bluuebunny/crossref_metadata_2025 huggingface dataset:
Tyrosine hydroxylase containing neurons lacking aromatic amino acid decarboxylase in the hamster brain
Authors: Vincent Steven R. , Hope Bruce T.
Published: January 2005

We have recently described populations of tyrosine hydroxylase‐immunoreactive neurons in the hamster brain in regions not known to contain catecholamine cell bodies. In the present study, the nature of the tyrosine hydroxylase immunoreactivity in the hamster brain was determined. In addition, these tyrosine hydroxylase‐immunoreactive cell groups were examined for their ability to express aromatic amino acid decarboxylase. Immunohistochemistry with two different antibodies to tyrosine hydroxylase identified immunoreactive cell bodies in regions known to contain catecholamine neurons, including the substantia nigra and locus ceruleus. In addition, tyrosine hydroxylase‐immunoreactive neurons were observed in other regions, including the basal forebrain, inferior colliculus, lateral parabrachial nucleus, and dorsal motor nucleus of the vagus. Western blotting indicated that hamster brain contained only one immunoreactive molecule, very similar in size to rat tyrosine hydroxylase. Thus it is likely that the immunohistochemical studies stained authentic hamster tyrosine hydroxylase. Indeed, in situ hybridization studies using a synthetic oligonucleotide probe against tyrosine hydroxylase mRNA resulted in specfic and heavy labelling of these novel tyrosine hydroxylase‐immunoreactive neurons.

When adjacent sections were stained with antibodies to aromatic amino acid decarboxylase, known catecholamine cell groups were stained. However, the novel tyrosine hydroxylase cell groups did not display any aromatic amino acid decarboxylase immunoreactivity. These results suggest that neurons are present in the hamster brain that are able to hydroxylate tyrosine to L‐DOPA, but that lack the ability to decarboxylate aromatic amino acids to produce dopamine or other catecholamines.
Choline acetyltransferase‐immunoreactive profiles are presynaptic to primary sensory fibers in the rat superficial dorsal horn
Authors: Ribeiro‐Da‐Silva A. , Claudio Cuello A.
Published: January 2005

The specific aim of this study was to search for morphological counterparts to the known antinociceptive effects of cholinomimetic drugs at the spinal cord level. For this, the light microscopic and ultrastructural distribution of choline acetyltransferase immunoreactivity was studied in laminae I‐III of the rat cervical spinal cord. Immunoreactivity was present in cell bodies in lamina III, and in dendrites and axons of all three laminae. Immunoreactive axonal varicosities were often presynaptic to the central varicosities of type II synaptic glomeruli in lamina II and lamina III, less often presynaptic to the central elements of type I glomeruli in lamina II, and often presynaptic to dendrites in both type I and type II glomeruli. In addition, immunoreactive dendrites were often postsynaptic to the central varicosities of glomeruli of all morphological types. These results indicate that (1) primary sensory fibers excite cholinergic interneurons; (2) the acetylcholine released by the axon terminals of these interneurons modulates both nociceptive and non‐nociceptive sensory information at the spinal cord level through both pre‐ and postsynaptic mechanisms. Furthermore, our results reinforce current ideas on reciprocal sensory interaction between thick and fine afferent fibers.
Interaural time sensitivity in the inferior colliculus of the albino cat
Authors: Yin T. C. T. , Carney L. H. , Joris P. X.
Published: January 2005

Anatomical studies of the Creel albino cat have demonstrated a pronounced atrophy of cells in the medial superior olive, a structure thought to be important for the detection of interaural time differences (ITDs). We looked for physiological abnormalities in the binaural interaction of cells in three albino cats by recording from single cells in the central nucleus of the inferior colliculus to ITDs of tones and noise. We found that the sensitivity to ITDs of tones and noise was somewhat diminished in the albino cats as compared to normally pigmented cats, though this deficit was only evident when a population of cells was examined. The range of sensitivity of individual cells for both tones and noise was the same in albinos and pigmented animals. Our anatomical measurements showed a smaller reduction in cross‐sectional area of cells in the medial superior olive than that reported earlier, and the cell bodies in the medial superior olive of the albinos were less elongated than in normal cats.
Cutaneous dermatomes for initiation of three forms of the scratch reflex in the spinal turtle
Authors: Mortin Lawrence I. , Stein Paul S. G.
Published: January 2005

The turtle spinal cord produces three forms of the hindlimb scratch reflex. Each scratch form is intiated in response to gentle mechanical stimulation of a distinct set of sites in the periphery, termed the receptive field for that scratch form. The turtle spinal cord consists of 8 cervical segments (C1‐C8), 10 dorsal segments (D1‐D10), 2 sacral segments (S1, S2), and about 16 caudal segments (Ca1‐Ca16). First, we recorded cutaneous afferents in peripheral nerves to reveal the tactile dermatomes of segments D3‐D8. These segments innervate regions of the body between the forelimb and hindlimb, directly lateral to their spinal cord segments. Adjacent segments innervate adjacent and partially overlapping regions of the periphery. Second, we used successive spinal cord transections combined with either (a) behavioral analysis in turtles with limb movements or (b) electroneurographic recordings in immobilized turtles, and mapped the zone of remaining sensibility after each transection to measure the borders of dermatomes D2‐Ca2. This technique revealed that adjacent dermatomes are innervated by non‐adjacent spinal segments in regions near the hip. Segments D8 and Ca1 innervate adjacent and partially overlapping regions ventral to the hip. There is a similar discontinuity in the innervation of the shell and skin dorsal to the hip. These discontinuities correlate with the innervation of the hindlimb skin by segments D8‐Ca1.

