bluuebunny/crossref_metadata_2025 huggingface dataset:
Noradrenergic projections to brainstem nuclei: Evidence for differential projections from noradrenergic subgroups
Authors: Grzanna Reinhard , Chee Won K. , Akeyson Edward W.
Published: January 2005

Retrograde transport of the fluorescent tracer True Blue was used in combination with immunohistochemical staining of dopamine‐β‐hydroxylase (a marker protein for noradrenergic neurons) to determine the origin of noradrenergic projections to three cranial nerve nuclei: (1) the motor nucleus of the trigeminal nerve, (2) the motor nucleus of the facial nerve, and (3) the spinal trigeminal nucleus pars interpolaris. Noradrenergic cells in the rat brainstem were divided into sub groups and their numbers were determined in serial sections stained with an antiserum to rat dopamine‐β‐hydroxylase. Following tracer injections into the three brainstem nuclei, retrogradely labeled noradrenergic neurons were counted and the percentage of True Blue‐labeled noradrenergic cells in each subgroup was calculated.

Injections of tracer into the three cranial nerve nuclei resulted in distinctly different labeling patterns of noradrenergic cells. Of the total number of norepinephrine neurons projecting to the motor nucleus of the trigeminal nerve, 68% were observed within the A7 cell group; 75% of those innervating the motor nucleus of the facial nerve were found in the A5 cell group, and 65% of those projecting to the spinal trigeminal nucleus pars interpolaris were present in the locus ceruleus and subceruleus. These findings indicate that norepinephrine cells in the rat brainstem do not constitute a homogeneous population of cells but that several discrete systems can be identified that differ not only in topography but also in the terminal distribution of their axons. This combined retrograde transport‐immunohistochemical study reveals a much higher degree of topographic order in the projections of norepinephrine neurons than has previously been recognized, The observation of differential projections of noradrenergic subgroups argues against the notion of a global influence of these cells over functionally diverse areas of the brainstem.
Topographical organization of olivocerebellar and corticonuclear connections in the rat—An WGA‐HRP study: I. Lobules IX, X, and the flocculus
Authors: Bernard Jean‐François
Published: January 2005

The organization of the olivocerebellar and corticonuclear relations for vermal lobules IX and X and the flocculus has been studied in the rat by using microinjections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP). This axonal tracer allowed us to study simultaneously the olivocortical connections (revealed by retrograde transport) and corticonuclear connections (revealed by anterograde transport) from a single injection in the cerebellar cortex.

The results indicate that four modules can be distinguished, each of which consists of a region of cerebellar cortex receiving afferents from a single small region of the inferior olive (IO) and sending efferents to one or several portions of the cerebellar nuclei and/or vestibular nuclei.

The first module includes a medial part of lobule X as well as all the flocculus. It receives afferents from the dorsal cap (dc) and sends efferents to the small cell (s) zone of the dentate nucleus as well as to the medial vestibular (VM) nucleus and subnucleus y.

The second module includes a medial parasagittal region located in lobules IX and X. It receives afferents from the ventrolateral outgrowth (vlo) and/or beta nucleus (vlo+beta nucleus) and sends efferents principally to the ventrolateral part of fastigial nucleus and to the superior vestibular (VS), inferior vestibular (VI), and VM nuclei.

The third module includes a lateral parasagittal region in lobules IX and X. It receives afferents from the dorsomedial cell column (dmcc) of 10 and sends efferents principally to the interpositus nucleus and subnucleus y.

The fourth module includes the most lateral part of lobules IX and Xa. It receives afferents from the principal olive (PO) and sends efferents to the s zone of the dentate nucleus.

These results are comparable to those obtained in the cat although a few differences are discussed.
Projections to the inferior colliculus from the anteroventral cochlear nucleus in the cat: Possible substrates for binaural interaction
Authors: Oliver Douglas L.
Published: January 2005

The projections to the inferior colliculus of the cat are shown in autoradiographs after injections of 3H‐amino acids into the anteroventral cochlear nucleus and anterograde axonal transport. Labeled bands of axons are seen in the central nucleus of the inferior colliculus, parallel to the fibrodendritic laminae, and in layers 3 and 4 of the dorsal cortex. A bilateral projection to the lateral, low‐frequency part of the inferior colliculus is observed. In contrast, the more ventromedial, mid‐ and high‐frequency parts receive only a contralateral input. The projections from the cochlear nucleus to both the contralateral midbrain and bilaterally to the superior olivary complex appear to be tonotopically organized. After HRP injections in the inferior colliculus, small numbers of stellate neurons are labeled in the lateral and ventral low‐frequency parts of the anteroventral cochlear nucleus on the ipsilateral side. EM autoradiographs show labeled axonal endings from both sides of the anteroventral cochlear nuclei are present in the same proportion in pars lateralis. Axonal endings from either cochlear nucleus have small, round synaptic vesicles and make asymmetric synaptic contacts on dendrites. Axons from the contralateral side also make axosomatic contacts on large disc‐shaped or stellate cells. Neurons from the ipsilateral anteroventral cochlear nucleus apparently make more synaptic endings per cell as compared to neurons from the contralateral side. Together, bilateral inputs from the anteroventral cochlear nucleus can account for a third of the endings with round synaptic vesicles in pars lateralis of the central nucleus.

