bluuebunny/crossref_metadata_2025 huggingface dataset:
Supraspinal projections to the ventromedial lumbar spinal cord in adult male rats
Authors: Shen Peter , Arnold Arthur P. , Micevych Paul E.
Published: January 2005

In the present study, the fluorescent tract tracing compound Fluorogold was used to study the afferents of the SNB (spinal nucleus of the bulbocavernosus), which is found in the ventromedial spinal grey and innervates penile muscles of the male rat. Fluorogold was iontophoretically injected into the SNB, which was located by recording antidromic activation of the motoneurons after stimulating the bulbocavernosus muscle, Retrogradely labeled cells were found in laminae I, V–IX, and area X of the lumbar spinal cord, suggesting segmental input to the SNB. Supraspinally, the greatest number of labeled cells were in the medulla oblongata, particularly in the lateral vestibular nucleus, gigantocellular reticular nucleus, and ventral and alpha divisions of the gigantocellular reticular nucleus. Labeled cells were also observed in the medullary raphe nuclei, the ventral medullary nucleus, and the spinal vestibular nucleus. In the pons, labeled cells were observed in the nucleus locus coeruleus, nucleus subcoeruleus, and caudal pontine reticular nucleus. No labeled cells were present in the cerebellum, rostral pons, mesencephalon, and cerebral cortex. The most rostral occurrence of labeled cells was in the medial parvicellular division of the hypothalamic para ventricular nucleus. These potential afferents to the SNB identified in male rats imply that the inputs to motoneurons that innervate sex‐specific muscles involved in male reproductive behavior may be similar to the inputs to lumbar motoneurons described in the female rat that innervate muscles involved in female sexual behavior.
Axonal regeneration and sprouting following injury to the cerebral–buccal connective in the snail Achatina fulica
Authors: Croll Roger P. , Baker Michael W.
Published: January 2005

Axonal sprouting and regeneration were studied in the land snail Achatina fulica following a unilateral crush to the cerebral–buccal connective. Both normal projection patterns and changes induced by injury were examined with axonal filling techniques. As expected, most staining was lost shortly after the crush when filling across the lesion site. Much of this decrease is attributable to the direct disruption of fiber pathways, but evidence also indicates that a limited amount of retraction of some neurites occurred during the first week. A subsequent, gradual increase in the numbers of stained elements culminated in supernumerary counts of fibers in many pathways and in some novel labeling of cell bodies, Maximum numbers of supernumerary fibers usually occurred 21–28 days after the lesion. Most of these extra neurites and cell bodies subsequently disappeared, and by day 35 the appearance of projections generally returned to within the ranges observed in normal, unlesioned animals. Together the results demonstrate the extent of neuritic regeneration, sprouting, and retraction that occurs in vivo within the gastropod nervous system following injury. The study also indicates the usefulness of such in vivo approaches to understand the long‐term processes that contribute to the restoration of morphological and functional integrity.
Development of two morphological types of retinopetal fibers in chick embryos, as shown by the diffusion along axons of a carbocyanine dye in the fixed retina
Authors: Frttzsch B. , de Caprona M.‐D. Crapon , Clarke P. G. H.
Published: January 2005

Centrifugal fibers to the retinas of chick embryos and hatched chicks have been examined and traced following staining by diffusion along their axonal membranes of the carbocyanine dye DiI in fixed tissue.

In the older embryos and hatched chicks, the report of Dogiel (Arch. Mikrosk. Anat. 44:622–648, 1895) has been confirmed that there are two very different morphological types of centrifugal fiber. The restricted type ends as a relatively thick fiber, lacking varicosities, that runs for a short distance in the most sclerad level of the inner plexiform layer before terminating in a pericellular nest overlying the flask‐shaped body of a single amacrine cell. Thin filaments occasionally leave the pericellular net, apparently to terminate on adjacent cells. The widespread type also runs in the most sclerad level of the inner plexiform layer, but it is thin, varicose, and highly branched, and its terminal arbor may span more than 1 mm, remaining at the same level. Both types of terminal arbor issue from parent axons in the optic fiber layer of the retina. A single parent axon gives either a single terminal fiber of the restricted type or several terminals of the widespread type, but never a mixture of the two. It is argued that the restricted and widespread types originate respectively from the neurons of the contralateral isthmo‐optic nucleus and from the “ectopic” neurons scattered outside the isthmo‐optic nucleus.

In development, the centrifugal fibers reach the retina between E9 and E10 and initially run radially in the optic fiber layer, parallel to the retinofugal fibers but avoiding the dorsal retina. They dive into the inner plexiform layer at about E12. By E13, the terminal arbors are forming, and the widespread and restricted types can already be distinguished. The widespread type continues to increase its territory until about E18, and then appears to remain stable, whereas the restricted type attains its maximum ramification between E13 and E15 and then contracts. Prior to the retraction, the terminal territories of the restricted type fibers overlap, which may provide the anatomical basis for the interaxonal competition that apparently contributes to neuronal death in the isthmo‐optic nucleus between E13 and E16. Axons of ganglion cells exhibit transient side branches between E11 and E13; these never reach as deep as the level where the centrifugal fibers run.
Connections of the retrosplenial granular a cortex in the rat
Authors: van Groen Thomas , Michael Wyss J.
Published: January 2005