The rostral scratch receptive field is innervated by sensory afferents entering spinal segments D3‐D6; the pocket scratch receptive field is innervated by D6‐D8; the caudal scratch receptive field is innervated by S2, Ca1, and more caudal segments. The rostral‐pocket transition zone is innervated mainly by one segment, D6; the ventral part of the caudal‐pocket transition zone is innervated by two non‐adjacent segments, D8 and Ca1. Thus the motor pattern blends elicited by stimulation of sites within the rostral‐pocket transition zone must be produced in response to a very different distribution of sensory inputs than the blends elicited by stimulation of sites within the caudalpocket transition zone.
Glial fibrillary acidic protein and vimentin immunohistochemistry in the developing and adult midbrain of the lizard Gallotia galloti
Authors: Monzon‐Mayor M. , Yanes C. , Ghandour M. S. , De Barry J. , Gombos G.
Published: January 2005

The distribution of glial fibrillary acidic protein (GFAP)‐and vimentin‐containing cells was studied by immunohistochemistry in the midbrain of the lizard Gallotia galloti. At embryonic stage 32 (E32), vimentin immunoreactivity appeared first in cell bodies located in the ventricular walls, in radial fibers, and subpial end‐feet and increased in these structures until E34/E35. Faint GFAP immunoreactivity gradually appeared in the same structures between E34 and E37, and this increased until adulthood, whereas vimentin immunoreactivity decreased after E35, becoming limited to a few end‐feet and fibers in the adult, mainly in the tegmentum. Thus, in developing Gallotia midbrain a shift from vimentin‐containing to GFAP‐containing intermediate filaments begins around E36 or E37. At E40, in addition to the cell bodies in the ependymal area, dispersed GFAP‐positive cells, possibly immature astrocytes appeared. These cells showed the same shift. In the adult lizard, GFAP‐positive radial glia are still present and coexist with GFAP‐positive astrocytes, which are prefentially located in the marginal optic tract and the oculomotor nuclei, but are absent in the fasciculus longitudinalis medialis. Optic tectum, pretectum, tegmentum, and isthmic nuclei are the areas richest in GFAP‐positive radial fibers: these were much less abundant in the deep mesencephalic nuclei. Thus, in this lizard, GFAP‐positive astrocytes display a clear cut regional distribution: they are present in mesencephalon, whereas they are absent in telencephalon Yanes et al.: J. Comp. Neurol.,′90:295:559–568.
Immunolocalization of cellular retinoic acid binding protein to müller cells and/or a subpopulation of GABA‐positive amacrine cells in retinas of different species
Authors: Milam Ann H. , De Leeuw A. Margreet , Gaur Vinod P. , Saari John C.
Published: January 2005

Retinoic acid (RA) and its specific binding protein, cellular RA binding protein (CRABP), are found in relative abundance in bovine and rat retinas. Since RA does not participate in the visual cycle, the presence of RA and its binding protein in retina suggests that they may be involved in other aspects of retinoid action. As an initial step in identifying the role of RA and its binding protein in retina, monoclonal antibodies were prepared against CRABP purified from bovine retina and used to localize this antigen by immunocytochemistry in retinas of different species. Human and monkey retinas showed specific cytoplasmic labeling of Müller cells. Cat, bovine, rabbit, rat, turtle, and chick retinas showed specific cytoplasmic labeling of some somata in the inner nuclear and ganglion cell layers and characteristic strata in the inner plexiform layer. Cat and bovine retinas also showed cytoplasmic labeling of Müller cells. Immunoreactivity in these species was absent with nonimmune serum or abolished when the antibodies were preabsorbed with purified antigen. Chameleon, goldfish, and frog retinas were nonreactive.

We used double‐labeling immunofluorescence experiments to determine if the CRABP‐positive cells were also positive for known neurotransmitters or associated enzymes. CRABP‐positive amacrine cells of cat, cow, rabbit, rat, and chick represented a subset of the more numerous γ‐aminobutyric acid (GABA)‐positive amacrine cells. However, turtle CRABP‐positive amacrine cells were negative for GABA despite the fact that turtle retina contains many GABA positive cells. CRABP‐positive amacrine cells in rat retinas were not immunoreactive for glycine, choline acetyltransferase, somatostatin, or tyrosine hydroxylase.

To test whether CRABP‐positive somata in the ganglion cell layer were ganglion cells, we retrogradely labeled the ganglion cells of rat retinas with rhodamine dextran. No rhodamine labeled ganglion cells were positive with anti‐CRABP, indicating that the CRABP‐positive cells in the ganglion cell layer are probably amacrine cells.

