bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative study of the Purkinje cell dendritic spines in the rat cerebellum
Authors: Napper R. M. A. , Harvey R. J.
Published: January 2005

The number of spines on an individual Purkinje cell in the cerebellar cortex of the rat was determined by stereological methods. Investigations were based on thin section electron micrographs, freeze fracture replicas, and horseradish peroxidase labeled cells. Purkinje cell dendritic spines in our embedded material had a mean length of 1.4 ± 0.05 μm and mean neck and head diameters of 0.22 ± 0.01 μm and 0.45 ± 0.02 μm, respectively. From these dimensions, an estimate of spine volume in embedded material of 0.132 μm3 was obtained. The density of dendritic spines in our fixed material was 8.15 × 108 or 7.24 × 108 per μl of molecular layer from volume fraction and density per mm2, respectively. The number of spines per linear micron of Purkinje cell spiny branchlet was 17.2 from freeze fracture and 17.6 from horseradish peroxidase labeled dendrites. These all indicate that there are between 154,000 and 175,000 spines on the dendritic tree of each Purkinje cell, considerably more than previously reported for the rat.
Number of parallel fiber synapses on an individual Purkinje cell in the cerebellum of the rat
Authors: Napper R. M. A. , Harvey R. J.
Published: January 2005

In the present study, stereological techniques applied to electron micrographs of the molecular layer of the rat cerebellum have been used to estimate the number of parallel fiber synapses on the dendritic tree of a single Purkinje cell. Quantitative features of the parallel fiber to Purkinje cell dendritic spine synapses and of the parallel fibers were investigated as a preliminary to estimating the number of synapses. Parallel fiber to Purkinje cell synapses are flattened disclike structures with a mean axial ratio of 1.47 and a mean diameter of 319 μm in fixed tissue. The density of synapses in our fixed material was 8.17 × 108 per μl of molecular layer. Determination of the length density of the synapses per unit area of micrograph indicated a synapse density of 8.03 × 108 per μl. These densities give a total number of synapses per Purkinje cell of 1.74 × 105 and 1.71 × 105, respectively. Estimation of the number of parallel fiber varicosities and of varicosity length gave a density of 9.31 × 108 varicosities per μl of molecular layer and determining the mean number of parallel fiber to Purkinje cell synapses per varicosity gave a synapse density of 9.82 × 108 per μl, equivalent to 2.09 × 105 per Purkinje cell. The reasons why this estimate is likely to be too high are discussed. We conclude that there are some 175,000 parallel fiber synapses on an individual Purkinje cell dendritic tree in the cerebellar cortex of the rat, considerably more than previously reported.
Anatomy of the adrenergic system in the medulla oblongata of the tree shrew: PNMT immunoreactive structures within the nucleus tractus solitarii
Authors: Mittendorf Andrea , Denoroy Luc , Flügge Gabriele
Published: January 2005

The adrenergic system in the medulla oblongata of tree shrews was investigated by immunocytochemistry with an antibody against phenylethanolamine‐N‐methyltransferase. Two groups of adrenegic cells, which are equivalent to those of other species, were detected: Group C1 in the ventrolateral medulla and group C2 in the dorsomedial medulla.

Adrenergic cells in C1 are located around the lateral reticular nucleus or between its subdivisions. They are mostly multipolar with branched processes. In group C2, some immunoreactive cell bodies smaller than those in C1 and many nerve terminals are found in the motor nucleus of the vagus, but most of the adrenergic cells and fibers are observed in the nucleus tractus solitarii. The cytoarchitecture of this nucleus resembles that described before for the rhesus monkey. In contrast to the rat, the subnucleus gelatinosus, which according to other authors receives cardiac and gastric afferents, is a prominent structure in immunocytochemically as well as conventionally stained sections. Adrenergic cell bodies and their fibers form a ring around this nucleus, but no immunoreactive structures are found within it. In the dorsomedial part of the nucleus tractus solitarii, adrenergic neurons are accumulated. They are often located in close proximity to blood vessels. Elongated immunoreactive neurons in the medial subdivision of the nucleus also seem to project in the direction of the dorsal area.

Our data give new information about the adrenergic system in the medulla oblongata, especially in the nucleus tractus solitarii of the tree shrew, a species that provides a useful model of a small primate brain.
Effects of kynurenate and other excitatory amino acid antagonists as blockers of light‐ and kainate‐induced retinal rod photoreceptor disc shedding
Authors: Besharse Joseph C. , Spratt Gwendolyn , Reif‐Lehrer Liane
Published: January 2005

