bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular labeling of neurons in the medial accessory olive of the cat: I. Physiology and light microscopy
Authors: Ruigrok T. J. H. , de Zeeuw C. I. , van der Burg J. , Voogd J.
Published: January 2005

This study is the first of three reports on the detailed morphology of horseradish peroxidase injected neurons in the medial accessory olive of the cat.

Intracellular, in vivo recordings of olivary cells were made and their response to mesodiencephalic stimulation was tested. In 44 units a short latency action potential could be recorded, which was very suggestive of a monosynaptic excitatory pathway. The short latency response was frequently followed by a long latency (mean 188 msec) or rebound action potential. Recordings were followed by intracellular iontophoresis of horseradish peroxidase.

A total of 21 neurons, all located within the medial accessory olive were chosen for morphological analysis. Cells could be divided into two categories on the basis of their overall morphological appearance. Type I cells (n = 5) had sparsely branching dendrites that radiated away from the soma and were usually found in the caudal part of the medial accessory olive. The axon usually originated from the soma. Type II cells (n = 16) were located more rostrally. They had larger cell bodies with dendrites that ramified extensively, forming a globular structure (mean diam. 338 μUm). The axon usually originated from a first order dendrite. No recurrent axon collaterals were observed on either type I or II cells. Both cell types carried long and complex spiny appendages; however, they were most numerous on the second and higher order dendrites of type II cells. Since the soma of these cells is usually not found in the centre of its dendritic field, even if the cell is located in the center area pf the neuropil, it is suggested that the dendritic trees of up to 100 neurons may be intricately interwoven, establishing clusters with intensive intercommunication by means of dendritic gap junctions. The abundance, length and complexity of the spiny appendages suggest an important role in this process, but may also be relevant instruments in enhancing the computational capabilities of these neurons, especially in time sensitive processes.

When relating the physiological and the morphological results, it was noted that both type I and type II cells could respond to mesodiencephalic stimulation and were both able to trigger a rebound action potential. No significant correlations were found between cell size and the latency of the rebound.
Intracellular labeling of neurons in the medial accessory olive of the cat: III. Ultrastructure of axon hillock and initial segment and their GABAergic innervation
Authors: De Zeeuw C. I. , Ruigrok T. J. H. , Holstege J. C. , Schalekamp M. P. A. , Voogd J.
Published: January 2005

The gamma‐aminobutyric acid (GABA) synaptic input of identified axons in the cat inferior olive was studied by use of combination of intracellular labeling with horseradish peroxidase and postembedding gold‐immunocytochemistry. With this technique olivary cells were physiologically identified and light microscopically reconstructed, and the horseradish peroxidase reaction product and the immunogold labeling were subsequently simultaneously visualized for electron microscopic investigation with the use of serial ultrathin sections.

The axons of cell type I (characterized by dendrites which radiate away from the cell body) originated from the soma, whereas those of type II neurons (characterized by dendritic trees which curve back towards the soma) were derived from a primary dendrite. The axons of olivary neurons stand out by the length of their axon hillock (up to 21 μm) and initial segment (up to 40 μm). The hillock forms various spiny appendages which were located within glomeruli together with dendritic spines of other olivary neurons. Axonal spines of type II neurons were more numerous and complex looking than those of type I. The axonal spines, the shaft of the axon hillock, and the transition between the hillock and initial segment were primarily innervated by GABAergic terminals (65%) but non‐GABAergic terminals (35%) were present as well. The terminals apposed to the axons of type I neurons contacted mainly the axonal shafts, whereas most of the terminals adjacent to the axons of type II neurons established synaptic contacts with the axonal spines. The initial segments were largely devoid of synaptic input. Distally, the initial segment acquired a myelin sheath.
Vasopressin in the brain of the golden hamster: The distribution of vasopressin binding sites and of immunoreactivity to the vasopressin‐related glycopeptide
Authors: Dubois‐Dauphin M. , Pevet P. , Triboilet E. , Dreif'Uss J. J.
Published: January 2005

Using in vitro light microscopic autoradiography and immunocytochemistry, the distribu‐ tion of vasopressin binding sites and that of the vasopressin‐related glycopeptide are described in the brain of golden hamster (Mesocricetus auratus). Vasopressin binding sites and immunoreactive axones were observed in the suprachiasmatic nucleus, in the anterior hypothalamus/median preoptic area, in the medial preoptic nucleus, in the bed nucleus of the stria terminalis, in the habenular complex, in the thalamic paraventricular nucleus, and in the nucleus of the solitary tract.

In addition we observed binding sites in regions where no immunoreactivity could be evidenced: the lateral septa1 nucleus, the central amygdaloid nucleus, the subiculum, the dentate gyrus, the anterodorsal and anteroventral thalamic nuclei, the superior colliculus, the vestibular nuclei, and in the prepositus hypoglossal nucleus.

