bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of 125I‐neurotensin binding sites in human forebrain: Comparison with the localization of acetylcholinesterase
Authors: Szigethy E. , Quirion R. , Beaudet A.
Published: January 2005

The distribution of 125I‐neurotensin binding sites was compared with that of acetylcholinesterase reactivity in the human basal forebrain by using combined light microscopic radioautography/histochemistry. High 125I‐neurotensin binding densities were observed in the bed nucleus of the stria terminalis, islands of Calleja, claustrum, olfactory tubercle, and central nucleus of the amygdala; lower levels were seen in the caudate, putamen, medial septum, diagonal band nucleus, and nucleus basalis of Meynert. Adjacent sections processed for cholinesterase histochemistry demonstrated a regional overlap between the distribution of labeled neurotensin binding sites and that of intense acetylcholinesterase staining in all of the above regions, except in the bed nucleus of the stria terminalis, claustrum, and central amygdaloid nucleus, where dense 125I‐neurotensin labeling was detected over areas containing only weak to moderate cholinesterase staining. At higher magnification; 125I‐neurotensin‐labeled binding sites in the islands of Calleja, supraoptic nucleus of the hypothalamus, medial septum, diagonal band nucleus, and nucleus basalis of Meynert were selectively associated with neuronal perikarya found to be cholinesterase‐positive in adjacent sections. Moderate 125I‐neurotensin binding was also apparent over the cholinesterase‐reactive neuropil of these latter three regions. These data suggest that neurotensin (NT) may directly influence the activity of magnocellular cholinergic neurons in the human basal forebrain, and may be involved in the physiopathology of dementing disorders such as Alzheimer's disease, in which these neurons have been shown to be affected.
Development of neuropeptide Y (NPY) immunoreactive neurons in the rat occipital cortex: A combined immunohistochemical‐autoradiographic study
Authors: Cavanagh Marion E. , Parnavelas John G.
Published: January 2005

The postnatal development of neuropeptide Y (NPY)‐immunoreactive neurons, previously labeled with [3H]thymidine on embryonic days E14–E21, has been studied in the rat occipital cortex. Immunohistochemistry combined with autoradiography showed evidence of a modified “inside‐‐out” pattern of maturation. NPY‐neurons are generated between E14 and E20 and are found in layers II–VI of the cortex and the subcortical white matter. NPY neurons from all these birthdates are overproduced at first, although cells generated at E16 produce the greatest excess, followed by E15 and E17. Some of these transient neurons are found in the “wrong” layer for their birthdates, and their elimination produces a more “correct” alignment at maturity. However, most of the NPY neurons that survive are generated at E17, and these cells are found throughout layers II–VI with a preponderance in layer VI. This evidence is strongly suggestive of cell death rather than merely cessation of production of NPY.
Plasticity of dorsal root and descending serotoninergic projections after partial deafferentation of the adult rat spinal cord
Authors: Polistina Dean C. , Murray Marion , Goldberger Michael E.
Published: January 2005

Plasticity of dorsal root (DR) and descending serotoninergic (5‐HT) projections following dorsal rhizotomy fromL2 to S1 sparing L5 was studied by means of an intra‐animal comparison in the adult rat spinal cord. Projections of the chronically and acutely spared root were compared by cholera‐toxin conjugated horseradish peroxidase (CT‐HRP) injected into the sciatic nerves as the transganglionic tracer. Projections in unoperated controls, operated controls (acute bilateral spared root), and in experimental animals (chronic spared root on one side and acute spared root on the other) were mapped and the density was measured with an image analysis system. Labeled DRG cells and motor neurons were counted to determine if there were differences in the delivery of the label between the two sides. Measurements of the area of the dorsal horn and, separately, of the superficial laminae were made to control for shrinkage.

DR projections were symmetrical in operated and unoperated controls, but a significant increase in DR projection density was found from L6 to L3 in the dorsal horn and Clarke's nucleus at L1 on the chronic spared root side in animals in which an equal number of DRG cells was labeled on the two sides. Density of 5‐HT immunoreactivity was symmetrical in controls. Ipsilateral to chronic spared root rhizotomy, the area fraction occupied by 5‐HT projections increased in Clarke's nucleus and in the superficial dorsal horn of all partially deafferented segments except L5, the spared root segment.

Partial deafferentation of the adult rat lumbosacral spinal cord may therefore elicit sprouting from the spared dorsal root and, outside of the dorsal root projection zone, sprouting from the spared descending 5‐HT system. Plasticity of dorsal root projections and of 5‐HT projections occur in different regions; in regions of the increased spared root projection, no increase is seen in 5‐HT projections, suggesting that sprouting in the adult rat spinal cord is regulated, perhaps by competitive or hierarchical mechanisms.
Hypothalamic galanin‐immunoreactive neurons projecting to the posterior lobe of the rat pituitary: A combined retrograde tracing and immunohistochemical study
Authors: Arai R. , Onteniente B. , Trembleau A. , Landry M. , Calas A.
Published: January 2005

To identify the galanin‐immunoreactive neurons projecting to the posterior lobe of the pituitary in the rat hypothalamus, a retrograde tracer (complex of wheat germ agglutinin‐enzymatically inactive horseradish peroxidase‐colloidal gold) was injected into the posterior lobe of the pituitary. Sections of the hypothalamus were treated with a combination of silver enhancement of retrogradely transported tracer and immunohistochemistry of galanin. Of the total number of hypothalamic cells doubly labeled with retrograde tracing and galanin‐immunostaining, 56–60% were found in the supraoptic nucleus, 18–23% in the retrochiasmatic nucleus, 8–10% in the lateral magnocellular portion of the paraventricular nucleus. The ratio of (number of doubly labeled cells/number of galanin‐immunoreactive cells) in each of the above regions was similar to the ratio of (number of retrogradely labeled cells/number of Nissl‐stained cells) in the supraoptic nucleus. Of all retrogradely labeled cells in the hypothalamus, 51–56% also contained galaninlike immunoreactivity.