Photoreceptor disc shedding in the retina involves detachment of discs from distal outer segments and phagocytosis of those discs by adjacent pigment epithelial cells. The disc‐shedding process balances the continuous renewal of photosensitive membrane. In amphibians, rod disc shedding normally is light‐stimulated. However, excitatory amino acids such as kainate stimulate disc shedding independent of a dark‐light transition. Excitatory amino acid‐induced disc shedding is accompanied by toxic changes within the retina. To evaluate the possible role of an endogenous excitatory amino acid in the regulation of light‐evoked disc shedding, we examined the effects of excitatory amino acid antagonists on kainate‐induced and light‐evoked disc shedding and on retinal toxicity. Using eyecups from Rana pipiens, we found that kynurenate, D‐O‐phosphoserine, and cis‐2,3‐piperidine dicarboxylic acid (cis‐PDA) all block both the neurotoxic and disc‐shedding effects of kainate. Kynurenate and D‐O‐phosphoserine, but not cis‐PDA, also block light‐evoked disc shedding. Our analysis suggests that kynurenate blocks the mechanism by which light “triggers” disc shedding rather than directly inhibiting disc detachment and phagocytosis. The observation that cis‐PDA antagonizes the effects of kainate, but not light, suggests that the receptor mediating the kainate effect on disc shedding may not be involved in the normal initiation of the response by light. In contrast, our data on kynurenate suggest that it antagonizes an endogenous mechanism involved in the normal control of disc shedding. Thus, analysis of the differences between cis‐PDA and kynurenate as antagonists in the retina may yield important insight into the mechanism by which light initiates disc shedding.
Morphological and electrophysiological identification of gigantocellular tegmental fied neurons with descending projections in the cat: II. Bulb
Authors: Mitani Akira , Ito Keihachiro , Mitani Yuko , McCarley Robert W.
Published: January 2005

There are three different descending projections from the bulbar gigantocellular tegmental field (BFTG) in the cat, as defined by intracellular recording and intracellular horseradish peroxidase (HRP) techniques. The first pathway arises from neurons which send axons to the contralateral medial longitudinal fasciculus (cMLF neurons); cMLF neurons show excitatory postsynaptic potentials (EPSPs) after stimulation of the ipsilateral pontine gigantocellular tegmental field (PFTG). Most cMLF neurons have large ellipsoid‐polygonal somata (mean, 56.8 μm), thick axons (average diameter, 3.09 μm), mostly non‐spiny dendrites and dendritic fields flattened in the anteroposterior direction. No cMLF neurons with axon collaterals in the BFTG are present in the data of this study. The second pathway arises from neurons which send axons to the ipsilateral MLF (iMLF neurons); iMLF neurons show EPSPs after stimulation of the ipsilateral PFTG. Most iMLF neurons have large ellipsoid‐polygonal somata (mean, 60.2 μm), thick axons (average diameter, 3.00 μm), mostly non‐spiny dendrites and dendritic fields that are only slightly flattened in the anteroposterior direction. As with cMLF neurons, no iMLF neurons with axon collaterals in the BFTG are present in the data of this study. The third pathway arises from neurons that send axons directly into the ipsilateral caudal bulbar reticular formation (iBRF neurons). Most iBRF neurons have smaller ellipsoid‐polygonal somata (mean, 38.6 μm), thinner axons (average diameter, 1.84 μm), mostly nonspiny dendrites, and dendritic fields that are flattened in the anteroposterior direction. In contrast to cMLF and iMLF neurons, axon collaterals are present in 73% of iBRF neurons. About half of iBRF neurons have bifurcated axon collaterals with both anterior and posterior projections, and in these neurons antidromic spike potentials are elicited by stimulation of the ipsilateral PFTG.
Localization of immunoreactive GABA and enkephalin and NADPH‐Diaphorase‐positive neurons in fetal striatal grafts in the quinolinic‐acid‐lesioned rat neostriatum
Authors: Roberts Rosalinda C. , Difiglia Marian
Published: January 2005

Fetal striatal tissue grafts have been shown to partially reverse the biochemical and behavioral deficits induced by excitotoxic lesions. To determine if grafted striatal neurons contain neurochemical markers similar to those in neurons in the caudate nucleus and to establish the morphological characteristics and relative frequency of labeled neurons in the grafts, the localization of immunoreactive GABA and leucine‐enkephalin (ENK) and of NADPH‐diaphorase (NADPH‐d) activity was examined in fetal striatal grafts at the light and electron microscopic levels. Striatal tissue from 17‐day fetuses was grafted into the caudate nucleus of adult rats 1 week after intracaudate injections of either a low or high dose of quinolinic acid. At the light microscopic level, immunoreactive GABA and ENK and NADPH‐d‐positive neurons, processes, and punctate structures were present within adjacent sections of the same grafts. The frequency and morphological features of these labeled cell populations were similar in grafts placed into either minimally or extensively lesioned striata. Immunoreactive GABA and ENK neurons in the grafts constituted 28% and 13.5%, respectively, of the neuronal population of the graft and their mean diameters were 22 and 14% larger, respectively, than neostriatal neurons that contained the same chemical markers. NADPH‐d‐positive neurons in the grafts formed 3.5% of total grafted neurons and exhibited characteristics of neostriatal NADPH‐d‐containing aspiny cells, including medium‐sized somata, indented nuclei, and varicose dendrites.