Morphological similarities among the ascending inputs to the inferior colliculus are discussed. Both direct circuits from the cochlear nucleus to the inferior colliculus and indirect circuits via the superior olivary complex or lateral lemniscus may display banding patterns, nucleotopic organization, or differential synaptic organization. The direct inputs from the anteroventral cochlear nucleus to the colliculus may influence binaural interactions which occur in the superior olivary complex. In addition, direct inputs may create new binaural responses in the inferior colliculus that are independent of lower centers.
Disappearance of Rohon‐Beard neurons from the spinal cord of larval Xenopus laevis
Authors: Lamborghini Janet E.
Published: January 2005

Rohon‐Beard neurons are primary sensory cells located in the spinal cord of embryonic lower vertebrates. The kinetics of their normal, gradual, but complete disappearance in Xenopus tadpoles has been followed. Levels of acid phosphatase activity, a common histochemical correlate of cell death, were assayed and found to increase at the time of onset of disappearance of Rohon‐Beard cells. Ultrastructural examination revealed the presence of numerous secondary lysosomes, swelling of endoplasmic reticulum and mitochondria, and a decrease in nuclear density. The disappearance of Rohon‐Beard neurons may be attributed to autophagic cell death involving lysosomal acid hydrolases. This process begins only a few days after the maturation of voltage‐ and neurotransmitter‐dependent membrane conductances and the electrical uncoupling of these neurons. The loss of Rohon‐Beard neurons in embryos whose development was arrested by crowding was appropriate for the developmental stage of the animals rather than their chronological age.
Monoclonal antibody reveals radial glia in adult avian brain
Authors: Alvarez‐buylla Arturo , Buskirk Daniel R. , Nottebohm Fernando
Published: January 2005

An antibody prepared against adult canary brain, 40E‐C, stains ventricular zone cells that send long, unbranched processes into the forebrain parenchyma. We identify these cells as radial glia. The same antibody also stains a subset of brain astroglia and reacts with nonbrain material such as mesenchyme, Sertoli cells, and the Z‐line of muscle. A weaker reaction is given by erythrocytes and some endothelial cells. 40E‐C also reacts with the radial glia of the developing rat brain but fails to show any such glia in adult rodent brain. Western blot analysis shows that this antibody recognizes vimentin, a molecule shared by all 40E‐C‐positive cell types. We believe that the presence of radial glia in the adult avian forebrain and their apparent absence in mammals is related to neurogenesis in adulthood, which occurs in birds and much less or not at all in mammals. In addition, the presence of radial glia in adult birds may also relate to other, stillhypothetical, differences in the physiology of adult avian and mammalian brains.
Development of corticogeniculate synapses in the cat
Authors: Weber Arthur J. , Kalil Ronald E.
Published: January 2005

The development of corticogeniculate synapses was studied in 16 cats ranging in age from newborn to adult. Tritiated proline was injected into areas 17 and 18 of the visual cortex in order to label corticogeniculate terminals in lamina A of the dorsal lateral geniculate nucleus. The labeled terminals were then characterized ultrastructurally using electron microscopic autoradiography.

Labeled synaptic profiles were found in newborn kittens, indicating that corticogeniculate connections are present in the cat at birth. Morphologically, however, many corticogeniculate endings in newborn and 1‐week‐old kittens are different from those in older animals in that they do not form well‐defined terminal boutons, and their synaptic vesicles are often loosely packed. In kittens 2 weeks of age and older, corticogeniculate axons end as RSD terminals exclusively; i.e., they are relatively small in size and contain round, densely packed synaptic vesicles, and occasionally an electron‐dense mitochondrion (Guillery: Z. Zellforsch. 99: 1–38, '69). However, not all RSD terminals in the LGN represent input from visual cortex. Injections of 3H‐proline into the mesencephalic reticular formation also label RSD terminals selectively in the lateral geniculate nucleus.

At all ages corticogeniculate axons make synaptic contacts with dendrites exclusively, and they are always presynaptic. This suggests that the essential pattern of corticogeniculate synapses is formed early and is not altered during subsequent development. Quantitatively, there is no significant change in the size of corticogeniculate terminals or their synaptic vesicles in kittens 2 weeks of age (the youngest measured) and older. In contrast, the synaptic contact lengths of these terminals decrease about 28% between 2 and 12 weeks. During this same period there is approximately a twofold increase in the density of corticogeniculate terminals in the neuropil of lamina A. Since the volume of neuropil in lamina A increases almost fourfold between 2 and 12 weeks, the doubling of corticogeniculate terminal density represents about an eightfold increase in terminal number. After 12 weeks there is little change in the length, density, or number of corticogeniculate synaptic contacts, which suggests that the morphological development of the corticogeniculate pathway is essentially complete by this age.
Relationship between natural variations in motoneuron number and body size in Xenopus laevis: A test for size matching
Authors: Sperry David G.
Published: January 2005

During normal development, tadpoles of Xenopus laevis demonstrate large variations in body size that are carried through metamorphosis. This variation in size exists at the stages when lumbar lateral motor column (L‐LMC) motoneurons are produced and when neuronal cell death in this neuron population occurs. Body size, hindlimb size, motoneuron number, and motoneuron size (i.e., neuron nuclear cross‐sectional area) were measured in animals from three developmental stages: one prior to significant amounts of cell death, one at the peak rate of cell death, and one after cell death. The hypothesis that neuron population size is matched to peripheral size was tested by using the natural size variation found at each of these stages.

