bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structural survey of the rat's brainstem sensory trigeminal complex
Authors: Ide Linda S. , Killackey H. P.
Published: January 2005

The fine structural organization of the principal sensory trigeminal nucleus was compared with that of the spinal trigeminal nucleus (subnuclei oralis, interpolaris, and the deep layers of caudalis) in adult albino rats. Direct comparisons indicate similarities between all of the subdivisions of the brainstem trigeminal complex both in the major morphological classes of neurons present and in basic patterns of synaptic connections. Major differences between the several subdivisions occur in the relative numbers and distribution of the different cell types.

The spinal trigeminal nucleus is distinguished by more numerous large (22–40 μm) polygonal neurons which give rise to long straight primary dendrites. Both the perikaryal surface and the thick primary dendrites of many of these cells are densely innervated by synaptic terminals. Especially large cells of this type are a prominent feature of subnucleus oralis. By contrast, the principal sensory nucleus is distinguished by its high density of small to medium‐sized (8–20 μm) round or ovoid neurons. These smaller neurons tend to receive a sparse axosomatic innervation. In addition to these differences the spinal trigeminal neuropil is distinguished by the striking manner in which it is broken up by large rostrocaudally oriented bundles of myelinated axons. Proximal dendrites of polygonal and fusiform neurons often wrap around these large axon bundles.

Morphologically heterogeneous populations of synaptic terminals with round vesicles (R terminals) and terminals with predominantly flattened vesicles (F terminals) occur in all of the subdivisions of the trigeminal complex. Both types of terminal make primarily axodendritic synapses, but both also make axosomatic synapses, and axospinous synapses with somatic as well as dendritic spines. In addition, axoaxonic synaptic contacts from F terminals onto large R terminals are seen in all subdivisions. Convincing examples of presynaptic dendrites were not observed in any of the brainstem subdivisions.

Synaptic glomeruli, characteristic groupings of dendrites and synaptic terminals, are found throughout the brainstem trigeminal complex. The dendritic elements in these glomeruli tend to be small‐diameter dendrites, spines, and large, spinelike appendages. Within the glomerulus these elements are postsynaptic to a single large R terminal and may also be postsynaptic to smaller F terminals. In addition, axoaxonic synaptic contacts from the F terminals onto the R terminal are a consistent feature of trigeminal synaptic glomeruli. Serial reconstructions of glomeruli indicate that both the R and the F terminals commonly occur as boutons en passant, with single axons innervating multiple glomeruli. Within the trigeminal complex synaptic glomeruli are often grouped together into clusters, which we have termed “glomerular nests.” We suggest that the peripherally related afferent segmentation characteristic of the rat's brainstem trigeminal complex is reflected in the distribution of these nests.
Developing pigeon retina: Light‐evoked responses and ultrastructure of outer segments and synapses
Authors: Bagnoli Paola , Porciatti Vittorio , Lanfranchi Alberto , Bedini Celina
Published: January 2005

Morphological development of photoreceptor outer segments and synapses in the foveal region of the pigeon retina was studied by electron microscopy. In addition, the maturation of outer retina function was investigated by recording electroretinographic (ERG) responses to either flash or pattern stimuli. The first ERGs to unpatterned or patterned stimulation can be recorded at 4–6 days posthatching. These results are consistent with anatomical analysis of pigeon photoreceptor and synapse development. Indeed, photosensitive lamellae in the outer segments can be observed simultaneously with the appearance of the first retinal responses to light. A few synapses can already be seen in the outer plexiform layer at the time photoreceptor disks first appear. In contrast, numerous synapses are already present in the inner plexiform layer when photoreceptor lamellae have yet to appear. A comparable maturation pattern has been reported to occur in chicks toward the end of the incubation time.
Dark rearing prolongs physiological but not anatomical plasticity of the cat visual cortex
Authors: Mower George D. , Caplan Caren J. , Christen William G. , Duffy Frank H.
Published: January 2005

Recent studies (Cynader and Mitchell, '80; Mower et al., '81) have shown that total dark rearing prolongs susceptibility to the physiological effects of monocular deprivation (MD) in visual cortex beyond the normal age limits. The present study addressed whether this delayed physiological plasticity is accompanied by delayed anatomical plasticity in the geniculocortical pathway.

Ocular dominance (OD) columns as defined by transsynaptic autoradiography following injection of 3H proline into one eye were studied both qualitatively and quantitatively in 17 cats. Compared to normal rearing (N‐3), both binocular eyelid suture (N‐2) and total dark rearing (N‐3) resulted in incomplete segregation of OD columns in area 17. This apparent immaturity after binocular deprivation, however, did not reflect a delayed capacity for development and plasticity. Visual experience after dark rearing produced no marked changes. In cats who experienced MD after dark rearing, injection of either the nondeprived (N‐2) or deprived eye (N‐3) resulted in a nearly uniform distribution of label throughout layer IV of area 17. The same result occurred with binocular vision after dark rearing (N‐1). MD from birth, however, produced expansion of columns from the nondeprived eye (N‐1) and contraction of columns from the deprived eye (N‐1). MD imposed after 4 months of normal vision resulted in normal OD columns (N‐1).