At the electron microscopic level most GABA‐positive neurons in the grafts contained indented nuclei and most immunoreactive ENK somata had unindented nuclei. Dendrites and dendritic spines with GABA or ENK immunoreactivity were present in the grafts where they were postsynaptic to unlabeled axons. Immunoreactive GABA and ENK axon terminals formed synapses with unlabeled neuronal profiles in the grafts. These findings demonstrate that fetal striatal grafts contain chemically defined neuronal populations that form synaptic connections within the graft and share some features with corresponding cell groups in the neostriatum. These results provide an anatomical basis for the graft‐induced recovery from behavioral and biochemical deficits caused by instrastriatal lesions reported in other studies.
Optic synapse number but not density is constrained during regeneration onto surgically halved tectum in goldfish: HRP‐EM evidence that optic fibers compete for fixed numbers of postsynaptic sites on the tectum
Authors: Hayes William Pär , Meyer Ronald L.
Published: January 2005

The number of optic synapses in the half tectum of goldfish was counted by using an improved HRP‐labeling protocol and a columnar sampling method that spanned the entire optic innervation layer, S‐SO‐SFGS. It was previously found by using this procedure in intact tectum that the normal number of optic synapses was regenerated by 30 days and maintained thereafter even in the absence of impulse activity. This suggested that the number of synapses in this system was intrinsically fixed. In order to examine whether this limit was imposed by optic fibers or by target cells, optic synapses were counted in surgically halved tecta which received compressed optic projections consisting of regenerating optic fibers from the entire retina. We reasoned that if synapse number is a function of the number of afferents, then there should be twice the normal number of optic synapses per column; on the other hand, if their number is fixed by target, then their number per column should be normal.

We found that the number of optic (labeled) synapses was normal in sample columns from fish at 70 days and 160 days after optic nerve crush. Thus, retinal ganglion cells, on average, formed half as many synapses on the half tectum compared to intact tectum, indicating the number of optic synapses was limited by the tectum. The number of nonoptic (unlabeled) synapses was also found to be normal. By contrast, the S‐SO‐SFGS was found to be 88–103% thicker compared to normal fish, apparently because of a 20‐fold increase in the number of optic fibers. As a result, the density of synapses was about half normal in half tecta, and so, in contrast to synapse number, synaptic density is not constrained during regeneration.

We infer from these data that optic fibers compete for limited numbers of postsynaptic sites during regeneration and suggest that this competition promotes neural map refinement and the various plasticities described for this projection.
Electron microscope study of Golgi‐stained cells in lamina II of the rat spinal dorsal horn
Authors: Todd Andrew J.
Published: January 2005

Seven Golgi‐stained cells in lamina II of the rat spinal dorsal horn were examined by electron microscopy. One of the cells studied was an islet cell, two were stalked cells, and the remaining four cells could not be classed into either group.

The islet cell and three of the unclassified cells possessed presynaptic dendrites and formed synapses onto a variety of dendritic spines and shafts within lamina II. The axons of the islet cell and of one of the unclassified cells formed symmetric axodendritic synapses mainly onto dendritic shafts.

The two stalked cells and the remaining unclassified cell did not possess vesicle‐containing dendrites. This last cell bore some resemblance to a stalked cell and may have represented an atypical example of one.

Most of the synapses involving the cells took place outside synaptic glomeruli, but all seven cells were postsynaptic to central axons within glomeruli and in most cases to both type I and type II central axons, suggesting a monosynaptic input from myelinated and unmyelinated primary afferent axons. In addition, most of the cells were postsynaptic to vesicle‐containing dendrites.

It is concluded that certain cells, which do not belong to the stalked or islet classes, possess presynaptic dendrites and function as presumed inhibitory interneurones within lamina II. The target of the cells with presynaptic dendrites includes other cells within lamina II and may also include cells in deeper laminae of the dorsal horn. Further evidence will be needed in order to determine whether all cells in lamina II that do not possess presynaptic dendrites form a single functional class.
Development of the rat thalamus: II. Time and site of origin and settling pattern of neurons derived from the anterior lobule of the thalamic neuroepithelium
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

Short‐survival, sequential, and long‐survival thymidine radiograms of rat embryos, fetuses, and young pups were analyzed in order to examine the time of origin, settling pattern, and neuroepithelial site of origin of the anterior thalamic nuclei–the lateral dorsal (lateral anterior), anterodorsal, anteroventral and anteromedial nuclei–and of two rostral midline structures–the anterior paraventricular and paratenial nuclei. The neurons of the lateral dorsal nucleus are generated over a 3‐day period between days E14‐E16 and their settling pattern displays a combined lateral‐to‐medial and dorsal‐to‐ventral neurogenetic gradient. The bulk of the neurons of the anteroventral nucleus are generated over a 3‐day period between days E15‐E17 and settle with an oblique lateral‐to‐medial and ventral‐to‐dorsal neurogenetic gradient. The bulk of the neurons of the anteromedial nucleus are generated over a 2‐day period between days E16‐E17 and show the same settling pattern as the anteroventral nucleus. The neurons of the anterodorsal nucleus are generated over a 3‐day period between days E15‐E17 and show a lateral‐to‐medial neurogenetic gradient. The bulk of the neurons of the central part and lateral part of the paraventricular nucleus are generated over a 2‐day period (E16‐E17 and E17‐E18, respectively) and each part displays a ventral‐to‐dorsal neurogenetic gradient. Finally, the bulk of the neurons of the paratenial nucleus are generated over a 4‐day period between days E15‐E18 and settle with a lateral‐to‐medial neurogenetic gradient.