In conclusion: (1) galanin‐immunoreactive fibers in the posterior lobe of the pituitary originate mainly in the supraoptic nucleus, retrochiasmatic nucleus, and lateral magnocellular portion of the paraventricular nucleus, (2) most of galanin‐immunoreactive cells in these regions project to the posterior lobe of the pituitary, and (3) about half the neurons constituting the hypothalamo‐neurohypophyseal system contain galaninlike immunoreactivity.
Distribution of lumbar dorsal root fibers in the lower thoracic and lumbosacral spinal cord of the rat studied with choleragenoid horseradish peroxidase conjugate
Authors: Rivero‐Melián C. , Grant G.
Published: January 2005

Spinal cord projections from lumbar dorsal root ganglia (DRGs) were investigated in adult rats following injections of choleragenoid horseradish peroxidase (B‐HRP) into each of the six lumbar DRGs. This method is known to label primarily thick fibers. Labeling was found in all laminae except in the outer part of lamina II. Labeled fibers and terminal‐like structures were found 8–13 segments rostral and 1–5 segments caudal to the injected DRGs.

A somatotopic organization was revealed in laminae III, where the labeling seemed to be organized in mediolateral zones. Some of these protruded as fingerlike processes through segments rostral and caudal to the root entry level. An interdigitating pattern for these fingerlike processes was seen between some DRGs, while an extensive overlap was found between other DRGs. Many zones were found to correspond to the known central projections of peripheral sensory nerves supplied by the injected ganglion. This suggests that the central projection of a DRG is highly related to the projections of the peripheral nerves included in the DRG.

The projections to lamina IV were organized in a similar manner as in lamina III, even though the projections showed a higher degree of overlap than in lamina III. No clear somatotopic organization was found in laminae V‐IX.

Provided that the topographical relationship between central projections of single peripheral nerves and of DRGs correspond to their peripheral projections, the results of this study, together with results of earlier studies suggest that the outlines of dermatomes are highly related to the territories of peripheral nerves included in the dermatomes.
The mechanoreceptive origin of insect tympanal organs: A comparative study of similar nerves in tympanate and atympanate moths
Authors: Yack J. E. , Fullard J. H.
Published: January 2005

A chordotonal organ occurring in the posterior metathorax of an atympanate moth, Actias luna (L.) (Bombycoidea: Saturniidae), appears to be homologous to the tympanal organ of the noctuoid moth. The peripheral anatomy of the metathoracic nerve branch, IIIN1b1 was examined in Actias luna with cobalt‐lysine and Janus Green B, and compared to its counterpart, IIIN1b (the tympanal branch), in Feltia heralis (Grt.) (Noctuoidea: Noctuidae). The peripheral projections of IIIN1b1 were found to be similar in both species, dividing into three branches, the second (IIIN1b1) ending as a chordotonal organ. The atympanate organ possesses three sensory cell bodies and three scolopales, and is anchored peripherally via an attachment strand to the undifferentiated membranous region underlying the hindwing alula, which corresponds to the tympanal region of the noctuoid metathorax. Extracellular recordings of the IIIN1b1 nerve in Actias luna revealed a large spontaneously active unit which fired in a regular pattern (corresponding to the noctuoid B cell) and smaller units (corresponding to the noctuoid acoustic A cells) which responded phasically to low frequency sounds (2 kHz) played at high intensities (83–96 dB, SPL) and also responded phasically to raising and lowering movements of the hindwing.

We suggest that the chordotonal organ in Actias luna represents the evolutionary prototype to the noctuoid tympanal organ, and that it acts as a proprioceptor monitoring hindwing movements. This system, in its simplicity (consisting of only a few neurons) could be a useful model for examining the changes to the nervous system (both central and peripheral) that accompanied the evolutionary development of insect tympanal organs.
Marginal neurons in the urodele spinal cord and the associated denticulate ligaments
Authors: Schroeder D. M. , Egar M. W.
Published: January 2005

Marginal neurons have been described in the spinal cords of a variety of vertebrates including lamprey, reptiles, birds, and mammals but not in amphibians. There has been speculation about a motor function for these neurons but recent experimental evidence in lampreys indicates that they are intraspinal mechanoreceptor neurons. Additional evidence on reptiles and birds demonstrates that the marginal neurons are closely associated with the denticulate ligaments. In the present investigation, we have examined the spinal cords of Necturus, Ambystoma tigrinum, and A. mexicanum with light and electron microscopic techniques. Marginal nuclei were found in the ventrolateral position immediately internal to the pia and to the denticulate ligament. The marginal neurons were scattered in a continuous column of neuropil without segmental accumulation. They were approximately 30 to 50 μm in diameter and fusiform with dendrites extending from the poles, parallel with the length of the spinal cord. Neuronal fingerlike processes, like those found in peripheral mechanoreceptors and in the marginal nuclei of reptiles, were also found in the three species of urodeles studied. The structure of the denticulate ligaments, similar in the three different amphibians, was composed of collagen, elastin, and fibroblasts, all of which were concentrated in the segmental lateral processes.
Amacrine cells of the rhesus monkey retina
Authors: Mariani Andrew P.
Published: January 2005

