bluuebunny/crossref_metadata_2025 huggingface dataset:
Origins and terminations of bulbospinal axons that contain serotonin and either enkephalin or substance‐P in the North American opossum
Authors: Reddy V. K. , Cassini P. , Ho R. H. , Martin G. F.
Published: January 2005

We have shown previously that some enkephalin, substance‐P, and serotoninergic neurons in the medullary raphe and adjacent reticular formation project to the spinal cord in the opossum. In the present study we have combined the retrograde transport of True Blue and immunofluorescence histochemistry to determine whether methionine enkephalin or substance‐P containing bulbospinal neurons are serotoninergic. Furthermore, we have used the same immunofluorescence protocol to determine whether spinal axons cocontain the same substances.

Neurons that immunostained for both enkephalin and serotonin were observed in many brainstem nuclei. However, those that projected to the spinal cord were limited to the nuclei raphe magnus and obscurus, and the ventral part of nucleus reticularis gigantocellularis, pars ventralis. Neurons that immunostained for both substance P and serotonin were fewer in number, but some of the ones in the above nuclei and within the nucleus raphe pallidus, projected to the spinal cord.

Spinal axons exhibiting both enkephalin‐ and serotonin‐like immunoreactivity were observed in the superficial laminae of the dorsal horn, lamina X, and the intermediolateral cell column, whereas those showing both substance‐P and serotonin‐like immunoreactivity were seen primarily in lamina X, the intermediolateral cell column, and the ventral horn. Some of the axons in the ventral horn were in close apposition to presumed motoneurons. Comparison of the above results with those obtained from previous studies of bulbospinal projections has allowed us to infer the origins of axons that innervate different spinal targets.
Differential growth and remodelling of ganglion cell dendrites in the postnatal rabbit retina
Authors: Wong Rachel O. L.
Published: January 2005

The postnatal dendritic maturation of small field type 1 (SF1), medium field type 1 (MF1) and type 2 (MF2), and large field type 1 (alpha) ganglion cells in the rabbit retina was compared qualitatively and quantitatively. Dendritic tree structure was revealed by intracellular injection of the fluorescent dye Lucifer yellow, and the stained cells were then morphologically separated on the basis of soma area, dendritic field size, total dendritic length, number of nodes, and mean internodal distance. Cells in the visual streak and an area inferior to the streak were sampled from retinae between birth and adulthood.

The dendrites of all studied classes of rabbit ganglion cells were extensively covered by short spine‐like appendages. As in cat retina, many dendritic spines disappeared by the end of the third postnatal week, at which stage the adult dendritic form could be recognised. However, there was differential loss in the number of spines from the dendrites of the four cell classes. In both the streak and inferior retina, adult SF1 cells had the same number of spines/dendritic unit length througout postnatal life, whereas MF1 and MF2 ganglion cells lost at least half of their number of spines/unit dendritc length by maturity. Alpha ganglion cells lost virtually all their dendritic spines by adulthood. In both retinal locations, there were small changes in the number of nodes (dendritic branch points) of small field and medium field ganglion cells but alpha cells lost between 70 to 80% of their nodes by adulthood. The dendrites of ganglion cells with contrasting morphology thus undergo differential remodelling during postnatal maturation. The completion of the period of dendritic remodelling coincided with the first appearance of adult receptive field organisation, suggestion, suggesting that structural remodelling, in particular that involving dendritic spines, may be associated with the development of the cell's synaptic circuitry.

The dendrites of neighbouring postnatal ganglion cells in the rabbit retina also grow by different amounts; the increase in dendritic tree area, total dendritic length, and mean internodal distances of alpha cells exceeded that of small field and medium field cells in corresponding retinal positions. This implies that retinal dendrites elongate by active growth rather than by “passive stretching.”.
Synaptic organization of neurotensin immunoreactive amacrine cells in the chicken retina
Authors: Li Hai‐Biao , Lam Dominic Man‐Kit
Published: January 2005

Immunohistochemistry was utilized to investigate the light and electron microscopic localization of neurotensinlike immunoreactive (NT) amacrine cells in the chicken retina. The NT cells possess oval cell bodies (7 μm in diameter) that are located in either the second or third tier of cells from the border of the inner nuclear and inner plexiform layers. The processes of such cells extend into the inner plexiform layer where they ramify as a narrow plexus in sublamina 1 and as a broad plexus in sublaminas 3 and 4. Additionally, stained processes are observed occasionally within sublamina 5.

At the ultrastructural level, NT‐positive somas exhibit a rather dense and evenly distributed peroxidase reaction product throughout their cytoplasm. The nucleus of NT amacrine cells possess a round, unindented nuclear membrane. NT‐immunoreactive processes in the inner plexiform layer interact synaptically only with non‐NT cells. NT processes receive synaptic input mainly from the processes of amacrine cells and to a lesser degree from bipolar cells. The large majority of NT‐stained varicosities form presynaptic contacts onto the processes of amacrine cells, but are also presynaptic to bipolar cell axon terminals. Moreover, each of the above synaptic relationships can be identified in each of sublaminas 1 and 3 to 4 of the inner plexiform layer. In addition, NT processes are presynaptic to processes devoid of synaptic vesicles that may originate from ganglion cells. Finally, NT processes occasionally form synaptic contacts onto somas situated in the most proximal row of the inner nuclear layer.
Distribution and synaptic organization of serotoninergic and noradrenergic axons in the lateral geniculate nucleus of the rat
Authors: Papadopoulos Georgios C. , Parnavelas John G.
Published: January 2005