Observations are presented that the anterior thalamic nuclei, constituting the distinct “limbic thalamus,” derive from a discrete neuroepithelial source. This is the crescent‐shaped germinal matrix lining the diencephalic (medial) wall of the hitherto unrecognized anterior transitional promontory, which we call the anterior thalamic neuroepithelial lobule. On day E16 three migratory streams leave the anterior neuroepithelial lobule and, on the basis of their labeling pattern in relation to the neurogenetic gradients of the anterior thalamic nuclei, they are identified, from dorsal to ventral, as the putative migratory streams of the anterodorsal, anteroventral, and lateral dorsal nuclei. On day E17 the putative migratory stream of the anteromedial nucleus appears to leave the same neuroepithelial region that on the previous days was the source of the anteroventral nucleus. Dorsally, two neuroepithelial patches persist after day E17 and these are identified as the putative cell lines of the anterior paraventricular and paratenial nuclei.
Serotoninlike immunoreactivity in the central and peripheral nervous system of the scale worm Harmothoe imbricata (polychaeta)
Authors: Miron Marie‐José , Anctil Michel
Published: January 2005

The distribution of serotoninergic neurons in the nervous system of the scale worm Harmothoe imbricata was visualized in the anterior half of the body by the peroxidase‐antiperoxidase (PAP) immunohistochemical method with a specific antiserotonin antibody. Immunoreactive neuronal somata were localized in discrete ganglion cell masses of the dorsally situated cerebral ganglion and in segmental ganglia of the ventral nerve cord. They also make up the majority of neurons present in the parapodial ganglia. Large and small varicose fibers stained in the neuropile of all the above‐mentioned ganglia but also in interganglionic connectives and segmental nerves. On the basis of soma size and location and of fiber distribution, the reactive neurons were identified as primarily interneuronal with a few motoneurons and presumptive afferent neurons. The presence of a motor component was substantiated by observations of several reactive varicose fibers spread over longitudinal muscle layers of the trunk. In addition, neurites of the subepidermal nerve plexus and enterochromaffinlike cells of the gut epithelium reacted with the serotonin antibody. It is concluded that serotoninergic pathways are ubiquitous elements in the organization of the central and peripheral nervous system of this polychaete. The significance of these findings in relation to other annelid groups and to the physiological role of serotonin is discussed.
Connections of the dorsal nucleus of the lateral lemniscus: An inhibitory parallel pathway in the ascending auditory system?
Authors: Shneiderman Amiram , Oliver Douglas L. , Henkel Craig K.
Published: January 2005

This study examines the dorsal nucleus of the lateral lemniscus (DNLL) and its afferent and efferent connections. In Nissl‐stained material, DNLL has three parts: dorsal, ventral, and lateral. Although each part contains neurons with similar Nissl patterns, the subdivisions may be distinguished by the size, shape, and orientation of the cells. The lateral DNLL contains a mixture of DNLL neurons and cells from the sagulum.

Afferent connections to DNLL were investigated with anterograde axonal transport techniques. Bilateral inputs to DNLL arise from the anteroventral cochlear nucleus and lateral superior olive, while unilateral inputs are provided by the ipsilateral medial superior olive and the contralateral DNLL. The inputs appear to have a tonotopic organization. Afferent fibers to DNLL form horizontal bands that are continuous both mediolaterally and rostrocaudally. All parts of DNLL do not share the same inputs, and a medial‐to‐lateral gradient in the labeling of some pathways is evident.

To study the efferent connections of DNLL, both retrograde and anterograde axonal transport techniques were used. The DNLL projects to the inferior colliculus and the contralateral DNLL. The topography of these projections suggests that areas of similar tonotopic organization are connected. In the inferior colliculus, the projection is heaviest to the central nucleus and extends to the adjacent dorsal and caudal cortex, the rostral pole nucleus, and the ventrolateral nucleus. Axons from DNLL terminate along the fibrodendritic laminae of the central nucleus as bands that are prominent on the contralateral side, whereas those on the ipsilateral colliculus are more diffuse.

The afferent and efferent connections of DNLL constitute a multisynaptic pathway, parallel to the other ascending pathways to the inferior colliculus. The other ascending pathways include the direct pathways from the cochlear nucleus to the inferior colliculus and the indirect pathways via the superior olivary complex. Ascending pathways are discussed as to their relationship to the subdivisions of the inferior colliculus, the laterality of their projections, and their banding patterns in the central nucleus. In contrast to the excitatory pathways to the inferior colliculus, the neurons in DNLL may use GABA as a neurotransmitter. Axons from the DNLL terminate in the inferior colliculus as bands that could have a unique inhibitory function. Thus, the multisynaptic, DNLL pathway may provide feed‐forward inhibitory inputs to the inferior colliculus, bilaterally, and to the contralateral DNLL.
Morphology of physiologically identified second‐order vestibular neurons in cat, with intracellularly injected HRP
Authors: Ohgaki Tohru , Curthoys Ian S. , Markham Charles H.
Published: January 2005

The morphology of horizontal canal second‐order type I neurons was investigated by intracellular staining with horseradish peroxidase (HRP) and three‐dimensional reconstruction of the cell bodies and axons.