The ranges of values for the measurements at the three stages were large. Significant correlations between body size and motoneuron number, as well as between motoneuron number and muscle fiber number, were present after cell death. Since these correlations emerged as cell death reduced neuron numbers, size matching may have occurred and cell death may have adjusted the L‐LMC motoneuron population's size to variation in body size. In addition to the correlations between body size and motoneuron number at the end of cell death, neuron numbers before and after cell death were significantly correlated among groups of siblings. The possibility that the number of neurons after cell death was also influenced by differences in the number of L‐LMC progenitors is discussed.
The entorhinal cortex of the monkey: I. Cytoarchitectonic organization
Authors: Amaral D. G. , Insausti R. , Cowan W. M.
Published: January 2005

As an essential preliminary to a series of experimental studies of the afferent and efferent connections of the monkey entorhinal cortex, we have carried out a detailed analysis of its cytoarchitectonic organization. Primarily on the basis of features observed in Nissl‐ and fiber‐stained preparations, supplemented with Golgi‐stained material and preparations stained for heavy metals by Timm's method and histochemically for acetylcholinesterase, the entorhinal cortex has been divided into seven fields that are named according to their rostrocaudal and mediolateral positions except for one rostrally located field that is named for the prominent input that it receives from the olfactory bulb. At rostral levels, the entorhinal cortex is marked by a number of morphological inhomogeneities. The neurons tend to be organized in patches that are surrounded by large, thick, radially oriented bundles of fibers. At caudal levels, the entorhinal cortex has a more distinctly laminated appearance, reminiscent of that in the neocortex, and most of the neurons and fiber fascicles are arranged in discrete radial columns. The cortical region adjoining the entorhinal cortex laterally, which is commonly known as the “perirhinal cortex,” is in fact composed of two separate fields corresponding to areas 35 and 36 of Brodmann. Area 35 occupies the fundus and part of the lateral aspect of the rhinal sulcus. Area 36 extends from the lateral bank of the rhinal sulcus into the inferior temporal gyrus, where it borders fields TA and TE rostrally, and field TF of the parahippocampal gyrus caudally. The surface extents of each of the entorhinal fields have been determined by making “unfolded” two‐dimensional maps of the region and measuring the areas with a computerized digitizing system.
The entorhinal cortex of the monkey: II. Cortical afferents
Authors: Insausti R. , Amaral D. G. , Cowan W. M.
Published: January 2005

The entorhinal cortex of the monkey is commonly viewed as the major link between the cerebral cortex and the other fields of the hippocampal formation. Until recently, however, little was known about the origins of the cortical projections to the entorhinal cortex, and most of the available information is still based on degeneration studios. We have carried out a systematic analysis of these connections by placing small injections of the retrograde tracer wheat germ agglutinin conjugated to horseradish peroxidase into each of the fields of the entorhinal cortex of the Macaca fascicularis monkey, Retrograde labeled cells were observed in several areas of the frontal and temporal lobes, the insula, and the cingulate cortex. In the frontal lobe, the greatest number of labeled cells were observed in the orbital region and specifically in areas 13 and 13a: labeled cells were also seen in areas 14, 11, and 12. In the dorsolateral frontal cortex, labeled cells were observed mainly in the rostral half of area 46; occasionally cells were also seen in areas 9, 8, and 6. In the cingulate cortex, labeled cells were observed in area 25, area 32, and rostral levels of area 24; fewer cells were observed at caudal levels of area 24 or in area 23. The retrosplenial region (areas 30 and 29), including its caudal extension along the rostral calcarine sulcus and its ventral extension into the temporal lobe, contained numerous labeled cells. In the temporal lobe, retrogradely labeled cells were arranged in two rostrocaudally oriented bands. Rostral to the hippocampal formation, the first band encompassed the priform and periamygdaloid cortices and areas 35 and 36; the labeling in area 36 was continuous to the temporal pole. At more caudal levels this band was located immediately lateral to the hippocampal formation and included areas 35 and 36 rostrally and areas TH and TF caudally. The second band was situated in the superior temporal gyrus where labeled cells were observed in several distinct cytoarchitectonic fields, including the parainsular cortex in the fundus of the inferior limiting sulcus. In the insula proper, retrogradely labeled cells were seen mainly in the rostral or agranular division; far fewer were observed in the dysgranular and granular insula. Whereas there is little available physiological information concerning many of the cortical regions that project to the entorhinal cortex, on anatomical grounds they may be generally characterized as poly sensory associational regions.
Organization of sensory and motor nuclei of the trigeminal nerve in lampreys
Authors: Koyama Hiromichi , Kishida Reiji , Goris Richard C. , Kusunoki Toyokazu
Published: January 2005

