bluuebunny/crossref_metadata_2025 huggingface dataset:
The vocal control pathways in budgerigars differ from those in songbirds
Authors: Striedter Georg F.
Published: January 2005

Previous studies concluded that parrots and oscine songbirds, two taxa that have independently evolved the ability to learn vocalizations, possess similar neural circuits for vocal control. These investigations suggested, however, that the vocal control systems of parrots and songbirds may also differ in several respects. Most importantly, auditory inputs to the vocal control system derive from Field L in songbirds, but this area does not appear to project to the vocal control system in parrots. The principal aims in the present study were, therefore, to determine (1) exactly how similar the vocal control system in budgerigars is to that in songbirds and (2) whether the vocal control system in budgerigars receives auditory inputes from areas other than Field L.

Biotinylated and fluorescently labeled dextrans were injected into five telencephalic nuclei of the vocal control system in budgerigars and into the physiologically identified auditory portions of the frontal neostriatum and nucleus basalis. The results indicate that the forebrain voca; control system in budgerigars is only superficially similar to that in songbirds. Many of the vocal control nuclei differ between the two taxa in both cytoarchitecture and connections. The nuclei in budgerigars that are comparable to those of the accessory loop of the vocal control system in songbirds, for example, do not form an accessory loop in budgerigars. The vocal control systems in the two taxa differ most significantly in the source of their auditory inputs. In songbirds, auditory information is conveyed to the vocal control system via Field L, whereas, in budgerigars, the auditory inputs to the vocal control system derive from nucleus basalis and the frontal neostratum. A phylogenetic analysis suggests that the midbrain and medullary vocal control pathways are homologous across all birds, but that most of the vocal control circuits in the forebrain have probably evolved independently in parrots and songbirds. © 1994 Wiley‐Liss, Inc.
Taste bud expression of human blood group antigens
Authors: Smith David V. , Klevitsky Raisa , Akeson Richard A. , Shipley Michael T.
Published: January 2005

Some human blood group antigens are expressed by rodent epithelial cells at different stages of differentiation. Since adult taste cells are continually replaced throughout life, we investigated the expression of the H, B, A and Lewisb blood group determinants by cells of the rat fungiform, foliate and vallate papilae. We employed antibodies against the trisaccharide structures of the H, B, and A blood group antigens and against the Lewisb blood group epitope in studies of normal and denervated taste buds. The antibody against the H antigen reacted with the majority of cells in all taste buds and with cells in the spinous layer of the tongue epithelium. The B antigen was expressed by the majority of taste cells but not by other epithelial cells. The expression of the A antigen was significantly less in the fungiform taste buds than in the vallate or foliate taste buds. The A antigen was also abundantly expressed in the acini of the lingual salivary glands. The Lewis b epitope was expressed by a subset of cells in taste buds of the fungiform, foliate and vallate papillae. Taste buds are trophically dependent upon gustatory nerve innervation. Transection of the chorda tympani or the IXth nerve resulted in the loss of expression of these molecules from the gustatory epithelium, indicating that they are expressed only on differentiated taste cell. The blood group antigens are lactoseries carbohydrates; they are differentially expressed in developing cochlear hair cells and olfactory neurons and may play roles in cell‐cell recognition, adhesion, and other interactions important in the developing nervous system. They could have similar functions in the taste and olfactory systems, where the receptors are continually renewed and new synapses between the receptors and their neural targets continually form. © 1994 Wiley‐Liss, Inc.
Triceps surae motoneuron morphology in the rat: A quantitative light microscopic study
Authors: Chen Xiang Yang , Wolpaw Johathan R.
Published: January 2005

The rat is now the model of choice for many studies of motor function. However, little quantitative information on the structure of rat motoneurons is available. In conjunction with efforts to define the physiologic and anatomic substates of operantly conditioned plasticity in the spinal cord, 13 physiologically identified triceps surae motoneurons in the rat lumbar spinal cord were labeled intracellularly with horseradish peroxidase and completely reconstructed and measured with a computer‐based neuron‐tracing system.

Somata were all located in the ventral horn of lumbar segments 4–5, had and average diameter of 35 μm, and had 6–12 dendrites. Dendrites remified throughout the ventral horn and also penetrated the white matter. Their spread was greater in the rostocaudal and dorsoventral directions (1.53 ± 0.24 mm and 1.35 ±0.23 mm, respectively) than in the mediolateral direction (0.85 ± 0.14 mm). Regardless of soma location, dendritic fields usually extended throughout the ipsilateral coronal cross‐section of the ventral horn.

As a result, the ventral or lateral extent of the field was correlated strongly with the soma's distance from the ventral or lateral border, respectively, of the ventral horn. Furthermore, although soma locations in the coronal plane varied widely, the centers of the dendritic fields tended to cluster near the center of the ventral horn. Dendrites constituted 96.2–98.4% (mean ± SD = 97.3 ± 0.7%) of the total neuronal surface area. Each of the 104 dendrites studies had an average of 13 branch points and 27 segments. First‐order segment diameters ranged from 1.4 to 11.7 μm (mean ±SD = 5.3 ± 2.1 μm). Total dendritic length, surface area, volume, number of dendritic segments, and maximum segment order were correlated strongly with diameter of the first‐order segment. Proceeding distally between branch points, the mean decrease in dendritic diameter (i. e., tapering) ± the standard deviation was 22 ± 8% of the proximal diameter. The average ratio ± the standard deviation of the sum of the average diameters of each daughter segment raised to the 1.5 power to the average diameter of the parent segment raised to the 1.5 power (i. e., Rall's ratio; Rall, 1959) was 0.87 ± 0.08.

