bluuebunny/crossref_metadata_2025 huggingface dataset:
Monoaminergic systems in the brainstem and spinal cord of the turtle Pseudemys scripta elegans as revealed by antibodies against serotonin and tyrosine hydroxylase
Authors: Kiehn Ole , Rostrup Egill , Møller Morten
Published: January 2005

With the aim of gaining more insight into the monoaminergic regulation of spinal motor systems in the turtle, we have studied the distribution of 5‐HT (5‐HTir) and tyrosine hydroxylase immunoreactivity (THir) in the brainstem and spinal cord of Pseudemys scripta elegans. 5‐HTir cell bodies were located in the midline in nucleus raphe inferior, nucleus raphe superior, and laterally in nuclei reticularis superior and inferior and nucleus reticularis isthmi. THir cell bodies were located in the commissural nucleus, nucleus tractus solitarii, the locus coeruleus‐subcoeruleus complex, nuclei reticularis superior and inferior, the pretectal area, and substantia nigra, 5‐HTir and THir tracts were found in lateral and ventral bundles superficially in the brainstem.

5‐HTir fibers in the spinal cord were located in a large dorsolateral and a smaller ventrolateral tract. In the gray matter, a high concentration of 5‐HTir fibers were observed in areas I–IV and in the lateral motor column of cervical and lumbar enlargements. Areas V–VIII and area X were less intensively innervated, with the lowest fibre concentration in areas VII–VIII and area X. Throughout the spinal cord, THir nerve fibres were located in the same areas but with a lower density. Small bipolar 5‐HTir and THir cell bodies were found ventromedially to the central canal especially in cervical and lumbosacral segments. Large THir cells were found in area IX in the caudal sacral and coccygeal spinal cord. THir cerebrospinal fluid‐contacting cells were also found in the most caudal part of the brainstem and the upper cervical spinal cord.

The well developed spinal 5‐HT system and the less developed THir system provides an anatomical explanation for the monoaminergic modulation of turtle motoneuron membrane properties, which has been observed in electrophysiological experiments. © 1992 Wiley‐Liss, Inc.
Cellular localization of the neural cell adhesion molecule L1 in adult rat neuroendocrine and endocrine tissues: Comparisons with NCAM
Authors: Grant Nancy J. , Leon Catherine , Aunis Dominique , Langley Keith
Published: January 2005

The tissue distribution and cellular localization of the neural cell adhesion molecule L1 was determined by immunocytochemistry at the optical and ultrastructural levels in adult rat neuroendocrine tissues and pancreatic endocrine cells. L1 was found to be abundant in the neurohypophysis but undetectable in the rest of the pituitary gland. It was barely detectable in the normal rat endocrine pancreas, but a rat pancreatic insulinoma cell line was found by immunofluorescence to express low levels of L1. In the adrenal medulla, it was present on a sub‐population of chromaffin cells and its density appeared to be lower on surfaces exposed to the extracellular matrix. Double immunolabelling showed this sub‐population to consist of noradrenergic chromaffin cells. Adrenergic chromaffin cells were found not to express L1. In addition, the tissue distribution and cellular localization of NCAM mRNAs was determined by in situ hybridization, extending our previous studies on the cellular expression of NCAM proteins in endocrine and neuroendocrine tissues. This confirmed that the NCAM message has a wider cellular distribution than L1 within the hypophysis and the adrenal gland. In addition to secretory cells, L1 immunoreactivity was detected in glial cells, in particular in the pituicytes of the neurohypophysis, which further distinguishes them from astrocytes, their counterparts in the central nervous system. These data are discussed in terms of the different embryological origins of the various endocrine tissues examined and also in terms of the specific design constraints imposed on these tissues during their development. © 1992 Wiley‐Liss, Inc.
Distribution of modulatory inputs to the stomatogastric ganglion of the crab, Cancer borealis
Authors: Coleman Melissa J. , Nusbaum Michael P. , Cournil Isabelle , Claiborne Brenda J.
Published: January 2005

The pyloric and gastric mill neural networks in the crustacean stomatogastric ganglion receive modulatory inputs from more anteriorly located ganglia via the stomatogastric nerve. In this study we employed biocytin backfilling and immunostaining, as well as electron microscopy, to determine the origin of these inputs in the crab, Cancer borealis. Fiber counts from electron micrographs of sections through the stomatogastric nerve showed that this nerve contains 55–60 medium to large diameter fibers (1–13 m̈m). These fibers were individually wrapped by several layers of membrane, presumably glial in origin. There was also a single cluster of jointly wrapped, small diameter (< 1 m̈m) fibers that may originate from peripheral sensory somata. Biocytin backfills revealed that approximately two thirds of the individually wrapped fibers in this nerve originate from somata in the other three ganglia of the stomatogastric nervous system, including the paired commissural ganglia and the single oesophageal ganglion. There were approximately 20 biocytin‐labeled somata in each commissural ganglion and 3 somata in the oesophageal ganglion. An additional ten somata were localized to the stomatogastric ganglion itself. This accounts for nearly all of the medium to large diameter fibers in the stomatogastric nerve. We used double‐labeling with backfills and immunocytochemistry to determine that there are two proctolin‐immunoreactive neurons and four FMRFamide‐like immunoreactive neurons among the biocytin‐labeled neurons in each commissural ganglion. Both peptides modulate neural network activity in the stomatogastric ganglion. Thus, our results demonstrate that most inputs to the stomatogastric ganglion originate from somata in the commissural ganglia, and that at least one third of these neurons contain a peptide known to modulate network activity in the stomatogastric ganglion. © 1992 Wiley‐Liss, Inc.
Immunocytochemical localization of kynurenine aminotransferase in the rat striatum: A light and electron microscopic study
Authors: Roberts Rosalinda C. , Du Fu , McCarthy Kathleen E. , Okuno Etsuo , Schwarcz Robert
Published: January 2005