Anterograde and retrograde HRP transport were used to elucidate the primary central projections of the trigeminal nerve in a lamprey, Lampetra japonica, by application to the ophthalmic, apical, basilar, suborbital, and mandibular branches of the trigeminal nerve. (1) Most of the trigeminal and a few facial ganglion cells were labeled. The ganglion cells of each nerve were distributed in separate areas within their respective ganglia. (2) Some ipsilateral medullary and spinal dorsal cells were labeled after HRP application to the ophthalmic and apical nerves, but there was no contralateral labeling. (3) Most of the neurons of the trigeminal motor nucleus were labeled, and when the apical or the basilar nerve was labeled, in each case a cluster of small motor neurons was found ventrolateral to the classic motor nucleus. (4) Miscellaneous neurons were found scattered along the course of the descending trigeminal tract and nucleus in all cases except after application to the mandibular branch. The shape, size, and distribution patterns of these neurons were varied, and several characteristics indicated that they were sensory in nature. (5) In the rostral part of the medulla, sensory fibers of each nerve showed restricted localization within the descending trigeminal tract and nucleus. When compared to the distribution of the same fibers in the hagfish Eptatretus burgeri, another member of the cyclostomes, the distribution pattern in the lampreys studied was closer to the type seen in gnathostomes.
Early postnatal development of glial cells in the canine cervical spinal cord
Authors: Lord Kim E. , Duncan Ian D.
Published: January 2005

To study qualitative and quantitative changes in the glial cell population of young postnatal dogs, the cervical spinal cords of 20 beagle pups, ranging in age from 1 to 28 days, were prepared for light and electron microscopy. Glial cells in the lateral corticospinal tract were classified and quantified directly on the electron microscope. Quantification was performed by means of a stereological method designed to correct for sampling bias, and glia were classified according to morphological criteria as immature glial cell precursors, light and dark oligodendrocytes, astrocytes, and microglia.

Glial cell precursors, which include undifferentiated glioblasts, oligodendroblasts, and astroblasts, predominated in the first few days after birth, constituting 43% of the glial cell population, and then declined to less than 5% by 28 days. Light and dark oligodendrocytes differed morphologically in their electron density and the appearance of their organelles. Light oligodendrocytes increased slightly prior to myelination, and then declined, whereas dark oligodendrocytes continued to increase throughout the 4‐week period and became the predominant cell type at 28 days (66%). In contrast to the oligodendroglial population, the sizes of the astroglial and microglial cell populations were relatively stable.

This study shows that the population of immature glial cell precursors, abundant at birth in the lateral corticospinal tract, appear to be differentiating primarily into oligodendroglia, because this population exhibits a rapid increase in size, and relatively little change occurs in the astrocyte population. The trends in glial cell development in the dog are similar to those reported for rodents, although there may be some variation in the maturation and activity of oligodendrocytes.
Changing glial organization relates to changing fiber order in the developing optic nerve of ferrets
Authors: Guillery R. W. , Walsh C.
Published: January 2005

The structures of the developing eye‐stalk and the relationships of early retinofugal fibers as they pass through the stalk, chiasm, and tract have been studied by light and electron microscopical methods in fetal ferrets aged 23–27 days. The early eye‐stalk can be divided into two parts: a narrow extracranial part has a narrow lumen and is lined by few cells, whereas a thicker intracranial part has a wider lumen and is lined by several rows of cells. At the earliest stages no axon bundles are recognizable in the stalk, but fibers of the supraoptic commissure are already beginning to cross the midline in the diencephalon. Subsequently, as retinofugal axons invade the stalk, the glia of the extracranial part of the stalk have an interfascicular distribution and axon bundles are separately encircled by glial cytoplasm. In the intracranial part, as in the chiasm and tract, the glial cells occupy a periventricular position and send slender radial cytoplasmic processes to the subpial surface; these pass between groups of axons that here lie immediately deep to the subpial glia. Whereas axonal growth cones have no evident preferred distribution in the extracranial stalk, they tend to accumulate near the pial surface intracranially. The boundary between the two types of organization shifts as development proceeds so that the interfascicular glial structure of the early extracranial stalk first encroaches upon the intracranial parts and later appears in the chiasm. The characteristic adult arrangement of fibers in an age‐related order in the optic chiasm and tract, but not in the optic nerve, can be understood if axonal growth cones are guided toward the pial surface by radial glia but not by interfascicular glia. From the distribution of the growth cones, this is what appears to happen.
Early uncrossed component of the developing optic nerve with a short extracerebral course: A light and electron microscopic study of fetal ferrets
Authors: Guillery R. W. , Walsh C.
Published: January 2005

During the study of the developing optic nerve described in the preceding paper (Guillery and Walsh, '87), small bundles of nerve fibers were seen passing between the optic nerve and the ipsilateral hypothalamus of 24‐to 27‐day‐old prenatal ferrets. The bundles appear before any other fiber groups of the retinofugal pathway and are identifiable while the main portions of the retinofugal system are growing into the optic tracts. The bundles, made up of 50 or more axons, leave the optic nerve, emerge through the otherwise continuous layer of subpial glia and through the basal lamina of the nerve, run a short, naked, extracerebral course among collagen fibers and presumed fibroblasts, and then re‐enter the central nervous system, passing rostrally and dorsally to the superficial parts of the ipsilateral hypothalamus away from the region of the chiasm. These fibers represent the earliest link between the optic nerve and the brain, but their course is not followed by the majority of retinofugal fibers developing later, which pass toward one or the other optic tract.
Amacrine cells in the ganglion cell layer of the cat retina
Authors: Wässle Heinz , Chun Myung Hoon , Müller Frank
Published: January 2005

Following transection of the optic nerve, ganglion cells in the cat retina undergo retrograde degeneration. However, many small profiles (≤ 10 μm) survive in the ganglion cell layer. Previously considered to be neuroglia, there is now substantial evidence that they are displaced amacrine cells. Their density increases from approximately 1,000 cells/mm2 in peripheral retina to 7,000 cells/mm2 in the central area. Their total number was found to be 850,000, which is five times the number of ganglion cells and also five times the number of astrocytes.