In comparison with cat α‐motoneurons, rat motoneurons had smaller soma diameters, fewer dendrites, smaller total surface areas, and shorter total dendritic lengths. However, the number of terminations per dendrite was similar in the two species, so that rat motoneurons had more terminations per unit dendritic length. This greater branching density indicates that the dendritic fields of rat motoneurons are more compact and their branching structures are more densely packed that those of cat motoneurons. © 1994 Wiley‐Liss, Inc.
The return of phosphorylated and nonphosphorylated epitopes of neurofilament proteins to the regenerating optic nerve of Xenopus laevis
Authors: Zhao Yangu , Szaro Ben G.
Published: January 2005

Neurofilament proteins of mammalian axotomized peripheral axons, which regenerate effectively, resemble those of embryonic axons. However, injured centrally projecting mammalian axons, which fail to regenerate, have very different neurofilament compositions than during development. If changes in neurofilament composition after injury reflect the ability of axotomized neurons to regenerate effectively, then the neurofilaments of centrally projecting axons that can regenerate should more closely resemble those of developing axons. In this study, the neurofilament compositions of injured optic axons of the frog, Xenopus laevis, were examined, since these axons can regenerate a fully functional projection. Antibodies to phosphorylated and nonphosphorylated forms of neurofilament proteins that had been used previously to study the neurofilament composition of newly developing X. laevisoptic axons were used in immunocytochemical studies to examine the return of neurofilaments to the optic nerve after an intraorbital nerve crush. Intraocularly injected wheat germ agglutinin conjugated to horseradish peroxidase was used to label the regenerating axons independently of their neurofilaments. Neurofilament immunoreactivities disappeared rapidly from crushed axons during the first week after surgery. By nine days after surgery, antibodies to nonphosphorylated form of middle (NF‐M) and low molecular weight (NF‐) neurofilament proteins and the Xenopusneuronal intermediate filament protein (XNIF) began to stain the nerve just beyond the lesion. By this time, however, growing axonal terminals had reached the optic chiasm. Antibodies to phosphorylated epitopes of NF‐M began to stain axons at 15 days, just as growing axons began to arrive at the optic tectum. Nonphosphorylated high molecular weight neurofilament protein (NF‐H) began to appear in axons between 18 and 21 days after surgery. Thus, the reappearance of neurofilaments during optic axon regeneration resembled the general pattern seen during development. The chief difference between development and regeneration was that neurofilament epitopes took longer to emerge during regeneration. One possibility is that cues encountered along the optic pathway influence the neurofilament composition of retinal ganglion cell axons. Then, the greater distance travelled by regenerating axons could account for the longer time taken for their neurofilament compositions to mature. © 1994 Wiley‐Liss, Inc.
Development changes in the distribution of gamma‐aminobutyric acid‐immunoreactive neurons in the embryonic chick lumbosacral spinal cord
Authors: Antal Miklós , Berki Ágnes C. , Horváth László , O'Donovan Michael J.
Published: January 2005

The development of γ‐aminobutyric acid (GABA)‐immunoreactive neurons was investigated in the embryonic and posthatch chick lumbosacral spinal cord by using pre‐ and postembedding immunostaining with an anti‐GABA antiserum. The first GABA‐immunoreactive cells were detected in the ventral one‐half of the spinal cord dorsal to the lateral motor exception of the lateral motor column, appeared throughout the entire extent of the ventral one‐half of the spinal gray matter by E6. Thereafter, GABA‐immunoreactive neurons extended from ventral to dorsal regions. Stained perikarya first appeared at E8 and then progressively accumulated in the dorsal horn, while immunoreactive neurons gradually declined in the ventral horn. The general pattern of GABA immunoreactivity characteristic of mature animals had been achieved by E12 and was only slightly altered afterwards. In the dorsal horn, most of the stained neurons were observed in laminae I–III, both at the upper (LS 1–3) and at the lower (LS 5–7) segments of the lumbosacral spinal cord. In the ventral horn, the upper and lower lumbosacral segments showed marked differences in the distribution of stained perikarya. GABAergic neurons were scattered in a relatively large region dorsomedial to the lateral motor column at the level of the upper lumbosacral segments, whereas they were confined to the dorsalmost region of lamina VII at the lower segments.