Axons penetrated in and around the abducens nucleus were identified as originating from type I neurons by their characteristic firing pattern to horizontal rotation and by their monosynaptic response to stimulation of the ipsilateral vestibular nerve. A total of 47 type I neurons were stained. The cell bodies were located in the rostral portion of the medial vestibular nucleus (MVN) and were large or medium sized and had rather elongated shapes and rich dendritic arborizations. The neurons were divided into two groups: those which projected to the contralateral side of the brain stem (type Ic neurons) and those which projected to the ipsilateral side of the brainstem (type Ii neurons).

All stem axons of type Ic neurons crossed the midline and bifurcated into rostral and caudal branches in the contralateral medial longitudinal fasciculus (MLF). Two or three collaterals arising close to this bifurcation distributed terminals in a relatively wide area in the contralateral abducens nucleus. Some of these collaterals projected further to the contralateral MVN and thus are vestibular commissural axons. Some of the rostral and caudal stem axons had collaterals which projected to the contralateral nucleus prepositus hypoglossi (PH), nucleus raphe pontis, or medullary reticular formation.

There were at least six classes of type Ii neurons, most of which distributed to a relatively limited region in the ipsilateral abducens nucleus and they were categorized according to their future projections into the following categories: (A) no further collaterals beyond the abducens nucleus; (B) collaterals in the abducens nucleus and a branch descending and terminating in ipsilateral PH; (C) projected to the abducens nucleus, PH, and an area rostral to the abducens nucleus; (D) projected to the abducens nucleus and to ipsilateral reticular formation rostral and caudal to the abducens nucleus; (E) collaterals in the abducens nucleus and a thick caudal stem axon entering and descending in ipsilateral MLF; (F) a thick caudal stem axon entering and descending in ipsilateral MLF and no collaterals to the abducens nucleus. Some type Ii neurons also had recurrent collaterals which projected back to the ipsilateral MVN; these may inhibit type II neurons during ipsilateral rotation.
Changes with age in the morphology of the cochlear nerve in rats: Light microscopy
Authors: Hoeffding Virginia , Feldman Martin L.
Published: January 2005

Cochlear nerve morphology was examined in a series of rats ranging in age from young adulthood to advanced age in order to assess the extent of fiber loss and the nature of degenerative changes with age. The animals were perfused via the aorta with mixed aldehydes. Blocks including the cochlear nerves were removed, embedded in Araldite, and sectioned in a plane transverse to the longitudinal axis of the nerve. Analysis of the material included counts of normal and degenerating fibers and of glial cells, maps of fiber packing densities, and measurements of the cross‐sectional area of the nerve.

The median number of normal fibers in the young adult animals (2‐3 months) was 21,218. This number was reduced by 21% at 26.5 months and by 24% in the oldest group (35‐36 months). The number of degenerating myelin sheaths was first seen to be significantly increased at 6 months, reached a peak at 26.5 months, and declined at 35‐36 months. There was an age‐related increase in the cross‐sectional area of the nerve, amounting to about 60% at 26.5 months and to about 50% at 35–36 months. Fiber packing density decreased evenly with age over the area of the nerve. The increased cross‐sectional area and decreased fiber packing density appeared to be related to increases in the thickness of myelin sheaths and in the area occupied by interneural elements.
Markers shared between dorsal root and enteric ganglia
Authors: Kirchgessner A. L. , Dodd J. , Gershon M. D.
Published: January 2005

Although the bowel is known to contain intrinsic primary afferent neurons with mucosal projections these cells have not been identified. The current study was undertaken to determine whether carbohydrate differentiation antigens or enzymatic markers common to primary sensory neurons could be found in enteric neurons. Subpopulations of sensory neurons of rat dorsal root ganglia (DRG) can be identified by the immunocytochemical detection of lactoseries and globoseries carbohydrate differentiation antigens with monoclonal antibodies (MAbs) and by the histochemical demonstration of carbonic anhydrase (CA)‐ or fluoride‐resistant acid phosphatase (FRAP) activities; therefore, these markers, and their coincident expression with neuropeptides, were studied in neurons of the rat small intestine. Subsets of enteric neurons were demonstrated by a MAb (1B2/1B7) recognizing ≥ 45%, and by a MAb (α‐SSEA‐1) recognizing ≤ 0.1 %, of DRG neurons, as well as by CA, but not FRAP activity. 1B2/1B7 + neurons were found in both the submucosal (∑46% of neurons) and myenteric plexuses (∼2% of neurons). Submucosal 1B2/1B7+neurons with mucosal projections also displayed vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) but not substance P (SP) or calcitonin‐gene‐related peptide (CGRP) immunoreactivities. SSEA‐1+neurons were only found in the myenteric plexus, did not project to the mucosa (and thus are unlikely to be primary afferents), and were SOM+or ENK+but VIP−and NPY−. CA activity was intense in ∼39% of the neurons of the submucosal plexus and in mucosal nerve fibers. Some (∼20%) of the submucosal CA neurons were also CGRP+, but VIP−and NPY−; therefore, MAb 1B2/1B7 and CA activity mark different nonoverlapping sets of submucosal neurons. Following the neonatal administration of capsaicin (50 mg/kg), 1B2/1B7 immunoreactivity was lost from all submucosal neurons; however, VIP immunoreactivity was not depleted from the cell bodies. Although it cannot yet be concluded that the MAb 1B2/1B7 or CA markers demonstrate the intrinsic sensory neurons of the gut, the presence in the bowel of both is consistent with the supposition that sensory neurons related to those of DRG are also found in the intestine. The functional and possible developmental significance of this relationship remains to be defined.
Development of spinocerebellar afferents in the clawed toad, Xenopus laevis
Authors: van der Linden J. A. M. , ten Donkelaar H. J. , de Boer‐van Huizen R.
Published: January 2005