In the golden hamster, exogenous vasopressin excites single neurones located in the suprachiasmatic nucleus and induces flank‐marking behavior when microinjected into the preoptic area. Our results provide a morphological basis for similar effects exerted by endogenous vasopressin. A comparison of the present data with those previously described in the rat reveals marked species differences in the brain distribution of vasopressin and of its binding sites.
Development of the anterior olfactory nucleus in normal and unilaterally odor deprived rats
Authors: Brown Jessica L. , Brunjes Peter C.
Published: January 2005

The development of a second order structure in the olfactory pathway, the anterior olfactory nucleus, was examined in both normal rat pups and in subjects which underwent unilateral naris closure on postnatal day 1 (P1)Naris occlusion in neonatal rats produces a constellation of changes within the first relay in the pathway, the olfactory bulb, including a 25% reduction in total volume. Such large changes suggest that higher order structures might also be affected. Anterior olfactory nucleus development was quantified in several ways. Laminar volumes were computed by using serial section planimetry. In control animals differential development was observed, with regions extending most rostrally (e.g., pars externa and pars lateralis)exhibiting the least growth. The anterior olfactory nucleus on the “deprived” side of subjects with a single naris occluded was identical in size to that observed in controls, suggesting that the procedure has little effect on the growth of the structure. Dendritic development within the pars lateralis was examined in control animals at P10, P20, P30, and adults. Developmental increases in numbers of both branches per cell and spines were noted, but mean branch length remained relatively constant. Finally, the effects of naris occlusion on histological patterns of succinate dehydrogenase (SDH) staining and 2‐deoxyglucose uptake within pars lateralis were examined at P20 to test for more subtle effects of naris occlusion. SDH staining was quite similar in deprived and control rats at P20. However, 3H‐2‐DG uptake was decreased in rostral areas of the anterior olfactory nucleus ipsilateral to the deprived olfactory bulb, suggesting that naris closure does affect the structure.
The anterior ectoylvian sulcal auditory field in the cat: II. A horseradisha peroxidase study of its thalamic and cortical connections
Authors: Clarey Janine C. , Irvine Dexter R. F.
Published: January 2005

The thalamic and cortical projections to acoustically responsive regions of the anterior ectosylvian sulcus were determined by identifying retrogradely labelled cells after physiologically guided iontophoretic injections of horseradish peroxidase. The medial division of the medial geniculate nucleus, the intermediate division of the posterior nuclear group, the principal division of the ventromedial nucleus, and the lateroposterior complex were consistently labelled after these injections, although each animal showed slightly different patterns of labelling. The suprageniculate nucleus and the lateral and medial divisions of the posterior nuclear group were also labelled in most experiments. The cortex of the suprasylvian sulcus was the most consistently and densely labelled cortical region; each experiment showed a slightly different pattern of labelling throughout the suprasylvian sulcus, with an overall tendency for greater labelling in the ventral (lateral) bank of the middle region of the sulcus. Other cortical regions labelled less consistently included the anterior ectosylvian sulcus itself, the insular cortex of the anterior sylvian gyrus, and the posterior rhinal sulcus. In three experiments the contralateral cortex was examined and a small number of labelled cells was located in the anterior ectosylvian and suprasylvian sulci.

Input from extralemniscal auditory thalamus is compatible with previously described auditory response properties of anterior ectosylvian sulcus neurons. The results also confirm the presence of input from visual and multimodal regions of thalamus and cortex, and therefore support claims of overlap of modalities within the sulcus. This overlap, as well as input from motor regions, suggests that the anterior ectosylvian sulcal field serves a sensorimotor role.
Mosaic organization of the hippocampal neuroepithelium and the multiple germinal sources of dentate granule cells
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

This study deals with the site of origin, migration, and settling of the principal cell constituents of the rat hippocampus during the embryonic period, The results indicate that the hippocampal neuroepithelium consists of three morphogenetically discrete components—the Ammonic neuroepithelium, the primary dentate neuroepithelium, and the fimbrial glioepithelium—and that these are discrete sources of the large neurons of Ammon's horn, the smaller granular neurons of the dentate gyrus, and the glial cells of the fimbria.

The putative Ammonic neuroepithelium is marked in short‐survival thymidine radiograms by a high level of proliferative activity and evidence of interkinetic nuclear migration from day E16 until day E19. On days E16 and E17 a diffuse band of unlabeled cells forms outside the Ammonic neuroepithelium. These postmitotic cells are considered to be stratum radiatum and stratum oriens neurons, which are produced in large numbers as early as day E15. A cell‐dense layer, the incipient stratum pyramidale, begins to form on day E18 and spindle‐shaped cells can be traced to it from the Ammonic neuroepithelium. This migratory band increases in size for several days, then declines, and finally disappears by day E22. It is inferred that this migration contains the pyramidal cells of Ammon's horn that are produced mostly on days E17 through E20.

The putative primary dentate neuroepithelium is distinguished from the Ammonic neuroepithelium during the early phases of embryonic development by its location, shape, and cellular dynamics. It is located around a ventricular indentation, the dentate notch, contains fewer mitotic cells near the lumen of the ventricle than the Ammonic neuroepithelium, and shows a different labeling pattern both in short‐survival and sequential‐survival thymidine radiograms. By day E18, the reduced primary dentate neuroepithelium is surrounded by an aggregate of proliferative cells; this is the secondary dentate matrix. On the subsequent days spindle‐shaped cells that have retained their proliferative capacity migrate from the progressively receding secondary dentate matrix to the dentate gyrus itself. The latter, representing a tertiary germinal matrix, becomes highly active during the perinatal period.