The early expression of GABA immunoreactivity may indicate a trophic and synaptogenetic role for GABA in early phases of spinal cord development. The localization of GABAergic neurons in the ventral horn and their distribution along the rostrocaudal axis of the lumbosacral spinal cord coincide well with previous physiological findings, suggesting that some of these GABAergic neurons may be involved in neural circuits underlying alternating rhythmic motor activity of the embryonic chick spinal cord. © 1994 Wiley‐Liss, Inc.
Highly selective effects of nerve growth factor, brain‐derived neurotrophic factor, and neurotrophin‐3 on intact and injured basal forebrain magnocellular neurons
Authors: Koliatsos Vassilis E. , Price Donald L. , Gouras Gunnar K. , Cayouette Michelle H. , Burton Louis E. , Winslow John W.
Published: January 2005

Cholinergic neurons of the basal nucleus complex (BNC) respond to nerve growth factor (NCF), the first member of a polypeptide gene family that also includes brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3), and neurotrophin‐4/5 (NT‐4/5), NGF, BDNF, and NT‐3 are enriched in hippocampus. In addition, NGF and, more recently, BDNF have been shown to stimulate the cholinergic differentiation and enhance the survival of BNC cells in vitro. The present investigation was designed to test, in a comparative fashion, the in vivo effects of human recombinant NGF, BDNF, and NT‐3 with confirmed activities in vitro on cholinergic and γ‐aminobutyric acid (GABA)‐ergic BNC neurons. The specific questions asked were whether and, to what extent, biologically active recombinant neurotrophins stimulate the transmitter phenotypes of intact cholinergic and GABAergic neurons of the BNC, and whether, and to what extent, recombinant neurotrophins protect the transmitter phenotypes of axotomized cholinergic and GABAergic neurons of the BNC following complete transections of the fimbria‐fornix (measured by ChAT mRNA hybridization). Our results confirm the profound stimulatory and p75NGFRexpression in both intact and axotomized cholinergic neurons and to exert minor effects on some cholinergic markers (e.g., ChAT immunoreactivity). NT‐3 had no influence on GABAergic neurons. Taken together, these results indicate that, despite their significant sequence homologies and their shared abundance in target fields of BNC neurons, NGF, BDNF, and NT‐3 show striking differences in their efficacies as cholinergic trophic factors. GABAergic neurons of the BNC are resistant to neurotrophins. The result of the present investigation establish that NGF excels among neurotrophins as a trophic factor for intact and injured basal forebrain cholinergic neurons. © 1994 Wiley‐Liss, Inc.
Regional distribution of GABAA receptor binding sites in cat somatosensory and motor cortex
Authors: Schwark Harris D. , Li Jianying , Fuchs Jannon L.
Published: January 2005

Inhibition in primary sensory cortex plays a role in neuronal response to periperal stimuli. For many neurons in cat primary somatosensory cortex, blockade of GABAA receptors by bicuculline results in receptive field enlargement. The magnitude of this effect varies with the neuron's adaption characteristics and its location in particular laminae and submodality regions. To test whether these variation are correlated with the distribution of GABAA receptors, we analyzed [3H] muscimol binding in cat primary somatosensory and motor cortical areas. The highest levels of binding were in layers IV was distinguished by highest levels were in layers V–VI. In somatosensory cortical areas, layer IV, levels of binding were significantly higher in posterior area 3b than in anterior area 3b. These difference may correspond to the rapidly adaption and slowly adapting submodality regions which have been described in this area. The laminar distribution of [3H] muscimol binding differed from that of [3H]flunitrazepam, and neither resembled the distribution of magnitude of bicuculline's effects on receptive field size. The laminar distribution of [3H] muscimol binding was highly correlated with the area density of GABA‐immunoreactive neurons described in a companion study. © 1994 Wiley‐Liss, Inc.
Synaptology of physiologically identified ganglion cells in the cat retina: A comparison of retinal X‐ and Y‐cells
Authors: Weber A. J. , Stanford L. R.
Published: January 2005

It has long been known that a number of functionally different types of ganglion cells exist in the cat retina, and that each responds differently to visual stimulation. To determine whether the characteristic response properties of different retinal ganglion cell types might reflect differences in the number and distribution of their bipolar and amacrine cell inputs, we compared the percentages and distributions of the synaptic inputs from bipolar and amacrine cells to the entire dendritic arbors of physiologically characterized retinal X‐ and Y‐ cells. Sixty‐two percent of the synaptic input to the Y‐cell was from amacrine and bipolar cells. We found no significant difference in the distributions of bipolar or amacrine cell inputs to X‐ and Y‐ cells, or ON‐center and OFF‐center cells, either as a function of dendritic branch order or distance from the origin of the dendritic arbor. While, on the basis of these data, we cannot exclude the possibility that the difference in the proportion of bipolar and amacrine cell input contributes to the functional differences between X‐ and Y‐ cells, the magnitude of this difference, and the similarity in the distributions of the input from the two afferent cell types, suggest that mechanisms other than a simple predominance of input from amacrine or bipolar cells underlie the differences in their response properties. More likely, perhaps, is that the specific response features of X‐ and Y‐ cells originated in differences in the visual responses of the bipolar and amacrine cells that provides their input, or in the complex synaptic arrangements found among amacrine and bipolar cell terminals and dendrites of specific types of retinal ganglion cells. © 1994 Wiley‐Liss, Inc.
Distinct spatiotemporal expressions of five NMDA receptor channel subunit mRNAs in the cerebellum
Authors: Watanabe Masahiko , Mishina Masayoshi , Inoue Yoshiro
Published: January 2005