Kynurenine aminotransferase is the biosynthetic enzyme for kynurenic acid, an antagonist of excitatory amino acid receptors. Because of the possible role of kynurenic acid in basal ganglia diseases, the distribution of kynurenine aminotransferase immunoreactivity was examined in the adult rat striatum at the light and electron microscopic levels. Kynurenine aminotransferase immunoreactivity was detected in glial cells and in neurons. The preadsorption control vastly reduced or eliminated specific staining at both the light and electron microscopic levels. Kynurenine aminotransferase positive glial cells were abundant and contained a robust and homogeneous distribution of reaction product in both the nucleus and cytoplasm. The majority of neurons, both medium and large, were immunostained and exhibited granular kynurenine aminotransferase immunoreactivity in the cytoplasm of somata and proximal dendrites. At the ultrastructural level, kynurenine aminotransfease immunoreactive astrocytic processes were apparent throughout the neuropil where they often encircled capillaries and surrounded axospinous synapses. Reaction product was associated with the cytoplasmic matrix, filaments, rough endoplasmic reticulum, and the nucleus. In neurons, the majority of label occurred in round membrane‐bound cytoplasmic organelles located adjacent to the Golgi apparatus, rough endoplasmic reticulum, and the cell or nuclear membranes. Cisternae and vesicles were identifiable in some of the labeled profiles. Polyribosomes and rough endoplasmic reticulum were also labeled. These data provide an anatomical basis for biochemical studies that have suggested the presence of striatal kynurenine aminotransferase in both astrocytes and neurons. © 1992 Wiley‐Liss, Inc.
Development of callosal connections in the sensorimotor cortex of the hamster
Authors: Norris Carolyn R. , Kalil Katherine
Published: January 2005

To investigate the development of corpus callosal connectivity in the hamster sensorimotor cortex, we have used the sensitive axonal tracer 1,1 dioctadecyl‐3,3,3′,3′, tetramethylindocarbocyanine perchlorate (DiI), which was injected either in vivo or in fixed brains of animals 3‐6 days postnatal. First, to study changes in the overall distribution of developing callosal afferents we made large injections of DiI into the corpus callosal tract. We found that the anterogradely labeled callosal axons formed a patchy distribution in the contralateral sensorimotor cortex, which was similar to the pattern of adult connectivity described in earlier studies of the rodent corpus callosum. This result stands in contrast to previous retrograde studies of developing callosal connectivity which showed that the distribution of callosal neurons early in development is homogeneous and that the mature, patchy distribution arises later, primarily as a result of the retraction of exuberant axons. The initial patchy distribution of callosal axon growth into the sensorimotor cortex described in the present study suggests that exuberant axons destined to be eliminated do not enter the cortex. In addition, small injections of DiI into developing cortex resulted in homotopic patterns of callosal topography in which reciprocal regions of sensorimotor cortex are connected, as has been shown in the adult.

Second, to study the radial growth of callosal afferents we followed the extension of individual callosal axons into the developing cortex. We found that callosal axons began to invade the contralateral cortex on about postnatal day 3, with little or no waiting period in the callosal tract. Callosal afferents then advanced steadily through the cortex, never actually invading the cortical plate but extending into layers on the first day that they could be distinguished from the cortical plate. The majority of callosal axons grew radially through the cortex and did not exhibit substantial branching until postnatal day 8, the age when the cortical plate disappears and callosal afferents reach the outer layer of cortex. This mode of radial growth through cortex prior to axon branching could serve to align callosal afferents with their radial or columnar targets before arborizing laterally. © 1992 Wiley‐Liss, Inc.
Sympathetic nerves in adult rats regenerate normally and restore pilomotor function during an anti‐NGF treatment that prevents their collateral sprouting
Authors: Gloster Andrew , Diamond Jack
Published: January 2005