The development of spinocerebellar projections in the clawed toad, Xenopus laevis, was studied with horseradish peroxidase as an anterograde and retrograde tracer. Early in development cells of origin of spinocerebellar projections were found, contralaterally, in or close to the medial motor column. In older tadpoles ipsilaterally projecting spinal neurons were also labeled from the cerebellum. These are virtually indistinguishable from the large primary motoneurons that occupy a very similar position in the spinal cord. Most of the labeled spinal cells were found in the thoracic spinal cord; they lie halfway between the brachial and lumbar secondary motor columns. Surprisingly, no primary spinocerebellar projection arising from dorsal root spinal ganglion cells could be demonstrated in X. laevis tadpoles and adult toads. Therefore, fibers in the cerebellum that were labeled anterogradely from the spinal cord can be expected to originate exclusively from the secondary spinocerebellar tract cells. These fibers appear to cross the cerebellum in or at the border of the granular layer.

The present data suggest that in X. laevis early in the development of the cerebellum a distinct secondary spinocerebellar projection is already present, originating in neurons that can be compared with the “spinal border cells” in mammals. The relative sparseness of this secondary spinocerebellar projection and the apparent absence of primary spinocerebellar afferents probably indicate that spinocerebellar pathways are only of minor importance in X. laevis. The possibility remains, however, that the expansion of the secondary spinocerebellar pathway only starts when metamorphosis has been completed.
Localization of putative GABAergic neurons in the larval tiger salamander retina by immunocytochemical and autoradiographic methods
Authors: Yang Chen‐Yu , Yazulla Stephen
Published: January 2005

Putative GABAergic neurons in the larval tiger salamander retina were localized by a comparative analysis of glutamate decarboxylase immunoreactivity (GAD‐IR), GABA‐like immunoreactivity (GABA‐IR), and high‐affinity 3H‐GABA uptake at the light microscopical level. Preliminary data showed that all GAD‐IR neurons were double labeled for GABA‐IR. However, because the weak somatic labeling with GAD‐IR, we could not determine if the converse were true. Neurons commonly labeled with GABA‐IR and 3H‐GABA uptake include horizontal cells, type I (outer) and type II (inner) bipolar cells, type I (inner) and type II (outer) amacrine cells, and cell bodies in the ganglion cell layer (GCL). In addition, interplexiform cells were identified with GABA‐IR. The presence of GABA‐IR ganglion cells was indicated by GABA‐IR fibers in the optic fiber layer and optic nerve as well as by a GABA‐IR cell in the GCL that included a labeled axon. The percentage of labeled somas in the inner nuclear layer (INL) compared to all cells in each layer was similar for the two methods: 30% in INL 1 (outer layer of somas), 15% in INL 2 (middle layer), 43–52% in INL 3 (inner layer), and about 21–26% in the GCL. Labeled processes were found in three bands in the inner plexiform layer, with the densest band located in the most proximal part. Postembedding labeling of 1‐μm Durcupan resin sections for GABA‐IR showed the same general pattern as obtained with 10‐μm cryostat sections, with additional staining, however, of type II (inner) bipolar cell Landolt's clubs. Extensive colocalization of labeling was indicated, and we conclude that GABA‐IR can serve as a valid and reliable marker for GABA‐containing neurons in this retina and suggest that GABA serves as a transmitter for horizontal cells, several types of amacrine cell, a type of interplexiform cell, and perhaps a small percentage of type I and type II bipolar cells and ganglion cells.
Sensory innervation of the hairs of the rat hindlimb: A light microscopic analysis
Authors: Millard Catherine L. , Woolf Clifford J.
Published: January 2005

The sensory innervation of the hair follicles of the furry skin of the rat hindlimb has been investigated by using the Winkelmann silver technique to stain peripheral axons and their terminals. This technique was found to stain only large‐ and medium‐sized dorsal root ganglion cells and all laminae of the dorsal horn except lamina II, and therefore it is likely that, while A beta and A delta afferent fibres in the skin are stained, C fibres are not. Small vellus hairs were the commonest type of hair on the hindlimb particularly above the ankle. Many were not innervated. Those that were had lanceolate terminals arranged as palisades parallel to the hair shaft with circumferential presumptive Ruffini piloneural complexes and free nerve endings external to this. Circumferential innervation patterns without palisades were not uncommon but palisades without circumferential fibres were rare. Guard hairs which varied considerably in size were the next commonest hair type. Considerably more of these were innervated, by three‐to‐15 afferents forming both palisades of ten‐to‐30 lanceolate terminals and circumferential terminals. Both the innervated vellus and guard hairs had an associated vertical fibre projecting toward the epidermis. Tylotrichs, the largest hairs on the hindlimb, were rare (1–2%) and were only found above the ankle, but all were densely innervated by many axons. A prominent single nerve contributed to an annular complex by forming a bilaminar arrangement of lanceolate and circumferential terminals within the outer connective tissue sheath. Each tylotrich had an associated Merkel cellneurite complex (haarscheiben).