The putative fimbrial glioepithelium is situated between the primary dentate neuroepithelium and the tip of the hippocampal rudiment. Observations in methacrylate sections and thymidine radiograms suggest that the cells of this germinal matrix, unlike typical neuroepithelial cells, do not undergo interkinetic nuclear migration. The fimbrial glioepithelium is clearly present by day E16, two days before the fimbria becomes a distinct fiber tract. As the fimbria emerges, cells of the putative glial matrix migrate into it.
Migration and distribution of two populations of hippocampal granule cell precursors during the perinatal and postnatal periods
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

Methacrylate‐embedded sections and short‐survival thymidine radiograms of the hippocampal dentate gyrus were examined in perinatal and postnatal rats in order to trace the site of origin and migration of the precursors of granule cells and study the morphogenesis of the granular layer. The densely packed, spindle‐shaped cells of the secondary dentate matrix (a derivative of the primary dentate neuroepithelium) stream in a subpial position towards the granular layer of the internal dentate limb during the perinatal and early postnatal periods. By an accretionary process, the crest of the granular layer forms on day E21 and on the subsequent days the granular layer of the internal dentate limb expands progressively in a lateral direction. Granule cells differentiation, as judged by the transformation of polymorph, darkly staining small cells into rounder, lightly staining larger granule cells, follows the same gradient from the external dentate limb to the internal dentate limb. The secondary dentate matrix is in a process of dissolution by day P5. This matrix is the source of what will later become the outer shell of the granular layer composed of early generated granule cells. The thicker inner shell of the granular layer, formed during the infantile and juvenile periods, derives from an intrinsic, tertiary germinal matrix. On day E22, the dentate migration of the secondary dentate matrix becomes partitioned into two components: (a) the subpial component of extradentate origin, referred to in this context as the first dentate migration, and (b) the second dentate migration. The latter is distributed in the basal polymorph layer throughout the entire dentate gyrus and is henceforth recognized as the tertiary dentate matrix. The tertiary dentate matrix is prominent between days P3 and P10. It is postulated that the great increase in granule cell population during the infantile period is principally due to cells derived from this intrinsic matrix of the dentate gyrus. Between days P20 and P30 the tertiary dentate matrix disappears in the basal polymorph layer and henceforth proliferative cells become largely confined to the subgranular zone at the base of the granular layer. The subgranular zone is the source of granule cells produced during the juvenile and adult periods.
Medullary projection of nonaugmenting inspiratory neurons of the ventrolateral medulla in the cat
Authors: Otake Kazuyoshi , Sasaki Hiroshi , Ezure Kazuhisa , Manabe Motomu
Published: January 2005

In Nembutal‐anesthetized, immobilized, and artificially ventilated cats, we studied the morphological characteristics of inspiratory neurons with nonaugmenting firing patterns. HRP was injected intracellularly into a total of 22 neurons of the Bötzinger complex (BÖT) and the ventral respiratory group (VRG). In 20 cases somata with their axonal trajectories were stained, and in two cases only axons were stained. None of the neurons stained could be antidromically activated by stimulation of the cervical cord. The somata of 20 neurons were located in the vicinity of the nucleus ambiguus or the retrofacial nucleus (RFN) between 600 μm and 2,800 μm caudal to the rostral end of the RFN. Their axons could be traced for a distance of several millimeters on the side of the somata, and showed various projection patterns. According to these projection patterns, the 20 neurons were tentatively classified into four groups: A (8/20), B (4/20), C (6/20), and motoneurons (2/20). Group A neurons gave off extensive axon collaterals that arborized and distributed boutons predominantly in the BÖT and the VRG areas. Group B neurons had less extensive axon collaterals with various projection patterns, projecting rarely to the BÖT or the VRG area. Group C neurons sent their stem axons, without issuing any axonal collaterals, to the contralateral side in five cases and to the ipsilateral pons in one case. The two motoneurons had axons leaving the brainstem without any intramedullary collaterals. Thus, the nonaugmenting inspiratory neurons showed morphological variations, which may play different roles in neural control of respiration.
Identification of spinal neurons in the embryonic and larval zebrafish
Authors: Bernhardt Robert R. , Chitnis Ajay B. , Lindamer Laurie , Kuwada John Y.
Published: January 2005

Previous studies indicated that the developing fish spinal cord was a simple system containing a small number of distinguishable neuronal cell types (Eisen et al., Nature 320:269–271, '86; Kuwada, Science, 233:740–746, '86). To verify this we have characterized the cellular anatomy of the spinal cord of developing zebrafish in order to determine the number, identities, and organization of the spinal neurons. Spinal neurons were labeled by intracellular dye injections, application of an axonal tracer dye to all or subsets of the axonal tracts, and application of antibodies which recognize embryonic neurons. We found that nine classes of neurons could be identified based on soma size and position, pattern of dendrites, axonal trajectory, and time of axonogenesis. These are two classes of axial motor neurons, which have been previously characterized (Myers, J. Comp. Neurol. 236:555–561, '85), one class of sensory neurons, and six classes of interneurons. One of the interneuron classes could be subclassified as primary and secondary based on criteria similar to those used to classify the axial motor neurons into primary and secondary classes.