We have used nerve growth factor (NGF) administration to study the NGF dependency of the reinnervation of denervated skin by sympathetic nerves inthe adult rat. Sympathetic pilomotor fields were revealed by electrical stimulation of selected dorsal cutaneous nerves; the affected skin rapidly assumed a “gooseflesh” appearance, sharply demarcated from surrounding unstimulated skin. Examined 2‐5 days after section of neighboring nerves, the “isolated” pilomotor field of the spared nerve was found to be coextensive with an area of amine‐fluorescent fibers that were associated with pilomotor muscles and blood vessels. After its isolation, a pilomotor field begins to expand into the surrounding deprived territory, reaching a maximum size at approximately 40 days. Fluorescence studies confirmed that new sympathetic fiber growth had occurred into the expanded regions of such fields. Daily injections of polyclonal anti‐NGF serum completely prevented these pilomotor field expansions. Following termination of the anti‐NGF treatment, expansion proceeded normally. Finally, if the onset of anti‐NGF treatment was delayed until pilomotor field expansion had already commenced, further expansion was halted. Regeneration of sympathetic fibers wasevoked by crushing a selected nerve. Recovery of pilomotor function in the totally denervated skin was first detected at about 20 days postcrush, and the field progressively enlarged over the next 40 days. Although the imposed NGF deprivation is known to cause a demonstrable shrinkage, and presumably atrophy, of sympathetic ganglia, the anti‐NGF treatment appeared to impair neither the restoration of a pilomotor field after nerve crush, nor its continued expansion into skin regions well beyond that originally supplied by the nerve, i.e., into territory whose invasion by collateral sprouts would have been totally prevented by the treatment. During such NGF deprivation, fluorescent regenerating fibers were visualized in the nerve trunk. We conclude that even though the regenerating and collaterally sprouting sympathetic fibers probably utilise the same degenerating dermal pathways to reach and functionally reinnervate the same denervated targets, only the collateral sprouting of the uninjured axons is dependent upon endogenous NGF. These findings extend the results described earlier for nociceptive fibers, andsuggest that the contrasting dependencies upon growth factors of sproutingand regeneration might apply throughout the adult nervous system. © 1992 Wiley‐Liss, Inc.
Translaminar deficits in the retinae of albinos
Authors: Jeffery Glen , Kinsella Brian
Published: January 2005

The central retina in albino mammals is poorly developed. There is a general reduction in ganglion cell density compared with the normal animal, and there are irregularities in the center to periphery gradient in ganglion cell density. It is not known whether, and if so to what extent, this abnormality is associated with deficits in other retinal layers.

In this study the distribution of cells in the ganglion cell layer has been determined in horizontally sectioned eyes from pigmented and albino ferrets. This was undertaken to define the location of the region of highest cell density and the relative cell gradients around it. Detailed counts and measurements were then undertaken to determine the cell density within, and thickness of, the inner and the outer nuclear layers in these animals.

All the albino animals had an abnormal distribution of cells in the ganglion cell layer in the central retina when compared with pigmented animals. The extent of this abnormality was variable. No differences between pigmented and albino animals could be found in the packing density of cells within the inner or the outer nuclear layer. However, in the pigmented animals there was a clear increase in the thickness of these layers associated with the region of highest density in the ganglion cell layer. This feature was absent in the albino animals, where the gradient in layer thickness was less marked and frequently contained irregularities. These abnormalities were most obvious in the outer nuclear layer. © 1992 Wiley‐Liss, Inc.
Electron microscopic immunocytochemical study of the distribution of parvalbumin‐containing neurons and axon terminals in the primate dentate Gyrus and Ammon's horn
Authors: Ribak Charles E. , Seress László , Leranth Csaba
Published: January 2005

Five green monkeys were examined with light and electron microscopic preparations to explore the regional differences in the distribution of parvalbumin (PV)‐positive neurons and axon terminals in the primate hippocampus. PV‐positive neurons were mainly found in the hilus of the dentate gyrus and the strata oriens and pyramidale of Ammon's horn. In electron microscopic preparations, the PV‐positive cells displayed nuclear infoldings, intranuclear rods, a large rim of perikaryal cytoplasm with numerous organelles and both asymmetric and symmetric axosomatic synapses. One prominent PV‐positive cell type in CA1 was a large multipolar neuron that resembled the large basket cells of the neocortex. Although most PV‐positive dendrites were aspiny and postsynaptic to numerous axon terminals, some PV‐positive dendrites in the molecular layer of the dentate gyrus displayed filipodia‐like appendages with no synapses or spines that were postsynaptic to multiple axon terminals. The PV‐positive dendrites in the hilus and stratum oriens were apposed at specialized junctions that resembled gap junctions. PV‐positive axons were concentrated in the principal cell layers, and formed axosomatic, axodendritic, and axon initial segment synapses. In cases where these axons were observed to appose the surface of granule cells for a long length, only one axosomatic symmetric synapse per cell was found. In the hilus, PV‐positive axon terminals formed synapses onto thorny excrescences of spiny cells. Both semithin sections and electron microscopic preparations indicated that more PV‐positive axon terminals formed symmetric axosomatic synapses with pyramidal cells in CA2 than in CA1 and CA3. Also, CA2 displayed a unique plexus of PV‐positive axon terminals in stratum lacunosum moleculare.

These results indicate that the PV‐positive hippocampal cells form a subset of GABAergic local circuit neurons, including the basket and chandelier cells. The ubiquitous finding of PV‐positive dendrites linked by gap junctions throughout the dentate gyrus and Ammon's horn adds further data to indicate that this subset of GABAergic neurons is linked electrotonically. The synaptic organization of PV‐positive neurons in the hippocampus suggests their participation in both feedback and feedforward inhibition. The PV‐positive neurons in the hippocampus are only a proportion of the basket and chandelier cells, whereas virtually all of these cells in neocortex are PV‐positive. © 1993 Wiley‐Liss, Inc.
Localization of cannabinoid receptor mRNA in rat brain
Authors: Matsuda Lisa A. , Bonner Tom I. , Lolait Stephen J.
Published: January 2005