Differences in the distribution, innervation density, and phase in the growth cycle of the different hair types were found for skin from different regions of the hindlimb, which, together with the extent of the polyneuronal innervation of most follicles, has important implications for the processing by the somatosensory system of the afferent input generated by brushing hairs.
Behavioral and anatomical correlates of immunologically induced rejection of nigral xenografts
Authors: Carder Renee K. , Snyder‐Keller Abigail M. , Lund Raymond D.
Published: January 2005

Cell suspensions derived from the ventral mesencephalon of CD‐1 mice were unilaterally transplanted into the striatum of neonatal Sprague‐Dawley rats that had been bilaterally dopamine depleted. Thirty‐eight percent of the grafts survived. Tyrosine‐hydroxylase‐immunoreactive neurons within the transplant innervated the host striatum with a dense fiber plexus. The grafts appeared to exert some degree of functional control over motor behavior in that these animals made contralateral rotations in response to amphetamine and tail pinch. In order to provide additional evidence that the motor behavior is associated with the transplant itself, the graft was removed. This was achieved by using a mouse skin graft to provoke an immunological response against the transplanted neural tissue. The immunological response resulted in the specific loss of the transplant with little or no damage to the surrounding neural tissue. The amount of rotation observed after tail pinch and amphetamine injection was severely affected by neural graft rejection. The loss of turning was associated most directly with the loss of tyrosine hydroxylase immunoreactivity within the transplant rather than with the massive reduction of tyrosine‐hydroxylase‐positive fibers in the ipsilateral host striatum. These data suggest that dopamine cells in mouse nigral grafts play an essential role in eliciting rotational behavior in neonatally dopamine depleted rats. They also show the value of skin grafting as a technique for specifically removing neural xenografts.
Axons added to the regenerated visual pathway of goldfish establish a normal fiber topography along the age‐axis
Authors: Bernhardt Robert , Easter Stephen S. , Raymond Pamela A.
Published: January 2005

Throughout a goldfish's life, new generations of ganglion cells are added on the retinal margin and their axons extend centrally to occupy predictable positions in the retinotectal pathway, adjacent to their predecessors and subjacent to the pia. The stacking of successive generations of axons defines the age‐axis of the pathway. This study examined whether an ordered array of predecessor axons is a prerequisite for the patterned growth of new axons. One optic nerve was crushed intraorbitally and the fish was injected with 3H‐thymidine to label the proliferating cells on the retinal margin. The ring of 3H‐thymidine‐labeled cells separated retina that was present at the time of nerve crush (inside the ring) from new retina added afterward (outside). After a period of 14–16 months postcrush, both tectal lobes received two punctate applications of horseradish peroxidase (HRP), one in the central and the other in peripheral tectum, to retrogradely label contralateral retinal ganglion cell bodies and their axons.

The pattern of HRP labeling from the control tectum confirmed earlier work: axons on the central tectum had somata in the central retina, and axons on the peripheral tectum had somata in the peripheral retina. The labeled cells and axons were both in predictable patterns. The somata that were backfilled from applications to the center of the experimental tectum lay inside the radioactive ring and had therefore regenerated their axons. The patterns of their labeled axons in the optic pathway and of their somata in the retina were typical of the regenerated condition as described in earlier studies. The somata backfilled from the periphery of the experimental tectum were outside the radioactive ring and had been added after the optic nerve crush. The patterns of their labeled axons and somata were comparable to the normal pattern. These observations indicate that new axons do not depend on an ordered array of predecessors to reestablish normal order along the age‐axis of the pathway.
Topography and cytoarchitecture of the motor nuclei in the brainstem of salamanders
Authors: Roth Gerhard , Nishikawa Kiisa , Dicke Ursula , Wake David B.
Published: January 2005

The organization of the motor nuclei of cranial nerves V (including mesencephalic nucleus), VI, VII, IX, and X is described from HRP‐stained material (whole mounts and sections) for 25 species representing five families of salamanders, and the general topology of the brainstem is considered. Location and organization of the motor nuclei, cytoarchitecture of each nucleus, and target organs for nuclei and subnuclei are described. The trigeminal nucleus is separated distinctly from the facial and abducens nuclei and consists of two subnuclei. The abducens nucleus consists of two distinct subnuclei, one medial in location, the abducens proper, and the other lateral, the abducens accessorius. The facial nucleus has two subnuclei, and in all but one species it is posterior to the genu facialis. The facial nucleus completely overlaps the glossopharyngeal nucleus and partially overlaps that of the vagus. In bolitoglossine plethodontid salamanders, all of which have highly specialized projectile tongues, the glossopharyngeal and vagus nuclei have moved rostrally to overlap extensively and intermingle with the anterior and posterior subnuclei of the facial nerve. In the bolitoglossines there is less organization of the cells of the brainstem nuclei: dendritic trunks are less parallel and projection fields are wider than in other salamanders. Some aspects of function and development are discussed; comparisons are made to conditions in anurans; and phylogenetic implications are considered.
Central projections of the rat radial nerve investigated with transganglionic degeneration and transganglionic transport of horseradish peroxidase
Authors: Ygge Jan
Published: January 2005