Antisera raised against the monoamines serotonin (5‐HT) and noradrenaline (NA) were employed in a study designed to provide a detailed description of the distribution, morphology, and synaptic organization of the serotoninergic and noradrenergic afferents in the lateral geniculate nucleus (LGN) of the rat. The distribution patterns of the two types of immunoreactive fibers were distinct and largely complementary to each other. NA axons were particularly concentrated in the dorsal lateral geniculate nucleus (LGd), with the ventral lateral geniculate nucleus (LGv) and the intergeniculate leaflet (IGL) receiving substantially fewer fibers. In contrast, 5‐HT axons, although present throughout the LGN, were preferentially concentrated in the LGv and IGL.

5‐HT and NA axon terminals and axonal varicosities, examined in single and serial ultrathin sections, formed conventional synapses in the extraglomerular neuropil. The types of synapses and the nature of the postsynaptic targets were different for the two monoamines. 5‐HT afferents formed asymmetrical synapses on dendritic spines and shafts of both presumptive relay cells and interneurons but established symmetrical synapses on cell bodies. However, NA afferents formed almost exclusively symmetrical synapses on dendritic spines and shafts and made no contacts with cell bodies.

The present findings suggest that the 5‐HT and NA afferents of the rat LGN, which are likely to influence certain stages of visual processing, exhibit distinct organizational principles and act at restriced sites as do other classical neurotransmitter systems.
Synaptic organization in the adult ferret medial superior olive
Authors: Brunso‐bechtold J. K. , Henkel C. K. , Linville C.
Published: January 2005

The ultrastructure of the medial superior olive (MSO) was studied in the adult ferret. The synaptic terminals were categorized on the basis of morphology and their distribution determined. There are three types of synaptic terminals: R terminals, containing round vesicles; Ov terminals, containing ovoid vesicles; and P terminals, containing vesicles of varying morphologies. R terminals are the dominant terminal type on both the somata and dendrites. Ov and P terminals are equally prevalent on the dendrites; however, P terminals are significantly more common than Ov terminals on the somata. Furthermore, P terminals are significantly more common on the somata than on the dendrites. These results suggest that there is some segregation of types of afferent synapses on MSO cells.
Morphology of single intracellularly stained axons terminating in area 3b of macaque monkeys
Authors: Garraghty Preston E. , Sur Mriganka
Published: January 2005

We have studied the morphology of single thalamocortical axons innervating area 3b of postcentral somatosensory cortex in macaque monkeys. We recorded from axons in the white matter below the representation of the hand in postcentral cortex in two monkeys (Macaca fascicularis) by using micropipettes filled with horseradish peroxidase (HRP). When an axon was recorded, we delineated its receptive field and determined its modality, and if cutaneous, whether it was slowly or rapidly adapting (SA or RA). We then impaled the axon and injected it with HRP. We recorded and successfully injected many more RA than SA axons, possibly because of differences in their true proportions. The RA axonal arbors varied in mediolateral extent from 350 to 800 μ with a mean of 600 μ One of the RA axons gave rise to four separate arbors spanning 2.5‐3.0 mm of cortex. The single SA axon we recovered was 370 μ in width. We suggest that the individual terminal zones underlie the columnar parcellation of the somatosensory cortex. The presence of arbors spanning several such columns suggests that all regions within the arbor may not be equally effective in driving cortical cells under normal conditions, and such arbors may provide the substrate for a cortical response to alterations in the pattern of input.
Statistical analysis of corticopontine neuron distribution in visual areas 17, 18, and 19 of the cat
Authors: Bjaalie Jan G. , Diggle Peter J.
Published: January 2005

The spatial organization of visual corticopontine neurons was studied both at a “large scale” (in relation to cortical visual field maps) and at a “small scale” (in relation to cortical modular organization). Large injections of horseradish peroxidase‐wheat germ agglutinin were made in the pontine nuclei. In complete series of sections from parts of areas 17, 18, and 19, the position of each retrogradely labeled neuron was recorded with an x‐y plotter connected to the microscope stage. Each cell was thus given a set of x, y, and z coordinates. After alignment of the sections, three‐dimensional computer reconstructions of the distribution of the labeled cells were made. With program RPOP (developed by Blackstad and Bjaalie, ′88), the reconstructions were studied with different rotations, scaling, etc. In addition, section‐independent parts of reconstructions were isolated („windows”︁) and further analyzed. Curved parts were automatically unfolded for inspection of distribution patterns and determination of cell densities. The spatial distribution of the labeled cells was analyzed within small windows, where density gradients are negligible.

We confirm and extend previous demonstrations of a large‐scale aggregation of visual corticopontine cells due to density gradients by showing that densities of corticopontine neurons increase linearly as a function of distance from paracentral to lower visual field representations in area 17 (and partly in areas 18 and 19). We demonstrate that density gradients are steeper in area 17 than in area 18. For example, clear‐cut differences between the areas in mediolateral density gradients are found. These findings are discussed in relation to the different visual field maps of the areas and the existence of a similar visual field representation in corticopontine projections from different visual areas.