Cannabinoid receptor mRNA was localized in adult rat brain by 35S‐tailed oligonucleotide probes and in situ hybridization histochemistry. Labelling is described as uniform or non‐uniform depending on the relative intensities of individual cells expressing cannabinoid receptor mRNA within a given region or nucleus. Uniform labelling was found in the hypothalamus, thalamus, basal ganglia, cerebellum and brainstem. Non‐uniform labelling that resulted from the presence of cells displaying two easily distinguishable intensities of hybridization signals was observed in several regions and nuclei in the forebrain (cerebral cortex, hippocampus, amygdala, certain olfactory structures). Olfactory‐associated structures, basal ganglia, hippocampus, and cerebellar cortex displayed the heaviest amounts of labelling. Many regions that displayed cannabinoid receptor mRNA could reasonably be identified as sources for cannabinoid receptors on the basis of well documented hodologic data. Other sites that were also clearly labelled could not be assigned as logical sources of cannabinoid receptors. The localization of cannabinoid receptor mRNA indicates that sensory, motor, cognitive, limbic, and autonomic systems should all be influenced by the activation of this receptor by either exogenous cannabimimetics, including marijuana, or the yet unknown endogenous “cannabinoid” ligand. © 1993 Wiley‐Liss, Inc.
Development of the mesencephalic nucleus of the trigeminal nerve in chick embryos: Target innervation, neurotrophin receptors, and cell death
Authors: Von Bartheld Christopher S. , Bothwell Mark
Published: January 2005

The goal of this study was to determine whether processes of neurons in the mesencephalic nucleus of the trigeminal nerve (Mes V) of chick embryos arrive in their peripheral target prior to the period of developmental cell death, and to determine whether neurons with early target contact survive to a greater extent than neurons with processes that reach their peripheral target later. The arrival of Mes V nerve fibers in the masticatory muscles was determined by injecting the fluorescent tracer DiI, and the position of labeled and unlabeled neurons was mapped in subdivisions of the Mes V nucleus. Developmental changes in the numerical configuration of Mes V subdivisions were studied in DiI‐labeled as well as Nissl‐stained material. The expression of law‐affinity (p75) neurotrophin receptors was investigated throughout development of the Mes V nucleus with in situ hybridization to assess whether and how levels of expression of this trophic receptor may relate to target innervation and cell death. The extent of cell death was evaluated by counting pyknotic nuclei.

Processes of Mes V neurons invade their peripheral target between 5 and 7 days of incubation (E5–7). At E7–12, between 800 and 1,400 labeled Mes V neurons were distributed throughout the two main subdivisions of the Mes V nucleus, the tectal commissure and the optic tectum. Only few Mes V neurons were labeled in the posterior commissure or outside the brain. Cell counts in Nissl‐stained material from E7–13 revealed that the numbers of Mes V neurons in the optic tectum decreased to about 40–60%, and in the tectal commissure to 20–25%, whereas Mes V neurons in the posterior commissure disappeared almost entirely. Few Mes V neurons remained in the leptomeninges at E8–10, but a considerable number was found outside the midbrain at E11, indicating ongoing migration of some Mes V neurons. Neurotrophin receptors were differentially expressed in the Mes V nucleus: Before and after the period of cell death, 90–100% of Mes V neurons expressed neurotrophin receptors, whereas during, and immediately preceding the period of developmental cell death (E9–E13), merely 70% of Mes V neurons expressed this receptor. These findings are consistent with the hypothesis that early target contact may provide an advantage for the survival of Mes V neurons and that competition for trophic factors may occur in the peripheral target of this nucleus prior to the period of cell death. © 1993 Wiley‐Liss, Inc.
Cholinergic innervation of the human cerebellum
Authors: de Lacalle Sonsoles , Hersh Louis B. , Saper Clifford B.
Published: January 2005

Cholinergic innervation of the human cerebellum was investigated immunocytochemically by using a polyclonal rabbit antiserum against choline acetyltransferase. Immunoreactive structures were found throughout the cerebellar cortex but were localized predominantly in the vermis, flocculus, and tonsilla. These included (1) a population of Golgi cells in the granular layer; (2) a subpopulation of mossy fibers and glomerular rosettes; (3) thin, varicose fibers closely associated with the Purkinje cell layer and the molecular layer; and (4) a relatively dense network of fibers and terminals contributing to the glomerular formations in the granular layer. In the cerebellar nuclei, some cells stained positively for choline acetyltransferase, and a terminal field pattern could be detected with a distinct but sparse network of varicose fibers. Acetylcholine appears to be a primary transmitter in the vestibulocerebellar pathways at several levels, which may account for the potent effects of muscarinic antagonists in diminishing vestibular vertigo in humans. © 1993 Wiley‐Liss, Inc.
Estimate of the total number of neurons and glial and endothelial cells in the rat spinal cord by means of the optical disector
Authors: Bjugn Roger , Gundersen Hans Jørgen G.
Published: January 2005

The total numbers of neurons and glial and endothelial cells in five rat spinal cords were estimated by stereological techniques.

Each spinal cord was divided into 12 slabs of equal length. One transverse and one oblique slice was cut from each slab. The volumes of gray and white matter of each cord were then estimated by point‐counting techniques on the transverse slices. By means of optical disectors and systematic sampling, the numerical densities of different cell types were estimated on 35 m̈‐thick plastic sections from the oblique slices. The total cell number was calculated by multiplying the numerical density by the total volume of gray and white matter.

On average there were 15.1 and 21.1 million cells in white and gray matter, respectively. Of the cells in gray matter, 6.4 million were judged to be neurons, 4.3 million to be endothelial, and 10.3 million to be glial. Of the neurons, 1.7 million were located in the cervical region, 2.5 million in the thoracic, 1.6 million in the lumbar, and 0.6 million in the sacro‐coccygeal region.