Other retinoid binding proteins thought to be involved in the visual cycle have been localized to Müller and retinal pigment epithelium cells. This study reveals that CRABP immunoreactivity is present in Müller and/or amacrine cells, depending on the species. CRABP immunoreactivity in amacrine cells of certain species was an unanticipated and provocative result. Its significance remains to be determined.
Hippocampal and midline thalamic fibers and terminals in relation to the choline acetyltransferase‐immunoreactive neurons in nucleus accumbens of the rat: A light and electron microscopic study
Authors: Meredith Gloria E. , Wouterlood Floris G.
Published: January 2005

The synaptic interactions between terminals of allocorticostriatal and thalamostriatal fibers and the cholinergic neurons in the nucleus accumbens were investigated using degeneration and dual labelling immunocytochemistry in Wistar rats. The presumptive cholinergic neurons were labelled with antibodies directed against choline acetyltransferase and the afferent fibers were labelled anterogradely with Phaseolus vulgaris‐leucoagglutinin.

Fibers from the subiculum of the hippocampal formation and from the midline and intralaminar thalamus project densely into the medial nucleus accumbens where they overlap a relatively dense population of choline acetyltransferase‐immunoreactive neurons. Varicosities containing Phaseolus vulgaris‐leucoagglutinin juxtapose the immunoreactive neurons.

To study the possibility that the cholinergic neurons could be the synaptic targets of these incoming fibers, the subiculum, the fornix, and the midline/intralaminar thalamus were lesioned in separate animals and brain sections were immunoprocessed for choline acetyltransferase and studied with the electron microscope. In addition, dual‐labelling electron microscopic immunocytochemistry was employed. In total, 164 synaptic terminals from the subiculum/hippocampus and 130 from the midline/intralaminar thalamus were examined; all formed asymmetrical synaptic specializations. No hippocampal endings were seen to contact the somata or primary dendrites of the choline acetyltransferase‐immunoreactive neurons; however, three were found in synaptic contact with distal, immunolabelled dendritic shafts. Most hippocampal terminals established contacts with unlabelled spines. Fifteen percent of the thalamic endings were found to synapse on the somata and the primary and distal dendrites of the choline acetyltransferase‐immunoreactive neurons. The remaining thalamic terminals established synaptic junctions with small unlabelled dendrites or spines. These findings have important implications not only for our understanding of the synaptic organization of the hippocampal and thalamic projections to the nucleus accumbens, but also for the contribution of the cholinergic neurons to the circuitry of this nucleus.
Functional recovery after spinal cord hemisection in guinea pigs: The effects of applied electric fields
Authors: Borgens Richard B. , Blight Andrew R. , McGinnis Michael E.
Published: January 2005

Right lateral hemisection of the lower thoracic spinal cord was performed in 216 adult guinea pigs. Animals that proved suitable for the study were divided into one control and two experimental groups. Experimental animals were implanted with intraperitoneal stimulators delivering regulated current of 35 or 50 μA through electrodes placed 1 cm rostral and caudal of the hemisection. The cathode was cranial to the lesion in one group (n= 67) and caudal in the other (n= 33). Control animals (n= 62) were implanted with sham stimulators and electrodes delivering no current. The functional status of the animals was measured by tactile stimulation of the back skin to elicit the cutaneus trunci muscle reflex, and by the vestibulospinal free‐fall response. The cutaneous response ipsilateral and caudal to the lesion was lost following hemisection and did not recover in any of the control animals or in animals with cathode caudal to the lesion. Recovery of the response was found in 9 of 67 animals in the cathode rostral group, between 56 and 139 days after injury. Toe spreading recovered spontaneously in 80–90% of animals in all groups. Of the possible mechanisms of skin reflex recovery, most current evidence points to regrowth of ascending nerve fibers in the lateral funiculus of the spinal cord local to the lesion.
GABA‐like immunoreactivity in the macaque monkey retina: A light and electron microscopic study
Authors: Grünert Ulrike , Wässle Heinz
Published: January 2005

The distribution of GABA‐like immunoreactivity in the macaque monkey retina was studied by using postembedding techniques on semithin and ultrathin sections. At the light microscopic level, both inner and outer plexiform layers showed strong GABA‐like immunoreactivity in the central retina. All the horizontal cells, some bipolar cells, 30–40% of amacrine cells, occasional interplexiform cells, and practically all displaced amacrine cells were labeled. In the peripheral retina (beyond 5 mm eccentricity), the outer plexiform layer and the horizontal cells were not labeled, but all other cell types showed the same labeling pattern as in the central retina.

Synapses of the inner plexiform layer involving a pre‐ or postsynaptic GABA‐labeled process were studied electron microscopically. Synapses involving a GABA‐labeled presynaptic amacrine cell process made up 80% of the synapses observed. These GABA‐labeled amacrine processes synapsed onto amacrine, bipolar, and ganglion cell processes as well as onto amacrine and ganglion cell bodies.

Synapses involving a postsynaptic GABA‐labeled process made up 20% of the synapses studied. The GABA‐like immunoreactive processes were postsynaptic to bipolar cells at the dyads and to amacrine cells at conventional synapses.
Histaminelike immunoreactive neurons innervating putative neurohaemal areas and central neuropil in the thoraco‐abdominal ganglia of the flies Drosophila and Calliphora
Authors: Nässel Dick R. , Pirvola Ulla , Panula Pertti
Published: January 2005

The fused thoraco‐abdominal ganglia of the flies Calliphora vomitoria and Drosophila melanogaster were investigated immunocytochemically with antisera against histamine. In both insect species, 18 histaminelike immunoreactive (HA‐IR) neurons were resolved in these ganglia. Six of these neurons have cell bodies in the thoracic neuromeres and 12 in the fused abdominal neuromeres. All cell bodies are situated ventrally. In Calliphora all cell bodies are arranged in a segmental pattern. In Drosophila only the thoracic cell bodies have a segmental arrangement, whereas the abdominal ones are clustered anteriorly close to the last thoracic neuromere.