Although the retrosplenial granular a cortex (Rga) is situated in a critical position between the hippocampal formation and the neocortex, few studies have examined its connections. The present experiments use both retrograde and anterograde tracing techniques to characterize the afferent and efferent connections of Rga. Cortical projections to Rga originate in the ipsilateral area infraradiata, the retrosplenial agranular and granular b cortices, the ventral subiculum, and the contralateral Rga. Subcortical projections originate in the claustrum, the diagonal band of Broca, the thalamus, the midbrain raphe nuclei, and the locus coeruleus. The thalamic projections to Rga originate mainly in the anterodorsal (AD) and laterodorsal (LD) nuclei, with sparse projections arising in the anteroventral (AV) and reuniens nuclei. Each projection to Rga terminates in distinct layers of the cortex. The thalamic projection from AD terminates primarily in layers I, 111, and IV of Rga, whereas the s o n s arising from the LD nucleus have a dense terminal plexus only in layer I. The projections arising from the subiculum end predominantly in layer 11, whereas the postsubiculum projects to layers I and 111‐V. Axons from the contralateral Rga form a dense terminal plexus in layers IV and V, with a smaller number of terminals in layers I and VI. Rga projects ipsilaterally to the AV and LD nuclei of the thalamus and to the anterior cingulate, retrosplenial agranular, and postsubicular cortices. Contralaterally it projects to the retrosplenial agranular and Rga cortices. Rga projections to the thalamus terminate ipsilaterally in the dorsal part of LD and bilaterally in AV. Together, these data suggest that Rga integrates thalamic with limbic information.
Segregation of afferent projections in the central nervous system of the leech Hirudo medicinalis
Authors: Peinado Alejandro , Zipser Birgit , Ml Eduardo R.
Published: January 2005

Sensory axons originating in peripheral tissues converge onto each segmental ganglion in the central nervous system (CNS) of the leech, where they segregate into well‐defined regions of the synaptic neuropil. Here we report on several aspects of the molecular and anatomical organizations of these afferent projections1 that bear upon the hypothesis that surface markers are involved in organizing these axons as they grow into the CNS. First, we show that the distribution of some surface markers in the adult is restricted to axons of peripheral origin and is not present on the neighboring axons of central neurons. Second, we demonstrate that the number of afferents increases postembryonically as the leech increases in size, suggesting that at least some of the cues employed by afferent axons to grow to appropriate central targets must be present throughout the life of the animal. We then show, using anterograde axonal tracing and immunohistochemistry, that there is both convergence and divergence of afferent axons into highly specific regions of the neuropil. Lastly, we examine the distribution of surface markers present on different subsets of afferents and show that axons having one type of marker segregate from those having the second type.

Our results, considered together with previous observations in this system, provide new clues about the organization of afferent projections in the nervous system of the leech. They also suggest how a relatively small number of molecular markers might mediate fiber‐fiber interactions to organize afferent axons as they grow into the CNS.
Nuclei of origin of monoaminergic, peptidergic, and cholinergic afferents to the cat trigeminal motor nucleus: A double‐labeling study with cholera‐toxin as a retrograde tracer
Authors: Fort Patrice , Luppi Pierre‐Herve , Sakai Kazuya , Salvert Denise , Jouvet Michel
Published: January 2005

The aim of the present study was to determine the brainstem afferents and the location of neurons giving rise to monoaminergic, cholinergic, and peptidergic inputs to the cat trigeminal motor nucleus (TMN). This was done in colchicine treated animals by using a very sensitive double immunostaining technique with unconjugated cholera‐toxin B subunit (CT) as a retrograde tracer.

After CT injections in the TMN, retrogradely labeled neurons were most frequently seen bilaterally in the nuclei reticularis parvicellularis and dorsalis of the medulla oblongata, the alaminar spinal trigeminal nucleus (magnocellular division), and the adjacent pontine juxta‐trigeminal region and in the ipsilateral mesencephalic trigeminal nucleus. We further observed that inputs to the TMN arise from the medial medullary reticular formation (the nuclei reticularis magnocellularis and gigantocellularis), the principal bilateral sensory trigeminal nucleus, and the dorsolateral pontine tegmentum.

In addition, the present study demonstrated that the TMN received (1) serotonergic afferents, mainly from the nuclei raphe obscurus, pallidus, and dorsalis; (2) catecholaminergic afferent projections originating exclusively in the dorsolateral pontine tegmentum, including the Kölliker‐Fuse, parabrachialis lateralis, and locus subcoeruleus nuclei; further, that (3) methionin‐enkephalin‐like inputs were located principally in the medial medullary reticular formation (nuclei reticularis magnocellularis and gigantocellularis and nucleus paragigantocellularis lateralis), in the caudal raphe nuclei (Rpa and Rob) and the dorsolateral pontine tegmentum; (4) substance P‐like immunoreactive neurons projecting to the TMN were present in the caudal raphe and Edinger‐Westphal nuclei; and 5) cholinergic afferents originated in the whole extent of the nuclei reticularis parvicellularis and dorsalis including an area located ventral to the nucleus of the solitary tract at the level of the obex.

