bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for the presence, synthesis, immunoreactivity, and uptake of GABA in the nervous system of the snail Helisoma trivolvis
Authors: Richmond J. E. , Bulloch A. G. M. , Bauce L. , Lukowiak K.
Published: January 2005

In the present study several techniques were employed to test the hypothesis that gamma‐aminobutyric acid (GABA) is a neurotransmitter in the central nervous system (CNS) of the pond snail Helisoma trivolvis (Mollusca, Pulmonata). First, by using chromatographic techniques, the presence of GABA and its differential distribution among the ganglia constituting the CNS was demonstrated. Second, de novo synthesis of 3H‐GABA from 3H‐glutamate was shown by the CNS. Levels of both endogenous and newly synthesized GABA were greatest in the buccal, cerebral, and pedal ganglia. Third, indirect immunohistochemistry of wholemounts revealed a central network of GABA‐like immunoreactive neurons. With the possible exceptions of two pairs of fibers in nerve trunks, all projections from GABA‐immunoreactive neurons were confined to the CNS, suggesting a predominantly central role for GABA. Stained neurons were found on the dorsal surface of the buccal ganglia and throughout the cerebral and pedal ganglia. No GABA‐immunoreactive cell bodies were observed in the parietal, pleural, or visceral ganglia. Finally, uptake of 3H‐GABA was examined autoradiographically in sectioned ganglia. A pattern of radiolabelled cells was observed that closely resembled the distribution of GABA‐immunoreactive neurons.

The data described above fulfill several criteria necessary to establish GABA as a transmitter in the nervous system of Helisoma. Taken together with previously obtained pharmacological evidence demonstrating that GABA acts on Helisoma central neurons, GABA is considered to be a strong candidate for a neurotransmitter in Helisoma.
Prenatal specification of callosal connections in rhesus monkey
Authors: Schwartz Michael L. , Goldman‐Rakic Patricia S.
Published: January 2005

Anatomical tracing and quantitative techniques were used to examine the tempo and pattern of maturation for callosal projection neurons in the monkey prefrontal cortex (PFC) during fetal and postnatal development. Nineteen monkeys were injected with retrograde tracers (fluorescent dyes, horseradish peroxidase conjugated to wheat germ agglutinin [WGA‐HRP] or HRP crystals) at various ages between embryonic day 82 (E82) and adulthood. The size of injection sites was varied in fetal, newborn, and adult cases.

In adults, labeled neurons were found in greatest density in the homotopic cortex of the opposite hemisphere and considerable numbers were also observed in a constellation of heterotopic areas including the medial and lateral orbital cortex, the dorsomedial convexity, and the pregenual cortex. The majority of labeled neurons were consistently concentrated in the lower half of layer III in all areas. In cases with large injection sites, callosal neurons of layer III formed a continuous and uninterrupted band that extended over the entire lateral surface of the prefrontal cortex spanning both homotopic and heterotopic areas. In contrast, in cases with small injection sites, the labeling of layer III neurons exhibited discontinuities.

Between embryonic ages E82 and E89, injections limited to the cortical layers labeled only a small number of neurons in the opposite hemisphere, indicating that few callosal axons have invaded the cortex by this age. However, by E111 comparable injections labeled a large number of callosal neurons and many features of their distribution were adult‐like. The number and constellation of cytoarchitectonic areas that were labeled in the frontal cortex of the opposite hemisphere were the same as in adults and the majority of callosal neurons were found in supragranular layer III. Finally, in fetal animals beyond E111, labeled neurons extended as a nearly unbroken band over a wide expanse of the dorsolateral PFC, resembling the pattern seen in adult monkeys with large injections.

The conclusion we draw from these results, together with our earlier findings (Schwartz and Goldman‐Rakic: Nature 299:154, 1982), is that callosal neurons whose axons enter the cortical layers of the primate prefrontal cortex achieve their mature laminar and areal distribution prior to birth and do so largely by cumulative processes.
Development of the calcium‐binding proteins parvalbumin and calbindin in monkey striate cortex
Authors: Hendrickson A. E. , van Brederode J. F. M. , Mulligan K. A. , Celio M. R.
Published: January 2005

The development of immunoreactivity for the calcium‐binding proteins parvalbumin (PV) and calbindin‐D28K (Cal) was studied in Macaca nemestrina striate, cortex from fetal (F) 60 days to postnatal (P) 5 + years. We correlated changes in PV and Cal staining patterns with the well‐documented developmental sequence for primate striate cortex neuron generation and maturation, synaptogenesis, and thalamocortical axon interactions in an attempt to deduce a functional role for these proteins.

Our major finding is that Cal and PV have diametrically opposed developmental patterns except in layer 1. At F60 days both are present only in neurons of layer 1 and the number of labeled cell bodies and processes increases up to F125 days. Almost all Cal+ and PV+ cells in layer 1 disappear by P12 weeks. Cal is present by F113 days in pyramidal and stellate neurons, particularly layers 4–6. The number and staining density of cells in layers 2–6 increases up to birth and then both decline by P9–12 weeks. Supragranular layers show a second increase in Cal labeling from P20–36 weeks, and then there is a slow decline to the adult pattern which is reached by P1–2 years. Cell bodies in layers 4A, 4Cα, and deep 4Cβ are heavily Cal+ during pre‐and early post‐natal periods, but upper 4Cβ remains unlabeled.