The type of small‐scale distribution (randomness or non‐randomness, aggregation into clusters, bands, etc.) was studied with statistical methods. Such analysis shows that the labeled cells within small zones are non‐randomly distributed in all three areas. In most cases, the analysis indicates an aggregated spatial distribution. A possible relationship to the cortical map of direction selectivity is discussed. To our knowledge, this study is the first to combine the use of three‐dimensional computer reconstructions of a population of labeled neurons, with subsequent statistical analysis of apatial point (cell distribution) patterns.
Monoclonal antibody rat 401 recognizes schwann cells in mature and developing peripheral nerve
Authors: Friedman Beth , Zaremba Sam , Hockfield Susan
Published: January 2005

Monoclonal antibody Rat 401 recognizes subsets of cells in the developing central and peripheral nervous systems. Previous studies have shown that in the central nervous system (CNS) Rat 401 immunoreactivity diminishes sharply with cellular differentiation. Here we have examined the time course, cellular localization, and biochemical nature of the Rat 401 antigen in the rat peripheral nerve. In contrast to the CNS, in the periphery Rat 401 immunoreactivity is maintained into adulthood. Rat 401 staining is restricted to Schwann cells in mature peripheral nerve. Myelin‐related Schwann cells are intensely immunoreactive, whereas nonmyelin‐related Schwann cells are weakly immunoreactive. Unlike many Schwann cell markers, Rat 401 staining is maintained in cultured Schwann cells that lack axon contact. Biochemical analyses show that the antigen recognized by Rat 401 in the peripheral nerve is identical to that in embryonic CNS. The results demonstrate that the capacity for maintained Rat 401 immunoreactivity is restricted to Schwann cells as these cells are stained in adult animals as well as in embryos. In contrast, the same antigens are lost from the CNS at an early stage of development.
Cytoskeletal components of the adherens junctions between the photoreceptors and the supportive müller cells
Authors: Williams David S. , Arikawa Kentaro , Paallysaho Taru
Published: January 2005

The outer limiting “membrane” (OLM) of the vertebrate retina comprises a series of heterotypic adherens junctions between the photoreceptors and the supportive Müller cells. These junctions appear to support the photoreceptors, which in teleosts, anurans, and birds are motile, and thus help them maintain their orientation with respect to incoming light. In an unusual role for this type of junction, they also provide a semipermeable barrier, preventing the diffusion of some proteins out of the extracellular space that surrounds the inner and outer segments of the photoreceptors. Using immunoelectron microscopy, we examined the association of actin, myosin, alpha‐actinin, and vinculin with the OLM junctions of the adult chicken retina. Vinculin was detected close to the plasma membrane in the cytoplasmic plaques of the junctions, as it was in the adherens junctions of the retinal epithelium. Labelling of actin, myosin, and alpha‐actinin was spread more throughout the plaques and was distributed unevenly about the junctions; labelling was much more extensive in the Müller cells than in the photoreceptors. Thus, the junctions of the OLM show similarity to the other adherens junctions in that their cytoplasmic plaques contain actin, myosin, alpha‐actinin, and vinculin. But the large aggregation of actin, myosin, and alpha‐actinin in the Müller cells, and their resulting asymmetrical distribution about the junctions, is unusual, and possibly an adaptation for the special function of the OLM junctions, in providing both structural support for the motile photoreceptors and a semipermeable barrier.
Axonal regrowth in the amyelinated optic nerve of the myelin‐deficient rat: Ultrastructural observations and effects of ganglioside administration
Authors: Marciano F. F. , Gocht A. , Dentinger M. P. , Hof L. , Csiza C. K. , Barron K. D.
Published: January 2005

It has been postulated that myelin degradation products may inhibit regrowth of mammalian central axons and that central nervous system (CNS) myelin and oligodendrocytes may constitute a “nonpermissive substrate” for axonal growth. To address these issues, we utilized an X‐linked rat mutant, myelin‐deficient or md. In the optic nerve of this mutant, 40 days and more postnally, normal myelin is absent and oligodendrocytes are few (Dentinger et al. Brain Res. 344:255–266, 1985). Twenty‐eight days before sacrifice, we operated on four groups of 50‐day‐old md rats and age‐matched normal littermates according to the following protocols: (1) unilateral intraorbital optic nerve crush; (2) beginning within 1 hour of nerve crush, daily intraperitoneal injection of GM1 ganglioside (20 mg/kg) dissolved in phosphate‐buffered saline (PBS); (3) daily intraperitoneal injection of PBS alone, also begun within 1 hour of nerve crush; (4) severance of the optic nerve immediately behind the papilla 16 or 21 days after the primary crush lesions. Additionally, normal and md rats were killed 4 and 14 days after unilateral optic nerve injury. Nerves of unoperated md rats and their normal littermates were also processed. In the operated animals that did not receive GM1, ultrastructural analysis 4, 14, and 28 days after lesioning revealed that md optic nerves contained significantly greater numbers of regenerating axons, including growth cones and varicosities, than nerves of normal rats. Notably, 28 days postoperatively, (group 1), regenerating axons were still abundant in md nerve, whereas, in nerves of normally myelinated littermates, axonal numbers were diminished markedly. Regenerating optic axons of both md and normally myelinated rats were oriented by linear astrocytic arrays and often were enclosed by astrocytic cytoplasm. In normal litternates, GM1 administration (group 2) induced a significant increase in the number of axons within the operative lesion. Paradoxically, GM1 inhibited the ordinarily robust regeneration of md axons. PBS‐injected md and normal rats (group 3) showed no significant differences from noninjected, operated animals. Severance of the nerve at the papilla (group 4) 7–12 days before sacrifice confirmed the origination of axonal regrowth by retinal ganglion cells. The data provide in vivo support for a role of myelin breakdown products or the secretory products of oligodendroglia in the inhibition of regenerative axonal sprouting within mammalian CNS.
Synaptology of luteinizing hormone‐releasing hormone (LHRH)‐immunoreactive cells in the nervus terminalis of the gray short‐tailed opossum (monodelphis domestica)
Authors: Zheng Li‐Mou , Pfaff Donald W. , Schwanzel‐Fukuda Marlene
Published: January 2005