Transganglionic degeneration and transganglionic transport of HRP were used for investigation of the spinal cord and brainstem projections from the superficial, cutaneous (SR) and deep, muscular (DR) branches of the radial nerve. The HRP study included a numerical and size analysis of labelled dorsal root ganglion (DRG) cells.

In degeneration experiments the SR nerve was found to project somatotopically to laminae III–IV, but degeneration was also found in lamina I and inconsistently in lamina II. Transection of the DR nerve was found to give rise to a small amount of degeneration, which in “sham” operations was established to result from the skin injury during dissection of the DR nerve.

With the HRP method, the SR nerve was found to project somatotopically to laminae I–IV, whereas the DR nerve projected more diffusely to the medial part of laminae V–VII. HRP application to the SR and DR nerves resulted in labelling of a mean of 1,024 and 310 DRG cells, respectively. These labelled neurons had a median cell area of 381 and 562 μm2 for the SR and DR nerves, respectively, and both small and large cells were labelled in both types of experiments. In the lower brainstem, projections from the SR nerve were found only in the ipsilateral dorsal part of the main cuneate nucleus (MCN) with both methods. Brainstem projections from the DR nerve that were found only with the HRP method were found in the ipsilateral ventral part of the MCN together with a projection to the ipsilateral external cuneate nucleus. No projections were found to the central cervical nucleus.

The present results indicate that cutaneous compared to muscular primary sensory neurons are much more prone to react with transganglionic degeneration after peripheral nerve transection. Furthermore, in the rat the SR nerve projects somatotopically, whereas the DR nerve does not. Both nerve branches are connected to small and large spinal ganglion cells, although the median cell area is larger in muscular neurons.
Morphological study of flight motor neurons in the cricket
Authors: Wang S. , Robertson R. M.
Published: January 2005

The motor innervation of the major flight muscles powering the fore‐ and hindwings of the cricket Teleogryllus oceanicus was investigated. The morphology of the motor neurons was determined by filling them via their axons in the periphery with either Lucifer Yellow or cobalt chloride followed by silver intensification. Details of the location of branches of motor neurons within the ganglion were obtained by serially sectioning ganglia containing filled neurons. For each flight muscle at least two motor neurons were found. The somata of motor neurons were located in two clusters in the ganglion, the anterior lateral cluster and the posterior lateral cluster. Motor neurons in the same cluster had similar morphologies. Most of the arborizations of these motor neurons were in the dorsal neuropil with a few branches in the lateral intermediate neuropil. The morphology of flight motor neurons was compared with the morphology of leg motor neurons in consideration of the possible functional organization of the ganglion. A comparison was made between motor neurons innervating homologous muscles of the cricket and the locust to determine the extent of the difference between the flight systems of these two groups.
Glycine‐immunoreactive projection of the cat lateral superior olive: Possible role in midbrain ear dominance
Authors: Marie Richard L. Saint , Ostapoff E.‐Michael , Morest D. Kent , Wenthold Robert J.
Published: January 2005

Neurons in the lateral superior olive are optimally excited by stimulation of the ipsilateral ear, as are those in the inferior colliculus by stimulation of the contralateral ear. This reversal of ear dominance may result, in part, from distinct crossed excitatory and uncrossed inhibitory pathways ascending from the lateral superior olive. To explore this possibility, immunoreactivity for two putative inhibitory neurotransmitters, glycine and GABA, was examined in projection neurons that retrogradely transported horseradish peroxidase from the cat inferior colliculus.

The results suggest that the projection from the lateral superior olive can be segregated, immunocytochemically, into three components: (1) a crossed, glycine‐negative (−) projection; (2) an uncrossed, glycine‐positive (+) projection; and (3) an uncrossed, glycine(−) projection. Additional evidence suggests that the terminal fields of the two uncrossed projections may distribute differently within the inferior colliculus. Glycine(+) or glycine(−) projection neurons, crossed or uncrossed, do not differ in the size, shape, or location of their somata. However, most glycine(−) neurons are heavily encrusted with glycine(+) endings; glycine(+) neurons have 40–60% fewer of these endings. Glycine(−) neurons located in the lateral limb have fewer glycine(+) perisomatic endings than those in the medial limb. Few projection neurons are GABA(+), and GABA(+) perisomatic endings are rare in the lateral superior olive.

Thus, there is a heavy uncrossed projection from the cat lateral superior olive to the inferior colliculus that may be glycinergic and inhibitory. Furthermore, there is a bilateral projection that is not glycinergic or GABAergic, which may be excitatory. The potential contribution of these pathways to contralateral ear dominance in the inferior colliculus is discussed.