In both species the six thoracic neurons supply processes to the synaptic neuropil in the thoracic neuromeres and to the dorsal neural sheath. The processes in the neural sheath run anteriorly in the lateral portions of the ganglion into the cervical connective. In a few regions laterally arborizing terminals are found in putative neurohaemal areas. These areas were investigated by electron microscopic immunocytochemistry in Calliphora. The HA‐IR terminals (containing small granular vesicles were found outside the “blood‐brain barrier” below the acellular basal lamina of the neural sheath. Release of histamine into the circulation is therefore theoretically possible. The central processes of the six thoracic HA‐IR neurons may interact synaptically with large numbers of other neurons in the neuropil, and the peripheral varicose fibers from the same HA‐IR neurons possibly are neurohaemal release sites. The abdominal HA‐IR neurons, in contrast, form extensive arborizations within the synaptic neuropil only. Both thoracic and abdominal neurons have ipsilateral and contralateral branches as well as processes that invade more than one neuromere. A single HA‐IR neuron thus invades large volumes of synaptic neuropil. Histamine may be used by neurons of the ventral ganglia both as neurotransmitter (or neuromodulator) and as a circulating neurohormone released from the neural sheath.
Calcium‐binding proteins as markers for subpopulations of GABAergic neurons in monkey striate cortex
Authors: Van Brederode J. F. M. , Mulligan K. A. , Hendrickson A. E.
Published: January 2005

Recent studies have shown that the presence of immunoreactivity for parvalbumin (PV‐IR) and calbindin‐D 28k (Cal‐IR) can be used as markers for certain types of gamma‐aminobutyric acid (GABA) immunoreactive interneurons in monkey cerebral cortex. Little quantitative information is available regarding the features that distinguish these two subpopulations, however. Therefore, in this study we localized PV‐IR and Cal‐IR neurons in Macaca monkey striate cortex and analyzed quantitatively their laminar distribution, cell morphology, and co‐localization with GABA by double‐labeling immunocytochemistry. PV‐IR was found in nonpyramidal cells in all layers of the cortex, although PV‐IR cells in layer 1 were rare. In contrast, Cal‐IR was found mainly in nonpyramidal cells in two bands corresponding to layers 2–3 and 5–6. We found very few double‐labeled PV‐IR/Cal‐IR cells but confirmed that almost all PV‐IR and Cal‐IR cells are GABAergic. Overall, 74% of GABA neurons in striate cortex displayed PV‐IR compared to only 12% that displayed Cal‐IR and 14% that were GABA‐IR only. Quantitative analysis indicated that the relative proportion of GABA cells that displayed PV‐IR or Cal‐IR showed conspicuous laminar differences, which were often complementary. Cell size measurements indicated that PV‐IR/GABA cells in layers 2–3 and 5–6 were significantly larger than Cal‐IR/GABA cells. Analysis of the size, shape, and orientation of stained cell bodies and proximal dendrites further demonstrated that each subpopulation contained several different types of smooth stellate cells, suggesting that Cal‐IR and PV‐IR are found in functionally and morphologically heterogeneous subpopulations of GABA neurons.

There was a thick bundle of PV‐IR axons in the white matter underlying the striate but not prestriate cortex. PV‐IR punctate labeling matched the cytochrome oxidase staining pattern in layers 4A and 4C, suggesting that PV‐IR is present in geniculocortical afferents as well as intrinsic neurons. Cal‐IR neuropil staining was high in layers 1, 2, 4B, and 5, where cytochrome oxidase staining is relatively low. We did not find a preferential localization of either PV‐IR or Cal‐IR cell bodies in any cytochrome oxidase compartments in layers 2–3 of the cortex. These findings indicate that PV and Cal are distributed into different neuronal circuits.
Visual projections induced into the auditory pathway of ferrets. I. Novel inputs to primary auditory cortex (AI) from the LP/pulvinar complex and the topography of the MGN‐AI projection
Authors: Pallas Sarah L. , Roe Anna W. , Sur Mriganka
Published: January 2005