Electrophysiological studies revealed a high proportion of binocular cells within layer IV in cats who experienced monocular or binocular vision after dark rearing. Outside of layer IV there were clear environmental effects on OD of single cells in these cats. Measurements of cell sizes in the clateral geniculate nucleus showed shrinkage of cells innervated by the deprived eye when MD was initiated at birth (N‐3). MD after dark rearing (N‐4) produced no differences in cell sizes.

It is concluded that (1) visual input is necessary for the formation of normal OD columns, (2) the critical period for formation and environmental modification of OD columns is limited to early life, and (3) the physiological effects of visual experience after dark rearing reflect changes occurring beyond the geniculocortical pathway.
Distribution of central cholinergic neurons in the baboon (papio papio). II. A topographic atlas correlated with catecholamine neurons
Authors: Satoh K. , Fibiger H. C.
Published: January 2005

The topographic distribution of central cholinergic and catecholaminergic neurons has been investigated in the baboon (Papio papio). The perikarya were mapped on an atlas through the brain and spinal cord employing sections processed for acetylcholinesterase (AChE) pharmacohistochemistry coupled with choline acetyltransferase (ChAT) immunohistochemistry or aqueous catecholamine‐fluorescence histochemistry. Compared with subprimates, there is a remarkable increase in the volume occupied by and the number of cholinergic cells contained in the nucleus basalis and nucleus tegmenti pedunculopontinus (subnucleus compacta). The elaboration of these parts of the cholinergic system is accompanied by a large extension of catecholaminergic cell groups in the midbrain (groups A8–A10), particularly the substantia nigra (pars compacta), and in the dorsolateral pontine tegmentum (A5–A7 complex). Although cholinergic and catecholaminergic soma generally occupy distinctly different regions of the brain, a close apposition of cholinergic and noradrenergic neurons occurs in the dorsolateral pontine tegmentum. In the peripeduncular region ChAT‐positive cells and green fluorescent neurons of the A6–A7 complex form parallel lines and do not intermingle as has previously been demonstrated in the cat. Two distribution patterns, aggregated or disseminated, are another common feature of central cholinergic and catecholaminergic perikarya. The cholinergic neurons in the nucleus tegmenti pedunculopontinus and the catecholaminergic neurons in A6–A7 complex display both patterns. This comparative study of three transmitter systems in the baboon suggests that the cholinergic as well as the catecholaminergic neurons that give rise to ascending telencephalic and dorsal diencephalic projections undergo phylogenetic development in terms of cell number and nuclear volume.
The projection of three extrathalamic cell groups to the cerebral cortex of the turtle Pseudemys
Authors: Ouimet Charles C. , Patrick Robert L. , Ebner Ford F.
Published: January 2005

Three extrathalamic subcortical inputs to the part of the cerebral cortex that is known to receive thalamic fibers in the turtle were examined in the present study. Direct projections from the locus coeruleus, the superior medial raphe nucleus, and a wide area of the basal telencephalon that lies ventromedial to the globus pallidus were demonstrated with the horseradish peroxidase method. Fluorescence histochemistry confirmed the presence of catecholamine‐containing fibers in the rostral half of dorsal cortex and also demonstrated a dense network of serotoninergic fibers. Biochemical analysis showed the concentration of both monoamines to be relatively high; the norepinephrine concentration was 709 ng/g and the serotonin concentration was 1,750 ng/g. No evidence was found to suggest the existence of either a dopamine fiber projection to cortex comparable to that of mammalian neocortex or the presence of an epinephrine pathway to turtle cortex equivalent to the epinephrine‐containing fibers in the pallium of amphibians. The coexistence of the projections from the thalamus with (1) noradrenergic projections from the locus coeruleus, (2) serotoninergic projections from the superior medial raphe nucleus, and (3) presumably cholinergic projections from the basal telencephalon provide at least four distinct subcortical inputs to the reptilian dorsal cortex. Neither thalamic nor similar extrathalamic inputs have been demonstrated in the dorsal pallium of amphibia. Mammalian neocortex, in contrast, has even more elaborately differentiated inputs of both types. These results support the idea that thalamic and extrathalamic inputs to cortex appear at the same time in vertebrate evolution, and that both types of inputs are required for the normal development and function of neocortex.
The callosal system of the superior parietal lobule in the monkey
Authors: Caminiti Roberto , Sbriccoli Alessandro
Published: January 2005