In the light of these anatomical data, the present report discusses the possible physiological involvement of TMN inputs in the generation of the trigeminal jaw‐closer muscular atonia occurring during the periods of paradoxical sleep in the cat.
Distribution of parvalbumin immunoreactivity in the visual cortex of Old World monkeys and humans
Authors: Blümcke Ingmar , Hof Patrick R. , Morrison John H. , Celio Marco R.
Published: January 2005

The macaque visual system has been frequently used as a model for understanding functional aspects of human vision. There are, however, few studies directly comparing biochemically defined neuronal populations in the visual cortex of the two species.

In this study we compared the distribution and morphological features of the parvalbumin‐immunoreactive neuronal subpopulation within humans and Old World monkeys (Macaca fascicularis and Macaca mulatta) by using monoclonal antibodies against the Ca2+‐binding protein parvalbumin (PV), a neuronal marker in the vertebrate cerebral cortex. Characteristic laminar density and distribution of PV is observed, matching that seen with cytochrome C‐oxidase and γ‐aminobutyric acid (GABA) immunoreactivity. Thus, parvalbumin is prominent in the layers receiving afferents from the dorsal lateral geniculate nucleus. Terminal fields are rich in layer IVA and IVC and moderate in the blob‐region of layer II–III of the monkey cortex. In the human visual cortex only layer IVC displays rich terminal fields. Parvalbumin is present in neurons within all layers of the cortex except layer I. Parvalbumin‐immunoreactive (PV‐ir) axons occur in different lamellae of the white matter containing axons belonging to association or projection neurons. The estimation of PV‐ir neurons, determined for 50 μm‐wide columns through the thickness of area 17, shows that the percentage of the total neuron number in area 17 of humans containing PV is 6.8 ± 2.0%, and in the macaque monkey, 11.5 ± 2.9%. The perikaryal area of PV‐ir neurons varies according to the layer and is comparable in humans (109.3 ± 40.8 μm2) and monkeys (94.3 ± 29.5 μm2). However, the relative number of large PV‐ir neurons is higher in humans. The immunoreactive product fills the thinnest cell processes and the shape of PV‐ir neurons can be easily traced with the aid of a camera lucida. The shape of the neurons is similar in the two species studied, and they probably belong to non‐spiny stellate, double‐bouquet, chandelier, and basket cell classes.

This study shows that parvalbumin acts as a marker for a subpopulation of interneurons in area 17, but it is also present in the geniculocortical as well as in corticocortical pathways. Moreover, the Old World monkey and human visual cortices have a similar, but not identical, distribution of this important calcium‐binding protein.
Sources of subcortical GABAergic projections to the superior colliculus in the cat
Authors: Appell Peter P. , Behan Mary
Published: January 2005

The goal of this study was to identify GABAergic input to the cat superior colliculus from neurons located in the caudal diencephalon, mesencephalon, pons and medulla. Cells efferent to the superior colliculus were labeled retrogradely with the tracer horseradish peroxidase, and an antibody to gamma‐aminobutyric acid was used to label GABAergic neurons in the same sections.

The results indicate that neurons in several distinct areas of the caudal diencephalon and brainstem are both immunocytochemically labeled for GABA and retrogradely labeled with horseradish peroxidase. These areas include zona incerta, nucleus of the posterior commissure, anterior and posterior pretectal nuclei, nucleus of the optic tract, superior colliculus, cuneiform nucleus, subcuneiform area, substantia nigra pars reticulata and pars lateralis, periparabigeminal area, external nucleus of the inferior colliculus, the area ventral to the external nucleus of the inferior colliculus, mesencephalic reticular formation, dorsal and ventral nuclei of the lateral lemniscus, and the perihypoglossal nucleus.

The role that such diverse inhibitory input to the superior colliculus might play, particularly in influencing eye movements, is discussed.
Extrinsic projections from area CA1 of the rat hippocampus: Olfactory, cortical, subcortical, and bilateral hippocampal formation projections
Authors: Van Groen Thomas , Wyss J. Michael
Published: January 2005

Hippocampal area CA1 provides the major cortical output of the hippocampus, but only its projections to the subiculum and lateral septal nucleus are well characterized. The present study reexamines these extrinsic projections by using anterograde and retrograde tracing techniques. Injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA‐L) in the septal one‐third of CA1 label axons and terminals in subicular, postsubicular, retrosplenial, perirhinal, and entorhinal cortices, lateral septal nucleus, and diagonal band of Broca. The septal CA1, injections also label terminal fields in contralateral CA1, and in contralateral subicular, postsubicular, perirhinal, and entorhinal cortices. Injections into the splenial one‐third of CA1 label axons and terminals in subiculum, postsubiculum, ventral area infraradiata, and lateral septal nucleus, but they do not label axons and terminals on the contralateral side of the brain. Injections in the temporal one‐third of CA1 label axons and terminals in subicular, parasubicular, entorhinal, and infraradiata cortices, anterior olfactory nucleus, olfactory bulb, lateral septal nucleus, nucleus accumbens, amygdala, and hypothalamus. The temporal CA1 injections label no axons on the contralateral side of the brain. These data demonstrate that CA1 has more widespread projections than previously appreciated, and they provide the first clear evidence that CA1 projects to the contralateral cortex and to the ipsilateral olfactory bulb, amygdala, and hypothalamus. The results also demonstrate a heterogeneity in the efferent projections originating in different septotemporal levels of CA1.
Distribution of mu, delta, and kappa opioid receptor binding sites in the brain of the one‐day‐old domestic chick (Gallus domesticus): An in vitro quantitative autoradiographic study
Authors: Csillag Andras , Bourne Rachel C. , Stewart Michael G.
Published: January 2005