Amacrine cells of the rhesus monkey, Macaca mulatta, were studied in 38 retinas Golgi‐impregnated as whole, flat preparations. By using criteria of dendritic morphology, span of arborization, and level of arborization in the inner plexiform layer, 26 types of amacrine cell ranging in size of dendritic span from 30 μm to 2 mm were identified and listed in increasing size of dendritic span. In some instances, different cell types could be grouped together due to similar morphological features. For example, 1 group, “knotty amacrine cells,” has small cell bodies and a profusion of small, varicose, intertwined processes that span up to 30 μm and are essentially monostratified, but each of the 3 types ends in different strata. Another group is 2 types with about 20 fine radiating processes spanning 1 mm that possess some prominent varicosities. One of these has all of its processes terminating in the innermost stratum of the inner plexiform layer (“spidery”‐type 2 amacrine cells). The other with predominantly similarly ending processes has some that also terminate in the outermost stratum (“spidery”‐type 1 amacrines). These 2 cell types likely correspond to the type 1 and type 2 indolamine‐accumulating amacrine cells in rabbit retina. Other types are individuals which cannot be grouped together but resemble familiar types in cat retina (AII and A13). Other types can be correlated with their putative neurotransmitter (type 1 CA‐dopamine) or transmitter/drug receptor (“spiny”‐benzodiazepine receptor) phenotype. Many types as yet have no known correlate from other Golgi studies or clues as to transmitter or receptor phenotype. This study provides evidence for an unprecedented number of amacrine cell types in the primate retina. The similar morphologies of different types of amacrine cell types within a group suggest other common features within these groups such as neurotransmitter phenotype.
Fields of origin and pathways of the interhemispheric commissures in the temporal lobe of macaques
Authors: Demeter Steven , Rosene Douglas L. , Van Hoesen Gary W.
Published: January 2005

The interhemispheric connections of the cortical areas of the temporal lobe and some neighboring regions were investigated in monkeys (Macaca mulatta and Macaca fascicularis) by anterograde autoradiographic tracing, following injection of radioactively labeled amino acids. The results revealed that the interhemispheric projections of the temporal lobe course through three interhemispheric commissures on their way to the opposite hemisphere. The anterior commissure receives fibers from virtually the entire temporal lobe, including the temporal pole, superior and inferior temporal gyri, and parahippocampal gyrus. Moreover, area 13 of the orbitofrontal cortex, the frontal and temporal subdivisions of the prepiriform cortex, and the cortical and deep nuclei of the amygdala also contribute fibers to the anterior commissure. The heaviest projections arise in the rostral third of the temporal isocortex. These projections become progressively lighter from more caudal regions.

By contrast, the corpus callosum receives fibers from the caudal two‐thirds of the temporal lobe, including the temporal pole, superior and inferior temporal gyri, and parahippocampal gyrus. The heaviest projections arise in the caudal third of the temporal lobe and cross primarily in the caudal third of the corpus callosum, including the splenium. Progressively lighter projections arise more rostrally. Fibers from proisocortical and isocortical areas of the posterior parahippocampal gyrus cross in the ventralmost part of the splenium (inferior forceps), whereas cortical areas lateral to the occipitotemporal sulcus give rise to fibers that cross in the caudal part of the body of the corpus callosum and dorsal splenium. The dorsal hippocampal commissure receives fibers exclusively from the parahippocampal gyrus.

The fibers of the corpus callosum, hippocampal commissure, and, to a lesser extent, the anterior commissure are intimately associated with the ventricular system as they course through the white matter of the temporal lobe. The fields of origin of the anterior commissure and corpus callosum overlap extensively over the caudal two‐thirds of the temporal lobe. The posterior parahippocampal gyrus is unique in that it gives rise to fibers that cross in all three commissures.
A multiple golgi analysis of the periaqueductal gray in the rabbit
Authors: Meller S. T. , Dennis B. J.
Published: January 2005

Four variants of the Golgi method have been used, in the rabbit, to reveal the morphological attributes of neurons within the periaqueductal gray. Of these methods, the Golgi‐Cox version provided the most satisfactory results in terms of both quality and quantity of cell impregnation.

In order to make comparison with other descriptions of Golgi characteristics of the periaqueductal gray, statistical analysis was carried out on the distinguishing features of individual neurons, following two different rationales. One method, primarily based on soma characteristics (shape, area, length, and width) and basic features of the primary dendrites (number, length, and number of end‐points) resulted in nine different categories of neurons being recognized: round, ovoid, spindle, pyriform, triangular, pyramidal, rhomboidal, polygonal, and stellate shaped cells.