PV is not seen until F155–162 days in layers 2–6. Large stellate and a few pyramidal cells appear first in layers 5/6 and 4Cα, but PV + stellate neurons are found in all layers except 4Cβ by P6 weeks. Layer 4Cβ contains a few PV+ cell bodies at P3 weeks, and light neuropile staining at P6 weeks, but then PV labeling rapidly increases so that by P12 weeks the density of 4Cβ exceeds that of 4Cα. Striate cortex has an adult pattern of cell number and neuropile density by P20 weeks.

These developmental patterns suggest that the highest density of Cal cell body staining does not correlate with synaptogenesis, or the postnatal critical period of visually driven, binocular interactions. Rather Cal appears when lateral geniculate axons arrive in cortex, persists over the entire span of thalamocortical interactions, and disappears during the decline of cortical plasticity. The appearance of PV is highly correlated with the onset of complex visually driven activity at birth, while both the number of PV+ cell bodies and the density of PV+ neuropile reach adult levels coincident with the completion of thalamocortical connections.
Distribution of 125I‐galanin binding sites, immunoreactive galanin, and its coexistence with 5‐hydroxytryptamine in the cat spinal cord: Biochemical, histochemical, and experimental studies at the light and electron microscopic level
Authors: Arvidsson Ulf , Ulfhake Brun , Cullheim Staffan , Bergstrand Anita , Theodorsson Elvard , Hökfelt Tomas
Published: January 2005

The distribution of galanin‐like immunoreactivity (GAL‐LI) in the spinal cord of the cat was studied by use of indirect histochemistry and the peroxidase‐antiperoxidase (PAP) technique. In the ventral horn GAL‐immunoreactive (IR) axonal fibers and terminals were most frequent in the ventral part of the motor nucleus. The GAL‐IR axons also contained 5‐hydroxytryptamine (5‐HT)‐LI, and they disappeared after spinal cord transection. It was concluded that these GAL‐IR fibers belong to the serotoninergic bulbospinal pathway. In the medulla oblongata from normal cats, scattered GAL‐IR cell bodies were encountered within the nucleus raphe obscurus and nucleus raphe pallidus. Electron microscopic observations revealed that the fine structure of the GAL‐IR axonal boutons in the motor nucleus was similar to that of 5‐HT‐IR boutons with a varying number of immunoreactive large dense core vesicles. The postsynaptic element in all cases studied was a dendrite.

A dense GAL‐IR axonal plexus was found in the superficial laminae I‐II of the dorsal horn. Coexistence was found between the GAL‐ and substance P‐LI in fibers within the dorsal horn plexus. Spinal cord transection did not alter the pattern of GAL‐LI in the dorsal horn, while the vast majority of GAL‐IR axonal swellings disappeared following dorsal root sectioning. Electron microscopic observations in lamina II (substantia gelatinosa) revealed that the GAL‐IR axonal terminals could be divided into two main groups. One with small to medium‐sized axonal buttons formed synaptic contacts with both dendritic and axonal profiles. The other formed the central axon terminals of glomeruli, suggesting that GAL‐LI may be present in C‐type primary afferents. Numerous small GAL‐IR cell bodies were encountered in laminae II and III. GAL‐IR cell bodies were also observed in lamina X.

The dorsal root ganglia contained a low but consistent number of small to medium‐sized GAL‐IR cell bodies, which all contained immunoreactive calcitonin gene‐related peptide (CGRP). Following peripheral sciatic nerve transection, the number and the labeling intensity of GAL‐IR cell bodies in the corresponding dorsal root ganglia showed a moderate increase.

Radioimmunoassay revealed that the concentration of GAL‐LI increased along the rostrocaudal axis of the normal spinal cord, and was about three times higher in the dorsal than in the ventral regions. The concentration in the dorsal root ganglia was intermediate to those seen in the corresponding dorsal and ventral cord regions. Autoradiography showed a high density of 125I‐GAL binding sites in the superficial laminae of the dorsal horn throughout the spinal cord.
Morphogenesis of adrenergic cells in a frog parasympathetic ganglion
Authors: Heathcote R. David , Chen Aileen
Published: January 2005

The development of the parasympathetic cardiac ganglion of the frog Xenopus laevis was marked by the differentiation of a population of adrenergic small intensely fluorescent (SIF) cells. The neural crest contributes precursors for both SIF cells and the well‐studied cholinergic cardiac ganglion neurons; this situation provided an opportunity to determine whether morphogenesis of the two cell types was correlated. Accordingly, we examined the initial differentiation, developmental regulation, and territorial domain of cardiac SIF cells for comparison with their cholinergic neuron neighbors.