Light and electron microscopic immunocytochemistry were used to examine the structure of LHRH neurons and fibers in the nervus terminalis of the gray short‐tailed opossum (Monodelphis domestica).

LHRH‐immunoreactive neurons and fibers form a loose plexus within the fascicular network of the ganglion terminale on the median surface of the olfactory bulb. There are at least two populations of LHRH‐immunoreactive neurons within the network of the ganglion terminale: fusiform and round neurons similar to those described in the forebrain. At the ultrastructural level, axosomatic and axodendritic contacts were seen between LHRH‐immunoreactive and nonimmunoreactive elements in the ganglion terminale. These contacts were classified as (1) synaptic input, with asymmetric synapses seen between a nonimmunoreactive axon terminal and a LHRH‐immunoreactive cell body or a nonimmunoreactive axon terminal and a LHRH‐immunoreactive dendritic process. (2) synaptic output, with symmetric synapses seen between LHRH‐immunoreactive and nonimmunoreactive processes.

This study is the first systematic examination of the ultrastructure of the LHRH‐immunoreactive neurons and their synaptic contacts in the nervus terminalis. The possible integrative roles for this LHRH‐immunoreactive system are discussed.
Synaptic connections of rod bipolar cells in the inner plexiform layer of the rabbit retina
Authors: Strettoi Enrica , Dacheux Ramon F. , Raviola Elio
Published: January 2005

We have reconstructed from electron micrographs of a continuous series of thin sections the synaptic connections of the axonal arborizations of all the rod bipolar cells contained in a small region of the retina of the rabbit.

We observed that all rod bipolars share the same pattern of connectivity and are probably functionally equivalent. As a rule, they do not contact ganglion cells. Their prevalent synaptic output is on narrow‐field, bistratified, and indoleamine‐accumulating amacrine cells. Their dominant inputs are the reciprocal synapses from the indoleamine‐accumulating amacrines, but they also receive a sizable number of synaptic contacts from other, non‐reciprocal, amacrine cells. The lateral spread of scotopic signals at the synapse between rod bipolars and narrow‐field, bistratified amacrines is small. Finally, in the rabbit, as in the cat, a narrow‐field, bistratified amacrine is inserted in series along the rod pathway.
Alpha2‐adrenergic binding sites in the medulla oblongata of tree shrews demonstrated by in vitro autoradiography: Species related differences in comparison to the rat
Authors: Flügge G. , Jurdzinski A. , Brandt S. , Fuchs E.
Published: January 2005

Alpha2‐adrenergic binding sites in the medulla oblongata of tree shrews and rats were detected and quantified by in vitro‐autoradiography with the α2‐antagonist 3H‐rauwolscine (3H‐RAUW).

The autoradiographic pattern of the radioligand binding in the tree shrew medulla oblongata resembles that which has been described by others for the human myelencephalon. This pattern coincides well with the occurrence of catecholaminergic structures detected by immunocytochemistry with antibodies against phenylethanolamine‐N‐methyltransferase and tyrosine hydroxylase. In contrast to the rat, where only the nucleus tractus solitarii and the nucleus dorsalis nervi vagi were labeled, five discrete nuclei specifically bound 3H‐RAUW in tree shrews. The highest number of binding sites was detected in the nucleus dorsalis nervi vagi (nX; Bmax: 333 fmoles/mg) and the nucleus tractus solitarii (NTS; 311 fmoles/mg), followed by the nucleus nervi hypoglossi nXII; 297 fmoles/mg), the nucleus reticularis parvocellularis (FRS; 230 fmoles/mg), and the area of the catecholamine cell groups A1 and C1 (area C1; 202 fmoles/mg). Maximal binding in the two labeled nuclei of the rat was 158 fmoles/mg. The discrete nuclei of the two species also showed different affinities for 3H‐RAUW with Kd ranging from 0.17 to 0.83 nM in tree shrews and 1.80 to 1.95 nM in rats.

Competition experiments revealed that the radioligand bound specifically to α2‐binding sites. In the tree shrew, nX, nXII and the area C1, also have a relatively high affinity for the α1‐antagonist prazosin which is a quality of the adrenoceptor subtype α2B. Furthermore, in the area C1, 3H‐RAUW binding was inhibited by the dopamine antagonist haloperidol.