The distribution of five NMDA receptor channel subunit mRNAs was examined in the mouse cerebellum from embryonic day 13 through postnatal day 56, by in situ hybridization with subunit‐specific oligonucleotide probes. At postnatal days 21 and 56, each cerebellar neuron displayed differential expressions of the ∈ subunit mRNAs. The granule cells showed hybridizing signals for the ∈1 and ∈3 subunit mRNAs, the molecular layer neurons for the ∈4 subunit mRNA, and the cerebellar nucleus neurons for the ∈1 and ∈4 subunit mRNAs, whereas the Purkinje cells did not express any ∈ subunit mRNAs. At early postmitotic stages of development, the ∈2 subunit mRNA appeared in each cerebellar neuron, including the Purkinje cells, and the ∈4 subunit mRNA appeared in neurons of the molecular layer and the cerebellar nuclei. The expression patterns in the cerebellum altered drastically during the first 2 postnatal weeks: the ∈1 and ∈3 subunit mRNAs appeared in the granule cells and the cerebellar nucleus neurons, whereas the ∈2 subunit mRNA disappeared from each neuron and the signal levels of the ∈4 subunit mRNA decreased remarkably. In contrast to the differential expressions of the four ∈ subunit mRNAs, intense signals for the ζ 1 subunit mRNA were observed in each cerebellar neuron from early postmitotic stages through the mature stage. These findings suggest that anatomical organization of the ∈ subunits is heterogeneous in the cerebellum both spatially and temporally, which would give rise to functional diversity of the NMDA receptor channel. © 1994 Wiley‐Liss, Inc.
Synaptic relationships between dopaminergic afferents and cortical or thalamic input in the sensorimotor territory of the striatum in monkey
Authors: Smith Y. , Bennett B. D. , Bolam J. P. , Parent A. , Sadikot A. F.
Published: January 2005

The cerebral cortex and the intralaminar thalamic nuclei are the major sources of excitatory glutamatergic afferents to the striatum, whereas the midbrain catecholaminergic neurones provide a dense intrastriatal plexus of dopamine‐containing terminals. Evidence from various sources suggests that there is a functional interaction between the glutamate‐ and dopamine‐containing terminals in the striatum. The aim of the present study was to determine the synaptic relationships between cortical or thalamic inputs and the dopaminergic afferents in the sensorimotor territory of the monkey striatum. To address this issue, anterograde tracing in combination with immunocytochemistry for tyrosine hydroxylase (TH) was carried out by light and electron microscopy.

Squirrel monkeys received injections of biocytin in the primary motor and somatosensory cortical areas or injections of eitherPhaseolus vulgaris‐leucoagglutinin (PHA‐L) or biocytin in the centromedian nucleus (CM) of the thalamus. Sections that included the striatum were processed to visualize the anterograde tracers alone or in combination with TH immunoreactivity. The anterogradely labelled fibres from the cerebral cortex and CM display a band‐like pattern and are exclusively confined to the postcommissural region of the putamen, whereas TH‐immunoreactive axon terminals are homogeneously distributed throughout the entire extent of the striatum. Electron microscopic analysis revealed that the anterogradely labelled terminals from the cerebral cortex form asymmetric synapses almost exclusively with the heads of dendritic spines. The thalamic terminals also form asymmetric synapses, but in contrast to cortical fibres, predominantly with dendrites (67.4%) and less frequently with spines (32.6%). The TH‐immunoreactive boutons are heterogeneous in morphology. The most common type (84% of the total population) forms symmetric synapses; of these the majority is in contact with dendritic shafts (72.1%), less with spines (22.5%) and few with perikarya (5.4%). In sections processed to reveal anterogradely labelled cortical fibres and TH‐immunoreactive structures, individual spines of striatal neurones were found to receive convergent synaptic inputs from both cortical and TH‐immunoreactive boutons. In contrast, anterogradely labelled thalamic terminals and TH‐immunoreactive boutons were never seen to form convergent synaptic contacts on the same postsynaptic structure.

These findings suggest that the dopaminergic afferents are located to subserve a more specific modulation of afferent cortical input than afferent thalamic input in the sensorimotor territory of the striatum in primates. © 1994 Wiley‐Liss, Inc.
Changes in fiber order in the optic nerve and tract of rat embryos
Authors: Chan S. O. , Guillery R. W.
Published: January 2005

In order to define the extent to which retinotopic order in the optic pathways may contribute to fiber segregation at the chiasm or to the formation of central maps, the arrangement of fibers in the optic nerve and tract of rat embryos, on embryonic days 16.5 and 18.5, has been studied by placing a small granule of Dil in one of the four quadrants of the retina and tracing the filled fibers through transverse sections of the retinofugal pathway with confocal microscopy. There is a distinct quadrant‐specific order in the optic stalk immediately behind the eye, with fibers from the ventral nasal, dorsal nasal, dorsal temporal, and ventral temporal retina arranged sequentially across the rostrocaudal axis of the cross section of the stalk. However, this distinct order is not maintained very far. There is a gradual increase in the degree of overlap between fibers from the different quadrants as the fibers pass towards the chiasm. The dorsal groups of fibers intermingle extensively along almost the entire length of the stalk, but the fibers from ventral sectors remain separate until they reach the prechiasmatic region, where the ventral temporal and the ventral nasal fibers spread the throughout the rostrocaudal extent of the stalk and the chiasm. The initial quadrant‐specific order is completely lost at the chiasm. However, beyond the optic chiasm, the fibers are reorganized into another distinct order. In the optic tract, there is a segregation of dorsal from ventral fibers, but the nasal and temporal groups remain intermingled.