Adrenergic SIF cells were present during the time when the first cholinergic precursors were becoming postmitotic. Although SIF cells were present first, cholinergic neurons differentiated almost 16 times faster during the first week of embryonic and larval development and outnumbered SIF cells at all subsequent stages. Nonetheless, the accumulation of both cell types were correlated, since the ratio of cholinergic neurons to SIF cells remained at approximately 10 to 1 up to adult life. Early in development, SIF cells and cholinergic neurons were clustered in the sinus venosus portion of the atrium. The asymmetric distribution of cholinergic neurons within the atrium was lost hut that of the SIF cells was maintained throughout life. These results identify relationships between the morphogenesis of two cell types in an autonomic ganglion and place constraints upon the cellular mechanisms that could produce the cells from their neural crest precursors.
Inhibition of axonal development after injection of neurofilament antibodies into a Xenopus laevis embryo
Authors: Szaro Ben G. , Grant Philip , Lee Virginia M.‐Y. , Gainer Harold
Published: January 2005

The ability to target specific cytoskeletal components in axons for disruption within intact developing embryos would provide a valuable tool for studying neuronal development. Neurofilaments are an attractive target for such an approach, because they are neuron specific and are expressed late in embryogenesis principally beginning during axon outgrowth. No pharmacological agents are currently available that disrupt neurofilaments without also affecting general development. One approach that has been used successfully to affect proteins in vivo is to inject specific antibodies into living cells. We employed this approach in Xenopus laevis embryos by injecting two antibodies directed against the middle molecular weight neurofilament protein (NF‐M) into a single blastomere of a two‐cell stage embryo. Injected antibodies could be detected for as long as 3.5 days in cells descended from the injected blastomere. Only cell bodies of neurons descended from anti‐NF‐M‐injected blastomeres contained abnormal accumulations of intermediate filament proteins, and peripheral nerve development was unilaterally retarded in these neurofilament antibody‐injected tadpoles. Such accumulations and peripheral nerve defects were not seen in neurons derived from uninjected blastomeres or from blastomeres injected with control antibodies. These data demonstrate the usefulness of specific antibodies to perturb neuronal development in intact frog embryos and, in addition, suggest a role for neurofilaments in axon elongation.
Epitopes located in spatially separate domains of each neurofilament subunit are present in parkinson's disease lewy bodies
Authors: Hill William D. , Lee Virginia M.‐Y. , Hurtig Howard I. , Murray John M. , Trojanowski John Q.
Published: January 2005

Subcortical Lewy bodies are the pathological hallmark of idiopathic Parkinson's disease. This study sought to determine the extent to which each neurofilament subunit [low (NF‐L), mid (NF‐M), or high (NF‐H)] was present in Lewy bodies by using light, confocal, and electron microscopy. A battery of 37 antineurofilament antibodies, characterized as to subunit specificity, epitope domain, and phosphorylation status, was employed to probe substantia nigra Lewy bodies from 15 Parkinson's disease cases. All 37 antibodies labelled Lewy bodies. The epitopes recognized by these antibodies included those in the NF‐L rod and tail domains; the NF‐M head, rod, and tail domains, as well as epitopes within, and flanking, the multiphosphorylation repeat site; and the NF‐H rod domain and multiphosphorylation repeat sites. With these probes, nearly the entire length of each subunit could be demonstrated in Lewy bodies. However, the staining pattern of the Lewy bodies suggested that the tail domains of NF‐M and NF‐H were present in the periphery of the Lewy body core and in the Lewy body corona, but they appeared to be altered or missing in the center of the Lewy body core. In contrast, the head domain of NF‐M, the tail domain of NF‐L, and the rod domains of all three subunits are present throughout the Lewy body. These results strongly suggest that the entire extent of each neurofilament subunit is found in Lewy bodies but that the neurofilament subunits may be altered during the processing of these filaments into Lewy bodies.
Gracile projection to the cat medial accessory olive: Ultrastructural termination patterns and convergence with spino‐olivary projection
Authors: Molinari Helen H. , Starr Kathy A. , Sluyters Romuald N.
Published: January 2005

The caudal medial accessory subdivision of the inferior olive (cMAO) receives information from the hindlimb from both the gracile nucleus and the lumbosacral spinal cord. This study determined which elements in cMAO serve as the postsynaptic targets of the gracile projection and whether these elements also receive input from the lumbosacral spinal cord. Gracile axons were labeled in cats by anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP), visualized with tetramethylbenzidine. Convergence of gracile and lumbosacral axons was evaluated by labeling in the same animal, one pathway by WGA‐HRP and the other by degeneration.

In cMAO, gracile axons synapse with equal probability on dendritic spines and distal dendritic shafts. This termination pattern contrasts markedly with that of other somatosensory inputs to the inferior olive and may account for the greater heterogeneity in responses to somatosensory stimuli displayed by neurons in cMAO. The distal dendritic shafts receiving gracile input were more likely than dendritic spines to receive convergent input from putative inhibitory synapses. The most likely source of these inhibitory synapses is the parasolitary nucleus, a structure that has been shown by others to receive input from the cerebellum. Thus the parasolitary nucleus may serve as an inhibitory relay between the cerebellum and cMAO.

The dendritic spines in cMAO that receive input from the gracile nucleus often receive additional input from the lumbosacral spinal cord. This convergence of somatosensory axons on dendritic spines may provide a mechanism through which the unusually complex receptive fields of neurons in cMAO are generated.
Ultrastructural evidence that early synapse formation on central vestibular sensory neurons is independent of peripheral vestibular influences
Authors: Petralia R. S. , Gill S. S. , Peusner K. D.
Published: January 2005

Migration and early differentiation of neurons of the tangential vestibular nucleus of the chick take place between embryonic days 5 and 8. In the absence of primary vestibular afferents (otocyst‐ablation), a previous light microscope study documented that early developmental events still occurred, but the neurons failed to complete differentiation and to survive. In order to understand why these neurons undergo normal early development, we have repeated the vestibular deafferentation paradigm followed by ultrastructural observations on these neuron.