The early cord (18–20 hours) is an extremely simple system and contains approximately 18 lateral cell bodies per hemisegment, which presumably are post‐mitotic cells. By this stage, five of the neuronal classes have begun axonogenesis including the primary motor neurons, sensory neurons, and three classes of interneurons. By concentrating on these early stages when the cord is at its simplest, pathfinding by growth cones of known identities can be described in detail. Then it should be possible to test many different mechanisms which may guide growth cones in the vertebrate central nervous system (CNS).
Long‐term survival and sprouting in culture by motoneurons isolated from the spinal cord of adult frogs
Authors: Kuffler Damien P.
Published: January 2005

Motoneurons of adult frog spinal cord have been retrogradely labeled with the carbocyanine derivative diI. Spinal cords were then dissociated and the labeled motoneurons partially purified by centrifugation over a bovine serum albumin (BSA) density gradient. The resulting cell suspension was plated on a substrate of innervated muscle extracellular matrix (ECM) to which the motoneurons attached and extended processes. Labeled adult motoneurons survived for more than 4 weeks in a defined medium in the absence of added serum or growth factors. These cultures of adult motoneurons provide a favorable preparation for studying molecular factors that influence process outgrowth and synapse formation.
Aromatic L‐amino acid decarboxylase‐immunohistochemistry in the cat lower brainstem and midbrain
Authors: Kitahama Kunio , Denoyer Michel , Raynaud Brigitte , Borri‐Voltattorni Carla , Weber Michel , Jouvet Michel
Published: January 2005

By indirect immunohistochemistry, the present study examined the distribution of neuronal structures in the cat medulla oblongata, pons, and midbrain, showing immunoreactivity to aromatic L‐amino acid decarboxylase (AADC), which catalyzes the conversion of L‐3, 4‐dihyroxyphenylalanine (L‐DOPA) to dopamine, and 5‐hydroxytryptophan to serotonin (5HT). With simultaneous and serial double immunostaining techniques, immunoreactivity to this enzyme was demonstrated in most of the catecholaminergic and serotonergic neurons. We could also demonstrate AADC‐IR cell bodies that do not contain tyrosine hydroxylase (TH‐) or 5HT‐immunoreactivity (called “D‐type cells”) outside such monoaminergic cell systems. At the medullo‐spinal junction, very small D‐type cells were found within and beneath the ependymal layer of the 10th area of Rexed surrounding the central canal. D‐type cells were localized in the caudal reticular formation, nucleus of the solitary tract, a dorsal aspect of the lateral parabrachial nucleus, and pretectal areas as have been reported in the rat. Furthermore, the present study describes, in the cat brainstem, new additional D‐type cell groups that have not been reported in the rat. Dense or loose clusters of D‐type cells were localized in the external edge of the laminar trigeminal nucleus, dorsal motor nucleus of the vagus, external cuneate nucleus, nucleus praepositus hypoglossi, central, pontine, and periaqueductal gray, superficial layer of the superior colliculus, and area medial to the retroflexus. D‐type cells were loosely clustered in the lateral part of the central tegmental field dorsal to the substantia nigra, extending dorsally in the medial division of the posterior complex of the thalamus and medial side of the brachium of the inferior colliculus. They extended farther rostrodorsally along the medial side of the nucleus limitans and joined with the pretectal cell group. Almost all these cells were very small and ovoid to round with 1–2 short processes with the exception of dorsal motor vagal cells, AADC‐IR axons were clearly identified in the vagal efferent nerves, longitudinal medullary pathway, dorsal tegmental bundle rostral to the locus coeruleus. Serotonergic axons were identified not only in the central tegmentum field and lateral side of the central superior nucleus, but also in the ventral surface of the medulla oblongata. We describe principal densely stained fiber plexuses in the cat brainstem. The findings of the present study provide a morphological basis for neurons that decarboxylate endogenous and exogenous L‐DOPA, 5HTP, and other aromatic L‐amino acids.
Descending neurons supplying the neck and flight motor of diptera: Organization and neuroanatomical relationships with visual pathways
Authors: Strausfeld Nicholas J. , Gronenberg Wulfila
Published: January 2005

In dipterous insects, a volume of behavioral and electrophysiological studies promote the contention that three wide‐field motion‐sensitive tangential neurons provide a necessary and sufficient input to specific channels that drive the torque motor during flight. The present studies describe the results of neuroanatomical investigations of the relationships between motion‐sensitive neuropil in the fly optic lobes and descending neurons that arise from a restricted area of the brain and supply segmental neck and flight motor neuropil. The present observations resolve at least 50 pairs of descending neurons supplying flight motor centers in the thoracic ganglia. The majority of descending neurons receive a distributed output from horizontal motion‐sensitive neurons. However, the same descending neurons are also visited by numerous small‐field retinotopic neurons from the lobula plate as well as hitherto undescribed small tangential neurons. Neuroanatomical studies, using cobalt, Golgi, and Texas red histology, demonstrate that these smaller inputs onto descending neurons have dendrites that are organized at specific strata in retinotopic neuropil and that these correspond to horizontal and vertical motion sensitivity layers. Conclusions that only a restricted number of wide‐field neurons are necessary and sufficient for visually stabilized flight may be premature. Rather, neuroanatomical evidence suggests that descending neurons to the flight motor may each be selectively tuned to specific combinations of wide‐ and small‐field visual cues, so providing a cooperative descending network controlling the rich repertoire of visually evoked flight behavior.
Thalamo‐cortical processing of vibrissal information in the rat. II. Spatiotemporal convergence in the thalamic ventroposterior medial nucleus (VPm) and its relevance to generation of receptive fields of S1 cortical “Barrel” neurones
Authors: Armstrong‐James Michael , Callahan Christopher A.
Published: January 2005