The results of this study indicate that the earliest fibers in the developing optic tract are arranged according to topographical rules that differ from those obtaining behind the eye. Since all topographical order is lost between these two levels, there must be an active storing mechanism in the region where the chiasm joins the tract. Possibly this mechanism is related to the development of the dorsoventral axis of the topographic maps in the central visual targets. © 1994 Wiley‐Liss, Inc.
Extent and time course of restoration of descending brainstem projections in spinal cord‐transected lamprey
Authors: Davis G. R. , McClellan Andrew D.
Published: January 2005

The purpose of the present study was to determine the numbers of descending brainstem projections to different levels of the spinal cord in normal larval sea lamprey (Petromyzon marinus) and to examine the restoration of these projections in animals 3–32 weeks after transection of the rostral spinal cord ( ∼ 10% of body length). In normal animals approximately 1, 250, 900, and 825 brainstem neurons projected to 20%, 40%, and 60% of body length, respecively. Spinal projections originated from the diencephaln, mesencephalon, three rhombencephalic reticular nuclei, Müller and Mauthner neurons, and four cell groups in the caudal rhombencephalon. In spinal cord‐transected animals the number of brainstem neurons projecting to 20% of body length increased with recovery time, and at 32 weeks post‐transection the total number and distribution of brainstem neurons was not significantly differnt from normal animals. Brainstem projections first appeared at 40% of body length by 8 weeks post‐transection, and were present at 60% of body length by 32 weeks post‐transection. There was substantial restoration of brainstem projections to 40% of body length but limited restoration to 60% of body length. The ∼ 50 brainstem neurons, including some Müller cells, that projected to 60% of body length at 32 weeks post‐transection indicate that restoration of descending projections in excess of 50 mm can occur within the central nervous system of this vertebrate. These anatomical results are discussed in relation to the time course of recovery of locomotor functions in spinal cord‐transected lampreys. © 1994 Wiley‐Liss, Inc.
Anatomical organization of the limb premotor network in the turtle (Chrysemys picta) revealed by in vitro transport of biocytin and neurobiotin
Authors: Sarrafizadeh Ramin , Houk James C.
Published: January 2005

The in vitro turtle brainstem‐cerebellum preparation has been a valuable tool in the study of central motor programs. In the present study, we investigate the anatomical organization of the turtle rubrocerebellar limb premotor network and its sensory connections in vitro by combining the rapid anterograde and retrograde transport of neurobiotin and biocytin with the extended viability of the isolated turtle brainstem‐cerebellum. These compounds retrogradely labeled soma, dendrites, and axons, and orthogradely labeled axons and, to a lesser extent, terminals.

The chelonian red nucleus receives a dense input form the contralateral lateral cerebellar nucleus and projects heavily to the contralateral spinal cord. Rubral axons sparsley innervate the lateral cerebellar nucleus and project heavily to the lateral reticular nucleus. Lateral reticular axons heavily innervate the lateral cerebellar nucleus before terminating in the pars laterlalis of the cerebellar cortex as mossy fibers. These prominent, recurrent loops among the lateral cerebellar nucleus, red nucleus, and lateral reticular nucleus constitute the turtle rubrocerebellar limb premotor network.

Sensory inputs to the red nucleus orginate in the contralateral dorsal column nuclei, the principle trigeminal nucleus, and the spinothalamic system. These sites project bilaterally to the lateral reticular nucleus. The lateral cerebellar nucleus receives a contralateral input from the dorsal column nuclei. The red nucleus projects sparsely to the dorsal column nuclei.

The red nucleus also receives an ipsilateral descending projection from the suprapeduncular nucleus, located in the diencephalon, and an ascending input from the rostral rhombencephalic reticular formation. An ipsilateral descending pathway originating in the red nucleus is likely to be the rubro‐olivary tract. © 1994 Wiley‐Liss, Inc.
Distributions of GABAA, GABAB, and benzodiazepine receptors in the forebrain and midbrain of pigeons
Authors: Veenman C. Leo , Albin Roger L. , Richfield Eric K. , Reiner Anton
Published: January 2005

Autoradiographic and immunohistochemical methods were used to study the distributions of GABAA, GABAB and benzodiazepine(BDZ) receptors in the pigeon fore‐ and midbrain. GABAA, GABAB and BDZ binding sites were found to be abundant although heterogeneously distributed in the telencephalon. The primary sensory areas of the pallium of the avian telencephalon (Wulst and dorsal ventricular ridge) tended to be low in all three binding sites, while the surrounding second order belt regions of the pallium were typically high in all three. Finally, the outermost rind of the pallium (termed the pallium externum by us), which surrounds the belt regions and projects to the striatum of the basal ganglia, was intermediate in all three GABAergic receptors types. Although both GABAA and benzodiazepine receptors were abundant within the basal ganglia, GABAA binding sites were densest in the striatum and BDZ binding sites were densest in the pallidum. Among the brainstem regions receiving GABAergic basal ganglia input, the anterior and posterior nuclei of the ansa lenticularis showed very low level of all three receptors, while the lateral spiriform nucleus and the ventral tegmental area/substantia nigra complex contained moderate abundance of the three binding sites. The dorsalmost part of the dorsal thalams (containing nonspecific nuclei) was rich all three binding sites, while the more ventral part of the dorsal thalamus (containig specific sensory nuclei), the ventral thalamus and the hypothalamus were poor in all three binding sites. The pretectum was also generally poor in all three, althrough some nuclei displayed higher level of one or more binding sites. The optic tectum, inferior colliculus, and central gray were rich in all three sites, while among the isthmic nuclei, the parvicellular isthmic was nucleus was conspicuously rich in BDZ sites. The REsults show a strong correlation of the regional abundance of GABA binding sites with previously described distributions of GABAergic fibers and terminals in the avaian forebrain and midbrain. The distribution of these binding sites is also remarkably similar to that in mammals, indicating a conservative evolution of forebrain and midbrain GABA systems systems among amniotes. © 1994 Wiley‐Liss, Inc.
Catecholaminergic systems in the zebrafish. II. Projection pathways and pattern of termination of the locus coeruleus
Authors: Ma PoKay M.
Published: January 2005