We found that the ultrastructural events associated with migration and differentiation in the deafferented tangential nucleus were essentially normal from 5 to 8 days. Most important, longitudinal fibers, presumably of central, nonvestibular origins, formed the first synapses at the same time and sequence as observed in normal embryos. Thus vestibular sensory neurons receive their first input from central fibers, initiating events in the formation of a central vestibular circuitry without the influence of peripheral vestibular fibers or endorga.
The earliest ultrastructural development of the tangential vestibular nucleus in the chick embryo
Authors: Petralia R. S. , Peusner K. D.
Published: January 2005

The tangential nucleus is a primary vestibular nucleus located where the vestibular fibers enter the medulla. It is composed of neurons that migrate between 5 and 8 days in the chick embryo. Although primary vestibular fibers enter the medulla at 3 days, the first synapses are formed at 5 days on the processes of neuron precursors by longitudinally coursing fibers. Since the major components, or their precursors, are present at 3 days within the presumptive nucleus, we are interested in determining what cellular interactions occur among these structures following their entry and during the time leading up to synapse formatio.

At 2 days, prior to the appearance of VIIth and VIIIth nerve fibers in the medulla, the tangential nucleus anlage contained processes and endfeet of primitive epithelial cells, separated from each other by enlarged extracellular spaces. Longitudinal fibers first appeared within these spaces coincident with the appearance of root fibers, including some identified VIIth motor axons, associated with the primordial VII/VIIIth ganglia. By 3 days, some vestibular and VIIth nerve fibers could be identified by their ultrastructure and relative positions within the marginal zone and nerve roots. However, it was not until 4 days that the presumptive tangential nucleus acquired its orderly, characteristic organization. Although synapses were rare from 2 to 4 days, attachment plaques and coated pits were observed commonly between structures, especially between future synaptic structures. Thus, we confirm that synapse formation begins at 5 days. This represents the first detailed ultrastructural study of cranial sensory nerve ingrowth into the medull.
Organization of the histaminergic system in the brain of the teleost, Trachurus trachurus
Authors: Inagaki Naoyuki , Panula Pertti , Yamatodani Atsushi , Wada Hiroshi
Published: January 2005

To accumulate phylogenetic information on the central histaminergic system, we investigated the histaminergic system in the brain of a teleost, the jack mackerel (Trachurus trachurus), using the indirect immunofluorescent method with antiserum against histamine. A small number of histamine‐ immunoreactive cell bodies were observed in the posterior hypothalamus around the posterior recess. Histamine‐immunoreactive fibers innervated the telencephalon, diencephalon, tegmentum, and rostral part of the medulla oblongata. The immunoreactive fibers were very sparse or absent in the olfactory bulb, optic tectum, cerebellum, caudal part of the medulla oblongata, spinal cord, and hypophysis. Ascending fiber bundles were seen in the basal hypothalamus, supplying fiber collaterals to the telencephalon and diencephalon, whereas descending fibers were observed in the midline of the lower brainstem. These findings suggest that the central histaminergic system of the jack mackerel is homologous to those of mammals, reptiles, and amphibians, although poorly developed compared with them. The histamine‐immunoreactive neuronal cell bodies found in the border area between the mesencephalon and rhomb encephalon of the river lamprey were not detected in the brain of the jack mackere.
Connectional studies of the primate lateral geniculate nucleus: Distribution of axons arising from the thalamic reticular nucleus of Galago crassicaudatus
Authors: Harting John K. , van Lieshout David P. , Feig Sherry
Published: January 2005

Anterograde and retrograde transport methods have been used to explore the interconnections between the thalamic reticular nucleus (TRN) and the dorsal lateral geniculate nucleus of Galago crassicaudatus. We first defined the region of the TRN, which is connected to the lateral geniculate nucleus, by examining the distribution of geniculo‐TRN axons, cortico‐TRN axons arising from area 17, and the location of TRN‐geniculate neurons. Following an intraocular injection of 3H‐proline/3 H‐leucine, trans‐synaptically transported protein is present bilaterally within the lateral portion of the caudal TRN. This same caudal and lateral region is also targeted by cortico‐TRN axons and contains neurons which project upon the lateral geniculate nucleu.

Light microscopic anterograde transport methods were used to analyze the distribution of TRN‐geniculate axons. Our data reveal that all layers and interlaminar zones of the dorsal lateral geniculate nucleus contain TRN axon.

Electron microscopic‐autoradiographic data support and extend our light microscopic findings by revealing labeled TRN terminals within all geniculate layers. These TRN profiles are the same size throughout the geniculate and exhibit morphological characteristics similar to Fl terminals described by others. That is, they possess predominantly pleomorphic vesicles, a dark cytoplasmic matrix, dark mitochondria, and symmetrical synaptic contacts. Two additional features of TRN terminals have been observed in some profiles. These include dense‐core vesicles and a dense, punctate cytoplasmic matrix, which is sometimes associated with the postsynaptic specialization. In addition to their morphology and size, the postsynaptic targets of TRN terminals are similar within the three sets (parvi‐, magno‐, and koniocellular) of geniculate layers. TRN profiles terminate upon dendrites of all sizes and somata. These findings suggest that the TRN modulates the retino‐geniculocortical pathway and that this modulation is occurring in all three streams.
Morphological differentiation of distinct neuronal classes in embryonic turtle cerebral cortex
Authors: Blanton Mark G. , Kriegstein Arnold R.
Published: January 2005