The callosal connections of the superior parietal lobule, area 5 of Brodmann, were studied in macaque monkeys (M. nemestrina and M. fascicularis) using anatomical techniques based on both anterograde and retrograde axoplasmic transport of wheat‐germ‐agglutinin‐conjugated horseradish peroxidase. From sagittal sections, two‐dimensional flattened computer reconstructions of the volumes of cortical tissue containing callosal‐projecting neurons (callosal efferent zone) and/or callosal terminal axons (callosal terminal territory) were obtained. Callosal zones were found in area 5, including the supplementary sensory area, in a limited part of area 6, i.e., in the supplementary motor area, in area 7b, in the cortex of the dorsal bank of the sylvian fissure, and in a limited part of area 7a, in the cortex of the upper third of the rostral bank of the superior temporal sulcus. Callosal neurons in all cortical areas studied, though with regional variations, predominated in layer IIIb, but were also very numerous in layers VI and V. They were rare in other cortical laminae. In the cortical regions projecting heterotopically to area 5, the tangential distribution of callosal neurons was discontinuous because of the presence of large acallosal regions. These were not observed in area 5, although here the distribution of callosal neurons waxed and waned in the tangential cortical plane. Callosal axons to and/or from area 5 crossed the midline in the posterior, presplenial part of the corpus callosum. In the superior parietal lobule they terminated in radial patches or columns, spanning layers I–IV. These columns of various width (200–2,000 μm) were separated by gaps of similar size, free of such terminals. Callosal neurons were present not only within, but also between, the callosal terminal columns. Callosal neurons located within the callosal terminal columns were, in a statistically significant, way, more numerous than those located between them. The callosal efferent zone occupied 71% of the tangential domain of area 5, whereas the callosal terminal territory occupied only 49% of it. This difference is statistically significant. The discontinuous columnar arrangement of callosal terminals and the periodic distribution of callosal neurons in the lateral part of area 5 defined three main bands of callosal connections of irregular shape which were oriented mediolaterally and ran parallel to the main architectonic borders, the border between areas 2 and 5 and that between 5 and 7.
Peptide neurons in the canine small intestine
Authors: Daniel E. E. , Costa M. , Furness J. B. , Keast J. R.
Published: January 2005

The distributions of peptide‐containing nerve fibers and cell bodies in the canine small intestine were determined with antibodies raised against seven peptides: enkephalin, gastrin‐releasing peptide (GRP), neuropeptide Y, neurotensin, somatostatin, substance P, and vasoactive intestinal peptide (VIP). Immunoreactive nerve cell bodies and fibers were found for each peptide except neurotensin. In the muscle layers there were numerous substance P, VIP, and enkephalin fibers, fewer neuropeptide Y fibers, and very few GRP or somatostatin fibers. The mucosa contained many VIP and substance P fibers, moderate numbers of neuropeptide Y, somatostatin, and GRP fibers and rare enkephalin fibers. Nerve cell bodies reactive for each of the six neural peptides were located in both the myenteric and submucous plexuses. The distributions of nerve cell bodies and processes in the canine small intestine show many similarities with other mammals, for example, in the distributions of VIP, substance P, neuropeptide Y, and somatostatin nerves. There are some major differences, such as the presence in dogs of numerous submucosal nerve cell bodies with enkephalinlike immunoreactivity and of GRP‐like immunoreactivity in submucous nerve cell bodies and mucosal fibers.
The connections between the olfactory bulb and the brain in the goldfish
Authors: Levine R. L. , Dethier S.
Published: January 2005

We have investigated olfactory bulb connections in the goldfish by using both horseradish peroxidase applied to olfactory tract lesions and wheat germ agglutinin‐conjugated peroxidase administered to the olfactory bulb. The projections from the bulb pass to the brain in two major bundles: the lateral and the medial olfactory tracts. The lateral tract innervates the posterior terminal field in the area dorsalis. The medial tract divides into two rami. The dorsolateral ramus is the most substantial olfactory bundle in the brain and innervates several targets in both the area dorsalis and the area ventralis. The ventromedial ramus appears to innervate targets in the area ventralis exclusively. In addition, fibers of the medial olfactory tract (both rami) innervate the preoptic nucleus as well as targets in the diencephalon and, possibly, in the mesencephalon as well. Olfactory fibers from the dorsolateral and ventro‐medial rami cross the midline in the dorsal and ventral olfactory decussations, respectively. Between these two decussations is a dense olfactory plexus which has not previously been reported, and which may serve as a nexus allowing interchange of fibers between the two olfactory rami.

The terminal nerve in the goldfish has two parts. The major part of the nerve projects to the ventral nucleus (Vv) and is far more extensive than has previously been reported. A much less substantial component of the terminal nerve projects to the two retinae.

There are four large groups of cells in the telencephalon which project to the olfactory bulb. Of these two, the dorsal and the anterolateral groups have not been described in previous studies of the goldfish. We also report weakly labeled bulbopetal cells in the nucleus preglomerulosus and in the locus ceruleus.
Expression of the L11 neuropeptide gene in the Aplysia central nervous system
Authors: Taussig Ronald , Kaldany Rashad‐Rudolf , Rothbard Jonathan B. , Schoolnik Gary , Scheller Richard H.
Published: January 2005

Neuron L11 in the abdominal ganglion of Aplysia californica is thought to be both cholinergic and peptidergic. In previous studies, we isolated a cDNA clone encoding the precursor for an L11 secreted protein(s) by differentially screening an abdominal ganglion cDNA library. We now report the isolation of genomic clones encoding the L11 cDNA sequences. Analysis of these clones reveals that the gene is present in a single copy per haploid genome. RNA blotting and cDNA cloning demonstrate that the L11 gene is expressed not only in the abdominal ganglion but in the head ganglia as well. To define the positions of cells expressing this gene and to follow their processes, we raised antibodies to synthetic peptides defined by the cDNA sequence. Histochemistry revealed about 100 neurons containing immunoreactive material. These cells arborize in the neuropil and are distributed throughout the central nervous system, representing about 0.5% of the Aplysia central neurons. In addition, cells in the abdominal ganglion send processes to the mantle floor at the base of the gill via the genital and branchial nerves. Our data suggest that this network of cells expresses the single L11 peptide gene.
The afferent and sympathetic components of the lumbar spinal outflow to the colon and pelvic organs in the cat. III. The colonic nerves, incorporating an analysis of all components of the lumbar prevertebral outflow
Authors: Baron R. , Jan̈ig W. , McLachlan Elspeth M.
Published: January 2005