Three highly specific opioid ligands—[D‐Ala2, Gly‐ol.]‐enkephalin (DAGO) for mu (m̈) receptor sites, [D‐Pen2, D‐Pen5]‐enkephalin (DPDPE) for delta (δ) sites, and U‐69593 for kappa (κ) sites—were used to determine the regional distribution of the three major subtypes of opioid receptor binding sites in the brains of 1‐day‐old domestic chicks by the technique of quantitative receptor autoradiography. Whilst there was a degree of heterogeneity in the binding levels of each of the ligands, some notable similarities existed in the binding of the μ and κp ligands in several forebrain regions, and in the optic tectum of the midbrain where μ and δ binding was very high. In the forebrain there was a high level of binding of μ and κ ligands in the hyperstriatum, and for the μ ligand there was a very distinct lamination of binding sites in hyperstriatum accessorium, intercalatum supremum, dorsale and ventrale. Levels of binding of the μ and κ ligands were also high in nucleus basalis, and (for μ only) in the neostriatum. The distribution of binding of the δ specific ligand in the forebrain showed marked differences to that of μ and κ, being particularly low in the hyperstriatum and neostriatum. Very high levels of labelling of δ binding sites were, however, found in the nucleus rotundus. Binding of the three ligands was generally low or absent in the cerebellum and medulla, apart from a distinct labelling of the granule cell layer by the μ‐ligand. A kinetic analysis was made of the binding of the three ligands to whole forebrain sections using scintillation counting methods. The μ‐ligand DAGO had the highest affinity, KD (1.0 n mol L−1), followed by the κ ligand U69593 (4.6 n mol L−1), and then the δ ligand DPDPE (6.0 n mol L−1). The Bmax varied from 14.6 f mol/mg tissue for the μ ligand to 6.3 fmol/mg tissue (δ), and 4.3 fmol/mg tissue (κ). However, an analysis of the kinetics of binding of the μ, δ, and κ ligands to individual forebrain regions by quantitative receptor autoradiography revealed a considerable variation in the affinity for binding sites and in maximal binding levels. A previous study was made of the distribution of the three opioid binding sites in adult pigeon brain by Reiner et al. (Journal of Comparative Neurology 280:359–382, 1989). The present data show some similarities to the earlier study, but there are also marked dissimilarities which may be due either to species specific, or age related, differences. In the domestic chick the greatest densities of opiate receptor binding sites appear to coincide with regions involved in higher order sensory processing and memory storage.
GABA: A dominant neurotransmitter in the hypothalamus
Authors: Decavel Chantal , Van Den Pol Anthony N.
Published: January 2005

To study the organization and distribution of the inhibitory amino acid neurotransmitter GABA in the medial hypothalamus, we used a postembedding immunocytochemical approach with colloidal gold. Quantitative analysis showed that half (49%) of all synapsing boutons studied were immunoreactive for GABA, based on immunogold staining of the suprachiasmatic, arcuate, supraoptic, and paraventricular nuclei. This was corroborated with pre‐embedding peroxidase immunostaining with antisera against glutamate decarboxylase, the GABA synthetic enzyme. These data suggest that GABA is the numerically dominant neurotransmitter in the hypothalamus, and emphasize the importance of inhibitory circuits in the hypothalamus.

Serial ultrathin sections were used to reconstruct GABA immunoreactive boutons and axons in three dimensions. With this type of analysis we found less morphological heterogeneity between GABA immunoreactive boutons than with single ultrathin sections. Single sections sometimes showed boutons containing only small clear vesicles, and others with both clear vesicles and small dense core vesicles. However, with serial sections through individual boutons, dense core vesicles were consistently found at the periphery of the pre‐synaptic GABA immunoreactive boutons, suggesting probable co‐localization of GABA with unidentified peptides in most if not all boutons throughout the hypothalamus.

A positive correlation was found between the density of small clear vesicles and the intensity of immunostaining with colloidal gold particles. GABA immunoreactive axons generally made symmetrical type synaptic specializations, although a small percentage made strongly asymmetrical synaptic specializations. Vesicles in GABA immunoreactive boutons were slightly smaller than those in non‐reactive boutons.

Synaptic efficacy is related to the position of the synapse on the post‐synaptic neuron. While the majority of GABA immunoreactive axons made synaptic contact with dendrites, the distribution of GABA immunoreactive synapses on somata and dendrites was the same as would be expected from a random distribution of all boutons. No preferential innervation of cell bodies by GABA immunoreactive terminals was found. Serial ultrathin sections showed that a GABA immunoreactive axon would sometimes make repeated synaptic contacts with a single postsynaptic neuron, indicating a high degree of direct control by the presynaptic GABAergic cell. Other immunoreactive axons made synaptic contact with a number of adjacent dendrites and cells, suggesting a role for GABA in synchronizing the activity of hypothalamic neurons. Based on the density of immunogold particles per unit area, varying concentrations of immunoreactive GABA were found in different presynaptic boutons in the hypothalamus.
Light‐stimulated rhabdom turnover in Limulus ventral photoreceptors maintained in vitro
Authors: Herman Karen G.
Published: January 2005

The role of light in turnover of photosensitive membranes was studied in isolated photoreceptors maintained in vitro. Ventral photoreceptors of the horseshoe crab, Limulus polyphemus, were used since they have been the subjects of many in vitro physiological studies. This study shows that the two classes of ventral photoreceptors, the large and small photoreceptors (Herman: companion paper), differ in their morphological response to light. The rhabdom of small photoreceptors is remarkable for its regularity, independent of lighting condition. The photosensitive microvilli of the rhabdom of small photoreceptors are narrow and almost always tightly packed in a hexagonal arrangement.