As a starting point for understanding the development of the cerebral cortex in reptiles and for determining how reptilian cortical development compares to that in other vertebrate classes, we studied the appearance and morphological differentiation of cerebral cortical neurons in embryonic turtles. 3H‐thymidine birthdate labeling and focal injections of horseradish peroxidase (HRP) in in vitro cortical slices revealed that replicating cells occupy the outer ventricular zone, and subsequently migrate to the ventricular surface where they divide. Postmitotic neurons begin differentiating and elaborating neurites while migrating back through the ventricular zone. On their arrival at the top of the ventricular zone, pyramidal and nonpyramidal neurons can be distinguished morphologically. Cells with multipolar apical dendritic tufts ascending in the marginal zone resemble immature pyramidal neurons. Neurons morphologically similar to these early pyramidal cells were retrogradely labeled by injections of the lipophilic tracer 1,1‐dioctadecyl‐3,3,3′,3′‐tetramethyl indocarbocyanine perchlorate (diI) in a known pyramidal cell target, the thalamus. Nonpyramidal neurons, resembling Cajal‐Retzius cells, had horizontally oriented long axons and dendrites coursing in the plexiform primordium, the future marginal zone. With further development morphological differences between cell types became accentuated, and pyramidal cell somata were segregated into a single cellular layer flanked by zones containing predominantly nonpyramidal cell.

Axon elaboration occurred early in embryonic development, as pyramidal cells sent axonal branches to the septum, thalamus, and cortical targets soon after their generation, and the intracortical axonal plexus became increasingly dense during embryonic life. Over a similar time course the distribution of projecting neurons labeled by thalamic diI injections changed from an initial homogeneous distribution to a preferential location in the superficial half of the cellular laye.

Results from this study demonstrate several features of cortical differentiation that are conserved in reptiles and mammals, including similar early morphological differentiation events, the early distinction of principal cell types, and the parallel development of pyramidal and nonpyramidal neurons. The context in which these similar developmental events occur, however, differs profoundly in reptiles and mammals, with differences in the timing and location of neurite elaboration and differences in the appearance and architectonic organization of the cortex. Comparison of cortical developmental patterns between reptiles and mammals shows that similar functional cortical circuits with balanced excitation and inhibition can emerge in diverse cortical structures.
Central course of digital axons within the median nerve of macaca mulatta
Authors: Brushart Thomas M. E.
Published: January 2005

The traditional view that axons are not functionally grouped within proximal human nerve is based on the interfascicular dissections of Sunderland ('45). However, microstimulation and microneurography (Schady et al., '83a; Hallin, '90) reveal proximal grouping of cutaneous sensory axons from small areas of skin. In the present studies, conjugates of horseradish peroxidase with wheat germ agglutinin (HRP‐WGA) were used to trace the course of digital nerve axons within the median nerve of Macaca mulatta. The electrophysiologic findings were confirmed, suggesting the potential for precise surgical realignment of functionally related axons even after proximal nerve transection.

Radial digital nerves were labeled in the thumb (bilateral, 1 animal), the index finger (unilateral, 2 animals), and the middle finger (bilateral, 1 animal). Median nerve cross sections were cut at 1‐cm intervals, treated with tetramethyl benzidine to demonstrate HRP‐WGA within axons, and compiled to form maps of each digital nerve “territory” within the median nerve. These territories were limited to a single, densely labeled fascicle at the wrist level. They expanded somewhat in the forearm to encompass clusters of labeled axons within a matrix of unlabeled axon profiles. The clusters were more loosely packed in the arm, occupying ⅓ to ⅙ of the nerve cross section at the entrance to the brachial plexus. The three digital nerve territories studied were widely separated at the wrist level. In the proximal arm, there was moderate intermingling of axons from adjacent digits, but those to the middle finger and thumb remained segregated. Territory configuration differed widely overall, but was moderately constant for each digit. The location of territories within the nerve was often strikingly similar from right to left and from animal to animal, with occasional prominent variations reflecting isolated rotation of one nerve.
Morphology and mosaics of VIP‐like immunoreactive neurons in the retina of the rhesus monkey
Authors: Lammerding‐Köppel M. , Thier P. , Koehler W.
Published: January 2005

Vasoactive intestinal peptide (VIP) is a 28‐amino acid peptide that has been demonstrated to reside in cells (=VIP+ cells) of the retinae of various vertebrate species. In an attempt to study the morphology and distribution of VIP+ cells in the retina of the rhesus monkey in more detail, we subjected VIP+ cells observed in cryostat sections or wholemounts of rhesus monkey retinae to a quantitative analysis. VIP+ cells were found to reside in the innermost row of the inner nuclear layer (INL) and in the ganglion cell layer (GCL) in similar numbers (estimate: 50 cells/mm2 at 6–10 mm eccentricity each) and only on rare occasions (12% of all VIP+ cells) in varying positions within the inner plexiform layer (IPL). Somata of VIP+ cells were circular and had a mean diameter of 9.1 μm. They gave rise to 1–3 main dendrites, which were usually oriented toward the IPL. Main dendrites ramified widely into thin fibers (dendritic field diameter < = 1 mm), carrying varicose swellings. The fibers that contributed to one and the same plexus of VIP+ fibers preferred the middle third of the IPL, independent of the positions of the parent somata. A quantitative analysis of nearest‐neighbour distances in the retinal wholemount preparation suggested that VIP+ cells in the GCL and in the INL might be distributed according to 2 independent mosaics. A comparison with Golgi‐stained material leads to the tentative equation of VIP+ cells with the “spiny” A12 amacrine cell of Mariani ('90). Whereas the low density and large dendritic field size of VIP+ cells might suggest a more widespread function, the varicose dendritic morphology seems to be more compatible with functionally independent dendritic subunits mediating localized effects.
Access to gastric tissue promotes the survival of axotomized neurons in the dorsal motor nucleus of the vagus in neonatal rats
Authors: Rinaman Linda , Levitt Pat
Published: January 2005