There are thus species related as well as regional differences with respect to the number, the affinity, and the pharmacological properties of α2‐binding sites in the medulla oblongata. In tree shrews, α2‐adrenoceptors can be autoradiographically quantified in regions which are not labeled in the rat, although former data predicted the existence of such receptors, e.g., in the area of the adrenaline cell group C1.
Light and electron microscopical studies on the spherical neurons in the electrosensory lateral line lobe of the gymnotiform fish, Sternopygus
Authors: Losier Bruno J. , Matsubara Joanne A.
Published: January 2005

Spherical cells are a principal cell type of the electrosensory lateral line lobe (ELLL) and play a crucial role in the jamming avoidance response (JAR) behavior. Since Sternopygus, a low frequency gymnotiform genus, does not display a JAR we searched for spherical cells in its ELLL. While present in Sternopygus, spherical cells differed remarkedly from those in the high‐frequency gymnotiforms, Eigenmannia and Apteronotus. This study reveals species‐characteristic differences in the morphology and synaptology of the spherical cell, a projection neuron located in the deep neuropil layer (DNL) of the ELLL. In contrast to the adendritic spherical cell of other species, the spherical neuron in Sternopygus exhibits an extensive basilar dendrite that extends into the primary electroreceptive afferent zone, the deep fiber layer (DFL). In Sternopygus, these neurons are distributed evenly across the full length of each tuberous subdivision, with cell densities highest in the centrolateral subdivision. At the ultrastructural level, the contacts on the soma, proximal, and distal dendrite of the spherical neuron in Sternopygus are asymmetrical chemical synapses, quite distinct from the electrotonic gap junctions found on the spherical neurons of other species.
Organization of projections from olfactory epithelium to olfactory bulb in the frog, Rana pipiens
Authors: Duncan H. J. , Nickell W. T. , Shipley M. T. , Gesteland R. C.
Published: January 2005

One hypothesis for the coding of olfactory quality is that regions of the olfactory epithelium are differentially sensitive to particular odor qualities and that this regional sensitivity is conveyed to the olfactory bulb in a topographic manner by the olfactory nerve. A corollary to this hypothesis is that there is a sufficiently orderly connection between the epithelium and the olfactory bulb to convey this topographical coding. Thus we examined topography in the projection from epithelium to bulb in the frog, which has been the subject of numerous electrophysiological studies but has not yet been examined using modern neuroanatomical techniques.

The tracer WGA‐HRP was applied to the ventral or to the dorsal olfactory epithelium, or both. Anterograde transport of label to the olfactory bulb was seen after as few as 2 days; label was still present in the bulb as long as 21 days postinjection. In cases where WGA‐HRP was applied to the entire epithelium, there was dense anterograde labelling of the ipsilateral olfactory bulb. In addition, a small medial portion of the contralateral bulb was labelled.

Injections limited to either the ventral or dorsal epithelium produced patterns of anterograde labelling in the glomerular layer of the olfactory bulb, which varied with the size and location of the injection. With very large injections in either the dorsal or ventral epithelium, label appeared to be evenly distributed in the glomerular layer. With smaller injections in the ventral epithelium, there was heavier labelling in the lateral than in the medial portions of the glomerular layer, although light labelling was found in all regions of the glomerular layer. In contrast, injection sites restricted to the dorsal epithelium produced more anterograde labelling in the medial than lateral portions of the glomerular layer. These patterns extended throughout the dorsal‐ventral extent of the bulb.

Within the limits of the anterograde tracing technique used, we were unable to detect any systematic relationship between the pattern of labelling in the glomerular layer and the medial‐lateral or rostral‐caudal location of the injection site in either the ventral or dorsal epithelium.

We conclude that in the frog, as in other amphibia, there is only a limited degree of topographic order between the epithelium and the olfactory bulb.
Substance P and enkephalins in the superficial layers of the rat superior colliculus: Differential plastic effects of retinal deafferentation
Authors: Miguel‐Hidalgo Jose Javier , Senba Emiko , Takatsuji Koichi , Tohyama Masaya
Published: January 2005

In this work we studied the effects of unilateral eye enucleation on the contents and distribution of leu‐enkephalin‐, met‐enkephalin‐arg6‐gly7‐leu8‐, and substance‐P‐like immunoreactivities (L‐ENK‐I, ENK‐8‐I, and SP‐I, respectively) in the superficial layers of the rat superior colliculus (SC) by means of the unlabelled antibody peroxidase‐antiperoxidase method. In the normal rat only a few L‐ENK‐I neurons appear dispersed in the stratum griseum superficiale. No immunostained somata appear in the stratum opticum. The most striking effect of unilateral enucleation was the dramatic appearance of a laminarly distributed population of L‐ENK‐I and/or ENK‐8‐I neurons in the dorsal stratum opticum of the SC contralateral to the enucleated side. This population of immunoreactive cells was observed with all the survival times examined in the present study (3, 7, 15, and 30 days) and was always accompanied by an increase in the immunostaining of L‐ENK‐I and/or ENK‐8‐I fibers in the contralateral stratum griseum superficiale. Enucleation also produced a decrease in the immunostaining of SP‐I dendrites that only became obvious 15 days after enucleation. However, the number of SP‐I somata or terminal‐like immunoreactive structures showed no detectable changes.