One hundred and twenty‐six cells, sampled in the vicinity of the D1 barreloid in the ventroposterior medial nucleus of the thalamus, were tested for magnitude and latency of response to brief deflections (3 ms; 1.14°) of vibrissae in adult rats under controlled conditions of light urethane anaesthesia. Similar results were achieved for D1 and non‐D‐dominant cells. D1‐dominant cells (N = 76) responded to the centre‐receptive field (D1) vibrissa with a mean of 1.08 spikes per stimulus at modal latencies of 3–12 ms (inter‐quartile range 4–5 ms) and to surrounding vibrissae with a mean of 0.26 spikes per stimulus at latencies of 3–41 ms (inter‐quartile range 5–8 ms). Surround‐receptive fields showed extensive overlap but were reduced and finally eliminated by deepening anaesthesia. A cell‐by‐cell analysis showed no correlation between latency and response magnitude for responses to surround vibrissae. Response magnitudes to the surround‐ and centre‐receptive field inputs for D1‐dominant barrel cells were some 2.5‐ and 1.7‐fold greater, respectively, than for thalamic cells under identical experimental conditions. The latencies to centre‐ and surround‐receptive field inputs for D1‐dominant barrel cells were 2.5 and 10–20 ms later than for thalamus, respectively. These data on a mismatch of latencies for surround‐ and centre‐receptive fields in thalamus and cortex support the notion that surround‐receptive fields of cortical barrel cells are almost entirely constructed intracortically during light an anaesthesia (Armstrong‐James et al., '91), although it is argued that surround‐receptive fields of thalamic cells conceivably could be relayed in other cortical states or serve a role in plasticity.
Chicken optic tract cells showing GABA‐like immunoreactivity: Morphological and immunocytochemical studies
Authors: Granda R. H. , Eyck G. R. Ten , Crossland W. J.
Published: January 2005

A population of cells has been found in the chick optic tract and chiasm exhibiting GABA‐like immunoreactivity (GABA+; Granda and Crossland, J. Comp. Neurol. 287:455–469, '89). It is not known, however, whether the cells are neurons. We have studied the GABA+ cells by using morphological and immunocytochemical methods. We found that there are more than 500 cells in each tract. At the light microscopic level, the cells possess processes resembling dendrites and axons. At the electron microscopic level, the organelle content of the cells is similar to that of neurons. The cells are immunoreactive with antibodies to MAP2 and neuron specific enolase, two proteins characteristic of neurons. Taken together the findings indicate that the GABA+ cells of the chick optic tract are neurons, perhaps similar to the interstitial neurons found in the white matter of other vertebrates.
Subpopulations of mesencephalic dopaminergic neurons express different levels of tyrosine hydroxylase messenger RNA
Authors: Weiss‐Wunder Linda T. , Chesselet Marie‐Françloise
Published: January 2005

Subpopulations of mesencephalic dopamine containing neurons possess different electro‐physiological, pharmacological, biochemical, and anatomical properties. In order to determine whether such differences are related to the regulation of tyrosine hydroxylase, the rate limiting enzyme in the synthesis of catecholamines, the regional distribution of tyrosine hydroxylase messenger RNA in these neurons was examined using in situ hybridization histochemistry. In the mouse, labelling for tyrosine hydroxylase messenger RNA associated with individual neurons was significantly less in the lateral substantia nigra pars compacta than in the medial substantia nigra pars compacta and the ventral tegmental area. A similar pattern of labelling was observed in the rat. Labelling for tyrosine hydroxylase messenger RNA was significantly less in the lateral substantia nigra pars compacta than in medial pars compacta (a densely cellular region), the area dorsal to the medial substantia nigra pars compacta (a less cell dense region), and the ventral tegmental area. Differences in levels of labelling for messenger RNA in mesencephalic dopamine neurons were not related to differences in cell size as measured in sections processed for tyrosine hydroxylase immunohistochemistry. The results suggest that tyrosine hydroxylase messenger RNA is differentially regulated in Subpopulations of mesencephalic dopamine neurons, supporting the view that these neurons are physiologically distinct.
Distribution of catecholamine uptake sites in human brain as determined by quantitative [3H] mazindol autoradiography
Authors: Donnan Geoffrey A. , Kaczmarczyk Stan J. , Paxinos George , Chilco Peter J. , Kalnins Renate M. , Woodhouse Dianne G. , Mendelsohn Frederick A. O.
Published: January 2005