Lesioning the vagus nerve in the neck (cervical vagotomy) results in a rapid and virtually complete loss of motoneurons in the dorsal motor nucleus of the vagus in neonatal rats. The present study sought to determine whether access to gastric target tissue will promote the survival of these motoneurons after axotomy. Quantitative analysis demonstrate that subdiaphragmatic vagotomy, which leaves the cut vagal axons in close proximity to their normal gastric targets, results in significantly less motoneuron loss than cervical vagotomy. Furthermore, the loss of motoneurons after cervical vagotomy can be significantly reduced by transplanting embryonic gastric tissue to the neck of vagotomized neonatal host rats, in the vicinity of the cut axons. The survival effect of transplanted gastric tissue appears specific because control‐transplants of embryonic bladder tissue fail to reduce motoneuron death after cervical vagotomy. Injections of the neural tracers Fluoro‐Gold and cholera toxin‐horseradish peroxidase into gastric transplants labeled surviving motoneurons in cervically vagotomized rats, whereas tracer injections into bladder transplants or into host cervical tissues did not. These results indicate that neonatal vagal motoneurons are capable of making the adjustments necessary to survive axotomy if they have access to gastric target cells. The apparent dependence of injured neonatal vagal motoneurons on gastric tissue offers a new system in which to examine in vivo the trophic interactions between neurons and their targets.
Generation and death of cells in the dorsal lateral geniculate nucleus and superior colliculus of the wallaby, setonix brachyurus (quokka)
Authors: Harman Alison M.
Published: January 2005

To study postnatal cell generation in primary visual centres of the quokka, tritiated thymidine was injected into pouch‐young aged postnatal day (P)1–P85. Brains were examined at P100, just before eye‐opening, when primary visual projections are essentially mature. Neurons in the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) were generated at P1–P10 and P1–P18 respectively. Peak numbers of labelled cells were seen at P3 and P5 in the dLGN and SC.

Cell death was assessed in the dLGN and SC of young aged P10–P150. Low numbers of dying cells were seen in the dLGN throughout this period, with a small peak at P85. A more substantial peak of cell death was seen in the SC, also at P85. In the quokka, the time interval between the peaks of cell generation and of cell death in the dLGN and SC is 70–80 days, considerably longer than the interval of 40 days between birth and death of retinal cells.
Fibroblast growth factor receptor‐bearing neurons in the CNS: Identification by receptor‐mediated retrograde transport
Authors: Ferguson Ian A. , Johnson Eugene M.
Published: January 2005

Neurons that internalize and retrogradely accumulate acidic (aFGF) or basic (bFGF) fibroblast growth factor were identified by autoradiography after injections of 125I‐aFGF or 125I‐bFGF into the adult rat central nervous system (CNS). Neuronal cell bodies within the lateral hypothalamus, pedunculpontine tegmental nucleus, laterodorsal tegmental nucleus, and the paracentral dorsal tegmental nucleus accumulated 125I‐aFGF. Neurons in the hippocampus, subiculum, the centrolateral, paracentral, central medial, and parafascicular thalamic nuclei, the supramammillary nucleus, and substantia nigra compacta accumulated 125I‐bFGF. The pattern of neuronal labeling with 125I‐bFGF in adult rats was similar to that observed in newborn guinea pigs. No 125I‐FGF labeling was observed in nerve growth factor (NGF) receptor‐bearing neurons, including the basal forebrain cholinergic neurons. Time‐course studies indicate that 125I‐FGF Was internalized at the terminals and retrogradely transported to the neuronal cell bodies. Neurons were retrogradely labeled either by injection of 125I‐bFGF into the lateral ventricle or by injection into innervated target tissues. Co‐injection of a 250‐fold excess of unlabeled FGF with the 125I‐FGF abolished the neuronal labeling. Co‐injection of wheat germ agglutinin (WGA), which nonspecifically blocks binding of 125I‐bFGF to its receptor, also prevented neuronal labeling. These studies demonstrate that specific neuronal populations within the CNS express functional receptors for aFGF and/or bFGF; in these neurons, aFGF and/or bFGF bind specifically to these receptors, are internalized and retrogradely transported to the neuronal soma in a manner analogous to NGF. The data indicate that FGF can provide trophic support to CNS neurons by both direct and indirect mechanisms.
Thalamic processing of vibrissal information in the rat: II. Morphological and functional properties of medial ventral posterior nucleus and posterior nucleus neurons
Authors: Chiaia Nicolas L. , Rhoades Robert W. , Fish Stephen E. , Killackey Herbert P.
Published: January 2005

