemically induced OB deafferentation in adult mice or unilateral odor deprivation in neonatal rats, steady‐state OB GAD messenger RNA levels remained essentially unchanged as assessed by Northern blot analysis 20–40 days after treatment. These results were confirmed by in situ hybridization analysis, which demonstrated a profound loss of juxtaglomerular TH messenger RNA but no accompanying decrease in regionally colocalized GAD message. Since GAD is found in nearly all dopaminergic OB cells, the preservation of juxtaglomerular GAD message implies that olfactory receptor neurons exert a differential transneuronal regulation of TH and GAD gene transcription.
Cultured epithelioid astrocytes migrate after transplantation into the adult rat brain
Authors: Emmett Caroline J. , Lawrence Jean M. , Raisman Geoffrey , Seeley P. John
Published: January 2005

A highly purified population of dividing epithelioid astrocytes has been prepared from postnatal rat corpus callosum. These cells were labelled in culture by incorporation of either [3H]thymidine or fluorescent microspheres and transplanted in a fibrin clot into the hippocampi of adult syngeneic rats. Transplanted cells divided in vivo and progressively migrated into the host brain from the site of implantation up to distances of about 1 mm. After a 1‐week survival, transplant cells stained strongly for glial fibrillary acidic protein and had the thick sinuous processes characteristic of stellate astrocytes. Artefactual transfer of radiolabel to host cells was ruled out by control experiments in which either the proportion of transplant cells that were radiolabelled was varied or radiolabelled transplant cells were killed prior to implantation. Astrocyte migration over the first days after implantation was determined to occur at a rate of approximately 100 μm per day. Transplant cells moved into both grey and white matter areas of the host brain and over the migratory period were commonly observed to be associated with blood vessels. Some transplant cells were directly juxtaposed against neuronal perikarya and dendrites. Many labelled astrocytes were located in areas that were apparently completely free of damage caused by implantation. These results define a class of mature astrocytic cells that have the ability to migrate through the adult brain. The existence of pathways for cell movement in the adult CNS has implications for the mechanisms of tissue remodelling after injury and transplantation, for regenerative repair of the CNS, and for the dynamics of cell‐cell contacts in the normal adult mammalian brain.
Ipsilateral cortical connections of primary somatic sensory cortex in rats
Authors: Fabri Mara , Burton Harold
Published: January 2005

The organization of ipsilateral cortical connections of the rat primary somatic sensory area (SI) was analyzed following small injections of multiple fluorescent tracers in the same case, into two or three SI body representations identified electrophysiologically. Labeling patterns were studied in tangential cortical sections and in flattened reconstructions from coronal sections. The cytochrome oxidase staining in tangential sections served as a control for injection location and to position labeling patterns found within granular portion of SI.

The results show that most connections made with SI are reciprocal. Their topographical organization show different degrees of precision in the different areas. Homotypical and heterotypical connections were defined, the latter being more evident within the granular portion of SI. The findings: (1) were consistent with subdividing rat SI into four distinct areas with each having its own pattern of connections, (2) revealed two topographically organized regions in parietal cortex lateral to SI called second somatosensory (SII) and parietal ventral (PV) areas, (3) confirmed a topographical pattern in motor cortex and suggested an organization for connections between SI and an agranular medial field, and (4) demonstrated three more regions in parietal cortex connected to SI: posterior to SI called parietal medial; lateral to PV called parietal rhinal; posterior to SII called parietal lateral. Differences were noted in the distinctions between and within the maps when label distributions were plotted separately from supra‐ and infragranular layers. These findings agree with previous parcellations of the rat SI (Chapin et al., 1987: J. Comp Neurol 263:326–346), squirrel PV and SII (Krubitzer et al., 1986: J. Comp Neurol 250:403–430), and the organization of rat corticospinal neurons in many of the same areas (Li et al., 1990: Somat Motor Res 7:315–335).
Identification and distribution of microglial cells in the cerebral cortex of the lizard: A histochemical study
Authors: Castellano Bernardo , Gonzalez Berta , Dalmau Ishar , Vela Jose Miguel
Published: January 2005

The histochemical demonstration of nucleoside diphosphatase as a specific microglial marker was used to study the distribution of this glial cell type in the cerebral cortex of Podarcis muralis and Podarcis hispanica. Our results showed that in both species, NDPase staining was specific for the microglial cell population and that microglial cells displayed a specific localization pattern in the different cortical areas. In the medial cortex, microglial cells were principally found in the outer and inner plexiform layers in the strata adjacent to the granular layer. Moreover, some microglial cells were found near the ependymal layer, but no microglial cells were normally present near the brain surface and never in the deep inner plexiform layer. In the dorsomedial cortex, microglial cells were found near the brain surface in the outer plexiform layer, in the upper part of the granular layer, and near the ependymal layer. No microglial cells were found, however, in the outer and inner plexiform layers adjacent to the granular layer. Finally, in the dorsolateral cortex, microglial cells were located in the upper part of the outer plexiform layer, in and bordering the granular layer, and scattered in the inner plexiform layer. This layered‐pattern distribution of microglial cell population in the cerebral cortex of the lizard differs from the apparently homogeneous distribution of microglia in the brain of mammals.