The methods used are simple to perform, and the counting necessary to obtain a reliable estimate of cell number from one spinal cord can be carried out during the course of 1 day. The only major problem is reliable criteria for unambiguous cell classification. © 1993 Wiley‐Liss, Inc.
Possible morphological substrates for GABA‐mediated presynaptic inhibition in the lamprey spinal cord
Authors: Christenson Johan , Shupliakov Oleg , Cullheim Staffan , Grillner Sten
Published: January 2005

Gamma‐aminobutyric acid (GABA) neurons intrinsic to the lamprey spinal cord are known to modulate synaptic transmission from interneurons active during locomotion and from mechanosensory dorsal cells. Many of these physiological effects are presynaptic. To establish the morphological substrates for these axo‐axonic interactions, an ultrastructural analysis was performed with an antiserum to fixed GABA. The GABA immunoreactivity (ir) was detected by postembedding peroxidase‐antiperoxidase and immunogold techniques. GABA‐ir terminals were found to make appositions with unlabelled axons located in the dorsal columns and in the ventrolateral aspect of the spinal cord. In the ventrolateral part of the cord, similar appositions between different GABA‐ir terminals were also observed. The immunolabelled terminals contained spherical to pleomorphic synaptic vesicles, and also glycogen granules and dense core vesicles. In some cases, the fine structure of the contacts between immunogold‐labelled terminals and unlabelled axons suggested a synaptic relationship. Such a relation was found in a relatively small proportion (2–3%) of the appositions studied. These specializations were always observed in close relation to an output synapse of the postsynaptic axon. It is suggested that the axo‐axonal contacts described may provide an effective modulation of the synaptic transmission from axons in the lamprey spinal cord. © 1993 Wiley‐Liss, Inc.
The diencephalon of the pacific herring, Clupea harengus: Retinofugal projections to the diencephalon and optic tectum
Authors: Northcutt R. Glenn , Butler Ann B.
Published: January 2005

The pattern of retinofugal projections to nuclei in the diencephalon and to the optic tectum was analyzed with horseradish peroxidase and autoradiographic methods in Clupea harengus, a clupeomorph teleost, for comparison with osteoglossomorph, elopomorph, and euteleost teleosts and with non‐teleost actinopterygians. Most retinal fibers decussate in the optic chiasm and project to nuclei in the preoptic area, ventral and dorsal thalamus, posterior tuberculum, synencephalon, and pretectum, as well as to the accessory optic nuclei and optic tectum. Some ipsilateral projections do not decussate in the optic chiasm, while others decussate and recross via the supraoptic (minor) and posterior commissures. The pattern of projections is similar to that seen in other actinopterygian fishes with several exceptions. The terminal field usually present lateral to nucleus anterior in the dorsal thalamus is extremely reduced despite the relatively large size of the nucleus. A dense terminal field lies within the cell plate of nucleus corticalis in the pretectum rather than dorsal to it. The tectal hemisphere is composed of two distinct lobules, and the dorsal optic tract projects to the more rostromedial lobule while the ventral optic tract projects to the more caudolateral lobule. The lack of a significant projection to nucleus anterior and the lobular morphology of the optic tectum appear to be apomorphic for Clupea. Other features of the pattern of retinal projections are also analyzed in actinopterygian fishes including Clupea, and several hypotheses are advanced as to which traits are plesiomorphic for actinopterygians and/or for teleosts. © 1993 Wiley‐Liss, Inc.
Frequency organization of the dorsal cochlear nucleus in cats
Authors: Spirou George A. , May Bradford J. , Wright Debora D. , Ryugo David K.
Published: January 2005

Sensory epithelia are often spatially reiterated throughout their representation in the central nervous system. Differential expression of this representation can reveal specializations of the organism's behavioral repertoire. For example, the nature of the central representation of sound frequency in the auditory system has provided important clues in understanding ecological pressures for acoustic processing. In this context, we used electrophysiological techniques to map the frequency organization of the dorsal cochlear nucleus in nine cats. Frequency responses were sampled in increments of 100–200 μm along electrode tracks that entered the dosomedial border of the nucleus and exited at the ventrolateral border. Electrode tracks were oriented parallel to the long (or strial) axis of the nucleus so that each penetration sampled neural responses for most of the cat's audible frequencies and remained in or near the pyramidal cell layer for several millimeters. Nearly identical distance versus frequency relationships were obtained for different rostral‐caudal locations within the same cat as well as for different cats. Frequency responses systematically decreased from above 50 kHz at the most dorsomedial locations in the nucleus to below 1 kHz in the most ventrolateral regions. The rate of frequency change was roughly three times greater in high frequency regions than in low frequency regions. In addition, the highest pyramidal cell density and longest rostral‐caudal axis was observed for the middle third of the dorsal‐ventral axis of the nucleus. As a result, roughly half of all pyramidal cells responded to frequencies between 8–30 kHz. The representation of neural tissue for these frequencies may be related to the importance of spectral cues in sound localization. © 1993 Wiley‐Liss, Inc.
The catecholaminergic system of the quail brain: Immunocytochemical studies of dopamine β‐hydroxylase and tyrosine hydroxylase
Authors: Bailhache Thierry , Balthazart Jacques
Published: January 2005