In contrast, the morphology of the rhabdom of the large ventral photoreceptors is different in the dark and in the light, and the rhabdom undergoes turnover during lighting transitions. When fully dark‐adapted, the photosensitive microvilli of large photoreceptors are narrow and well organized, sometimes in a crystalline array. However, in the light‐adapted state, the microvilli are much thicker and very irregular. The transitions between the dark and light‐adapted states, examined at midday, are rapid. After 5 minutes light exposure, the microvilli are dilated at their bases and shed membranes are present in the cytoplasm. By 30 minutes after light onset, the appearance of the rhabdom of large photoreceptors is indistinguishable from fully light‐adapted cells. The transition to the dark‐adapted state is equally rapid. Even at 5 or 12 minutes after light offset, most microvilli are narrow and quite regular, and by 30 minutes, the rhabdom usually appears to be fully dark‐adapted. These experiments show that both the synthetic and degradative phases of rhabdom renewal take place in isolated photoreceptors. No efferent neural activity is required to initiate turnover; rather, changes in illumination alone are sufficient to generate rhabdom turnover in large ventral photoreceptors in vitro.
Morphological characteristics and terminating patterns of masseteric neurons of the mesencephalic trigeminal nucleus in the rat: An intracellular horseradish peroxidase labeling study
Authors: Luo P. F. , Wang B. R. , Peng Z. Z. , Li J. S.
Published: January 2005

In order to study the morphological characteristics and terminating patterns of the neurons of the trigeminal mesencephalic nucleus (Vme),55 masseteric neurons in Vme in the rat were stained by intracellular injection of horseradish peroxidase (HRP). Labeled cells were distributed throughout the nucleus. These neurons were divided into three types: uni‐ or pseudounipolar (type A, n = 43), bipolar (type B, n = 5), and multipolar cells (type C, n = 7). Each type was further divided into two subtypes according to the largest diameter of the perikarya (type a ≥ 30 μm, type b < 30 μm).

The central processes of type Aa neurons projected to the following three groups of target nuclei: (1) nuclei functioning as interneurons, including supratrigeminal nucleus (Vsup), intertrigeminal nucleus (Vint), juxta‐trigeminal region (Vjux), and parvicellular nucleus of the pontomedullary reticular formation (PcRF); (2) motor nuclei, including the trigeminal motor nucleus (Vmo), accessory facial nucleus (NVIIacs), accessory abducens nucleus (NVIacs), and a small number of labeled axons in the oculomotor nucleus and trochlear nucleus; (3) sensory nuclei, including the dorsomedial part of the principal trigeminal sensory nucleus (Vpdm) and the dorsomedial part of subnucleus oralis of the trigeminal spinal nucleus (Vodm). Labeled processes were dense in the Vsup, Vmo, and Vpdm.

The proprioceptive pathway of the fifth nerve is discussed. Direct projections from type Aa neurons of Vme to the Vpdm and dorsolateral part of the Vsup contribute to conduction of the proprioceptive information from spindles of masticatory muscle to the contralateral thalamus in the rat.

Different axon morphology, distribution, terminal branch density, and terminating patterns of type Aa neurons were noted in different functional groups of the projecting nuclei, especially in the Vsup, Vmo, and Vpdm. The highest terminal branching density, the most extensive distribution, and two different types of branching patterns (claw‐like and comb‐like) were observed in Vsup. Selective distribution and single‐beaded or “Y”‐shaped terminal branches were observed in Vmo. In the Vpdm the axtinal branches were sparser than in the Vsup or Vmo, and had an arrangement like the branches of a weeping willow tree. These characteristics of anatomical organization might be related to the function of each projecting nucleus.
GABAergic circuitry in the rostral ventral medulla of the rat and its relationship to descending antinociceptive controls
Authors: Cho Hee Jung , Basbaum Allan I.
Published: January 2005

This study used postembedding immunocytochemistry to examine the organization of GABA‐immunoreactive synapses in the rostral ventral medulla (RVM) of the rat. To determine whether the outflow neurons of the RVM are under GABAergic control, we examined the distribution of GABA‐immunoreactive synapses upon bulbospinal projection neurons that were labelled by retrograde transport of wheatgerm agglutinin‐HRP from the cervical spinal cord. To study the possible convergence of GABAergic and periaqueductal gray (PAG) synaptic inputs to RVM neurons, we also made lesions in the PAG and examined the relationship between degenerating PAG axons and GABA‐immunoreactive terminals.