The alternative method principally characterized neurons by an assessment of the degree of dendritic spine development and prominent features of the dendritic tree (number of primary dendrites, length, number of branches, end‐points, and degree of spine development). This approach resulted in nine subgroups within three major classes being identified: three spiny, four moderately spiny, and two aspiny classes (subdivision of each of the groups being resultant on neuronal size and/or the degree of dendritic branching). There was no similarity between the nine groups found by the two methods.

Some, though little, correlation of neuron type was evidenced with respect to four zonal subdivisions of the periaqueductal gray complex. It remains to be seen how any of these readily recognizable morphological features, or the subgroups (derived on a statistical basis) into which they fall, might be shown to relate to function.
Specificity of corticospinal axon arbors sprouting into denervated contralateral spinal cord
Authors: Kuang Rong Zhen , Kalil Katherine
Published: January 2005

Previous studies have reported considerable plasticity in the rodent corticospinal pathway in response to injury. This includes sprouting of intact axons from the normal pathway into the contralateral spinal cord denervated by an early corticospinal lesion. We carried out the present study to obtain detailed information about the time course, origin, and degree of specificity of corticospinal axons sprouting in response to denervation. Hamsters (Mesocricetus auratus) ranging in age from 5 to 23 days received unilateral lesions of the left medullary pyramidal tract. Two weeks after the lesion, small regions of the right sensorimotor cortex opposite the lesion were injected with the plant lectin Phaseolus vulgaris leucoagglutinin (PHA‐L). After a further 2 week survival period, immunohistochemistry was carried out on frozen sections of the fixed brains and spinal cords. Detailed morphological analysis of PHA‐L labeled corticospinal axons revealed that sprouting from the intact corticospinal pathway into the contralateral denervated spinal cord occurred only at local spinal levels and not at the pyramidal decussation. Arbors sprouting into the denervated cord frequently arose from corticospinal axons that branched into the normal side of the cord as well. Sprouting was maximal after early lesions (5 days) and declined with lesions at later ages up to 19 days. Sprouting corticospinal axons arborized with the same degree of functional and topographic specificity as previously reported for normal corticospinal arbors (Kuang and Kalil: J. Comp. Neurol. 292:585–598, '90), such that axons arising from somatosensory cortex projected only to the dorsal horn, those from motor cortex innervated only the ventral horn, and normal forelimb and hindlimb topography was preserved. Sprouting fibers also had normal branching patterns. Parallel studies of developing corticospinal arbors showed that sprouting could not be attributed to maintenance or expansion of early bilateral connections. These results suggest that local signals, most likely similar to those governing normal corticospinal development, elicit corticospinal sprouting and determine specificity of axon arbors.
Thymic innervation in the rat: A light and electron microscopical study
Authors: Novotny G. E. K. , Sommerfeld H. , Zirbes T.
Published: January 2005

The innervation of the rat thymus was studied by light and electron microscopy in juvenile and aged rats. By light microscopy numerous fine nerves were found in the connective tissue septa penetrating between the thymic lobules. These septa were clearly delineated in the juvenile animals, but indistinct in the aged rats, thus creating the spurious impression that thymic parenchyma contains nerves. In the aged animals the nerves are thicker, tortuous, and more branched than in juvenile animals.

Electron microscopy confirms the light microscopic observations: no nerves were found within the thymic parenchyma. The thymic capsule and larger connective tissue septa contain bundles of myelinated and unmyelinated axons, surrounded by a perineural sheath. Within the extraparenchymal compartment, which is greatly enlarged in aged animals, efferent and sensory nerves, devoid of perineurium, were found to contact mainly reticular cells, and in rare instances plasma cells and lymphocytes. The majority of axonal varicosities are not closely related to cellular elements, and, in general, vesicles are relatively infrequent. The possible functional significance of these observations is discussed.
Location of motor pools innervating chick wing
Authors: Hollyday Margaret , Jacobson Richard D.
Published: January 2005

Intramuscular injections of HRP were used to map the spinal cord location of motoneurons innervating wing and shoulder girdle muscles in newly hatched chicks. Motor pools are grouped in the lateral motor column in relationship to embryonic origin of the muscles: muscles derived from the ventral muscle mass are innervated by medially lying motor pools, while muscles derived from the dorsal mass are innervated by lateral pools. Motor pool position is also well correlated with nerve supply. Muscles innervated by nerves diverging from common nerve trunks are innervated by neighboring motor pools. The rostro‐caudal organization of the motor pools reflects both proximo‐distal and antero‐posterior axes of the limb with proximal and anterior muscles innervated from rostral motor pools.
Sources of presumptive glutamatergic/aspartatergic afferents to the magnocellular basal forebrain in the rat
Authors: Carnes Kenneth M. , Fuller Terry A. , Price Joseph L.
Published: January 2005

The distribution of presumptive glutamatergic and/or aspartatergic neurons retrogradely labeled following injections of [3H]‐D‐aspartate into the magnocellular basal forebrain of the rat was compared with the distribution of neurons labeled by comparable injections of the nonspecific retrograde axonal tracer wheat germ agglutinin conjugated to horseradish peroxidase.