The organization of cortical circuitry responsible for processing sensory information is a subject of intense examination. However, it is not known whether cortical cells in different sensory cortices process information in a way that is specific to the modality of their input, or whether there are commonalities in processing circuitry across different cortices. In our laboratory, this question has been investigated at the level of the geniculocortical pathway by routing information of one sensory modality into the processing circuitry of another modality. Appropriate early lesions cause growth of retinal axons into the auditory thalamus (MGN) (Sur et al., Science 242: 1437, '88). Previously, we have established that the MGN carries the resulting visual information on to primary auditory cortex (AI), which thus contains visually responsive neurons and a topographic representation of the retina (Roe et al., Soc. Neurosci. Abstr. 14:460, '88; Sur et al., Science 242:1437, '88), In this paper, we describe anomalous projections from the dorsal part of the thalamus, specifically the lateral posterior/pulvinar complex, into AI. This result demonstrates that thalamic neurons belonging to one modality can be induced to project to cortex that is normally of a different modality. In addition, we have studied in detail the nature of the MGN to AI projection in these animals as compared to the normal projection. The MGN to AI projection appears to be unaltered by the lesions; the location and topography of labelled cells are similar to that in normal animals. Because the MGN to AI projection is still highly divergent along the “isofrequency” dimension when compared to the tonotopic dimension, our data suggest that visual topography in the cortical map is created within the auditory cortex, perhaps by activity‐dependent sharpening of the retinal representation during development.
Growth of injured rabbit optic axons within their degenerating optic nerve
Authors: Lavie V. , Murray M. , Solomon A. , Ben‐Bassat S. , Belkin M. , Rumelt S. , Schwartz M.
Published: January 2005

Spontaneous growth of axons after injury is extremely limited in the mammalian central nervous system (CNS). It is now clear, however, that injured CNS axons can be induced to elongate when provided with a suitable environment. Thus injured CNS axons can elongate, but they do not do so unless their environment is altered.

We now show apparent regenerative growth of injured optic axons. This growth is achieved in the adult rabbit optic nerve by the use of a combined treatment consisting of: (1) supplying soluble substances originating from growing axons to the injured rabbit optic nerves (Schwartz et al., Science, 228:600–603, 1985), and (2) application of low energy He‐Ne laser irradiation, which appears to delay degenerative changes in the injured axons (Schwartz et al., Lasers Surg. Med., 7:51–55. 1985; Assia et al., Brain Res., 476:205–212, 1988). Two to 8 weeks after this treatment, unmyelinated and thinly myelinated axons are found at the lesion site and distal to it. Morphological and immunocytochemical evidence indicate that these thinly myelinated and unmyelinated axons are growing in close association with glial cells. Only these axons are identified as being growing axons. These newly growing axons traverse the site of injury and extend into the distal stump of the nerve, which contains degenerating axons. Axons of this type could be detected distal to the lesion only in nerves subjected to the combined treatment. No unmyelinated or thinly myelinated axons in association with glial cells were seen at 6 or 8 weeks postoperatively in nerves that were not treated, or in nerves in which the two stumps were completely disconnected. Two millimeters distal to the site of injury, the growing axons are confined to a compartment comprising 5%–30% of the cross section of the nerve. A temporal analysis indicates that axons have grown as far as 6 mm distal to the site of injury, by 8 weeks postoperatively. Anterograde labeling with horseradish peroxidase, injected intraocularly, indicates that some of these newly growing axons arise from retinal ganglion cells.
Cytoarchitecture and fiber connections of the nucleus lateralis valvulae in the carp (Cyprinus carpio)
Authors: Ito Hironobu , Yoshimoto Masami
Published: January 2005

The cytoarchitecture and fiber connections of the nucleus lateralis valvulae of the carp (Cyprinus carpio) were studied by Nissl, Bodian, Golgi, and horseradish peroxidase methods. Chief cells composing the nucleus lateralis valvulae (NLV) are small and granular, and their axons terminate in the cerebellum. These neurons have no dendrite, and the cell body is enveloped in a single terminal of afferent fibers to the NLV. In order to observe local cell clustering, the NLV was three‐dimensionally reconstructed with the aid of a computer image analysis system.

Afferent sources to the NLV were the nucleus pretectalis superficialis pars magnocellularis (Northcutt and Braford, '84: Brain Res. 296:181–184), nucleus ventromedialis thalami (Ito et al., '86: J. Comp. Neurol 250:215–227), and the inferior lobe. The NLV projects to the inferior lobe and the cerebellum. In particular, the cerebellar projections were strong and topographically arranged. Some larger neurons lying just beneath the NLV, some of which were intermingled with the NLV neurons, projected to the torus longitudinalis.

On the basis of the local cell clustering as well as NLV‐cerebellar connections, three subdivisions of the NLV could be recognized, i.e., anterior, central, and posterior portions. The posterior portion was further subdivided into lateral and medial parts.
Auditory brainstem in the mole (Mogera): Nuclear configurations and the projections to the inferior colliculus
Authors: Kudo Motoi , Nakamura Yasuhisa , Tokuno Hironobu , Kitao Yasuko
Published: January 2005

Anatomical organization of the central auditory system in the mole was studied at the lower brainstem levels. The cyto‐, myelo‐, and chemoarchitectures were examined in Nissl, myelin, and acetylcholinesterase stained materials, and then the origins of the ascending afferents to the inferior colliculus (IC) were identified by injecting wheatgerm agglutinin conjugated to horseradish peroxidase (WGA‐HRP) into the unilateral IC and processing the tissue according to the standard retrograde tracing techniques. The results indicate that the auditory nuclei and pathways in the lower brainstem of the mole conform to the basic plan common to many other mammals. Nevertheless, several characteristic features are evidenced in the present study: (1) in the cochlear nucleus (CochN), granule cell fields are very large in both the ventral (VCN) and dorsal (DCN) nuclei; among several populations of neurons, fusiform cells in the DCN, multipolar cells in the VCN and DCN, and small spherical cells in the VCN project to the IC directly, (2) in the superior olivary complex (SOC), the medial nucleus (MSO) is well developed in comparison with that in the hedgehog, the opossum, the mouse, and the rat, although the general configuration of the SOC is similar to that in those mammals, most strikingly, the MSO projects to the IC bilaterally in the mole, and (3) the nuclei of the lateral lemniscus (NLL) show a great development and consist of three well‐differentiated parts of the dorsal, intermediate, and ventral nuclei. The projections from these subnuclei to the IC conform to the basic mammalian plan.
Direct catecholaminergic innervation of primate spinothalamic tract neurons
Authors: Westlund K. N. , Carlton S. M. , Zhang D. , Willis W. D.
Published: January 2005