Uptake of 3H‐muscimol followed by autoradiography labelled 75% of the displaced amacrine cells; hence, the majority seem to be GABAergic. Immunocytochemistry with an antibody directed against choline‐acetyltransferase labelled approximately 10% of the displaced amacrines in the peripheral retina and 17% in the central area. Uptake of serotonin (5–HT) followed by immunocytochemistry was found in 25–30% of displaced amacrines. NADPH diaphorase histochemistry labelled approximately 5% of displaced amacrine cells. The sum of the various percentages makes colocalization likely. Intracellular injection of Lucifer Yellow under microscopic control revealed that displaced amacrine cells constitute several morphological types.
Thalamic and corticocortical connections of the second somatic sensory area of the mouse
Authors: Carvell George E. , Simons Daniel J.
Published: January 2005

Thalamic and corticocortical connections of the second somatic sensory area (SII) in the mouse cerebral cortex were investigated by means of the retrograde transport of horseradish peroxidase. Focal injections of the enzyme were made in physiologically determined locations within the parietal cortex. Results show that SII receives substantial inputs from topographically appropriate regions within the ipsilateral ventrobasal nucleus and from the ipsilateral posterior group. The limb representation, which was previously found to be responsive to auditory stimulation, received inputs also from the medial division of the medial geniculate body. The SII face representation, which is largely unresponsive to auditory stimuli, received little or no input from the medial geniculate body. SII injections yielded retrograde labeling in the topographically appropriate region in the first somatic sensory area (SI), and SI injections retrogradely labeled cells in SII in a pattern consistent with previous electrophysiological maps. Homotypical regions within SI and SII therefore appear to be reciprocally interconnected. SII also receives inputs from the ipsilateral motor cortex and from contralateral SI and SII. Finally, injections into the SI paw but not face regions yielded retrograde labeling in the thalamic ventrolateral nucleus. Thus, the distal limb representations in SI and SII each receive inputs from a third major relay nucleus (i.e., medial geniculate to SII, ventrolateral nucleus to SI) whereas the face representations do not. These results indicate a close functional interrelationship between homotypical areas in SI and SII, though the two areas differ in several important respects. It is proposed that SII in mice may complement the function of SI by helping to define the overall sensory context in which detailed tactile discriminations are made.
Golgi study of the primate substantia nigra. I. Quantitative morphology and typology of nigral neurons
Authors: Yelnik Jerome , François Chantal , Percheron Gerard , Heyner Simone
Published: January 2005

Neuronal morphology was analyzed in the pars compacta, reticulata, and lateralis of the substantia nigra of humans and macaques. Golgi‐impregnated dendritic arborizations, reconstructed from serial sections, were described by using topological, metrical, and geometrical parameters measured in three dimensions. Morphological parameters were statistically analyzed. Cell bodies and axons were also described.

The primate substantia nigra comprises few local circuit microneurons. It consists mainly of large projection neurons having large cell bodies and sparsely branched dendritic arborizations. In all subdivisions, “complex endings” and “thin processes” can be found on nigral dendrites. Axons of large neurons occasionally had initial collaterals that never form profuse arborizations. Pars reticulata neurons had a cell body surface of 520 μm2, 4 dendritic stems, and 13 dendritic tips. The total dendritic length (L) was 7,100 μm, the highest dendritic length (Lm) 1,200 μm, and the mean length of dendritic segments 320 μm. Pars lateralis neurons were similar except for their larger cell bodies (650 μm2) and longer dendritic segments (440 μm). Pars compacta neurons had larger cell bodies (860 μm2), thicker and more numerous (5 stems, 19 tips), and longer dendrites (L = 10,500 μm; Lm = 1,400 μm). Large neurons of monkeys had the same topological characteristics as human neurons but shorter dendrites. The overall shape of arborizations was highly variable and not characteristic in any subdivision.