Cells retrogradely labeled by wheat germ agglutinin‐horseradish peroxidase were found in a wide range of limbic and limbic‐related structures in the forebrain and brainstem. In the telencephalon, labeled neurons were seen in the orbital, medial prefrontal, and agranular insular cortical areas, the amygdaloid complex, and the hippocampal formation. Labeled cells were also seen in the olfactory cortex, the lateral septum, the ventral striatopallidal region, and the magnocellular basal forebrain itself. In the diencephalon, neurons were labeled in the midline nuclear complex of the thalamus, the lateral habenular nucleus, and the hypothalamus. In the brainstem, labeled cells were found bilaterally in the ventral midbrain, the central gray, the reticular formation, the parabrachial nuclei, the raphe nuclei, the laterodorsal tegmental nucleus, and the locus coeruleus.

A significant fraction of the afferents to the magnocellular basal forebrain appear to be glutamatergic and/or aspartatergic. Only a few of the regions labeled with wheat germ agglutinin‐horseradish peroxidase were not also labeled with [3H]‐D‐aspartate in the comparable experiments. Most prominent among the non‐glutamatergic/aspartatergic projections were those from fields CA1 and CA3 of the hippocampus, the hilus of the dentate gyrus, the dorsal subiculum, the tuberomammillary nucleus, and the ventral pallidum. In addition, most of the lateral hypothalamic and brainstem projections to the magnocellular basal forebrain were not significantly labeled with [3H]‐D‐aspartate.

In addition to these inputs, a commissural projection from the region of the contralateral nucleus of the horizontal limb of the diagonal band was confirmed with both wheat germ agglutinin‐horseradish peroxidase and the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin. This projection did not label with [3H]‐D‐aspartate or [3H]‐GABA, suggesting that it is not glutamatergic/aspartatergic or GABAergic. Furthermore, double labeling experiments with the fluorescent retrograde tracer True Blue and antibodies against choline acetyltransferase indicate that the projection is not cholinergic.
Transcellular labeling of taste bud cells by carbocyanine dye (diI) applied to peripheral nerves in the barbels of the catfish, Ictalurus punctatus
Authors: Finger Thomas E. , Böttger Bärbel
Published: January 2005

In order to study the pattern of innervation of taste buds and the surrounding epithelium, the carbocyanine dye diI was applied to the nerve stump in isolated, paraformaldehyde‐fixed barbels obtained from channel catfish, Ictalurus punctatus. After a diffusion period of 7–41 days, the barbels were sectioned on a vibratome and examined with epifluorescence. Labeled axons were observed up to 1 cm from the site of application. Frequently, a fascicle of labeled axons turned outward toward the epithelium to innervate taste buds or to end apparently as free endings within the epithelium. Within 2–3 mm of the dye‐application site, many taste buds contained one or at most 5–10, labeled spindle‐shaped, presumed receptor, cells. In taste buds containing multiple labeled cells, the cells usually were arranged as intertwined pairs or triplets rather than being homogeneously distributed within the taste bud. In a few cases, labeled basal cells could be discerned among the labeled axons of the basal plexus. The cells of the taste bud apparently were labeled by transcellular passage of the dye from the nerve fibers into the cells. The limited number of labeled cells within each taste bud may indicate a special relationship between these cells and the nerve fibers innervating them.
Descending neurons supplying the neck and flight motor of diptera: Physiological and anatomical characteristics
Authors: Gronenberg Wulfila , Strausfeld Nicholas J.
Published: January 2005

In Diptera, dorsal neuropils of the pro‐, meso‐, and metathoracic ganglia supply motor neurons to neck and flight muscles. Motor circuits are supplied by more than 50 pairs of descending neurons (DNs) whose dendritic trees in the brain are restricted to dorsal neuropils of the deutocerebrum where they are grouped together into discrete clusters. Each cluster is visited by wide‐field motion‐sensitive neurons and by morphologically small‐field retinotopic elements. This organization suggests that flight descending neurons should respond to complex stimuli reflecting panoramic movement and small‐field motion. Intracellular recordings, combined with dye filling, confirm this. Certain descending neurons responding to visual flow fields terminate bilaterally in superficial pterothoracic neuropils, at the level of indirect (power) flight muscle motor neurons. Other DNs terminate laterally, and provide segmental collaterals to areas containing neck and direct (steering) flight muscle motor neurons. Such DNs are activated by wide‐field directional stimuli corresponding to pitch, roll, or yaw, and to small‐field stimuli. Appropriate directional mechanosensory stimuli also activate dorsal descending neurons. The significance of dorsal descending neurons for the control of flight is discussed and compared with studies on course deviation neurons in other insects. It is suggested that, in Diptera, dorsal descending neurons may separately be involved in the control of velocity, stabilization, and steering manoeuvres.
Dietary sodium chloride deprivation throughout development selectively influences the terminal field organization of gustatory afferent fibers projecting to the rat nucleus of the solitary tract
Authors: King Camille Tessitore , Hill David L.
Published: January 2005

In order to determine whether the developing central gustatory system responds to altered sensory experience, terminal fields of the chorda tympani nerve (CT) within the nucleus of the solitary tract (NTS) in control, NaCl deprived, and rats in which CT taste responses “recovered” from NaCl deprivation were investigated via anterograde transport of HRP. Rats fed a low sodium diet (0.03% NaCl) from the third day of gestation to at least 35 days postnatal exhibited both abnormally distributed and irregularly shaped CT terminal fields. Specifically, the dorsal zone of the field was the smallest in controls whereas it was the largest in deprived rats, occupying more medial and caudal territory within the nucleus. The portion of the field immediately ventral to the dorsalmost zone was characterized by a compact, oval shape in control rats and an irregular, broad configuration in deprived rats. Although it has been observed that deprivation‐induced changes in the neurophysiology of the CT are reversible, the central morphological alterations reported here remain abnormal. Restoration of 1.0% NaCl in the diet at 28 days postnatally, for at least 60 days, did not result in normal CT terminal fields. The pattern of the field in rats “recovered” from NaCl deprivation was comparable to that found in deprived rats, and the size of the field was three times that found in control and deprived rats.