The cell bodies of the lumbar sensory and sympathetic pre‐and postganglionic neurons that project to the colon along the inferior mesenteric artery of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The numbers, segmental distribution, location, and size of these labeled somata have been determined quantitatively. Afferent cell bodies were symmetrically distributed bilaterally in dorsal root ganglia T13–L5, with the maximum number (about 80%) in L3 and L4 and most of the rest in L2. Labeled afferent somata were small relative to the entire population of DRG cells. Occasionally a few preganglionic somata were labeled in the intermediate zone of L3 and L4 spinal cord segments. Postganglionic cell bodies were labeled bilaterally in the proximal lobes of the inferior mesenteric ganglion (70–95%), in accessory ganglia of the intermesenteric nerve and of the lumbar splanchnic nerves, and in lumbar paravertebral ganglia. The segmental distribution in the lumbar sympathetic trunk was symmetrical on both sides and was the same as that of the afferent cells. Labeled postganglionic cell bodies in both the IMG and the accessory ganglia were larger than labeled and unlabeled ganglion cells in the paravertebral ganglia. From these data, it is estimated that about 2,100 afferent neurons and about 29,000 postganglionic neurons project in the lumbar colonic nerves. In conjunction with equivalent data for the hypogastric and lumbar splanchnic nerves, the results provide a quantitative and spatial description of the afferent and efferent components of the lumbar innervation of the colon and pelvic viscera.
Anatomical organization of long ascending propriospinal neurons in the cat spinal cord
Authors: English Arthur W. , Tigges Johannes , Lennard Paul R.
Published: January 2005

Retrograde transport of lectin‐HRP conjugate (WGA‐HRP) was used to examine the anatomical organization of long ascending propriospinal neurons (LAPNs) projecting to the cervical enlargement (C5‐T1) and to the upper part of the cervical cord (C3‐4) in cats. Small injections (0.05–1.0 μl) of dilute (1–4%) WGA‐HRP were made into the C5‐T1 or C3‐4 regions. The field potential evoked from stimulation of the superficial radial nerve served to position the micropipette delivering injections. Small and localized populations of labelled LAPNs were found in the dorsal horn (laminae IV‐V), the intermediate zone (dorsal and medial lamina VII), and the ventral horn (ventral lamina VII, laminae VIII and IX). Ventral horn LAPNs projecting to the C5‐T1 region were preferentially located in rostral lumbar regions. Ventral LAPNs projecting to the C3‐4 region were more caudally situated. No regional differences in distribution of dorsal horn and intermediate zone LAPNs were noted in comparing the results of C3‐4 with C5‐T1 injection protocols. It is concluded that the caudally located ventral LAPNs may exert their influence on cervical motor output through C3‐4 propriospinal inter‐neurons. Other LAPNs are considered to exert their effect more directly, either at the C5‐T1 or the C3‐4 levels.
Noradrenergic and serotoninergic innervation of cortical, thalamic, and tectal visual structures in old and new world monkeys
Authors: Morrison John H. , Foote Stephen L.
Published: January 2005

Antisera directed against human dopamine‐ß‐hydroxylase and against serotonin were used to characterize the noradrenergic (NA) and serotoninergic (5‐HT) innervation of several cortical and subcortical visual areas in squirrel monkey (Saimiri sciureus) and cynomolgus monkey (Macaca fascicularis). Few species differences were observed for either monoamine. Cortical areas 17 and 18, as well as visual areas in the temporal and parietal lobe were found to exhibit regional specialization of both 5‐HT and NA innervation. Precisely at the border between areas 17 and 18, the laminar innervation patterns and density characteristic of NA fibers in area 17 (Morrison et al., '82a; Kosofsky et al., '84) shift so that layer IV of area 18 contains more fibers than layer IV of area 17, and the overall density of fibers in area 18 is higher. For 5‐HT, the highly laminated patterns characteristic of area 17 (Morrison et al., '82a; Kosofsky et al., '84) also observe this cytoarchitectonic boundary. Fibers in area 18 are more evenly distributed across laminae, and the overall density of fibers decreases. The visual region of the inferotemporal cortex was found to be very lightly innervated by NA fibers and very densely innervated by 5‐HT fibers. Area 7 of the parietal lobule was more densely innervated by NA fibers, and less densely innervated by 5‐HT fibers, than any other visual cortical region examined.

The visual thalamic nuclei exhibited even greater regional differences in the density of NA innervation. The lateral geniculate nucleus was found to be virtually devoid of NA fibers, while the pulvinar‐lateral posterior complex was densely innervated. The density of 5‐HT fibers was more uniform across thalamic visual nuclei. The lateral geniculate, pulvinar, and lateral posterior nuclei all exhibit a moderate to high density of immunoreactive fibers. In the mesencephalon, the superficial layers of the superior colliculus were found to be densely innervated by NA fibers, whereas 5‐HT fibers were most dense in the intermediate layers.