Catecholaminergic axonal varicosities identified by immunocytochemical staining for dopamine‐beta‐hydroxylase were observed at the light microscopic level apposing the somata of retrogradely labeled spinothalamic tract neurons in the monkey spinal cord, Three retrogradely labeled and two intracellularly labeled spinothalamic neurons were serially sectioned and examined at selected intervals at the electron microscopic level. Electron microscopic study revealed that axonal boutons directly contacted the somata and/or dendrites of lamina I, IV, and V spinothalamic tract neurons. All of the profiles apposing one of the retrogradely labeled lamina I spinothalamic tract neurons were categorized from eight planes of section spaced at 1‐μm intervals. Of the 305 profiles counted that were adjacent to this soma, 17 (5.6%) stained positively for dopamine‐beta‐hydroxylase. Of these 17 appositions, three were followed in serial sections to confirm that they had synaptic thickenings and alignment of vesicles along the membrane contacting the spinothalamic tract soma. Catecholaminergic boutons were observed apposing the somata and dendrites of intracellularly filled STT cells characterized as high threshold and wide dynamic range neurons. These observations clearly indicate a direct innervation of spinothalamic tract neurons by catecholaminergic neurons, providing anatomical data to support previous physiological findings demonstrating that catecholamines modulate nociceptive transmission.
Morphology of a population of mechanosensory ascending interneurones in the metathoracic ganglion of the locust
Authors: Newland Philip L.
Published: January 2005

A population of ascending interneurones with cell bodies in the metathoracic ganglion of the locust is described. Interneurones are characterised by their morphology (revealed by intracellular cobalt injection) and by their physiological responses to afferent stimulation. All interneurones have their somata in the ventral cortex of the ganglion, in an area just posterior to the medial tracheae. On the basis of gross morphology the interneurones can be divided into three groups: (1) those that have a main area of fine neurites ipsilateral to the soma and an ipsilateral ascending axon; (2) interneurones that also have their main neurites ipsilateral to the soma but have a contralateral ascending axon, and (3) interneurones that have their main neurites and an ascending axon contralateral to the soma. All interneurones are excited by stimulation of sensory receptors on the hind leg ipsilateral to the main neurites. Interneurones receiving excitatory inputs from tactile hairs on the hind leg have branches in the most ventral neuropil, whereas interneurones receiving input from leg proprioceptors have branches in the more intermediate and dorsolateral neuropil. The branching pattern of an interneurone and the size and position of the receptive field on the leg are correlated. Interneurones with extensive ventral branches have extensive receptive fields; interneurones with restricted branching patterns have restricted receptive fields. The position of the ventral branching reflects the position of the receptive field on the leg. An interneurone with a receptive field restricted to the femur has ventral branches in an anterior position in the ganglion; an interneurone with a receptive field restricted to the tarsus has ventral branches in a more posterior position.
Renewal of electrotonic synapses in teleost retinal horizontal cells
Authors: Vaughan Dana K. , Lasater Eric M.
Published: January 2005

In teleost retinas, the somata of same‐type cone horizontal cells are electrically coupled via extensive gap junctions, as are the axon terminals of same‐type cells. This coupling persists throughout the animal's life and is modulated by dopamine and conditions of light‐ vs. dark‐adaptation. Gap junction particle density in goldfish horizontal cell somata has also been shown to change under these conditions, indicating that these junctions are dynamic. We have used electron microscopy to examine gap junctions in bass horizontal cells with a fixation method that facilitates detection of gap junctions. Annular gap junction profiles were observed in the somatic cytoplasm of all cone horizontal cell types in both light‐ and dark‐adapted animals. Serial sections showed that most profiles represented gap junction vesicles free within the cytoplasm; the remainder represented vesicles still attached to extensive plasma membrane gap junctions by a thin cytoplasmic neck, suggestive of an intermediate stage in endocytosis. Observations of gap junction vesicles containing fragments of gap junctional membrane and/or fused with lysosomal bodies further supported this hypothesis. Because gap junctions persist between the horizontal cells, we propose that gap junction endocytosis and lysosomal degradation are balanced by addition of new junctions. While endocytosis has been widely demonstrated to serve in programmed removal of gap junctions (without subsequent replacement), from both nonneuronal cells and developing neurons, this study indicates that it can also function in the renewal of electrical synapses in the adult teleost retina, where gap junction elimination is not the goa.
Glycinergic contacts in the outer plexiform layer of the Xenopus laevis retina characterized by antibodies to glycine, GABA, and glycine receptors
Authors: Smiley John F. , Yazulla Stephen
Published: January 2005