The distribution of dopamine β‐hydroxylase and tryrosine hydroxylase, two key enzymes in the biosynthesis of catecholamine, was investigated by immunocytochemistry in the brain of male and female Japanese quail. Cells or fibers showing dopamine β‐hydroxylase and tyrosine hydroxylase immunoreactivity were considered to be noradrenergic or adrenergic, while all structures showing only tyrosine hydroxylase immunoreactivity were tentatively considered to be dopaminergic. The major dopaminergic and noradrenergic cell groups that have been identified in the brain of mammals could be observed in the Japanese quail, with the exception of a tuberoinfundibular dopaminergic group. The dopamine β‐hydroxylase‐immunoreactive cells were found exclusively in the pons (locus ceruleus and nucleus subceruleus ventralis) and in the medulla (area of the nucleus reticularis). The tyrosine hydroxylase‐immunoreactive cells had a much wider distribution and extended from the preoptic area to the level of the medulla. They were, however, present in larger numbers in the area ventralis of Tsai and in the nucleus tegmenti pedunculo‐pontinus, pars compacta, which respectively correspond to the ventral tegmental area and to the substantia nigra of mammals. A high density of dopamine β‐hydroxylase‐ and tyrosine hydroxylase‐immunoreactive fibers and punctate structures was found in several steroid‐sensitive brain regions that are implicated in the control of reproduction. In the preoptic area and in the region of the nucleus accumbens‐nucleus stria terminalis, immunonegative perikarya were completely surrounded by immunoreactive fiber forming basket‐like structures. Given that some of these cells contain the enzyme aromatase, these structures may represent the morphological substrate for a regulation of aromatase activity by catecholamines. The dopamine β‐hydroxylase‐immunoreactive fibers were also present in a larger part of the preoptic area of females than in males. This sex difference in the noradrenergic innervation of the preoptic area presumably reflects the sex difference in norepinephrine content in this region. © 1993 Wiley‐Liss, Inc.
Trigeminal nuclear complex of the ferret: Anatomical and Immunohistochemical studies
Authors: Boissonade Fiona M. , Sharkey Keith A. , Lucier Gregory E.
Published: January 2005

In order to establish the ferret as an animal model for studies of trigeminal pain, we describe the cytoarchitecture and neurochemistry of the trigeminal nuclear complex in the ferret and compare them to those of the cat and rat. The complex was divided as previously described, but the ferret differed in the extent of the nuclear boundaries. The neuroantomical distribution of substance P‐, calcitonin gene‐related peptide‐, galanin‐, enkephalin‐, serotonin‐, somatostatin‐, neuropeptide Y‐, and neurotensin‐immunoreactivity was determined throughout the rostrocaudal extent of the complex. In subnucleus caudalis, substance P‐, calcitonin gene‐related peptide‐, enkephalin‐, serotonin‐, somatostatin‐, neuropeptide Y‐, and galanin‐immunoreactivity was densest in laminae I and II. In subnucleus interpolaris, immunoreactivity for all the above neurochemicals was most dense along the lateral border and the ventral third of the caudal part of the subnucleus. Enkephalin‐immunoreactive cell bodies were present in subnucleus caudalis and interpolaris. In subnucleus oralis, labelling for substance P, calcitonin gene‐related peptide, galanin, enkephalin, and serotonin was most prominent in the dorsomedial part of the subnucleus. Somatostatin‐immunoreactive cell bodies were distributed throughout the spinal nucleus. Labelling of serotonin, substance P, calcitonin gene‐related peptide, galanin, enkephalin, and somatostatin was present in the main sensory nucleus. The motor nucleus contained fibers immunoreactive for substance P, enkephalin, serotonin and neuropeptide Y, and cell bodies immunoreactive for calcitonin gene‐related peptide. The majority of neurotensin‐immunoreactivity was found at the level of subnucleus caudalis, where it was densest in the trigeminal extension of the lateral cervical nucleus. The distribution of peptides in this species throughout the spinal nucleus is consistent with the notion that all the subnuclei may be involved in the processing of nociceptive inputs. © 1993 Wiley‐Liss, Inc.
Plasticity of auditory cortex associated with sensorineural hearing loss in adult C57BL/6J mice
Authors: Willott James F. , Aitkin Lindsay M. , McFadden Sandra L.
Published: January 2005

The representation of frequency was mapped in the primary auditory cortex (AI) of C57BL/6J (C57) mice during young adulthood (1.5–2 months) when hearing is optimal, and at 3, 6, and 12 months of age, a period during which progressive, high frequency, sensorineural hearing loss occurs in this strain. Maps were also obtained from CBA/CaJ mice which retain good hearing as they age.

In AI of young adult C57 mice, and CBA mice, characteristic frequencies (CFs) of multiple‐unit clusters were easily identified with extracellular recordings, and a general tonotopic organization was observed from dorsal (high frequency) to ventral and caudal (low frequency). In individual cases there appeared to be deviations from the above tonotopic organization, despite the fact that inbred mice are genetically invariant. As progressive loss of high frequency sensitivity ensued peripherally, a substantially increased representation of middle frequencies was observed in AI. There was no apparent change in the surface area of the auditory cortex despite the elimination of high frequencies, and virtually the entire auditory cortex became devoted to the middle frequencies (especially 10–13 kHz) for which sensitivity remained high. Similar age‐related changes were not observed in normal‐hearing CBA mice. These findings indicate that plasticity in the representation of frequency in AI is associated with high frequency hearing loss in C57 mice. © 1993 Wiley‐Liss, Inc.
Segmental arrangement of reticulospinal neurons in the goldfish hindbrain
Authors: Lee Robert K. K. , Eaton Robert C. , Zottoli Steven J.
Published: January 2005

The hindbrain is evolutionarily conserved among diverse vertebrate phyla. In vertebrate embryos, the hindbrain is segmentally organized as a series of overt swellings known as rhombomeres. In the larval zebrafish Brachydanio rerio, conspicuous and identifiable reticulospinal neurons are positioned in the center of rhombomeres. Segmentally homologous reticulospinal neurons that share a range of morphological, developmental, and biochemical features occupy adjacent rhombomeres.