These results show that retinal deafferentation of the superficial layers of the rat SC has different effects on some immunohistochemically distinguishable neuronal subgroups in the SC, suggesting different functional or trophic relationships of the retinal input to these groups of neurons.
Neonatal infraorbital nerve transection in the rat: Comparison of effects on substance P immunoreactive primary afferents and those recognized by the lectin Bandierea simplicifolia‐I
Authors: White Fletcher A. , Bennett‐Clarke Carol A. , Macdonald Gordon J. , Enfiejian Howard L. , Chiaia Nicolas L. , Rhoades Robert W.
Published: January 2005

Retrograde tracing, immunocytochemical, and histochemical methods were used to determine the manner in which different classes of trigeminal (V) ganglion cells respond to transection of their axons during infancy. Retrograde tracing with true blue (TB), histochemistry using the plant lectin Bandieraea simplicifolia‐I (BS‐I), and immunocytochemistry using an antiserum directed against substance P (SP) were carried out in the V ganglion and V brainstem complex of normal adult rats. In the adult V ganglion, 11.9 ± 1.9% of the cells that sent axons into the infraorbital nerve (ION) contained SP‐like immunoreactivity (SPLI) and 26.9 ± 3.6% bound the lectin BS‐I. Only 2.7 ± 1.6% of ION cells were labelled by both the SP antiserum and BS‐I. Transection of the ION on the day of birth had very different effects upon primary afferent neurons containing SPLI and those labelled by BS‐I. We have previously shown that such lesions result in a significant expansion of the portion of SpC innervated by primary afferents containing SPLI and we have also provided data consistent with the proposal that ganglion cells recognized by an antiserum directed against SP are more likely than other primary afferent neurons to survive neonatal axotomy. In the present study, combination of retrograde tracing with TB and lectin binding histochemistry showed that cells recognized by BS‐I were selectively lost after neonatal ION transection. Only 14.2 ± 4.4% of the ION ganglion cells that projected into this nerve at the time of the lesion and that survived neonatal axotomy were BS‐I positive when the animals reached adulthood. Neonatal ION transection also resulted in a permanent reduction in the density of BS‐I binding in SpC. Bandieraea simplicifolia‐I binding in the brainstem ipsilateral to the damaged nerve was almost completely gone within 1 day of the nerve transection and recovered only partially by the time the rats were 2 months of age. In alternate sections tested with the SP antiserum, there was a slight reduction in the density of SPLI in the deafferented SpC on postnatal days 4 and 5, but this change never approached that observed for BS‐I binding.
NADPH‐diaphorase reactive neurons of the rabbit retina: Differential sensitivity to excitotoxins and unusual morphologic features
Authors: Sagar Stephen M.
Published: January 2005

Various populations of retinal and brain neurons display different degrees of sensitivity to the toxic effects of excitatory amino acid agonists. To further define this phenomenon, the effects of intravitreal injections of kainic acid, N‐methyl‐D‐aspartate (NMDA), quinolinic acid, and ibotenic acid on NADPH‐diaphorase (NADPHd) reactive cells of the rabbit retina were examined. In normal rabbit retinas, NADPHd histochemistry selectively stains two populations of cells at the inner margin of the inner plexiform layer: large densely staining (Type I) and more numerous, smaller and lightly staining (Type II) cells. All of the toxins studied destroy both cell types at high doses. Kainic acid, however, at low doses destroys Type I cells but selectively spares Type II cells. NMDA injections result in a more complex and less consistent pattern of cell loss; overall, the Type I cells are perhaps slightly resistant to this agent as compared to Type II cells. The Type I neurons in this respect are analogous to striatal NADPHd‐reactive neurons, which have, at most, a slight relative resistance to NMDA neurotoxicity.

The excitotoxin lesions reduce the complexity of the fiber plexus in the inner plexiform layer and thereby reveal anatomic features of surviving NADPHd reactive neurons that are not apparent in normal retinas. In particular, each Type I cell gives off several fine, straight, beaded processes that emanate from dendrites and run several millimeters in the inner plexiform layer. These processes are presumably involved in long‐distance interactions within the retina. Excitotoxin lesions may provide a generally useful anatomic tool for elucidating morphological features of neurons stained by histochemical and immunohistochemical methods.
On variables that affect estimates of the true sizes and densities of radioactively labeled cell nuclei
Authors: Clark S. J. , Cynx J. , Alvarez‐Buylla A. , O'Loughlin B. , Nottebohm F.
Published: January 2005

Tritiated thymidine has been widely used as a nuclear marker of cell birth. The true diameters and packing densities (nuclei/μm3) of such radioactively labeled nuclei cannot be measured directly from tissue sections. Here we show that existing stereological corrections cannot be applied to data from radioactively labeled nuclei. We empirically measured the number of silver grains exposed by nuclei containing tritiated thymidine. The nuclei were separated from the photographic emulsion by known thicknesses of fixed, embedded avian telencephalon. The results of this experiment were used to develop an equation that estimates the number of silver grains exposed by a cell nucleus of any given diameter, containing a given amount of radioactive label, and located at any given distance from the photographic emulsion. The equation also allows one to calculate the probability that a label‐containing nucleus will be correctly classified as labeled. Simulations of the equation revealed that not all label‐containing nuclei are correctly classified by using commonly employed identification procedures and that larger nuclei are less likely to be correctly classified than smaller nuclei, given the same amount of label. The equation can be used to modify one class of existing sterological equations so as to be applicable to measurements of radioactively labeled nuclei. Finally, we discuss the assumptions and limitations of this modification.
Cholecystokinin innervation of monkey prefrontal cortex:An immunohistochemical study
Authors: Oeth Kristen M. , Lewis David A.
Published: January 2005