The locus coeruleus is a widely projecting isthmal noradrenergic nucleus. In the zebrafish, it consists of between three and ten neurons, most of which have multiple, bilaterally projecting axons. Immunohodolgical studies show that the locus coeruleus provides most, if not all, of the noradrenergic innervation of the brain rostral to the isthmus. The pathways and targets in the zebrafish are similar to ascending coeruleal projections of other vertebrates. Axons ascend through two amin pathways: the longitudinal catecholamine bundle and the periventricular catecholamine pathway. The former is a dense meshwork of varicosity‐bearing axons which ascends along the lateral longitudinal fasciculus into the mesencephalon. In the posterior tuberal area, this bundle dives ventrally and assumes a lateral position. In the diencephalon, it takes up a position ventral to the medial forebrain bundle, and follows this bundle into the telencephalon, where it joins the medial olfactory tract to enter the olfactory bulb. The periventricular catecholamine pathway is a diffuse pathway consisting of thick, smooth axons. It is associated with the medial longitudianl fasciculus. Rostral to the nucleus of the medial longitudinal fasciculus, this pathway joins the longitudinal catecholamine bundle around the medial forebrain bundle. The Periventricular pathway gives rise to coarse terminal arbors with large but sparse varicosities, whereas the longitudinal catecholamine bundle gives rise to terminal plexuses with fine and dense fibers and varicosities. Among the more densely innervated regions are the raphé nucleus, the interpeduncular nucleus, the torus semicircularis, parts of the hypothalamus, and the suprachiasmatic and preoptic areas. The tours longitudinalis, optic tectum, cerebellum, habenular complex, the dorsomedial zone of area dorsalis telencephali, and the olfactory bulb are moderately innervated. The nucleus glomerulosus, the torus lateralis and lateral subnuclei of the nucleus diffusus, and the anterior tuberal nucleus are devoid of noradrenergic innervation. © 1994 Wiley‐Liss, Inc.
Developmental distribution of GFAP and vimentin in the Brazilian opossum brain
Authors: Elmquist Joel K. , Swanson Jack J. , Sakaguchi Donald S. , Ross Lynne R. , Jacobson Carol D.
Published: January 2005

Cells of glial origin are involved in the morphogenesis of the mammalian central nervous system (CNS). Characterization of glial‐associated proteins during neurogensis and differentiation may aid in understanding the complexity of CNS development. We have utilized immunoblotting and immunohistochemistry to characterize the developmental profiles of glial fibrillary acidic protein (GFAP) and vimentin (VIM) in the brain of the Brazilian opossum, Monodelphis domestica. Typical of marsupials, CNS morphogenesis and neurogenesis in the opossum extend well into the postnatal period. Opossum GFAP and VIM were found as single bands at molecular weights consistent with those reported for other species, thus indicating conservation of the VIM and GFAO proteinns through mammalian evolution. Differential developmental trends were observed for both proteins with relative VIM levels decreasing and GFAP levels increasing with age. Vimentin‐like immunoreactivity (VIM‐IR) was present at day 1 of postnatal life throughout the brain. The density of VIM‐IR was maximal at 10 and 15 days postnatal (especially in radial glial elements) and decreased slightly by 25 days postnatal. In the adult brain, VIM‐IR was markedly reduced compared to that of younger ages. In contrast, GFAP‐like immunoreactivity (GFAP‐IR) in the brain of Monodelphis increased dramatically with age. No GFAP‐IR was observed in the 1 and 5 day postnatal brains. By 25 days postnatal, the pattern of GFAP‐IR in the brainstem resembled that of the adult. In the forebrain, more GFAP‐IR was present than at younger ages. The adult distribution of GFAP‐IR was very similar to that reported for other mammalian species. These results indicate that GFAP and VIM are reciprocally related during periods of morphogenesis and differentiation of the opossum brain. © 1994 Wiley‐Liss, Inc.
Functional architecture of vestibular primary afferents from the posterior semicircular canal of a turtle,Pseudemys (Trachemys) scripta elegans
Authors: Brichta A. M. , Peterson E. H.
Published: January 2005

Physiological studies inmany vertebrates indicate that vestibular primary afferents are not a homogeneous population. Such date raise the question of what structural mechanisms underlie these physiological differeneces and what functional role is played by afferents of each type. We have begun to answer these questions by characterizing the architecture of 110 afferents innervating the posterior canal ofPseudemys scripta.We emphasize their spatial organization because experimental evidence suggests that afferent physiological properties exhibit significant spatial heterogeneity.