Because of the importance of the catecholamine system in Parkinson's disease and its relevance to a variety of clinical movement disorders, catecholamine uptake sites were mapped in the human brain using [3H] mazindol autoradiography. Displacement studies with known dopamine (DA) and noradrenaline (NA) uptake blockers showed that binding in the striatum was to dopamine uptake sites; binding in the locus coeruleus was to noradrenergic uptake sites. By using the selective noradrenergic uptake blocker desmethylimipramine (DMI), a comprehensive map of both DA and NA uptake sites was generated. In general, catecholamine uptake sites were better seen in terminals than in cells of origin or axonal projections. In some areas, such as the locus coeruleus, punctate binding could be seen over individual pigmented cells. A variegated pattern of binding was seen in caudate nucleus and putamen and some correspondence of patches of low binding with striosomes was observed in the caudate. The highest levels of binding to DA uptake sites was observed in the striatum, where regional differences in binding occurred. The most dense binding was seen in the ventral striatum, and a rostral‐to‐caudal decrement in binding levels in caudate nucleus and putamen was evident. Binding was more intense in the putamen compared to the caudate and within the caudate lower values were seen laterally. The highest levels of binding to noradrenergic uptake sites were in the locus coeruleus and dorsal raphé, although these sites may be on terminals from other projections. Whereas uptake sites were more often evident in known catecholamine pathways, [3H mazindol binding was seen in some areas where catecholamine neurons or terminals had not been identified previously. These maps of the catecholamine uptake system add further information concerning the nature of the distribution of catecholamines in human brain and provide an important baseline for the study of disease and ageing processes.
Incorporation of 3H‐thymidine in the embryonic vomeronasal and olfactory epithelia of garter snakes
Authors: Holtzman David A. , Halpern Mimi
Published: January 2005

Previous studies have shown that the vomeronasal and olfactory epithelia of adult vertebrates provide good models for studying normal neuronal turnover and regeneration in response to axotomy. However, little is known about the cell dynamics in the embryonic vomeronasal and olfactory epithelia or the origins of different cell types in these structures. By using 3H‐thymidine autoradiography, both in vivo and in vitro, the origins of receptor and supporting cells and the survival of labelled cells in the embryonic vomeronasal and olfactory epithelia of garter snakes were examined. The results of this study suggest that the receptor and supporting cells of both epithelia arise from separate stem cells and that two subpopulations of stem cells exist for receptor cells in the embryonic vomeronasal epithelium. One subpopulation generates cells that migrate through the receptor cell columns, while another subpopulation remains at the base of the epithelium for approximately 50 days. Although it is unclear how long receptor cells in the embryonic olfactory epithelium survive, the results of this study suggest that they survive at least 37 days and may survive over 56 days. In addition, the development of these sensory epithelia appears different in early versus late embryos, and regeneration in the vomeronasal and olfactory epithelia of adult garter snakes appears similar to development during late gestation. Cells in the developing receptor cell layer of the olfactory epithelium lose their ability to incorporate 3H‐thymidine before those in the vomeronasal epithelium, suggesting that the onset of neuronal maturation occurs earlier in the olfactory epithelium than in the vomeronasal epithelium.
Localized denervation demonstrates the innervation pattern of olfactory bulb glomeruli and second order cells
Authors: Wellis David P. , Scott John W.
Published: January 2005

Sensory systems rely upon spatially organized projections for the faithful transfer of receptor activity into the central nervous system. While the mammalian olfactory nerve shows a regional topographical organization, data on the sources of variation within this projection are scarce. We evaluated the degree of precision of olfactory bulb glomerular innervation from the olfactory nerve layer (ONL) by making small cuts across the trajectory of the olfactory nerve fibers and assessing the resulting denervation by wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) labeling of primary nerve fibers. In control animals (no ONL cut), the ONL and glomerular layer showed intense labeling around the entire circumference of the bulb. Transneuronal labeling of the mitral cell layer and the external plexiform layer was also observed in animals surviving at least 2 days, which allowed us to study the nerve fiber innervation of second order cells as well. ONL cuts on the lateral face of the bulb produced a stripe of denervation, as evidenced by the absence of primary and transneuronal label in a well‐defined region. Fascicles of fibers within the ONL were never observed to enter the denervated region from more than one or two glomerular widths away, indicating a relatively tight limit of variation in the spatial termination of olfactory nerve fibers on the lateral bulb surface. This limit of variation does not hold around the circumference of the bulb since similar ONL cuts on the dorsal surface failed to produce a distinct stripe of denervation. Field potential measurements from the ONL after similar cuts supported the anatomic findings. These results show that primary olfactory axons and their terminals lie in parallel along the lateral face of the olfactory bulb. These spatial relationships of olfactory input to the bulb are maintained in the second order connections. This organization allows one to study the spatial aspects of interneuronally mediated synaptic mechanisms involved in olfactory coding.
Distribution of mRNAs coding for liver and heart gap junction proteins in the rat central nervous system
Authors: Micevych Paul E , Abelson Lauren
Published: January 2005