Knowledge of the circuitry of chemically identified systems in primate prefrontal cortex is limited. Although cholecystokinin is very abundant in prefrontal cortex (Geola et al.:Journal of Clinical Endocrinology and Metabolism 53(2):270–275, 1981; Taquet et al.: Neuroscience 27(3):871–883, 1988), the organization of cholecystokinin‐containing structures in primate prefrontal cortex has not been investigated. Using immunohistochemical and retrograde transport techniques, we characterized the cholecystokinin innervation of prefrontal cortex in macaque monkeys.

The use of two antibodies directed against different portions of the cholecystokinin molecule revealed that distinct forms of the molecule were differentially localized in the same cortical neurons. These small, nonpyramidal cholecystokinin‐positive neurons had a variety of somal morphologies and the density of labeled cells did not differ among cytoarchitectonic regions. Labeled neurons had a distinctive laminar distribution with the greatest density of cells present in layers II‐superficial III. Labeled fibers also had a distinctive laminar pattern of distribution that differed from that of the immunoreactive neurons. In granular prefrontal cortex, terminal fields were evident in layers II, IV, and VI, with the greatest density in layer VI. Agranular area 24 exhibited a bilaminar pattern of immunoreactivity with a band in layer II and a very dense terminal field in layers V–VI.

A high density of cholecystokinin‐binding sites has been found in layers III–IV of prefrontal cortex and other association areas in the monkey; this finding has been attributed to possible cholecystokinin‐containing afferents from the thalamus (Kritzer et al.: Journal of Comparative Neurology 263:418–435, 1987). The mediodorsal nucleus of the thalamus is known to be a source of afferents which terminate in layer IV of prefrontal cortex. However, combined retrograde transport and immunohistochemical techniques failed to reveal the presence of cholecystokinin‐positive neurons in the mediodorsal nucleus of the thalamus that project to prefrontal cortex. These findings, and other observations, suggest that the terminal field in layer IV is formed by descending axons that arise from cholecystokinin‐containing neurons in layers II and superficial III.

This study demonstrates that the cholecystokinin innervation of prefrontal cortex has a laminar specific organization that is preserved across cytoarchitectonic regions. This distribution of immunoreactive structures suggests a distinctive role of cholecystokinin in cortical circuitry that is common to every region of prefrontal cortex.
Variability of light‐evoked response pattern and morphological characterization of amacrine cells in goldfish retina
Authors: Djamgoz M. B. A. , Spadavecchia L. , Usai C. , Vallerga S.
Published: January 2005

Amacrine cells of the goldfish retina were characterized electrophysiologically and subsequently labelled by intracellular injection of horseradish peroxidase. An attempt was made to broaden the electrophysiological classification of the cells. Light‐evoked sustained amacrice cell responses were divided into two subtypes depending on colour opponency. Colour‐coded responses (red/depolarizing and green/hyperpolarizing) were found to arise in amacrine cells possessing highly polarized dendritic fields; the dendrites were monostratified in the proximal half (sublamina b) of the inner plexiform layer. Non‐colour‐opponent sustained responses also arose in monostratified units, but the level of dendritic ramification was in sublamina a or b (hyperpolarizing or depolarizing units, respectively). Transient (ON‐OFF) responses were associated mainly with bi‐ or multi‐stratified or diffuse amacrine cells. Some variability was observed in the sizes of the dendritic fields in different sublaminae. There was a tendency for units with brisk components of responses to be narrowly stratified in the inner plexiform layer. Some units possessed “distant” dendrites. Several aspects of structure‐function correlation in amacrine cells are discussed.
Reorganization of cranial sympathetic pathways following neonatal ganglionectomy in the rat
Authors: Smith Peter G. , Reddy Hemalatha
Published: January 2005

Postganglionic sympathetic innervation normally is distributed ipsilaterally to lateral cranial targets. However, contralateral outgrowth occurs following unilateral ganglionectomy in neonatal rats. This study was conducted to determine the prevalence, morphological features, ganglionic derivations, and temporal sequence of sympathetic reinnervation of denervated cranial targets.

Unilateral superior cervical ganglionectomy of mature rats revealed exclusively ipsilateral distributions of catecholaminergic histofluorescent fibers to orbital targets (Meibomian gland, tarsal muscle, orbital muscle, iris, ciliary body, vasculature) and the circle of Willis, with the exception of the anterior cerebral artery. In mature rats following neonatal unilateral ganglionectomy, all targets were reinnervated by fibers displaying morphologies and target relationships similar to normal innervation, but with lower densities. Acute excision of the remaining superior cervical ganglion eliminated all fibers in 7 of 8 preparations. In adult rats receiving neonatal bilateral superior cervical ganglionectomies, cerebral vasculature was reinnervated consistently, and orbital targets contained fluorescent fibers in 6 of 16 cases, indicating that reinnervation can derive from other sources when superior ganglion outgrowth is prevented. Observations in developing rats revealed fibers along the cranial portion of the contralateral optic nerve sheath at 2–3 days postganglionectomy, and within the orbit at later ages, reaching the most distal targets by 14 days.