The sensory surface of the posterior canal comprises paired, triangular hemicristae, which are innervated by two afferent types. Bouton afferents (66% of total afferents) are found over the entire sensory surface. They differ significantly in the shape and size of their collecting areas, number of boutons, soma size, and axon diameter; this morphological variation is systematically related to the afferent's spatial postion. In addition, multivariate analyses suggest that bouton afferents may comprise two subtypes: α afferents have delicate processes and are found throughout the crista; β afferents are more robust and are concentrated preferentially toward the canal center. Calyx‐bearing afferents comprise two morphological subtypes: dimorphs (13% of total afferents) bear calyceal and bouton endings; calyceal afferents (21%) bear calyceal endings only. Both types occur exclusively in an elliptical region near the center of each hemicrista; their morphology varies with radial distance from the center of this elliptical region.

Our data provide evidence that inPseudemys:(1) the classical vestibular afferents types (bouton, calyx, dimorph) are structurally heterogeneous, and (2) their spatial sampling characteristic are highly structured and distinctive for each type. These spatial patterns may shed light on regional differences in physiological profiles of vestibular afferents, and they raise questions about the role of this spatial heterogeneity in signaling head movement. © 1994 Wiley‐Liss, Inc.
Contralateral thalamic projections predominantly reach transitional cortices in the rhesus monkey
Authors: Dermon C. R. , Barbas H.
Published: January 2005

Connections between the thalamus and the cortex are generally regarded as ipsilateral, even though contralateral connections exist as well in several adult mammalian species. It is not known however, whether contralateral thalamocortical projections reach particular cortices or whether they emanate from specific nuclei. In the rhesus monkey different types of cortices, ranging from transitional to eulaminate, vary in their cortical connectional pattern and may also differ in thier thalamic connections. Because olfactory and transitional prefrontal cortices receive widespread projections, we investaged whether they are the target of projections from the contralateral thalamus as well. With the aid of retrograde tracers, we studied the thalamic projections of primary olfactory (olfactory tubercle and prepiriform cortex) and transitional orbital (areas PAPP, Pro 13) and medial (areas 25, 24, 32) areas, and of eulaminate (areas 11, 12, 9) cortices for comparison.

To determine the prevalence of neurons in the contralateral thalamus, we compared them with the ipsilateral in each case. The pattern of ipsilateral thalamic projections differed somewhat among orbital, medial, and olfactory cortices. The mediodorsal nucleus was the predominant source of projections to orbital areas, midline nuclei included consistently about 25% of the thalamic neurons directed to medial transitional cortices, and primary olfactory areas were distinguished by receiving thalamic projections predominantly from neurons in midline and intralaminar nuclei.

Notwithstanding some broad differences in the ipsilateral thalamofrontal projections, which appeared to depend on cortical location, the pattern of contralateral projections was thalamus were noted in midline, the magnocellular sector of the mediodorsal nucleus, the anterior medial and intralaminar nuclei, and ranged from 0 to 14% of the ipsilateral; they were directed primarily to olfactory and transitional orbital and medical cortices but rarely projected to eulaminate areas. Several thalamic nuclei projected from both sides to olfactory and transitional areas, but issued only ipsilateral projections to eulaminate areas. Though ipsilateral thalamocortical projections predominate in adult mammalian species, crossed projections are a common feature in development. The results suggest differences in the persistence of contralateral thalamocortical interactions between transitional and eulaminate cortices. © 1994 Wiley‐Liss, Inc.
Immunocytochemical localization of the GABAA receptor in the cerebral cortex of the lizard Psammodromus algirus
Authors: Guirado Salvador , Dávila Jose Carlos
Published: January 2005

This study examined the distribution and localization of the γ‐aminobutyric acid (GABA)A receptor in the brain cortex of a reptile by light and electron microscopy, to test whether cortical GABA inhibition is mainly mediated through the GABAA receptro complex. We used preembedding immunocytochemistry and a monoclonal antibody, raised against the receptor complex, that recognizes the β2 and β3 subunits of the receptor. GABAA receptors were distributed throughout the entire cerebral restricted to the plexiform layers of the cortex as seen by light microscopy. This granular aspect of the immunoreactivity most likely corresponds to the immunopositive dendritic and axonal profiles observed under the electron microscope. Some neurons in the medial and lateral cortices displayed pathches of immunoreactivity along the cell body and processes, and as a result their morphology was outlined. We discuss the possibility that these neurons were GABAergic as well. The immunocytochemical data demonstrate that the distribution and localization of GABAA receptors in discrete regions of the reptilian cerebral cortex resemble that of parts of the hippocampal formation of humans and rats, suggesting that the basic configuration of the GABA system in these regions is conserved. © 1994 Wiley‐Liss, Inc.
Expression of Mu opioid receptor mRNA in rat brain: An in situ hybridization study at the single cell level
Authors: Delfs Jill M. , Kong Haeyoung , Mestek Anton , Chen Yan , Yu Lei , Reisine Terry , Chesselet Marie‐Françoise
Published: January 2005