The present study examined the distributions of connexin43 mRNA and connexin32 mRNA in the central nervous system (CNS) of the rat by using in situ hybridization histochemistry. These connexins are the best studied gap junction proteins; connexin32 forms direct cell‐cell channels in the liver, as does connexin43 in the heart. There was a differential distribution of cells containing connexin32 mRNA compared with the population of cells which contained connexin43 mRNA, thus implying a regional specificity in the expression of connexins in the CNS. Cells containing connexin43 mRNA were uniformly distributed throughout the gray matter of the neuraxis. Several areas had a higher concentration of cells that express connexin43, such as layer IA of the piriform cortex, supraoptic and paraventricular nuclei of the hypothalamus, anterior cortical amygdaloid nucleus, the reticular part of the substantia nigra, lateral habenula, mesencephalic trigeminal nucleus, Purkinje cell layer of the cerebellum, facial nucleus, prepositus hypoglossal nucleus, and dorsal cochlear nucleus. The pattern of connexin43 hybridization and the morphology of connexin43 mRNA containing cells suggest that this gap junction forming protein is found predominantly in astrocytes, Con‐nexin32 mRNA was detected in discrete cell groups of the gray matter that appeared to be neurons, including cells in layer 2 of the neocortex, layer II of the piriform cortex, pyramidal cell layer of the hippocampus, granule and polymorphic cell layers of the dentate gyrus, islands of Calleja, olfactory tubercle, lateral thalamic nuclei, lateral habenula, and Purkinje cell layer of the cerebellar cortex. A large population of cells in white matter tracts that were labelled with the connexin32 riboprobe appeared to be oligodendrocytes. These studies suggest that neurons and glial cells express connexin32 mRNA, but only astrocytes express connexin43 mRNA. Many of the areas in which connexin mRNAs were demonstrated have electrically coupled cells, morphologically distinct gap junction plaques, and/or have immunocytochemically identifiable connexin proteins. These results indicate that cells with mRNAs coding for intercellular channels have a widespread distribution in the mammalian CNS.
Spatial relationships of axons arising from the substantia nigra, spinal trigeminal nucleus, and pedunculopontine tegmental nucleus within the intermediate gray of the cat superior colliculus
Authors: Harting John K. , Van Lieshout David P.
Published: January 2005

We have utilized two different anterograde transport methods (Phaseolus vulgaris leucoagglutinin [PHA‐L] immunocytochemistry and autoradiography) in the same experiment to compare the sublaminar location and arrangement of tectopetal axons arising from the substantia nigra pars reticulata, the spinal trigeminal nucleus, and the pedunculopontine tegmental nucleus.

Our findings reveal that the nigrotectal projection terminates in a patchy fashion within three horizontally oriented sublaminae of the stratum griseum superficial (SGI), the dorsal, middle and ventral. The middle tier of nigrotectal axons exhibits an exquisite, puzzle‐like, complementary spatial relationship with trigeminotectal axons. In contrast, axons arising from the pedunculopontine tegmental nucleus overlap with patches of nigrotectal axons within the middle tier. Thus the middle tier of the SGI consists of domains of overlapping nigral and pedunculopontine tegmental inputs which interdigitate with domains rich in somatosensory inputs.
The parabigeminogeniculate projection: Connectional studies in eight mammals
Authors: Harting John K. , Van Lieshout D. P. , Hashikawa T. , Weber J. T.
Published: January 2005

Anterograde and retrograde tracing methods have been used to analyze the origin and distribution of parabigeminogeniculate axons in the gray squirrel, the gopher, the rat, the opossum, the cat, the greater bushbaby, the squirrel monkey and the macaque monkey. Our findings reveal that parabigeminogeniculate axons most heavily innervate regions of the lateral geniculate that are also targeted by axons arising from the superior colliculus (tectogeniculate). These geniculate layers and zones of parabigeminal and tectal overlap contain small cells, and in several species are associated with the small W cell retino‐geniculocortical pathway.

In addition to the dense input to small‐celled layers and zones, parabigeminal axons in several species also innervate regions of the lateral geniculate nucleus that are relatively free of tectogeniculate axons and that are associated with the medium (X) and large (Y) cell streams.

Finally, our data reveal that the laterality of parabigeminogeniculate pathways varies across mammals, being primarily crossed in the gray squirrel, the gopher, the rat, and the opossum, bilateral in the cat, and primarily ipsilateral in the three primates.
Subregional topography of capillaries in the dorsal vagal complex of rats: II. Physiological properties
Authors: Gross Paul M. , Wall Katharine M. , Wainman Dan S. , Shaver Steven W.
Published: January 2005

The differentiated cytoarchitecture, neurochemistry, and capillary organization of the rat dorsal vagal complex prompted this comprehensive investigation of micro vascular physiology in 11 subdivisions of area postrema, 5 subnuclei of nucleus tractus solitarii (NTS), the dorsal motor nucleus of the vagus nerve, and 4 other gray matter structures in the dorsal medulla oblongata. Microvascular exchangeable volume (residual plasma volume), capillary blood and plasma flow, and unidirectional transfer constants for a tracer amino acid, [14C]α‐aminoisobutyric acid (AIB), varied considerably among the structures analyzed. Exchangeable volume, largest in area postrema medial zones (about 29 μl μl · g−1) and smallest in medullary gray matter (7–11 μl · g−1), correlated directly with subregional densities of capillaries and rates of tissue glucose metabolism. Capillary blood flow (range of 1,430–2,147 μl · g−1 · min−1), plasma flow, and tissue glucose metabolism (range of 0.48–0.71 μmol · g−1 · min−1) were linearly related in the dorsal vagal complex. The most striking quantitative difference among structures in this brain region were the rates of transcapillary influx and derived permeability X surface area (PS) products of [14C]AIB, which has physicochemical properties resembling those of hormones. PS products for AIB were negligible in most medullary gray matter regions (< 1 μl · g−1 · min−1, indicative of blood‐brain barrier properties), but were 20–59 × and 99–402 × higher in NTS subnuclei and area postrema, respectively. An extraordinary feature of the microcirculation in area postrema was the long‐duration transit of tracer sucrose and blood, a characteristic that would amplify the sensing ability of area postrema as it monitors the composition of the circulation.
Subcortical projections to the centromedian and parafascicular thalamic nuclei in the cat
Authors: Royce G. James , Bromley S. , Gracco C.
Published: January 2005