A hierarchical typology of nigral neurons is proposed, which comprises two neuronal species, the compacta and reticulata species, and a lateralis subspecies. Pallidal neurons (Yelnik et al., '84) belong to the reticulata species. The position of these species in relation to higher hierarchical levels is discussed.
Quantitative autoradiography of muscarinic and benzodiazepine receptors in the forebrain of the turtle, pseudemys scripta
Authors: Schlegel Jerry R. , Kriegstein Arnold R.
Published: January 2005

The distribution of muscarinic and benzodiazepine receptors was investigated in the turtle forebrain by the technique of in vitro receptor autoradiography. Muscarinic binding sites were labeled with 1 nM 3H‐quinuclidinyl benzilate (3H‐QNB), and benzodiazepine sites were demonstrated with the aid of 1 nM 3H‐flunitrazepam (3H‐FLU). Autoradiograms generated on 3H‐Ultrofilm apposed to tissue slices revealed regionally specific distributions of muscarinic and benzodiazepine binding sites that are comparable with those for mammalian brain. Dense benzodiazepine binding was found in the anterior olfactory nucleus, the lateral and dorsal cortices, and the dorsal ventricular ridge (DVR), a structure with no clear mammalian homologue. Muscarinic binding sites were most dense in the striatum, accumbens, DVR, lateral geniculate, and the anterior olfactory nucleus.

Cortical binding sites were studied in greater detail by quantitative analysis of autoradiograms generated by using emulsion‐coated coverslips. Laminar gradients of binding were observed that were specific for each radioligand; 3H‐QNB sites were most dense in the inner molecular layer in all cortical regions, whereas 3H‐FLU binding was generally most concentrated in the outer molecular layer and was least dense through all layers in the dorsomedial cortex. Because pyramidal cells are arranged in register in turtle cortex, the laminar patterns of receptor binding may reflect different receptor density gradients along pyramidal cell dendrites.
Anatomy of physiologically identified eye‐movement‐related pause neurons in the cat: Pontomedullary region
Authors: Ohgaki Tohru , Curthoys Ian S. , Markham Charles H.
Published: January 2005

Pause neurons (PNs) are inhibitory neurons close to the midline at the pontomedullary junction that fire tonically and then cease firing just prior to quick eye movements of visual or vestibular origin. Previous physiological evidence has shown that these neurons have a role of central importance in the generation of rapid eye movements in any direction and all major models of ocular motor control incorporate PNs as major elements. In this study in cats, we injected horseradish peroxidase intracellularly into somata or axons of physiologically identified PNs. After appropriate tissue preparation, cell body and axonal reconstructions were performed, with the aid of a camera lucida‐equipped microscope. Fifty‐three PNs were stained and reconstructed. These consisted of 17 cell bodies and dendrites and 36 axons. Seven of these included both cell bodies and axons. PN somas lay close to the midline in the nucleus raphe pontis and centralis superior, had extensive dendritic arborizations tending to arise from either pole of the elongated soma, and had axons which typically crossed the midline and bifurcated into long branches which extended rostrally and caudally, inferior to the medial longitudinal fasciculus. There were major terminal arborizations and boutons in areas just rostral and caudal to the abducens nucleus in areas where two types of premotor neurons, excitatory and inhibitory burst neurons, are concentrated. Many axosomatic contacts were noted. Other terminal arborizations and boutons were found close to the midline in a region rostral to abducens nucleus containing other neurons known to burst prior to quick eye movements, and in the nucleus reticularis gigantocellularis. Rostral stem axons could be traced to the level of the trochlear nucleus and inferior to the medial longitudinal fasciculus. The caudal stem axons could be traced parallel to the midline and inferior to the medial longitudinal fasciculus and as far caudally as the hypoglossal nucleus.
Organization of cortical and subcortical projections to area 6m of the cat
Authors: Olson C. R. , Jeffers I.
Published: January 2005

By analyzing regional variations of afferent connectivity, we have identified a medial subdivision of feline area 6 (area 6m) which differs from all surrounding sectors of the frontal lobe in its pattern of inputs. Area 6m is located in the ventral bank of the cruciate sulcus and on the adjacent medial face of the frontal, lobe and is partially coextensive with the medial frontal eye field as identified previously in electrophysiological experiments.

Area 6m is innervated by axons from visual, association, and oculomotor areas and does not receive projections from somesthetic or somatomotor areas. Cortical sources of input to area 6m include several retinotopically organized extrastriate visual areas (AMLS, ALLS, and PLLS), association areas with strong links to the visual system (area 7, granular insula, posterior ectosylvian gyrus, and cingulate gyrus), and a lateral division of area 6 (area 6l) with oculomotor functions. Thalamic afferents of area 6m derive from the paralamellar ventral anterior nucleus, from a dorsolateral division of the mediodorsal nucleus, and from the rostral intralaminar nuclei. The claustrum and the basolateral nucleus of the amygdala project to area 6m. Projections from area 7, the posterior cingulate area, the ventral anterior nucleus, and the mediodorsal nucleus are spatially ordered in a pattern such that parts of area 6 close to the fundus of the cruciate sulcus receive input from neurons positioned anteriorly in the cortical areas, dorsolaterally in the ventral anterior nucleus, and ventrolaterally in the mediodorsal nucleus.