These patterns of innervation indicate that, in these primate species, functionally related visual regions share common and distinguishable densities of NA innervation. Specifically, tecto‐pulvinar‐juxtastriate structures are more densely innervated than geniculo‐striate and inferotemporal structures. These relationships suggest that, within the visual system, NA fibers preferentially innervate the regions involved in spatial analysis and visuomotor response rather than those involved in feature extraction and pattern analysis. Although there are some examples of complementary innervation of cortical visual areas by 5‐HT and NA fibers, the 5‐HT innervation of visual areas at the mesencephalic, diencephalic, and telencephalic levels was of high density and exhibited less specialization than was evident for NA innervation.
Correlation of cell body size, axon size, and signal conduction velocity for individually labelled dorsal root ganglion cells in the cat
Authors: Lee Kyu Ho , Chung Kyungsoon , Chung Jin Mo , Coggeshall Richard E.
Published: January 2005

Measurements of cell body and peripheral and central axon sizes were made for primary sensory neurons outlined by the intracellular injection of HRP. Conduction velocities were also measured on the outlined processes. The sensory neurons were then subdivided into A and C cells on the basis of the conduction velocity of the impulses carried by the processes of these cells.

Central processes of both A and C cells are smaller than the peripheral processes, but the size differentiall is greater for the C cells. For A cells there is a linear relation between the size of the peripheral axon and the conduction velocity of the impulses carried by these axons, but the confidence limits are wide. For C cells there is a linear relation between the size of the central process and conduction velocity of the impulses carried by the processes, but for the peripheral processes two aberrant processes resulted in no correlation between process size and conduction velocity. For A cells, the size of the central and peripheral processes and the conduction velocity of the impulses carried by the peripheral processes are linearly correlated with cell body size. By contrast no such correlations can be demonstrated for C cells. This presumably implies an important difference in that the size of the cell body is correlated with axon size and impulse conduction velocity for A cells but not for C cells.

A widely accepted generalization is that large sensory cells give rise to myelinated axons and small sensory cells to unmyelinated axons. In this study, myelinated and unmyelinated are defined on the basis of impulse conduction velocity. For those cells that are clearly large (greater than 50 μm in diameter), the conduction velocity of the impulses carried by their processes is always greater than 2.5 m/s, and for those cells that are clearly small (less than 35 μm in diameter), the conduction velocity is always less than 2.5 m/s. Thus for these cells the above generalization holds. For the intermediate‐sized cells (35‐50 μm), however, the size of the cell body bears no predictable relation to the conduction velocity of the impulses carried by those processes, and thus to whether the axons are myelinated or unmyelinated. Thus the above generalization does not hold for this intermediate group of cells, and since there are many cells in this size range, we feel that the generalization that large cells give rise to myelinated axons and small cells to unmyelinated axons is an oversimplification.
Oral and facial representation within the medullary and upper cervical dorsal horns in the cat
Authors: Shigenaga Y. , Chen I. C. , Suemune S. , Nishimori T. , Nasution I. D. , Yoshida A. , Sato H. , Okamoto T. , Sera M. , Hosoi M.
Published: January 2005

Transganglionic transport of HRP was used to study the patterns of termination of somatic afferent fibers innervating oral and facial structures within the trigeminal nucleus caudalis and upper cervical dorsal horn of the cat. In separate animals, the superior alveolar, pterygopalatine, buccal, inferior alveolar, lingual, frontal, corneal, zygomatic, infraorbital, mental, mylohyoid, and auriculotemporal branches of the trigeminal nerve were traced in this experiment. The organization of the primary afferents innervating the oral structures is not uniform across laminae and at different rostrocaudal levels of the nucleus caudalis. The superior alveolar and pterygopalatins nerves mainly terminate in laminae I, II, and V at the level of the rostral one‐third of the caudalis. By contrast, the lingual, inferior alveolar and buccal nerve terminate in laminae I–V of, respectively, the rostral third, the entire length, and caudal two‐thirds of the caudalis. In addition, the lingual, buccal, and pterygopalatine nerves terminate in the dorsal and middle parts of the interstitial islands or pockets of lamina I neuropil extending to the rostral levels parallel to the nucleus interpolaris. Mediolaterally, in laminae I, II, and V of the rostral third an extensive overlap of projections was found between the branches from each trigeminal division, and some overlap was observed between projections from the mandibular and maxillary divisions. On the other hand, the projections of primary afferents innervating the facial structures are arranged in a somatotopic fashion in rostrocaudal and mediolateral axes over the laminae (I–1V) through the nucleus caudalis and upper cervical dorsal horn. Fibers from the perioral and perinasal regions terminate most rostrally in caudalis, and fibers from progressively more posterior facial regions terminate at successively lower levels. A mediolateral somatotopic arrangement was observed, with fibers from the ventral parts of face ending in the medial regions and fibers from the progressively more dorsal parts of the face ending in successively more lateral regions of the medullary and upper cervical dorsal horns. Corneal afferent terminals are concentrated in the outer parts of lamina II at the levels of the rostral parts of the caudal two‐thirds of the caudalis and the interstitial islands of lamina I. The maxillary division terminates first at the most caudal level of the caudalis, followed by the ophthalmic division descending as far as the C2 segment and the mandibular division reaching the most caudal level of the C2 segment. The clinical implications of this topographical arrangement are discussed, particularly with respect to the rostrocaudal somatotopic organization in the medullary and upper cervical dorsal horns.
A correlated light and electron microscopic immunocytochemical study of cholinergic terminals and neurons in the rat amygdaloid body with special emphasis on the basolateral amygdaloid nucleus
Authors: Carlsen Jørn , Heimer Lennart
Published: January 2005

The cholinergic innervation of the rat basolateral amygdaloid nucleus (BL) was determined by the immunocytochemical localization of the acetylcholine biosynthetic enzyme, choline acetyltransferase (ChAT).