Approximately 45% of all synapses in the RVM, which includes the midline nucleus raphe magnus and the nucleus reticularis paragigantocellularis lateralis, were GABA‐immunoreactive. The vast majority of GABA‐immunoreactive terminals contained round, clear, and pleomorphic vesicles and made symmetrical axodendritic synapses; axoaxonic synapses were not found. Almost 50% of the retrogradely labeled dendrites in the NRM were postsynaptic to GABA‐immunoreactive terminals. Several examples of convergence of degenerating PAG terminals and GABAergic terminals onto the same unlabelled dendrite were also found. These data indicate that the projection neurons of the RVM are urider profound GABAergic inhibitory control. The results are discussed with regard to the hypothesis that the analgesic action of narcotics and electrical stimulation of the midbrain PAG involves the regulation of tonic GABAergic inhibitory controls that are exerted upon spinally‐projecting neurons of the nucleus raphe magnus.
“Sunbursts” in the inner plexiform layer: A spectacular feature of Müller cells in the retina of the cat
Authors: Stone Jonathan , Holläunder Horstmar , Dreher Zofia
Published: January 2005

A previously unrecognised structure in the cat retina is described. Seen in Golgi‐impregnated, wholemounted retinas, each such structure comprises processes radiating across the inner plexiform layer from a dense, vellate core. The processes are numerous, and largely unbranched, and give the impression of rays radiating from a point source; the structure is therefore termed a “sunburst.” Evidence is presented from Golgi‐impregnated retinas, and from retinas labelled with monoclonal antibodies to Müller cells, that the core of each sunburst is the inner process of a Müller cell. The sunbursts are numerous and overlap extensively, so that when neighbouring sunbursts are impregnated, they are seen to form a dense mat of processes extending across the IPL. It is suggested that each Müller cell forms a sunburst and that sunbursts form a major glial component of the neuropil of the inner plexiform layer.
Comparative analysis of dopamine and tyrosine hydroxylase immunoreactivities in the brain of two amphibians, the anuran Rana ridibunda and the urodele Pleurodeles waltlii
Authors: Gonzalez Agustin , Smeets Wilhelmus J. A. J.
Published: January 2005

To gain more insight into the dopaminergic system of amphibians and the evolution of catecholaminergic systems in vertebrates in general, the distribution of dopamine and tyrosine hydroxylase immunoreactivity was studied in the brains of the anuran Rana ridibunda and the urodele Pleurodeles waltlii. In both species, dopamine‐immunoreactive (DAi) cell bodies were observed in the olfactory bulb, the preoptic area, the suprachiasmatic nucleus, the nucleus of the periventricular organ and its accompanying cells, the nucleus of the posterior tubercle, the pretectal area, the midbrain tegmentum, around the solitary tract, in the ependymal and subependymal layers along the midline of the caudal rhombencephalon, and ventral to the central canal of the spinal cord. Tyrosine hydroxylase (TH) immunohistochemistry revealed a similar pattern, although some differences were noted. For example, with the TH antibodies, additional cell bodies were stained in the internal granular layer of the olfactory bulb and in the isthmal region, whereas the same antibodies failed to stain the liquor contacting cells in the nucleus of the periventricular organ.

Both antisera revealed an almost identical distribution of fibers in the two amphibian species. Remarkable differences were observed in the forebrain. Whereas the nucleus accumbens in Rana contains the densest DAi plexus, in Pleurodeles the dopaminergic innervation of the striatum prevails. Moreover, cortical structures of the newt contain numerous DAi fibers, whereas the corresponding structures in the frog are devoid of immunoreactivity. The dopaminergic system in amphibians appears to share many features not only with other anamniotes but also with amniotes.
Organization of motor units in the axolotl: A continuously growing animal
Authors: Bewick G. S. , Rowlerson A. , Tonge D. A. , Holder Nigel
Published: January 2005

The characteristics of motor units in the iliotibialis posterior muscle of the axolotl hindlimb are described. Tension recording and intracellular electrophysiological methods demonstrate that the physiological properties of the population of motor units are continuously distributed rather than grouped into a series of discrete types. Overlap between motor units occurs and this is positively correlated with motor unit size but negatively correlated with differences in time to peak tension. Immunocytochemical staining with antimyosin antibodies combined with histochemical demonstration of actomyosin ATPase activity revealed at least four types of muscle fibre which were distributed asymmetrically within iliotibialis posterior. The results are discussed in terms of the continuous growth of the muscle and the interactions between muscle and nerve in the formation of the axolotl motor system.
Trajectory of spinocerebellar fibers passing through the inferior and superior cerebellar peduncles in the rat spinal cord: A study using horseradish peroxidase with pedunculotomy
Authors: Yamada Jinzo , Shirao Kuniaki , Kitamura Taiko , Sato Hitoshi
Published: January 2005