Our results indicate that area 6m probably is involved in the voluntary control of gaze and attention rather than in skeletomotor functions.
Thalamic projections to the hippocampal and entorhinal areas in the cat
Authors: Yanagihara Mamoru , Niimi Kahee , Ono Katsuhiko
Published: January 2005

The thalamic projections to the hippocampal formation and to the subicular and entorhinal areas in the cat have been studied with retrograde transport of horseradish peroxidase (HRP) or wheat germ agglutinin conjugated to HRP (WGA‐HRP) and anterograde transport of WGA‐HRP. Retrograde transport tracers injected in various parts of these cortices resulted in labeled cells in the midline, anterior, and lateral dorsal nuclei. Injections into the hippocampal formation or the subiculum led to retrograde labeling of cells in the reuniens nucleus of the ipsilateral thalamus throughout its rostrocaudal extent, whereas the restricted injections into the dentate gyrus and the inferior region of the hippocampus led to no labeling. Following an injection into the pre‐ and parasubiculum, a large number of labeled cells were seen not only in the reuniens nucleus but in other midline nuclei. In addition, a substantial number of labeled cells were also detected in the anterior and lateral dorsal nuclei, particularly in the anterodorsal nucleus, which contained densely arranged labeled cells throughout almost the entire rostrocaudal extent. An injection into the medial entorhinal area labeled a number of cells in the anterior nuclei and in the reuniens nucleus, particularly its dorsal part. Injections into various subdivisions of the lateral entorhinal area yielded different patterns of distribution of labeled cells in the thalamic nuclei. An injection into the ventromedial division (VMEA) led to abundant labeling of cells in the paraventricular and reuniens nuclei. After an injection into the ventral division (VLEA), numerous labeled cells were detected in the reuniens nucleus and a lesser number in the paraventricular nucleus at anterior levels. When an injection was made into the dorsal division (DLEA), a large number of labeled cells were detected in the reuniens nucleus, and less numerous labeled cells were found in the central medial nucleus. There appears to be a topographic arrangement of cortical projections of the reuniens nucleus. The pre‐ and parasubiculum receive projections from the most medial part of the reuniens nucleus near the midline, and the DLEA receives projections from the medial part of the nucleus. The cells projecting to the VLEA and MEA are distributed in the central part of the reuniens nucleus, and those to the VMEA are distributed in the lateral part. Anterograde experiments were also performed; injections of WGA‐HRP into the reuniens nucleus resulted in terminal labeling in the superficial layers of the subicular area and the neighboring hippocampus and in the entorhinal area.
Retinohypothalamic projection and suprachiasmatic nucleus of the house sparrow, Passer domesticus
Authors: Cassone Vincent M. , Moore Robert Y.
Published: January 2005

The distribution of retinohypothalamic projections and the organization of the suprachiasmatic region of the hypothalamus was investigated in the house sparrow (Passer domesticus). Retinohypothalamic projections (RHT) were studied by two anterograde tracing methods, and hypothalamic organization was investigated immunohistochemically with antisera against a number of substances known to be present in the mammalian suprachiasmatic nucleus (SCN): bombesin (BBS), glutamic acid decarboxylase (GAD), 5‐hydroxytryptamine (5HT), neuropeptide Y (NPY), neurotensin (NT), somatostatin (SS), substance P (SP), vasoactive intestinal polypeptide (VIP), and arginine vasopressin (AVP). Observations from these experiments were analysed within the framework of a cytoarchitectural study using Nissl‐stained material.

From this study, we have identified an area in the anterior hypothalamus which we believe is an avian homologue of the mammalian SCN. This area contains a nucleus located in close apposition to the optic chiasm between the dorsal supraoptic decussation (DSD) and the ventral lateral geniculate body (GLv) for much of its rostrocaudal extent. The central portion of this nucleus contains neurons that exhibit GAD‐ and BBS‐like immunoreactivity and is the terminal field for the RHT. For this reason, we term this nucleus the visual SCN. It also contains axon plexuses exhibiting 5HT‐like, SP‐like, and NPY‐like immunoreactivity and is bordered ventrally by AVP‐like, SP‐like, and NT‐like immunoreactive cells and medially by VIP‐like and SS‐like immunoreactive cells. Although it is not established that these cell groups together compose a single suprachiasmatic nucleus, the organization in the avian brain of a nuclear complex with a retinorecipient area surrounded by nonvisual components would be very similar to that of the mammalian SCN.
Deafferentation‐induced alterations in the rat dorsal horn: I. Comparison of peripheral nerve injury vs. rhizotomy effects on presynaptic, postsynaptic, and Glial processes
Authors: Kapadia Shanta E. , LaMotte Carole C.
Published: January 2005

Light microscopical degeneration and ultrastructural alterations in the rat spinal dorsal horn were studied following either cutting of the sciatic nerve or rhizotomy at L4 and L5; survival time for both procedures was 3 weeks. Fink‐Heimer silver methods showed minimal degeneration of afferent central processes after sciatic section, and limited ultrastructural changes were present. Both rhizotomy and nerve section resulted in degenerating terminals. Most were swollen and electron lucent, with loss of vesicles; some electron‐dense terminals were present, particularly after rhizotomy. Both procedures also produced significant degeneration of postsynaptic dendrites and soma, evidenced by either increases in electron density, or loss of organelles and cavitation, or accumulation of osmiophilic floccular material. Glial processes frequently were expanded and extended to engulf single degenerating terminals and dendrites, or terminal‐dendrite units; in other cases glial tongues separated terminals from their postsynaptic dendrite. Glial processes often wrapped around degenerating profiles or groups of profiles in several layers, sometimes forming complex labyrinths. These results confirm past descriptions of pre‐ and postsynaptic changes resulting from peripheral nerve section, but newly reveal that dendritic destruction and increased glial activity are also significant following rhizotomy. Documentation of these changes is relevant for studies of reorganization following nerve and spinal cord damage, as well as providing an ultrastructural basis for evaluation of effects of neurotoxins that affect primary afferents, as described in a companion paper.
Autoradiographic studies of cerebellar histogenesis in the premetamorphic bullfrog tadpole: I. Generation of the external granular layer
Authors: Uray Nándor J. , Gona Amos G. , Hauser Kurt F.
Published: January 2005