The primary objective of this study is to identify the totality of input to the centromedian and parafascicular (CM‐Pf) thalamic nuclear complex. The subcortical projections upon the CM‐Pf complex were studied in the cat with three different retrograde tracers. The tracers used were unconjugated horseradish peroxidase (HRP), horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP), and rhodamine‐labeled fluorescent latex microspheres (RFM).

Numerous subcortical structures or substructures contained labeled neurons with all three tracing techniques. These labeled structures included the central nucleus of the amygdala; the entopeduncular nucleus; the globus pallidus; the reticular and ventral lateral geniculate nuclei of the thalamus; parts of the hypothalamus including the dorsal, lateral, and posterior hypothalamic areas and the ventromedial and parvicellular nuclei; the zona incerta and fields of Forel; parts of the substantia nigra including the pars reticularis and pars lateralis, and the retrorubral area; the pretectum; the intermediate and deep layers of the superior colliculus; the periaqueductal gray; the dorsal nucleus of the raphe; portions of the reticular formation, including the mesencephalic, pontis oralis, pontis caudalis, gigantocellularis, ventralis, and lateralis reticular nuclei; the nucleus cuneiformis; the marginal nucleus of the brachium conjunctivum; the locus coeruleus; portions of the trigeminal complex, including the principal sensory and spinal nuclei; portions of the vestibular complex, including the lateral division of the superior nucleus and the medial nucleus; deep cerebellar nuclei, including the medial and lateral cerebellar nuclei; and lamina VII of the cervical spinal cord.

Moreover, the WGA‐HRP and rhodamine methods (known to be more sensitive than the HRP method) revealed several afferent sources not shown by HRP: the anterior hypothalamic area, ventral tegmental area, lateral division of the superior vestibular nucleus, nucleus interpositus, and the nucleus praepositus hypoglossi. Also, the rhodamine method revealed labeled neurons in laminae V and VI of the cervical spinal cord.
Organization of the cerebellum in the pigeon (Columba livia): II. Projections of the cerebellar nuclei
Authors: Arends J. J. A. , Zeigler H. Philip
Published: January 2005

The projections of the deep cerebellar nuclei in the pigeon have been delineated using autoradiographic and histochemical (WGA‐HRP) tracing techniques. A medial (CbM) and lateral (CbL) cerebellar nucleus are recognized and CbM may be further partitioned into internal, intermediate, and intercalate divisions. As in mammals, most extracerebellar projections of CbM travel in the fasciculus uncinatus (FU); the rest travel with those of CbL in the brachium conjunctivum (BC). In the pigeon, both of these pathways are bilaterally but primarily contralaterally projecting systems.

FU is a predominantly descending tract, with terminations within (1) the vestibular complex, (2) a column of contiguous medial reticular nuclei from pontine to caudal medullary levels; (3) the plexus of Horsley portion of the parvicellular reticular formation, continuing through the nucleus centralis medullae oblongatae, pars dorsalis, into intermediate layer VII of the cervical spinal cord, down to cervical segment 8–9; (4) the lateral reticular nucleus and the paragigantocellular reticular nucleus; (5) the dorsal lamella of the inferior olive. Rostrally FU terminals are found in the locus ceruleus and dorsal subcerulean nucleus. Minimal FU projections are also seen to the motor trigeminal nucleus and the subnucleus oralis of the descending trigeminal system. A small projection from the intercalate division of CbM travels in BC and projects upon the midbrain central grey, the intercollicular nucleus, the lateral tectal periventricular grey, the stratum cellulare externum and, sparsely, upon the dorsolateral thalamus.

The bulk of BC originates from the lateral cerebellar nucleus and consists of a massive ascending and a small descending branch. The ascending system projects upon the red nucleus and the dorsally adjacent interstitial nucleus of Cajal and midbrain central grey, the prerubral fields continuing into the stratum cellulare externum, the nucleus intercalatus thalami, the ventrolateral thalamic nucleus, the medial spiriform nucleus, the nucleus principalis precommissuralis, the nucleus of the basal optic root, the nucleus geniculatus lateralis pars ventralis, the dorsolateral thalamus, including the dorsal intermediate posterior, and the dorsolateral intermediate and anterior nuclei. BC also contains axons from the infracerebellar nucleus, which projects upon the trochlear and the oculomotor nuclei. The descending branch of BC distributes to the papilioform nucleus, the medial pontine nucleus, the gigantocellular and paramedian reticular nuclei, and, minimally, the rostral portions of the medial column and ventral lamella of the inferior olive.

Taken in conjunction with data on amphibia and reptiles the present findings suggest that the fundamental ground plan of vertebrate cerebellar organization involves a medial and lateral cerebellar nucleus. We conclude that, in the pigeon, these nuclei are homologous with the fastigial and interposed nuclei of mammals.