The mu (μ) opioid receptors, which mediate the effects of morphine, are widely distributed in brain. We have examined the distribution of mRNA encoding a μ opioid receptor in rat brain with in situ hybridization histochemistry at the single‐cell level to obtain information about the cell types synthesizing this receptor. Only neurons, not glia, were labeled in discrete brain regions. High levels of labeling were detected in the thalamus, striosomes of the caudateputamen, globus pallidus, and brain regions involved in nociception, arousal, respiratory control, and, possibly, addiction. The general distribution of the receptor mRNA paralleled that of μ opioid binding sites with some notable exceptions. These include the cerebral cortex, which contains binding sites, but very few labeled neurons. No labeling was observed in the cerebellum, a region devoid of μ binding sites. Three main findings emerged from these experiments: (1) the mRNA was present in regions mediating both the therapeutic (analgesia) and the unwanted (respiratory depression, addiction) effects of morphine, (2) the mRNA was very densely expressed by neurons known to receive dense enkephalin‐containing inputs, and (3) the dissociation between the presence of binding sites and absence of mRNA in some brain regions supports a presynaptic localization of μ opioid receptors in these areas. Alternatively, other subtypes of μ opioid receptors may be encoded by a different mRNA. These results provide new insights into the receptor types and neuronal circuits involved in the effects of endogenous opioids and morphine. © 1994 Wiley‐Liss, Inc.
Ontogenesis and taste bud cell turnover in the chicken. I. Gemmal cell renewal in the hatchling
Authors: Ganchrow Donald , Ganchrow Judith R. , Romano Rafael , Kinnamon John C.
Published: January 2005

Taste bud cell turnover rate was examined in oral epithelium of the precocial chick, which at hatching contains the adult complement of taste buds. Forty newly hatched chicks received single or double pulse injections of tritiated thymidine (specific activity was 6.7 Curies/ millimole; dosage was 0.5 micro Curies/g body weight, intraperitoneally). Anterior mandibular epithelium was processed for light microscopic autoradiography at 2 and 16 hours, as well as 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, and 20 days after the initial pulse. In a coded and randomized procedure, the section (7 μm) through the bud's center was selected for counting > 6 silver grains over round‐clear and gracile‐dense gemmal cell nuclei. The mean number of labelled cells/bud varied significantly (P ⩽ 0.01) during the first four posthatch days, yielding the fastest gemmal cell turnover rates (3.4–4.4 days) yet reported in vertebrates.

Average bud diameter also significantly changed during the first four posthatch days, and was reflected in shifts of the distribution of 40–69 μm and > 70 μm diameter buds. Both an increase in labelled bud cells and bud diameter during the first two posthatch days may reflect high proliferation rates in initially maturing buds. Subsequent decrease in bud diameter between 2 and 3 days postinjection may indicate splitting of large‐diameter (≥ 70 μm) buds and/or normal bud cell death due to failure of sensory afferentation. Bud‐splitting alone, however, cannot account for significant decreases in bud cell label which did not occur before 4–6 days postinjection. © Wiley‐Liss, Inc.
Antibodies against different forms of GnRH distinguish different populations of cells and axonal pathways in a urodele amphibian, Taricha granulosa
Authors: Muske Linda E. , Moore Frank L.
Published: January 2005

Neurons immunoreactive to the peptide hormone gonadotropin‐releasing hormone (GnRH) have been identified in the posterior diencephalon or anterior midbrain of diverse vertebrates. These cells are located caudal to the more well‐characterized GnRH neurons in the nervus terminalis and septo‐preoptic area, and are believed to express one or more of the nonmammalian forms of the GnRH. The present study utilized immunocytochemical techniques to determine whether the posterior GnRH group is present in a urodele amphibian, the newt Taricha granulosa. Antibodies directed against different molecular forms of GnRH were used to evaluate the immunological properties of GnRH‐containing neurons in amphibians. An antibody selective for mammalian GnRH labeled perikarya in the nervus terminalis (terminal nerve) and septo‐preoptic region, as described previously. Thick fibers that arise from terminal nerve and septo‐preoptic neurons project mainly to the median eminence, medial pallium and habenula. An antibody selective for chicken GnRH II labeled cell bodies in the paraventricular organ and posterior tubercle of the caudal diencephalon, and thin fibers that project widely throughout the central nervous system. Region‐specific staining with different GnRH antibodies supports the interpretation that different molecular forms of GnRH are expressed by neuroanatomically distinguishable systems. © 1994 Wiley‐Liss, Inc.
Imaging of individual normal and regenerating optic fibers in the brain of living adult goldfish
Authors: Danks Anne M. , Kim Patricia , Wang Ziren , Meyer Ronald L.
Published: January 2005

Retinal arbors in the tectum of living adult goldfish were imaged to determine whether the structural remodelling and refinement that occurs during development continues in adulthood. Individual optic fibers were labelled by making small injections of the lipophilic fluorescent dye DiI into ventral retina and viewing the exposed tectum through a fluorescence microscope equipped with a cooled CCD camera. Arbors were imaged in the living fish every 30–60 minutes for up to 7 hours.

Normal adult goldfish showed no evidence of arbor remodelling during this period, though dynamic movements of varicosities present along axon segments were observed. For comparison, regenerating optic fibers were similarly imaged in fish that had undergone optic nerve crush 2–6 weeks previously. In these fish, dynamic structural changes were seen, including branch remodelling, extension and retraction of growth cones, and movement of varicosities. © 1994 Wiley‐Liss, Inc.