The terminal fields of another nerve containing gustatory afferents, the lingual‐tonsilar branch of the glossopharyngeal nerve (LT‐IX), were studied for comparison. Interestingly, the pattern of the LT‐IX field was not altered by sodium deprivation. The relative size and topography of the LT‐IX fields in deprived rats were similar to controls. Thus, sodium deprivation appears to alter selectively the anatomical organization of the CT. Differences in vulnerability between the CT and LT‐IX terminal fields may derive from differences in the responsiveness of these nerves to NaCl, and/or to differences in the timing of early neural events.
Synaptic organization of projections from basal forebrain structures to the mediodorsal thalamic nucleus of the rat
Authors: Kuroda Masaru , Price Joseph L.
Published: January 2005

The synaptic organization of the mediodorsal thalamic nucleus (MD) in the rat was studied with the electron microscope, and correlated with the termination of afferent fibers labeled with wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP). Presynaptic axon terminals were classified into four categories in MD on the basis of the size, synaptic vesicle morphology, and synaptic membrane specializations: (1) small axon terminals with round synaptic vesicles (SR), which made asymmetrical synaptic contacts predominantly with small dendritic shafts; (2) large axon terminals with round vesicles (LR), which established asymmetrical synaptic junctions mainly with large dendritic shafts; (3) small to medium axon terminals with pleomorphic vesicles (SMP), which formed symmetrical synaptic contacts with somata and small‐diameter dendrites; (4) large axon terminals with pleomorphic vesicles (LP), which made symmetrical synaptic contacts with large dendritic shafts. Synaptic glomeruli were also identified in MD that contained either LR or LP terminals as the central presynaptic components. No presynaptic dendrites were identified.

In order to identify terminals arising from different sources, injections of WGA‐HRP were made into cortical and subcortical structures known to project to MD, including the prefrontal cortex, piriform cortex, amygdala, ventral pallidum and thalamic reticular nucleus. Axons from the amygdala formed LR terminals, while those from the prefrontal and insular cortex ended exclusively in SR terminals. Fibers labeled from tie piriform cortex formed both LR and SR endings. Based on their morphology, all of these are presumed to be excitatory. In contrast, the axons from the ventral pallidum ended as LP terminals, and those from the thalamic reticular nucleus formed SMP terminals. Both are presumed to be inhibitory. At least some terminals from these sources have also been identified as GABAergic, based on double labeling with anterogradely transported WGA‐HRP and glutamic acid decarboxylase (GAD) immunocytochemistry.
Identifiable reticulospinal neurons of the adult zebrafish, Brachydanio rerio
Authors: K. Lee Robert K. , Eaton Robert C.
Published: January 2005

Reticulospinal neurons of the larval zebrafish Brachydanio rerio have been categorized into 27 different types (Kimmel et al.: Journal of Comparative Neurology 205:112–127, 1982; Metcalfe et al.: Journal of Comparative Neurology 251:147–159, 1986). Nineteen of these occur as bilateral pairs which are individually identifiable. Since considerable remolding of brain structures (e.g., cell death and modifications of neuronal architecture) occurs during development, we ask if these cells are preserved in the adult zebrafish and the extent to which neuronal morphology of the larva is conserved during ontogeny. In our analysis, we studied reticular neurons from 84 brains retrogradely labelled from the spinal cord with HRP. We show that all reticulospinal types of the larva are retained without considerable change in morphology in the adult. Many neurons, including the Mauthner cell and two of its serial homologues, MiD2cm and MiD3cm, can be individually and unambiguously identified. In addition, the appearance of later developing (tertiary) neurons leads to an increase in the numbers of some neuron types. Although tertiary neurons are often isomorphic with neighboring cells, they can have unique morphologies of their own and, therefore, are also individually identifiable. We suggest that the appearance of tertiary neurons may serve to extend the behavioural repertoire of the embryo. Moreover, morphological repetitions in adjacent segments of the otic region (level of VIIIth nerve entry) may represent the replication of a functional motif, perhaps involving the C‐type escape response which is known to involve the Mauthner cell.
Distribution of cells containing mRNA encoding cholecystokinin in the rat central nervous system
Authors: Schiffmann S. N. , Vanderhaeghen J.‐J.
Published: January 2005

The distribution of cells containing mRNA encoding cholecystokinin was studied in the rat central nervous system by in situ hybridization histochemistry.