It is concluded that widespread sympathetic reinnervation of orbital and cerebrovascular targets derives primarily from the contralateral superior ganglion. Orbital ingrowth apparently originates intracranially and enters the orbit by an atypical pathway within the optic foramen.
Morphological and physiological characterization of descending ocellar interneurons in the American cockroach
Authors: Ohyama Takahiro , Toh Yoshihiro
Published: January 2005

In the present study two types of descending ocellar neurons have been morphologically and physiologically identified in the cockroach Periplaneta americana: a descending ipsilateral ocellar neuron (DIO‐neuron) and a descending contralateral ocellar neuron (DCO‐neuron). Both DIO‐and DCO‐neurons possess a cell body near the ocellar tract in the protocerebrum and extend dendritic processes into the ipsilateral ocellar nerve. An axon of the DIO‐neuron descends to the metathoracic ganglion, and its entire course is ipsilateral to the cell body. An axon of the DCO‐neuron crosses the median plane of the protocerebrum and descends through the contralateral ventral nerve cord to the second abdominal ganglion. Both axons possess masses of branches in each ganglion as well as in the brain. Both DIO‐and DCO‐neurons showed no spontaneous spike discharges, and responded with a few off‐spikes to ocellar illumination. They responded to various mechanical stimuli, like cereal stimulation with a train of spikes which was suppressed by ocellar illumination. Spikes of DCO‐neurons caused postsynaptic potentials and spikes in some interganglionic metathoracic interneurons, and spikes in motor nerves. These data are discussed in relation to the ocellar function of the cockroach as well as in comparison with that of other insects.
An ultrastructural and morphometric study of the effect of removal of retinal input on the development of the dorsal lateral geniculate nucleus
Authors: Brunso‐Bechtold J. K. , Vinsant S. L.
Published: January 2005

In normal development, cell layers in the dorsal lateral geniculate nucleus (dLGN) segregate from a relatively homogeneous cell group. If all retinal input is removed prior to this segregation, the layers fail to form. In the present study, we used ultrastructural and morphometric analyses to study dLGN development in the tree shrew following neonatal removal of retinal input. The goal of the present study was to determine whether there are differences between normal animals and enucleates in the development of dLGN cells and their interrelationships with each other and/or with the surrounding glia, which might explain the failure of cellular lamination in enucleated animals. The results indicate that although the development in enucleated animals may take place somewhat more slowly, by P90 cell size and density are not significantly different from normal. These results, coupled with the observation that the dLGN in enucleates is smaller than in normals, suggest that the removal of retinal input results in dLGN cell loss. At both the light and electron microscopic level, cells in the developing normal dLGN are arranged in bands of immediately adjacent cells. In enucleates, dLGN cells are less frequently in immediate contact and are arranged in small groups or clumps which may be separated by degenerating cells. The present data suggest that the presence of retinal input may be necessary to allow dLGN cells to maintain the intercellular relationships necessary for laminar segregation to take place.
Morphology and distribution of the glossopharyngeal nerve afferent and efferent neurons in the mexican salamander, axolotl: A cobaltic‐lysine study
Authors: Nagai Takatoshi , Matsushima Toshiya
Published: January 2005

Cobaltic‐lysine complex was used to label the afferent and efferent components of the glossopharyngeal nerve in the ganglion and brainstem of the Mexican salamander, axolotl (Ambystoma mexicanum). The distribution of afferent cell bodies in the combined glossopharyngeal‐vagus ganglion (the IX‐X ganglion) was reconstructed from serial sections, and the sizes of the cell bodies were measured. The central projection of afferents and the location of efferent cell bodies were determined by the tracer.

The afferent cell bodies in the ganglion were medium‐sized (ca. 25 μm). Cell bodies with a single process were seen. The ganglion was not clearly divided into superior and inferior ganglia, as is observed in mammals and frogs, but comprised a single ganglion. Labelled cells were diffusely distributed in the rostral part of the IX‐X ganglion. A few labelled cells also were seen in the caudal part, where the vagus nerve fibers and cell bodies were mainly distributed. Double labellings of the glossopharyngeal and vagus nerves with HRP and cobaltic‐lysine demonstrated that the ganglion cells of each nerve are not clearly separated in the IX‐X ganglion. In the brainstem, the majority of afferent fibers formed thick ascending and descending limbs in the solitary fasciculus. The remaining afferent fibers formed a thin bundle in the spinal tract of the trigeminal nerve, which had a short ascending limb and a long descending limb. These two bundles had terminal areas in the ipsilateral brainstem: in the dorsal gray matter for the solitary fasciculus and in the lateral funiculus for the spinal tract of the trigeminal nerve, respectively. The cell bodies of the efferent neurons possessed developed dendritic arborizations in the ventrolateral white matter, and formed a longitudinal cell column in the ventrolateral margin of the gray matter. Thus, the glossopharyngeal nerve system in the axolotl assumes a primordial form in its ganglions, but its topographical organization in the brainstem is basically similar to that in anurans.