The course of spinocerebellar fibers in the rat spinal cord was investigated by injecting horseradish peroxidase into the cerebellar anterior vermis after complete transection of the left inferior and right superior cerebellar peduncles. By this procedure, fibers passing via the inferior cerebellar peduncles (icp‐fibers) were labeled retrogradely on the right side of the spinal cord, whereas fibers passing via the superior cerebellar peduncles (scp‐fibers) were labeled on the left side. Crossed icp‐fibers were located diffusely in the anterior and lateral funiculi in the sacral to lower lumbar segments. They gradually migrated laterally and dorsally in these funiculi and received many uncrossed icp‐fibers moving laterally in the lateral funiculus from the gray substance in the upper lumbar to lower thoracic segments. These mixed fibers shifted more dorsally and laterally in the anterior and lateral funiculi to aggregate in the narrow peripheral zone of the lateral funiculus in the upper thoracic and lower cervical segments, and received many crossed fibers in the upper cervical segments. There were more icp‐fibers than scp‐fibers through the spinal cord. However, the extent of scp‐fibers in the anterior and lateral funiculi was essentially the same as that for icp‐fibers, except that a few scp‐fibers were found in the dorsolateral marginal zone of the lateral funiculus. It has been generally accepted that the dorsal spinocerebellar tract ascends in the dorsal half of the lateral funiculus and enters the cerebellum via the inferior cerebellar peduncle, whereas the ventral spinocerebellar tract ascends in the ventral half of it and takes the superior cerebellar peduncle route. The results of this study suggest that it is necessary to revise this concept.
The reticular thalamic nucleus (RTN) of the rat: Cytoarchitectural, Golgi, immunocytochemical, and horseradish peroxidase study
Authors: Spreafico R. , Battaglia G. , Frassoni C.
Published: January 2005

Experiments have been performed on adult albino rats in order to study the cellular organization of the thalamic reticular nucleus. For this purpose four approaches have been used: Nissl stain, Golgi impregnation, retrograde transport of horseradish peroxidase after injection in different thalamic nuclei, and immunocytochemistry with antibodies against GABA and glutamic acid decarboxylase. In sections through the horizontal plane, three morphologically different neurons have been observed. Cells with round perikarya and with multipolar dendrites were found predominantly in the rostral pole of the nucleus. Neurons with large fusiform cell body and with dendrites arborizing mainly on the horizontal plane were detected through the whole extent of the nucleus. Small fusiform neurons were observed almost exclusively in the medial third of the dorso‐ventral extent of the nucleus. The Golgi impregnation method demonstrated that dendrites of small fusiform neurons develop in the vertical plane perpendicular to the dendritic arborization of large fusiform neurons. In coronal sections neurons with round perikarya and with large fusiform cell bodies are detectable while small fusiform neurons are only rarely visible. These data have been confirmed by statistical form factor analysis. Moreover, by means of the horseradish peroxidase and the immunocytochemical study, it has been confirmed that all three groups of neurons project within the thalamus and that they are GABAergic. The data concerning the distribution within the nucleus of the three morphologically different neurons are discussed in relation to the topographic distribution of cortical sensory afferents and to the topographic maps within different sectors of the reticular nucleus.
Laminar and regional distribution of galanin binding sites in cat and monkey visual cortex determined by in vitro receptor autoradiography
Authors: Rosier A. M. , Vandesande F. , Orban G. A.
Published: January 2005

The distribution of galanin (GAL) binding sites in the visual cortex of cat and monkey was determined by autoradiographic visualization of [125I]‐GAL binding to tissue sections. Binding conditions were optimized and, as a result, the binding was saturable and specific. In cat visual cortex, GAL binding sites were concentrated in layers I, IVc, V, and VI. Areas 17, 18, and 19 exhibited a similar distribution pattern. In monkey primary visual cortex, the highest density of GAL binding sites was observed in layers II/III, lower IVc, and upper V. Layers IVA and VI contained moderate numbers of GAL binding sites, while layer I and the remaining parts of layer IV displayed the lowest density. In monkey secondary visual cortex, GAL binding sites were mainly concentrated in layers V–VI. Layer IV exhibited a moderate density, while the supragranular layers contained the lowest proportion of GAL binding sites. In both cat and monkey, we found little difference between regions subserving central and those subserving peripheral vision. Similarities in the distribution of GAL and acetylcholine binding sites are discussed.
Basic FGF‐like immunoreactivity in the developing and adult rat brainstem
Authors: Grothe Claudia , Zachmann Karolin , Unsicker Klaus
Published: January 2005

Although a variety of in vitro and in vivo actions of basic fibroblast growth factor (bFGF) on neuronal cells have been documented, the physiological role of this protein in the nervous system is still contested. Since the distribution of a molecule in the nervous system may provide cues for an understanding of its possible roles, we have begun to study its cellular localization in the central and peripheral nervous system using immunocytochemistry with an anti‐bFGF‐specific antibody. Here we provide an account on the distribution of bFGF‐like immunoreactivity (bFGF‐IR) in the brainstem of the developing and adult rat. Basic FGF‐IR was found to be widely distributed in motor and sensory nuclei. In all nuclei examined, only subpopulations of neurons were stained. Different staining patterns were found. For example, in the red nucleus weakly or unstained perikarya were surrounded by numerous immunoreactive fibers, often in close contact with the neuronal surface. In the reticular formation and facial nerve, many neuronal cell bodies showed a strong IR that extended into the processes. Glial cells were consistently unstained. During early postnatal development changes of the distribution of bFGF IR were found. From this wide distribution pattern of bFGF‐IR, we conclude that bFGF may have more general and, possibly, diverse functions rather than a restricted role for a particular subset of neurons. Variations in the staining pattern of nerve cell bodies in a single nucleus may suggest a function related to neuronal activity.
Somatosensory cortex of the neonatal pig: I. Topographic organization of the primary somatosensory cortex (SI)
Authors: Craner Sandra L. , Ray Richard H.
Published: January 2005

The cerebral cortex of adult mammals contains several somatotopic representations of the body surface. Although the organization of the various somatosensory cortices of numerous species of adult animals has been elucidated, data on the somatosensory representations of fetal and neonatal animals are limited. As part of an investigation into the perinatal development of the somatosensory cortices, it was necessary to delineate the organization of the somatosensory cortices of the perinatal pig. This study presents the topographical organization of the primary somatosensory cortex (SI) of the perinatal pig.