We have recently shown that reticulospinal neurons of the zebrafish survive ontogeny without considerable morphological modification and we suggested that homologous neurons may share similar functions at different stages of development (Lee and Eaton: Journal of Comparative Neurology 304:34–52, 1991). The goldfish Carassius auratus, a related cyprinid, is especially suited for neurophysiological and behavioral studies. However, it is not yet known if the various reticulospinal neurons of zebrafish are generalizable to other species such as the goldfish. Therefore, we sought to examine the extent to which reticulospinal neurons of the zebrafish are also present in the adult goldfish.

Analysis of 45 brains retrogradely labeled with horseradish peroxidase (HRP) from the spinal cord showed that reticulospinal neurons are arranged as a series of seven segments within the hindbrain; a regular interval of approximately 200 μm separates adjacent segments. Although the goldfish reticulospinal system has more neurons than the zebrafish, many reticulospinal neuron types continue to be identifiable. Moreover, comparisons of dendritic arborizations and axon paths between the two species showed that the morphology between various neuron types is virtually identical. The cross‐taxonomic similarities between the reticulospinal systems of these related cyprinids make it possible to pursue functional considerations of segmentally homologous neurons in the goldfish hindbrain. © 1993 Wiley‐Liss, Inc.
Architectionis, somatotopic organization, and ipsilateral cortical connections of the primary motor area (M1) of owl monkeys
Authors: Stepniewska Iwona , Preuss Todd M. , Kaas Jon H.
Published: January 2005

The ipsilateral cortical connections of primary motor cortex (M1) of owl monkeys were revealed by injecting WGA‐HRP and fluorescent tracers into M1 sites identified by intracortical microstimulation. In some of the same animals, the extent and somatotopic organization of M1 was determined by making detailed microstimulation movement maps and relating the results to cortical architectonics. Thus, delineation of M1 was based on a combination of physiological and anatomical characteristics. M1 comprised most, but not all, of the cortex rostral to area 3a where movements were evoked at low levels of current (40 μA or less). Analysis of somatotopic patterns and architectonics placed some of the low‐threshold sites in a ventral premotor field (PMV) and the dorsomedially situated supplementary motor area (SMA). Movements were also reliably elicited from a dorsal premotor area (PMD) at higher currents. M1 was characterized by a somatotopic global organization, representing hindlimb, trunk, forelimb, and face movements in a mediolateral sequence, and a mosaic local organization, with a given movement typically represented at several different sites. Architectionically, M1 was characterized by the absence of a granular layer IV and the presence of very large layer V pyramidal cells. However, M1 was not uniform in structure: pyramidal cells were larger caudally than rostrally, a feature we used to distinguish caudal (M1c) and rostral (M1r) subdivisions of the area. M1 resembles Brodmann's area 4, although the rostral subdivision has probably been considered as part of area 6 by some workers. Tracer injections of M1 revealed somatotopically distributed connections with motor areas PMD, PMV, and SMA, as well as in somatosensory areas 3a, 1, 2, and S2. Weaker connections were with area 3b, posterior parietal cortex, the parietal ventral area (PV), and cingulate cortex. M1r and M1c differed connectionally as well as architectonically, M1c being connected primarily with somatosensory areas, while M1r was strongly connected with both non‐primary motor cortex and somatosensory cortex. These results indicate that M1 interacts directly with at least three non‐primary motor areas and at least six somatosensory areas.
Topography of projections to the frontal lobe from the macaque frontal eye fields
Authors: Stanton G. B. , Bruce C. J. , Goldberg M. E.
Published: January 2005

Efferents from the frontal eye fields (FEF) to the ipsilateral frontal lobe were studied by autoradiography of tritiated tracers (leucine, proline, and fucose) in seven macaque monkeys that were used previously to describe subcortical connections. In four of the cases, tracer injection sites were confirmed by low thresholds for the electrical elicitation of saccadic eye movements. Cases were grouped as lFEF or sFEF cases according to large or small saccades that were characteristic of the injection site.

Projections from the FEF terminated in five frontal regions: (1) area FD on the dorsomedial convexity; (2) area FC (containing SEF) medial to the upper limb of the arcuate sulcus; (3) areas FD and FDΔ along the walls of the principal sulcus; (4) area FCBm on the deep, posterior wall of the arcuate sulcus inferior to the sulcal spur; and (5) the inferolateral cortex (area FDi) on the convexity and lateral two thirds of the anterior wall of the arcuate sulcus. Projections in sFEF cases tended to be confined to medial parts of dorsomedial FD and FC and the lateral wall of the principal sulcus and inferolateral convexity. Neither lFEF nor sFEF appeared to project to the SMA or pericingulate cortex. Label in these areas was found only in the cases in which tracer spread into non‐FEF areas.