Cholecystokinin mRNA containing neurons were considerably more numerous than the cholecystokinin‐like immunoreactive neurons detected by immunocytochemistry even after cholchicine pretreatment and appeared to be heavily, moderately, or lightly labeled. Such neurons were present in the olfactory bulb, olfactory nuclei, layers II–III and V–VI of the cerebral cortex, amygdaloïdnuclei, subiculum, hippocampus, claustrum, endopiriform nucleus, several hypothalamic nuclei, most of the thalamic nuclei, ventral tegmental area, substantia nigra, interfascicularis nucleus, linearis rostralis, central gray, Edinger‐Westphal nucleus, superior and inferior colliculi, parabrachial nucleus, reticular formation, raphe nuclei, and spinal trigeminal nucleus.

This distribution partly confirmed and partly extended the previous immunohistochemical descriptions. Several brain areas such as the thalamus and the colliculi contain cholecystokinin mRNA but are devoid of perikarya exhibiting cholecystokinin‐like immunoreactivity. The cerebral cortex and the hippocampus present a far higher density of cholecystokinin mRNA containing cells, including pyramidal neurons, than of perikarya containing cholecystokinin‐like immunoreactivity.

These results suggest that cholecystokinin or cholecystokinin‐related peptides could have a functional role in numerous cerebral pathways including long projections such as cortical or thalamic projections.
Incorporation of 3H‐thymidine in telencephalic structures of the vomeronasal and olfactory systems of embryonic garter snakes
Authors: Holtzman David A. , Halpern Mimi
Published: January 2005

Previous studies have shown that the vomeronasal and, possibly, olfactory systems are functional in newborn garter snakes. However, little is known about neurogenesis in these chemosensory pathways. In the companion paper, we describe the embryonic growth of the sensory epithelia for both the vomeronasal and olfactory systems. In the present study, we examine neurogenesis in the telencephalic structures of these chemosensory systems by using 3H‐thymidine autoradiography (ARG). The majority of neurogenesis appears to occur before birth in the accessory and main olfactory bulbs and their principal projection sites, the nucleus sphericus and lateral cortex, respectively. The data suggest that some postnatal neurogenesis may occur in the accessory and main olfactory bulbs and in the nucleus sphericus. Although the neuronal constituents of the accessory and main olfactory bulbs appear to mature concurrently, those of the lateral cortex appear to mature before those of the nucleus sphericus. Along with previous findings, this latter result supports the hypothesis that the olfactory system develops before the vomeronasal system in garter snakes. There appears to be a rostral to caudal gradient of neurogenesis within the mural layer of the nucleus sphericus. However, an “outside to inside” gradient of neurogenesis was not observed in the mantle layer of the lateral cortex, as described for other reptiles. Similarities and differences observed by other investigators in other reptilian species and mammals are discussed.
Ontogeny of somatostatin receptors in the rat somatosensory cortex
Authors: Gonzalez Bruno J. , Leroux Philippe , Bodenant Corinne , Vaudry Hubert
Published: January 2005

The distribution and density of SRIF receptors (SRIF‐R) were studied during development in the rat somatosensory cortex by in vitro autoradiography with monoiodinated [Tyr0‐DTrp8]S14. In 16‐day‐old fetuses (E16), intense labeling was evident in the intermediate zone of the cortex while low concentrations of SRIF‐R were detected in the marginal and ventricular zones. The highest density of SRIF‐R was measured in the intermediate zone at E18. At this stage, labeling was also intense in the internal part of the developing cortical plate; in contrast, the concentration of binding sites associated with the marginal and ventricular zones remained relatively low. Profound modifications in the distribution of SRIF‐R appeared at birth. In particular, a transient reduction of receptor density occurred in the cortical plate. During the first postnatal week, the density of receptors measured in the intermediate zone decreased gradually; conversely, high levels of SRIF‐R were observed in the developing cortical layers (II to VI). At postpartum day 13 (P13), a stage which just precedes completion of cell migration in the parietal cortex, the most intensely labeled regions were layers V–VI and future layers II–III. From P13 to adulthood, the concentrations of SRIF‐R decreased in all cortical layers (I to VI) and the pattern of distribution of receptors at P21 was similar to that observed in the adults.

Detailed analysis of the results revealed (i) a close association between the distribution of SRIF‐R and the areas containing migrating neuroblasts and (ii) a temporal correlation between the presence of SRIF‐R and the transient expression of the neuropeptide SRIF in the developing somatosensory cortex. Taken together, our data suggest the existence of two populations of SRIF‐R: a transient population, which could be implicated in the development of the parietal neocortex from E16 to P13, and a population of SRIF‐R only expressed after the first postnatal week, which is likely to be involved in the process of neurotransmission.
Complementary global maps for orientation coding in upper and lower layers of the cat striate cortex and their possible functions
Authors: Bauer R. , Leferink J. , Eckhorn R. , Jordan W.
Published: January 2005

Preferred stimulus orientations of striate cortical cells in the cat were analyzed for possible isotropic or anisotropic distributions. We separated the data twice, into central (0–5°) vs. peripheral subgroups and into upper vs. lower layer cells. In the central group, absolute orientations were counted; in the periphery, a radial test was adopted by normalizing the preferred stimulus orientation of a cell to the line connecting the receptive field center to the retinal center. We found that in the center, vertical and horizontal orientations are overrepresented. In the periphery, the histograms show complementary anisotropies for upper and lower layers, favoring a map for radial orientation detection in upper layers and a more concentric map for orientation detection in lower layers.