Multiunit microelectrode mapping methods were used to produce topographic maps of SI from barbiturate anesthetized pigs ranging in age from 7 days preterm to 2 months postpartum. It was demonstrated that the overall organization of this region of cortex was similar to that of other mammals: a somatotopic projection of predominantly the contralateral body surface was delineated in which the hindlimb is represented medially and the face laterally across the cortex. A disproportionately enlarged rostrum representation was mapped in detail, and multiple representations of the rostrum, face, and mouth were found. Several of these representations exhibited bilateral and ipsilateral input. The SI trunk and hindlimb representations were located on the medial wall of the hemisphere; these representations were small but their presence refutes speculation that ungulates do not have a complete body representation in SI.
Regular mosaics of large displaced and non‐displaced ganglion cells in the retina of a cichlid fish
Authors: Cook Jeremy E. , Becker David L.
Published: January 2005

Large retinal ganglion cells in the tilapid cichlid fish Oreochromis spilurus (standard length 15–54 mm) were filled with horseradish peroxidase and studied in flatmounts. Three types, with distinct patterns of dendritic stratification, formed spatially independent, nonrandom mosaics.

One type (about 0.3% of all ganglion cells) resembled the outer (off) alpha cells of mammals. They were very large, with thick primary dendrites and large, sparsely branched planar trees in the outer part of the inner plexiform layer (IPL). About 300 were arrayed regularly across each retina, their exact number and spacing depending on its size. Their somata were often displaced into the IPL, even where neighbours in the mosaic were orthotopic. Another type (0.8%) resembled the inner (on) alpha cells of mammals. These had slightly smaller somata that were never displaced and smaller trees in the middle layers of the IPL. About 800 were arrayed uniformly and regularly across each retina. A rarer type (0.06–0.08%) had two planar trees: one forming a coarse mosaic in the outer part of the inner plexiform layer (co‐planar with the trees of outer alpha‐like cells) and another in the outer plexiform layer. These “biplexiform” cells were smaller and rounder than alpha‐like cells and always displaced. The dendrites were finer and less tapered. Cells in which we could identify an outer plexiform tree failed to cover the retina completely, but were nonrandomly distributed.

We draw three main conclusions: (1) some nonmammalian vertebrates have separate inner and outer mosaics of large ganglion cells like those of mammals, (2) the vertical displacement of ganglion cell somata can vary widely within a single mosaic and may thus be functionally irrelevant, and (3) biplexiform ganglion cells exist in fish but differ in morphology from the biplexiform types described in some other vertebrates.
A collagen‐based nerve guide conduit for peripheral nerve repair: An electrophysiological study of nerve regeneration in rodents and nonhuman primates
Authors: Archibald Simon J. , Krarup Christian , Shefner Jeremy , Li Shu‐Tung , Madison Roger D.
Published: January 2005

When a peripheral nerve is severed and left untreated, the most likely result is the formation of an endbulb neuroma; this tangled mass of disorganized nerve fibers blocks functional recovery following nerve injury. Although there are several different approaches for promoting nerve repair, which have been greatly refined over recent years, the clinical results of peripheral nerve repair remain very disappointing. In this paper we compare the results of a collagen nerve guide conduit to the more standard clinical procedure of nerve autografting to promote repair of transected peripheral nerves in rats and nonhuman primates.

In rats, we tested recovery from sciatic nerve transection and repair by (1) direct microsurgical suture, (2) 4 mm autograft, or (3) entubulation repair with collagen‐based nerve guide conduits. Evoked muscle action potentials (MAP), were recorded from the gastrocnemius muscle at 4 and 12 weeks following sciatic nerve transection. At 4 weeks the repair group of direct suture demonstrated a significantly greater MAP, compared to the other surgical repair groups. However, at 12 weeks all four surgical repair groups displayed similar levels of recovery of the motor response.

In six adult male Macaca fascicularis monkeys the median nerve was transected 2 cm above the wrist and repaired by either a 4 mm nerve autograft or a collagen‐based nerve guide conduit leaving a 4 mm gap between nerve ends. Serial studies of motor and sensory fibers were performed by recording the evoked MAP from the abductor pollicis brevis muscle (APB) and the sensory action potential (SAP) evoked by stimulation of digital nerves (digit II), respectively, up to 760 days following surgery. Evoked muscle responses returned to normal baseline levels in all cases. Statistical analysis of the motor responses, as judged by the slope of the recovery curves, indicated a significantly more rapid rate of recovery for the nerve guide repair group. The final level of recovery of the MAP amplitudes was not significantly different between the groups. In contrast, the SAP amplitude only recovered to the low normal range and there were no statistically significant differences between the two groups in terms of sensory recovery rates.

The rodent and primate studies suggest that in terms of recovery of physiological responses from target muscle and sensory nerves, entubulation repair of peripheral nerves with a collagen‐based nerve guide conduit over a short nerve gap (4 mm) is as effective as a standard nerve autograft. Furthermore, preliminary results show that entubulation repair with this material can support axon regeneration and maturation over a nerve gap distance of at least 15 mm.