FEF projections terminated in column‐like patches of about 500–600 μm in diameter. Labeled axons and terminals were seen in all cortical layers regardless of location in the frontal lobe.
Changes in synaptic density after developmental compression or expansion of retinal input to the superior colliculus
Authors: Xiong Meijuan , Finlay Barbara L.
Published: January 2005

The retinal projection to the superior colliculus can be made abnormally dense by inducing a “compressed” retinal projection into a subnormal tectal volume, or abnormally spares by monocular enucleation early in development. Any or all of the features of cell number, axonal arbor, dendritic arbor, and synaptic density could potentially be adjusted to compensate for such variations in the convergence of one cell population on another. We have examined the consequences of neonatal partial tectal ablation or monocular enucleation for synaptic length, density, and relative numbers of synapse classes in the superficial gray layer of the hamster superior colliculus.

Monocular enucleation resulted in a reduction of synaptic density in the superficial gray layer of the colliculus ipsilateral to the remaining eye. This decrease in density was entirely accounted for by a reduction of the number of synapses with round vesicles, large asymmetric terminal specializations, and pale mitochondria characteristic of retinocollicular terminals (RLP synapses). There was no compensatory increase in any other synaptic class. RLP synapses were larger in monocular enucleates.

Partial tectal ablation had no effect on synaptic density, nor on the relative proportions of different synaptic types. Synapses of the RLP class were slightly smaller than normal. These results suggest that synaptic density is normally at a maximum that cannot be altered by increases in potential input. However, density may be reduced by decreasing the number of inputs. Terminal classes do not appear to compete with each other within the collicular volume, suggesting that postsynaptic cells control both the classes and numbers of their potential inputs.
Location of retinal ganglion cells contributing to the early imprecision in the retinotopic order of the developing projection to the superior colliculus of the wallaby (Macropus eugenii)
Authors: Marotte L. R.
Published: January 2005

The position of ganglion cells contributing to the early imprecision in retinotopic order in the developing retinocollicular projection in the wallaby (Macropus eugenii) has been determined.

Deposits of horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP) were made in the caudal pole of the superior colliculus (SC) at ages ranging from 22 days after birth, when sparse retinal axons have only just reached the caudal pole of the SC and are yet to cover its surface completely, to 96 days when the retinotopy of ganglion cell terminals in the SC is precise (Marotte, '90). From 30 days onwards, the deposit of WGA‐HRP resulted in a dense patch of retrogradely labelled retinal ganglion cells that could be seen to be appropriately positioned in nasal retina. However, at all ages prior to 92 days, there were inappropriately positioned labelled cells between the densely labelled patch and the central retina and both dorsal and ventral to the patch. They were not found in far distant regions of retina and composed a relatively small proportion of labelled cells. They reached a peak at 45 days, had decreased to low levels by 63 days, were rare by 81 days, and by 92 days were absent. This latter age fits with the time when retinotopy was judged to be precise in a previous study (Marotte, '90).

Inappropriately projecting cells never originate from the entire retina but only from regions adjacent to the appropriate region. Thus, during development there are no gross projection errors. Initially, ganglion cell axons are distributed on the colliculus in a coarse retinotopy. Refinement of the projection then follows, revealed by this technique as a loss of inappropriately projecting ganglion cells. This is complete by 92 days well before eye opening at around 140 days. © 1993 Wiley‐Liss, Inc.
Distribution of parvalbumin‐immunoreactive cells and fibers in the monkey temporal lobe: The amygdaloid complex
Authors: Pitkänen Asla , Amaral David G.
Published: January 2005

The calcium‐binding protein parvalbumin was immunohistochemically localized in the monkey amygdaloid complex. Parvalbumin‐immunoreactive neuronal cell bodies, fibers, and terminals were observed in several amygdaloid nuclei and cortical areas. Three types of aspiny neurons, ranging from small spherical cells (Type 1) to large multipolar cells (Type 2) and fusiform cells (Type 3) were observed in most amygdaloid regions, though the proportions of the cell types were different in each region. The density of parvalbumin‐immunoreactive fibers and terminals tended to parallel the density of labeled cell bodies. The highest densities of parvalbumin profiles were observed in the nucleus of the lateral olfactory tract, the periamygdaloid cortex (PAC2), the magnocellular division of the basal nucleus, the ventrolateral portion of the lateral nucleus, and the accessory basal nucleus. The regions containing the lowest densities of parvalbumin‐positive profiles were the medial nucleus, anterior cortical nucleus, central nucleus, and the paralaminar nucleus. In regions with fiber and terminal labeling, pericellular networks of fibers, reminiscent of basket cell terminations, were commonly observed to surround unstained neuronal cell bodies and proximal dendrites. In the magnocellular division of the basal nucleus, and to a lesser extent in the lateral nucleus, parvalbuminlabeled “cartridges” of axo‐axonic terminals were observed on the initial segments of unlabeled cells. Parvalbumin‐positive varicosities were also commonly observed in close apposition to the soma and dendrites of parvalbumin‐immunoreactive cells. Given the close correspondence between the distribution of parvalbumin‐positive neurons and a subset of GABAergic neurons in many brain regions, these data provide a first indication of the organization of the inhibitory circuitry of the primate amygdaloid complex. © 1993 Wiley‐Liss, Inc.