Extracellular recording, intracellular recording, intracellular horseradish peroxidase injection, and receptive field mapping techniques were employed to evaluate the physiological and morphological properties of medial ventral posterior nucleus (VPM) and posterior nucleus (POm) neurons in normal adult rats. Overall, we physiologically characterized 148 VPM and 121 POm neurons. Over 82% of the VPM cells were excited only by deflection of one or more mystacial vibrissae, 10% were activated by displacement of guard hairs, and the remainder were either excited by indentation of the skin or were unresponsive. Less than 40% of the POm cells were activated by vibrissa deflection, 18% were excited by displacement of guard hairs, and another 17% were unresponsive. Most of the rest of the POm cells were excited by stimulation of skin, mucosa, or activation of muscle‐related afferents. Small percentages of POm cells responded only to noxious stimulation, were classified as having a wide dynamic range, or were inhibited by peripheral stimulation. Electrical stimulation of either PrV or SpI activated most neurons in both VPM and POm. This excitation was almost invariably followed by a long‐lasting hyperpolarization which was generally strong enough to prevent responses to either electrical stimuli delivered in the brainstem or mechanical stimulation of the periphery. The receptive fields of vibrissa‐sensitive cells in POm were generally much larger than those of cells in VPM. Data obtained with extracellular recording indicated that VPM and POm cells responded to an average of 1.4 and 4.0 vibrissae, respectively. Intracellular recording from smaller samples of VPM and POm cells demonstrated the existence of inputs that were insufficient to produce spikes from the cell, but did yield epsp's. When both sub‐ and suprathreshold excitation were considered, the average number of vibrissa in the receptive field of a VPM cell was 2.7 and the value for POm cells became 7.8. HRP‐filled neurons recovered in POm (N = 20) generally had much larger dendritic arbors than neurons in VPM (N = 31). For the former cells, the size of the dendritic tree was significantly correlated with the number of vibrissa to which the cell responded; for the latter neurons, it was not.
Somatotopic organization of hindlimb skin sensory inputs to the dorsal horn of hatchling chicks (Gallus g. domesticus)
Authors: Woodbury C. Jeffery , Scott Sheryl A.
Published: January 2005

The somatotopic organization of skin sensory nerve projections to the lumbosacral dorsal horn of hatchling chickens was determined with the aid of transganglionic transport of horseradish peroxidase (HRP) processed with tetramethylbenzidine histochemistry, A total of eight hindlimb nerves were studied, five of which were purely cutaneous. When combined, the innervation fields of these nerves covered most of the hindlimb surface, allowing a nearly complete somatotopic map of the hindlimb to be generated.

This report describes a novel pattern of cutaneous nerve projections to the dorsal horn. Unlike other vertebrates, cutaneous nerves of chickens formed two separate, somatotopically organized projections across the mediolateral axis of the dorsal horn; when serially reconstructed and superimposed, these projections produced two nonoverlapping somatotopic maps of the skin surface lying side by side. Each of these separate maps was nearly identical to the other in overall topology. These two separate maps appear to represent distinct modalities of sensory information, as projections composing the medial map were preferentially labeled by choleragenoid‐HRP, whereas those composing the lateral map were preferentially labeled by wheat germ agglutinin‐HRP. In mammals, these HRP ligands selectively label the central projections of myelinated and unmyelinated cutaneous afferents, respectively. The present study, therefore, strongly supports the cytoarchitectonic findings of Brinkman and Martin (Brain Res. 56:43–62, ′73) that lamina III lies medial, rather than ventral, to lamina II in the chicken dorsal horn. Further, the present studies also suggest that laminae II and III of chickens are homologous to the homonymous laminae in the dorsal horn of mammals.
Dual serotoninergic projections to forebrain in the rat: Morphologically distinct 5‐HT axon terminals exhibit differential vulnerability to neurotoxic amphetamine derivatives
Authors: Mamounas Laura A. , Mullen Crystal A. , O'hearn Elizabeth , Molliver Mark E.
Published: January 2005

The cerebral cortex of the rat and other mammals is innervated by two morphologically distinct classes of serotoninergic (5‐HT) axon terminals: fine axons with minute varicosities and beaded axons characterized by large, spherical varicosities. Fine and beaded 5‐HT axons exhibit different regional and laminar distributions in forebrain and arise from separate brainstem nuclei, the dorsal and median raphe nuclei, respectively. Tha present neuroanatomic study, based on immunocytochemical methods to visualize 5‐HT axons, demonstrates that the two axon types differ markedly in their vulnerability to the neurotoxic amphetamine derivatives, methylenedioxyamphetamine (MDA), and p‐chloroamphetamine (PCA). While both drugs cause extensive degeneration of fine 5‐HT axons throughout forebrain, beaded 5‐HT axons are consistently spared. Fine 5‐HT axons, which richly innervate most regions of dorsal forebrain in control rats, are rarely seen 2 weeks after treatment with MDA or PCA; this loss of fine axons reflects a marked denervation that persists for months after drug administration. The serotoninergic axon terminals remaining after MDA or PCA administration are almost entirely of the beaded type and appear to be unaffected by both drugs. Over a wide range of doses (2.5–40 mg/kg PCA) and survival times (2 weeks to 2 months), these spared 5‐HT axons with large, spherical varicosities cannot be distinguished from the normal, beaded 5‐HT axons in control rats by morphologic criteria. Moreover, beaded 5‐HT axons exhibit a highly characteristic regional distribution which is the same in control as in MDA‐ and PCA‐treated rats: these axons innervate specific zones or layers within parietal and occipital cortex, hippocampus, cingulate cortex, entorhinal cortex, and the olfactory bulb, among other forebrain areas, and they form a dense plexus lining the ventricular system.