Electrophysiological experiments have predicted a direct synaptic input from glycinergic interplexiform cells (IPCs) to GABAergic horizontal cells in the Xenopus retina. However, previous ultrastructural studies failed to demonstrate this input. Here, we used three immunocytochemical approaches to investigate this issue. First, double‐label postembedding immunocytochemistry with GABA‐ and glycine‐like immunoreactivity (GABA‐LI and glycine‐LI) was used to study possible interactions of the glycinergic IPC with GABAergic horizontal cells. Processes postsynaptic to glycine‐LI IPC terminals in the outer plexiform layer (OPL) fell into two groups, small microtubule‐filled processes and larger electron‐lucent processes with sparse microtubules and occasional mitochondria. In no case did we find glycine‐LI synapses onto GABA‐LI cells or processes. Second, pre‐embedding immunocytochemistry was used to label GABA‐LI cells and processes in the OPL. GABA‐LI was sparse in horizontal cell axons and more intense in horizontal cell somas and in small processes. In agreement with our first set of experiments, GABA‐LI profiles did not receive input from conventional synapses. Third, we localized glycine‐receptor‐like immunoreactivity (GlyR‐LI) to several types of apparent synapses in the OPL. As expected, it was found at IPC synapses. Unexpectedly, GlyR‐LI was also subsynaptic at photoreceptor synapses onto second order neurons, both at ribbon and basal junction type synapses. At least some of the GlyR‐LI photoreceptor synapses were from cones. Also, GlyR‐LI was apposed to photoreceptors and to unidentified small diameter processes, where no other indication of synaptic input was evident. Because glycine‐LI is not found in photoreceptors, we suggest that glycine receptors at photoreceptor synapses are stimulated by glycine that diffuses from other sites, possibly from IPCs. This interpretation is consistent with available physiological studies of glycinergic effects in this retina.
Ultrastructure of cholinergic synaptic terminals in the thalamic anteroventral, ventroposterior, and dorsal lateral geniculate nuclei of the rat
Authors: Hallanger Ann E. , Price Steve D. , Lee Henry J. , Steininger Teresa L. , Wainer Bruce H.
Published: January 2005

The principal relay nuclei of the thalamus receive their cholinergic innervation from two midbrain cholinergic groups: the pedunculopontine tegmental nucleus and the laterodorsal tegmental nucleus. The different thalamic nuclei exhibit populations of cholinergic axons which vary in density and morphology when examined at the light microscopic level. However, the ultrastructure of the cholinergic terminals in different thalamic nuclei has not been described. This study was undertaken to confirm that synaptic contacts are formed by cholinergic axons in several principal thalamic relay nuclei, to describe their ultrastructural morphology, and to identify the types of postsynaptic elements contacted by cholinergic synaptic terminals. The thalamic nuclei examined in this study are the dorsal lateral geniculate nucleus, ventroposteromedial nucleus, ventroposterolateral nucleus, and anteroventral nucleus.

Our results confirm that cholinergic axons form synaptic terminals in these thalamic nuclei. Cholinergic synaptic terminals contact structures outside the characteristic synaptic glomeruli, are never postsynaptic, and have morphologies and postsynaptic targets which differ among the thalamic nuclei. In the ventroposterior nuclei, cholinergic terminals form asymmetric synaptic contacts onto larger dendrites in the extraglomerular neuropil. In the anteroventral nucleus, cholinergic terminals form both symmetric and asymmetric synaptic contacts onto dendrites and somata. Cholinergic terminals in the anteroventral nucleus are larger than those in other nuclei. In the dorsal lateral geniculate nucleus, cholinergic terminals contact both somata and dendrites in the extraglomerular neuropil, but the synaptic contacts in this nucleus are symmetric in morphology.
Topography of ganglion cells in human retina
Authors: Curcio Christine A. , Allen Kimberly A.
Published: January 2005

We quantified the spatial distribution of presumed ganglion cells and displaced amacrine cells in unstained whole mounts of six young normal human retinas whose photoreceptor distributions had previously been characterized. Cells with large somata compared to their nuclei were considered ganglion cells; cells with small somata relative to their nuclei were considered displaced amacrine cells. Within the central area, ganglion cell densities reach 32,000‐‐38,000 cells/mm2 in a horizontally oriented elliptical ring 0.4‐‐2.0 mm from the foveal center. In peripheral retina, densities in nasal retina exceed those at corresponding eccentricities in temporal retina by more than 300%; superior exceeds inferior by 60%. Displaced amacrine cells represented 3% of the total cells in central retina and nearly 80% in the far periphery. A twofold range in the total number of ganglion cells (0.7 to 1.5 million) was largely explained by a similar range in ganglion cell density in different eyes. Cone and ganglion cell number were not correlated, and the overall cone: ganglion cell ratio ranged from 2.9 to 7.5 in different eyes. Peripheral cones and ganglion cells have different topographies, thus suggesting meridianal differences in convergence onto individual ganglion cells.