ChAT‐immunoreactive (ChAT‐IR) elements were observed throughout the BL in the form of fine puncta and varicose fibers. Electron microscopy revealed that the immunoreactive puncta represented small terminals (0.3–1.2 μm), most of which formed synaptic contacts with unlabeled dendritic shafts or spines. Less frequently, ChAT‐IR terminals established synaptic contacts with large neuronal cell bodies, which had all the characteristics of projection neurons as defined on the basis of axonal projections to the ventral striatum. ChAT‐IR terminals were sometimes seen to form synaptic contacts with small neuronal cell bodies, including those of ChAT‐IR neurons. The ChAT‐IR boutons contained pleomorphic clear vesicles of varying size, and the large majority of the synapses were of the symmetric type.

Small ChAT‐IR neurons were observed in all parts of the BL. Although the ChAT‐IR cell bodies varied widely in shape from typical fusiform to round, most had a more or less oval shape with a major diameter of 10–14 μm. Most of the ChAT‐IR neurons seemed to display a radial bipolar dendritic pattern, but multipolar cells were also observed. The ChAT‐IR neurons contained an indented nucleus, which was often eccentrically located and surrounded by a thin or moderately thin rim of cytoplasm. The results obtained are discussed in relation to a quasi‐cortical organization of the BL.
Periventricular dopaminergic neurons terminating in the neuro‐intermediate lobe of the cat hypophysis
Authors: Luppi P. H. , Sakai K. , Salvert D. , Berod A. , Jouvet M.
Published: January 2005

The aim of the present study was to determine the exact origins of the dopaminergic hypothalamohypophyseal projections in the cat brain. For this purpose, we used a retrograde tracer technique with horseradish peroxidase (HRP) in conjunction with tyrosine hydroxylase (TH) immunohistochemistry as a marker for the dopaminergic neurons. After injections of the tracer into the neuro‐intermediate lobe, a substantial number of HRP‐labeled neurons was observed in the supraoptic and paraventricular neurosecretory nuclei. Furthermore, a cluster of HRP‐positive neurons was found in the tuberal component of the periventricular nucleus where few, if any, neurosecretory magnocellular cells are identified. TH immunohistochemistry on the same sections further revealed that virtually all these HRP‐containing neurons showed TH immunoreactivity. These double‐labeled neurons were medium in size and fusiform or ovoid and appeared to belong to the A14 dopamine cell group. In addition to these medium‐sized double‐labeled neurons, a magnocellular type of double‐labeled cell body was identified just adjacent to the organum vasculosum of the lamina terminalis and in and around the supraoptic and paraventricular nuclei. These double‐labeled cells appeared to be members of the A14 and A15 dopamine cell groups. In conclusion, the present study indicated that the dopaminergic projections to the cat neuro‐intermediate lobe might originate mainly in the medium‐sized cells located in the tuberal periventricular nucleus and partly in the large‐sized cells located in and around the supraoptic and paraventricular neurosecretory nuclei.
Optic tectum of the eastern garter snake, Thamnophis sirtalis. II. Morphology of efferent cells
Authors: Dacey Dennis M. , Ulinski Philip S.
Published: January 2005

Tectal efferent neurons were retrogradely filled from extracellular injections of horseradish peroxidase (HRP) into pathways efferent from the tectum. Tectorotundal neurons have cylindrical dendritic trees, 80–100 μm in diameter, that extend vertically across the central and superficial tectal layers. Apical and basal dendrites are laden with complex appendages. The axon gives rise to an intratectal, collateral arbor that extends horizontally into the stratum griseum centrale beyond the cell's dendritic tree. The parent axon exits the tectum laterally in the tectothalamic tract. Tectogeniculate neurons also have narrow, radially oriented, and highly branched apical dendrites, but their basal dendrites are infrequently branched and lack appendages. An intratectal axon collateral forms a small, spherical arbor overlapping the apical dendrites in sublayer c of the stratum fibrosum et griseum superficiale. The parent axon ascends vertically and just below the stratum opticum turns rostrad to follow the optic fibers to the diencephalon. Tectoisthmi neurons have small somata and thin, radial dendrites that arborize below the pial surface in the stratum zonale. An intratectal axon collateral forms a spatially restricted arbor ventral to the soma in register with the dendritic tree. Tectoisthmobulbar neurons have dendrites that arborize extensively in sublayer a of the stratum fibrosum et griseum superficiale. The axon exits the tectum without collateralizing and joins a smallcaliber component of the ventral tectobulbar tract. Ipsilateral tectobulbar neurons have stellate dendritic fields, 150‐250 μm in diameter, that are restricted to the deep layers of the tectum. Sparsely branched dendrites are appendage‐free but bear many short, fine spicules. The axon initially ascends from the soma and recurves into the stratum album centrale without collateralizing before joining a medium‐caliber component of the ventral tectobulbar tract. Crossed tectobulbar neurons have large, stellate dendritic trees with diameters ranging from 200 to 500 μm. Like ipsilateral tectobulbar neurons, their dendrites are appendage‐free but bear spicules. Their thick‐caliber axons exit the tectum without collateralizing and course deep in the stratum album centrale to reach the dorsal tectobulbar tract.
Regeneration of the cerebellofugal projection after transaction of the superior cerebellar peduncle in kittens: Morphological and electrophysiological studies
Authors: Kawaguchi Saburo , Miyata Hirofumi , Kato Nobuo
Published: January 2005