This study examines the time of origin of cells in the external granular layer (EGL) in the frog cerebellum during early stages of development. Premetamorphic bullfrog tadpoles were given multiple intraperitoneal injections of 3H‐thymidine (10 m̈Ci/g body weight per injection) at developmental stages ranging from 4 weeks to 1 year and were killed at either 6 or 12 months of age. Autoradiograms were analyzed to determine the time when cells of the EGL were generated by an examination of the labeling pattern in the neuroepithelial cap where EGL cells were presumably formed and in the EGL into which they migrated.

The developmental stage of the cerebellum in the 6‐month‐old tadpole was essentially the same as that of the 12‐month‐old animal except for an increased size in the older tadpole. The cerebellum in both age groups contained a distinct neuroepithelial cap and an EGL, which was somewhat better formed in the 12‐month‐old tadpole. Some heavily labeled cells were found in the neuroepithelial caps of 6‐month‐old tadpoles from injection times of 6 weeks to 6 months. In the cerebella of 12‐month‐old tadpoles, however, heavily labeled cells were found in the neuroepithelial cap only with the injection time of 12 months; with injection times from 7 to 11 months, the cells were labeled lightly. Labeled EGL cells were found in the cerebella of 6‐month‐old tadpoles from an injection time of 6 weeks on; with injection times from 10 weeks to 6 months some EGL cells contained heavy amounts of label. In the cerebella of 12‐month‐old tadpoles, labeling of EGL cells was not detectable with injection times of 7–9 months; they contained light to medium labeling with injection times of 10 and 11 months and heavy labeling when injected at 12 months. These results indicate that EGL cells are generated continuously in premetamorphic tadpoles from the age of 6 weeks to 12 months. Furthermore, these results suggest that the rate of EGL cell formation is faster during the second half‐year of development than during the first.
Somatostatin‐like immunoreactive material in the rabbit retina: Immunohistochemical staining using monoclonal antibodies
Authors: Sagar Stephen M.
Published: January 2005

Two mouse monoclonal antibodies to somatostatin‐14 were used with avidin‐biotin‐peroxidase immunohistochemical technique to examine the rabbit retina. In agreement with a previous study using a polyclonal anti‐serum, a sparse population (about 1,000 per retina) of neurons in the ganglion cell layer are immunoreactive for somatostatin; the vast majority of these cells are inferior to the myelinated fiber bundle. In addition, the monoclonal antibodies disclose a second neuronal population that forms a circumferential band of immunoreactive neurons around the extreme periphery of the retina. The cells in the body of the inferior retina have dendrites that ramify in the inner plexiform layer. Both the circumferential band of cells and the cells in the body of the inferior retina give off axonlike processes that run in the inner plexiform layer and do not enter the optic nerve. These long, straight varicose fibers form a meshwork that covers the entire retina. The superior retina, which contains only rare immunoreactive cell bodies, has a plexus of stained fibers comparable to that of the inferior retina.

The circumferential band of cells is relatively resistant to the neurotoxin kainic acid, explaining a previously reported observation that this toxin depletes only about 50% of the content of somatostatin‐like immunoreactivity from the rabbit retina. Moreover, the somatostatin immunoreactive neurons are not labeled by the intraocular injection of the fluorescent dye DAPI, which labels the cholinergic displaced amacrine cells of the rabbit retina. These observations imply that somatostatin‐like immunoreactivity is localized to two populations of associational ganglion cells, neurons with cell bodies in the ganglion cell layer, the axons of which remain within the retina.
Volumes of the components of the hippocampus in the aging F344 rat
Authors: Coleman Paul D. , Flood Dorothy G. , West Mark J.
Published: January 2005

Much of the recent data on cells, synapses, and other structures in the dentate gyrus and hippocampus as a function of age are packing density or volume fraction data. In order to estimate total numbers, volumes, or surface areas of cells, synapses, vessels, etc., as a function of age, the total volumes of the subregions of the dentate gyrus and hippocampus must be known. The volumes of these subregions, visualized with the Timm stain, have been determined in 24 F344 rats from 4 to 37 months of age. Volumes of the various structures showed age‐related increases which were statistically significant for the perforant path zone of the dentate gyrus molecular layer, as well as the total molecular layer, the hilus, and regio inferior and total mossy fiber systems. If the 4‐month age group is eliminated from consideration, only the ratio of the volume of the mossy fiber zones to the volume of the perforant path zones of the dentate molecular layer increases significantly with age. Our general finding of lack of volumetric reorganization of the subdivisions of the hippocampal region between 12 and 37 months suggests that studies of the packing densities of structures in most of these zones may be considered comparable across ages, assuming comparability of sampling regions.