Low convergence of foveal cones onto individual ganglion cells is an important mechanism for preserving high resolution at later stages of neural processing. Our improved estimates for the density of central ganglion cells allowed us to ask whether there are enough ganglion cells for each cone at the foveal center to have a direct line to the brain. Our calculations indicate that (1) there are so many ganglion cells relative to cones that a ratio of only one ganglion cell per foveal cone would require fibers of Henle radiating toward rather than away from the foveal center; and (2) like the macaque, the human retina may have enough ganglion cells to transmit the information afforded by closely spaced foveal cones to both ON‐ and OFF‐channels. Comparison of ganglion cell topography with the visual field representation in V1 reveals similarities consistent with the idea that cortical magnification is proportional to ganglion cell density throughout the visual field.
Cortical neurons expressing the cholecystokinin gene in the rat: Distribution in the adult brain, ontogeny, and some of their projections
Authors: Burgunder J.‐M. , Young W. S.
Published: January 2005

Recent studies of neuronal cholecystokinin (CCK) expression performed with more sensitive techniques have demonstrated that the distribution of the expression of this peptide is more widespread than previously thought. In the present study, hybridization histochemistry was used to map cortical neurons expressing the CCK gene in adult and developing rats. Retrograde tracing with Fluorogold in combination with hybridization histochemistry was used to demonstrate some of the projections of these neurons.

Neurons expressing the CCK gene were found in all areas of the neo‐ and allocortices. They were of several morphological types, including pyramidal neurons, and were found in almost all layers, albeit at different relative numbers and with different levels of expression. Generally, layers II and III, deep layer V, and layer VI had many neurons expressing CCK mRNA.

Cortical CCK expression was first detected on the 15th day of gestation in the primordial plexiform layer. Expression developed thereafter in a regular and continuous fashion until an adult‐like pattern was present on the 21st day after birth.

Cortical neurons containing CCK mRNA were found in almost all the projections studied. Many neurons in both neo‐ and allocortical areas with cortico‐cortical, associational, and commissural pathways contained CCK mRNA. Similarly, numerous corticostriatal neurons contained CCK mRNA; however, only a few corticothalamic neurons expressed CCK mRNA. These results demonstrate that in the rat cortex the distribution of projection neurons expressing CCK is much more widespread than had been previously shown and will stimulate further investigations into the role of CCK in these neurons.
Distribution of cholecystokinin‐like‐immunoreactive neurons in the guinea pig forebrain
Authors: Ciofi Philippe , Tramu Gerard
Published: January 2005

The distribution of cholecystokinin (CCK)‐immunoreactive nerve fibers and cell bodies was studied in the forebrain of control and colchicine‐treated guinea pigs by using an antiserum directed against the carboxyterminus of CCK octapeptide (CCK‐8) in the indirect immunoperoxidase technique. Virtually all forebrain areas examined contained immunoreactive nerve fibers. A dense innervation was visualized in: neocortical layers II‐III, piriform cortex, the medial amygdala, the medial preoptic area, a circumventricular organ‐like structure located at the top of the third ventricle in the preoptic area, the subfornical organ, the posterior bed nucleus of the stria terminalis, the posterior globus pallidus (containing labeled woolly fiber‐like profiles), the ventromedial hypothalamus, the median eminence, and the premammillary nucleus. A moderately dense innervation was visualized elsewhere excepted in the septum and thalamus where labeled axons were comparatively few. Immunoreactive perikarya were abundant in: neocortex (especially layers II‐III), piriform cortex, amygdala, the median preoptic nucleus, the bed nucleus of the stria terminalis, the hypothalamic paraventricular (parvicellular part), arcuate, and dorsomedial (pars compacta) nuclei, the dorsal and perifornical hypothalamic areas, and throughout the thalamus. Areas also containing a moderate number of labeled cell bodies were the medial preoptic area, the globus pallidus, the caudate‐putamen, and the periventromedial area in the hypothalamus. Immunostained perikarya were absent or only occasionally observed in the septum, the suprachiasmatic nucleus, the magnocellular hypothalamoneurohypophyseal nuclei, and the ventral mesencephalon. In the adenohypophysis corticomelanotrophs were labeled in both males and females, and thyrotrophs were labeled in females only.

This distribution pattern of CCK‐8 immunoreactivity is compared to those previously recorded in other mammals. This shows that very few features are peculiar to the guinea pig. It is discussed whether some interspecific differences in immunostaining are real rather than methodological.
Cytoarchitectonic atlas of the cochlear nucleus of the chinchilla, Chinchilla laniger
Authors: Morest D. Kent , Hutson K. A. , Kwok S.
Published: January 2005

A detailed cytoarchitectonic atlas of the chinchilla cochlear nucleus complex was prepared in the transverse plane with the Nissl method. Subdivisions of the cochlear nucleus were defined on the basis of cell size, cell packing density, and, in some cases, on cytological features of cell types. In general, the chinchilla cochlear nucleus has an organizational plan similar to that described for other mammalian species. As in other rodents, the chinchilla has a large and well‐developed dorsal cochlear nucleus consisting of three distinct layers. The ventral cochlear nucleus consists of two distinct nuclear masses, a posterior nuclear group and an anterior nuclear group, each composed of several subdivisions, which are qualitatively similar to those described for other mammals. Thus it is now possible to compare detailed observations, such as tonotopic maps, in the chinchilla with findings from the analogous cell populations in other mammals, such as the cat with considerable precision. In the chinchilla, three cell groups, previously undescribed in mammals, have been defined and their counterparts in the cat identified.