In contrast to the current concept of abortive regeneration of mammalian central axons, occurrence of marked, functionally active regeneration of the cerebellofugal projection was proved in kittens after complete transection of the decussation of the brachium conjunctivum (BCX). By means of the anterograde axonal transport of horseradish peroxidase that was injected into the cerebellar lateral and interpositus nuclei, the origin, course, and destination of the, regenerated fibers were identified unamhiguorisly and the time‐course of axonal regeneration was clarified. Functional connectivity of the regenerated cerebellothalamic projection was tested electrophysiologically. In eight out of 82 animals, marked regeneration of the cerebellofugal projection occurred; in the majority of the rest of the animals, trace amounts of regenerated fibers were observed. In the former but not in the latter animals, marked cerebellocerebral responses, as in intact animals, were evoked in the frontal motor and parietal association cortices. Most of the regenerated axons took a course similar to that of the normal projection and terminated in the normal projection areas, whereas a small proportion of fibers showed an aberrant course and termination. The cut ends of axons began to swell as early as 15 minutes after transaction, and the regenerated axons produced dense terminals in the thalamus by 19 days.
The pattern of spinal and medullary projections from a cutaneous nerve and a muscle nerve of the forelimb of the cat: A study using the transganglionic transport of HRP
Authors: Abrahams V. C. , Swett J. E.
Published: January 2005

The transport of HRP into the spinal cord and medulla in the cat has been examined from a forelimb cutaneous nerve, the lateral superficial radial nerve (LSR), and from the muscle nerves supplying both heads of the forelimb muscle, extensor carpi radialis (ECR). HRP transported by the LSR was widely distributed in the spinal cord throughout laminae I‐IV in the vicinity of the root entry zone and from spinal segments T1 to C5. HRP was also transported from the LSR to the medulla where there was intense patchy, discontinuous labelling in the main cuneate nucleus. The pattern of labelling in the cuneate nucleus did not follow any simple somatotopic plan. Exposure of the muscle nerve to HRP led to labelling in the spinal dorsal horn in lamina I, in the deep dorsal horn on the lamina V/VI border, and in lateral and medial lamina VI at sites that contain cells of origin of spinocerebellar tracts. The medial lamina VI label was contiguous with a deposit that extended medially to the central canal. The label in lateral lamina VI was patchy and formed a discontinuous column from T1 to C5. HRP transported by the muscle nerve also produced label in the more ventral regions of the cuneate nucleus where it had a lacy appearance, in part due to its extensive distribution around dendrites. A relatively dense, patchy, and discontinuous deposit of reaction product was also present in the external cuneate nucleus after muscle nerve exposure. This deposit was most intense on the dorsomedial surface of this nucleus, but another, less intense, deposit was also present ventrally.
A light and electron microscopic analysis of the mossy fibers of the rat dentate gyrus
Authors: Claiborne Brenda J. , Amaral David G. , Cowan W. Maxwell
Published: January 2005

The axon collaterals of dentate granule cells have been analyzed with the aid of a computerized microscope, following intracellular injections of horseradish peroxidase in hippocampal slice preparations. The axon of each granule cell gives rise to approximately seven primary collaterals; these collaterals usually divide into secondary and tertiary branches, which form an extensive plexus within the hilar region of the dentate gyrus. Individual axon collaterals vary greatly in length, but most have been found to be between 100 and 300 μm long. On average, the summed lengths of the collaterals (exclusive of the parent mossy fiber) are approximately 2,300 μm. Except for an occasional collateral that is given off by a mossy fiber in the proximal part of field CA3 of the hippocampus, the collaterals of the granule cell axons are confined to the hilar region; they are rarely seen in the granule cell layer itself and have never been observed in the molecular layer. In the longitudinal dimension of the dentate gyros, most of the collaterals are contained within a zone about 400 μm wide. The distribution of the collaterals within the hilar region is correlated with the location of the granule cell body. Those that arise from cells near the tip of the suprapyramidal blade tend to be confined to the region above field CA3; those from cells nearer the crest and from the infrapyramidal blade ramify widely throughout the hilus.

Two types of varicosities are present on the collaterals. Numerous small (∼2 μm), round varicosities are distributed unevenly along the collaterals; in electron micrographs these varicosities can be seen to make asymmetric synaptic contacts with dendritic shafts. On average, each granule cell collateral plexus his about 160 of these varicosities. The second type of varicosity is irregular in shape and ranges from 2 to 4 μm in diameter; there is usually only one sucil varicosity per collateral. In all respects except size, these varicosities rE semble the expansions found on the parent mossy fibers.