These results are possibly related to the probabilities different optic flow fields on the retina under natural conditions of stimulation. They are discussed as possible neuronal structures supporting figure‐ground discrimination, the distinction of self motion from object motion, and the location of objects in three‐dimensional space.
Evaluation of the influence of optic stalk melanin on the chiasmatic pathways in the developing rodent visual system
Authors: Colello R. J. , Jeffery Glen
Published: January 2005

In a number of mammalian species, fibre outgrowth in the developing retinofugal pathway is coincident with the presence of melanin in the retinal part of the optic stalk. The presence of melanin is transient in this developing system and has been proposed to play a role in the guidance of retinofugal fibres. Further, it has been suggested that this stalk melanin accounts for the differences between the size of the uncrossed retinal component in pigmented and nonpigmented strains. However, a recent study showed that there is no melanin in the optic stalk of Manchester rats during fibre outgrowth. Since such rats supposedly have a normal pigment distribution and a normal pattern of decussation at the optic chiasm, this finding appears to undermine the suggested role played by stalk melanin in establishing the laterality of retinal fibre projections in other mammalian species.

The aim of this study was to re‐evaluate the relationship between melanin in the stalk and the development of the retinofugal pathway in three strains of rat: the Wild type, Long Evans Hooded, and the Albino. The Albino rat, which lacks melanin‐bearing cells entirely, was shown to have the smallest uncrossed projection, approximately 1,340 ipsilaterally projecting cells (ipc), whereas the Long Evans (2,760 ipc) and the Wild‐type strain (2425 ipc) were found to have a larger uncrossed retinal component. In both pigmented strains, melanin was restricted to the eye cup and absent from the optic stalk throughout all stages of development. These results extend the finding that in the rat no correlation can be found between the size of the adult uncrossed retinofugal pathway and the existence of stalk melanin during development. Further, it was found that during initial outgrowth the distribution of fibres in the distal stalk was similar for all three strains, providing evidence that fibre topography does not account for the differences in the number of ipsilaterally projecting ganglion cell fibres.

Finally, the position of earliest uncrossed fibres in the stalk was determined in the mouse, an animal with melanin‐bearing cells in this region. It was found that these fibres intermingled with crossed fibres throughout the length of the stalk and that their position within the stalk was similar in both pigmented and albino strains. These observations suggest that stalk pigment plays no specific role in the development of the chiasmatic pathway of retinofugal fibres in either the rat or the mouse.
Vasoactive intestinal peptide binding sites and fibers in the brain of the pigeon Columba livia: An autoradiographic and immunohistochemical study
Authors: Hof Patrick R. , Dietl Monika M. , Charnay Yves , Martin Jean‐Luc , Bouras Constantin , Palacios José M. , Magistretti Pierre J.
Published: January 2005

The distribution of vasoactive intestinal peptide (VIP) binding sites in the pigeon brain was examined by in vitro autoradiography on slide‐mounted sections. A fully characterized monoiodinated form of VIP, which maintains the biological activity of the native peptide, was used throughout this study. The highest densities of binding sites were observed in the hyperstriatum dorsale, archistriatum, auditory field L of neostriatum, area corticoidea dorsolateralis and temporo‐parieto‐occipitalis, area parahippocampalis, tectum opticum, nucleus dorsomedialis anterior thalami, and in the periventricular area of the hypothalamus. Lower densities of specific binding occurred in the neostriatum, hyperstriatum ventrale and nucleus septi lateralis, dorsolateral area of the thalamus, and lateral and posteromedial hypothalamus. Very low to background levels of VIP binding were detected in the ectostriatum, paleostriatum primitivum, paleostriatum augmentatum, lobus parolfactorius, nucleus accumbens, most of the brainstem, and the cerebellum.

The distribution of VTP‐containing fibers and terminals was examined by indirect immunofluorescence using a polyclonal antibody against porcine VIP. Fibers and terminals were observed in the area corticoidea dorsolateralis, area parahippocampalis, hippocampus, hyperstriatum accessorium, hyperstriatum dorsale, archistriatum, tuberculum olfactorium, nuclei dorsolateralis and dorsomedialis of the thalamus, and throughout the hypothalamus and the median eminence. Long projecting fibers were visualized in the tractus septohippocampalis. In the brainstem VIP immunoreactive fibers and terminals were observed mainly in the substantia grisea centralis, fasciculus longitudinalis medialis, lemniscus lateralis, and in the area surrounding the nuclei of the 7th, 9th, and 10th cranial nerves. The correlation between the distribution of VIP binding sites and immunoreactive fibers and terminals was assessed in a restricted number of regions. A qualitatively good matching was found in the area corticoidea dorsolateralis, hyperstriatum dorsale, hyperstriatum accessorium, nucleus septi lateralis, nuclei dorsomedialis and dorsolateralis thalami, and in some hypothalamic areas. A striking mismatch occurred in the hyperstriatum ventrale, neostriatum, tectum opticum (high to moderate density of binding sites but only few immunoreactive profiles), and in the tuberculum olfactorium, median eminence, and spinal cord (lower density of binding sites but abundant immunoreactive profiles). The paleostriatum, lobus parolfactorius, and ectostriatum were virtually devoid of both binding sites and immunoreactive profiles. The results are discussed in relationto the know action of VIP in the rodent and avian brain and are compared with previous observations on the distribution of VIP binding in the central nervous system of other vertebrates.