Taken together, the results of this study demonstrate that fine 5‐HT axons are highly vulnerable to the neurotoxic effects of the amphetamine derivatives MDA and PCA, while beaded 5‐HT axons are markedly resistant. These findings are consistent with the hypothesis that there are two anatomically and functionally distinct sets of serotoninergic neurons projecting to forebrain. While both of these neuronal systems utilize 5‐HT as a neurotransmitter, they differ in several features: (1) origin from separate nuclei in the brainstem (the dorsal and median raphe), (2) two types of morphologically distinct axon terminals, (3) markedly different distribution and innervation patterns in forebrain, and (4) dissimilar pharmacological properties. The results further suggest that psychotropic amphetamine derivatives have a selective action upon fine serotoninergic axons that arise from the dorsal raphe nucleus.
Pattern or retinotectal projection in the megachiropteran bat Rousettus aegyptiacus
Authors: Thiele A. , Vogelsang M. , Hoffmann K.‐P.
Published: January 2005

The retinotopic organisation of the superior colliculus (SC) in the megachiropteran bat Rousettus aegyptiacus was examined with single and multi‐unit recordings and by tracing the retrograde and anterograde transport of horseradish peroxidase (HRP) between the retina and the SC.

The pattern of projection of the visual field onto the SC in Rousettus resembles the pattern found in most mammals. The whole of the contralateral visual field is represented and, in addition, a region of the ipsilateral visual field extending 25° beyond the vertical 0° meridian. The ipsilateral visual field is represented binocularly in the most anterior 300–500 μm of the rostral pole of the SC. The contralateral visual field up to 25° from the vertical meridian is represented through both eyes for the next 500–800 μm. The peripheral part of the contralateral visual field, 25°–110° from the vertical meridian is seen only by the nasal retina (the monocular crescent) of the contralateral eye and is represented in the caudal part of the SC.

Following multiple injections of HRP into one SC, ganglion cells were labeled in both the nasal and temporal‐hemiretina of the contralateral eye. In the retina ipsilateral to the injection site, labeled cells were restricted to the temporal hemiretina.

After injections of HRP into one eye, labeled terminals were found all over the contralateral SC, but in the ipsilateral SC they were restricted to a band that begins 300–500 μm caudal from the rostral pole and extends to the middle of the SC.

These results suggest that in Rousettus, unlike the megachiropteran bats described by Pettigrew, Jamieson, Robson, Hall, McAnally, and Cooper (Philosophical Transactions of the Royal Society of London Series B 325:489–559,1989), the retinotopic organisation of the SC is not primate‐like, but follows the general mammalian scheme. As the retinotopic organisation of the SC is not consistent among the megachiropteran bats, the pattern of this projection may not be a useful indicator of their phylogenetic origins.
Comparative analysis of the vasotocinergic and mesotocinergic cells and fibers in the brain of two amphibians, the anuran Rana ridibunda and the urodele Pleurodeles waltlii
Authors: González Agustin , Smeets Wilhelmus J. A. J.
Published: January 2005

To obtain more insight into the vasotocinergic and mesotocinergic systems of amphibians and the evolution of these neuropeptidergic systems in vertebrates in general, the distribution of vasotocin (AVT) and mesotocin (MST) was studied immunohistochemically in the brains of the anuran Rana ridibunda and the urodele Pleurodeles waltlii. In Rana, AVT‐immunoreactive cell bodies are located in the nucleus accumbens, the dorsal striatum, the lateral and medial part of the amygdala, an area adjacent to the anterior commissure, the magnocellular preoptic nucleus, the hypothalamus, the mesencephalic tegmentum, and in an area adjacent to the solitary tract. In Pleurodeles, AVT‐immunoreactive somata are confined to the medial amygdala, the preoptic area, and an area lateral to the presumed locus coeruleus. In both species, the distribution of MST‐immunoreactive cell bodies is more restricted: in the frog, MST‐immunoreactive somata are present in the medial amygdala and the preoptic area, whereas, in the urodele, cell bodies are found only in the preoptic area.

Both in Rana and Pleurodeles, AVT‐ and MST‐immunoreactive fibers are distributed throughout the brain and spinal cord. A major difference is that in Rana the number of MST‐immunoreactive fibers is evidently higher than that of AVT‐immunoreactive fibers, whereas the opposite is found in Pleurodeles. This holds, in particular, for the forebrain and the brainstem. The presence of several extrahypothalamic AVT‐immunoreactive cell groups and the existence of well‐developed extrahypothalamic networks of AVT‐ and MST‐immunoreactive fibers are features that amphibians share with amniotes. However, this study has revealed that major differences exist not only between species of different classes of vertebrates, but also within a single class. In order to determine whether features of these neuropeptidergic systems are primitive or derived, a broad selection of species of each class of vertebrates is needed.