Mossy fiber trajectories in the proximal part of field CA3 were studied after extracellular injections of HRP into localized regions of the granule cell layer. Granule cells at different locations around the blade send their mossy fibers to different depths within the pyramidal cell layer in the proximal part of field CA3. However, further distally, mossy fibers from all parts of the granule cell layer contribute to the suprapyramidal bundle that occupies the stratum lucidum.
Telencephalic projections from midbrain and isthmal cell groups in the pigeon. I. Locus coeruleus and subcoeruleus
Authors: Kitt Cheryl A. , Brauth Steven E.
Published: January 2005

Horseradish peroxidase (HRP) and amino acid autoradiography were used in pigeon to determine the trajectories and projection patterns of neurons within the locus coeruleus and subcoeruleus nuclei upon the cerebral hemispheres. The specific cell groups investigated include the locus coeruleus (LoC), nucleus subcoeruleus dorsalis, and nucleus subcoeruleus ventralis.

Efferents from each of these nuclei ascend to the telencephalon via the medial and lateral forebrain bundles, ansa lenticularis, and the quintofrontal and occipitomesencephalic tracts. A separate dorsally situated bundle derived from LoC neurons reaches many dorsal thalamic nuclei. The telencephalic projections of the LoC and subcoeruleus nuclei are bilateral and symmetrical, although projections to the contralateral hemisphere are sparse. Crossing fibers project to contralateral targets primarily via the dorsal supraoptic decussation and along the dorsal and ventral margins of the anterior commissure.

Within the telencephalon, the following neural structures receive input from neurons in the LoC and subcoeruleus cell groups: the paleostriatal complex including the paleostriatum augmentatum and lobus parolfactorius, septal nuclei, nucleus accumbens, olfactory tubercle, hippocampus and parahippocampal area, nucleus taeniae, dorsal archistriatum, lateral neostriatum, hyperstriatum dorsale, hyperstriatum ventrale, and preoptic area.

Large portions of the cerebral hemispheres including the hyperstriatum accessorium, much of the neostriatum and hyperstriatum ventrale, and all but the dorsal portion of the archistriatum receive little or no input from either the locus coeruleus or subcoeruleus cell groups. This is apparently different from the condition in mammals in which virtually all cortical fields receive input from neurons within the LoC. Moreover, the pattern of projections of the subcoeruleus nuclei upon telencephalic fields described here as well as recent histochemical data suggest that these cell groups are comparable to the lateral tegmental (A8) cell group of mammals rather than to the mammalian subcoeruleus nuclei.
Regeneration of motoneuron axons into the adult frog spinal cord. After ventral‐to‐dorsal‐root anastomosis
Authors: Liuzzi F. J. , Lasek R. J.
Published: January 2005

Motoneuron axons routed into the adult frog spinal cord via a ventral‐to‐dorsal‐root anastomosis regenerated into the white and the gray matters. The distribution, growth patterns, and arborizations of regenerated ventral root axons were compared to those of regenerated dorsal root axons within the same environment.

Within the spinal white matter, regenerating ventral root axons behaved very similarly to regenerating dorsal root axons. Here, the regenerating ventral root axons grew longitudinally beneath the pia and radially toward the spinal gray matter, particularly within the dorsolateral fasciculus. The location of the regenerating axons and the patterns of their growth within the white matter suggest that glial endfeet and radial glial processes play a major role in the determination of these axonal growth patterns.

When motor axons entered the gray matter, their arborizations were very similar to those of regenerated dorsal root axons, suggesting that these two very distinct populations of axons respond similarly to local cues within the spinal gray matter. One difference between the arborizations of these two populations of axons was the relative number of varicosities along axonal branches. Regenerated motoneuronal arborizations within the spinal gray matter had fewer en passant varicosities than regenerated dorsal root axonal arborizations. This difference may reflect the synaptogenetic response of the two types of axons to targets within the gray matter. The low number of en passant varicosities associated with the ventral root axonal aborizations suggests that these axons do not synapse with all available targets and that the rules governing synaptic specificity during development may apply during regeneration in the adult frog spinal cord.
Brainstem terminations of extraocular muscle primary afferent neurons in the monkey
Authors: Porter John D.
Published: January 2005

The central terminations of afferent nerve fibers from the extraocular muscles of the monkey were investigated by means of transganglionic transport of wheat germ agglutinin‐conjugated horseradish peroxidase (WGA/ HRP). Following injections of selected extraocular muscles with WGA/HRP, terminal labeling was apparent in the ipsilateral trigeminal sensory and cuneate nuclei. The density of trigeminal projections varied markedly from one rostrocaudal level to the next, being heaviest within the ventrolateral portion of pars interpolaris of the spinal trigeminal nucleus. A second extraocular muscle afferent representation was noted in ventrolateral portions of the cuneate nucleus. This projection was restricted to rostral portions of pars triangularis of the cuneate nucleus, partially overlapping the afferent termination from dorsal neck muscles.

It is likely that some of the problems encountered in formulating conclusions regarding the functional role of extraocular muscle proprioception are due to a lack of detailed information of the central termination pattern of muscle afferents. Taken together, the present findings should provide a basis for further anatomical and physiological studies designed to elucidate the role played by extraocular muscle proprioceptors in vision and oculomotor control.