bluuebunny/crossref_metadata_2025 huggingface dataset:
Bulbospinal projections in the primate: A light and electron microscopic study of a pain modulating system
Authors: Basbaum Allan I. , Ralston Diane D. , Ralston Henry J.
Published: January 2005

The projections of the nucleus raphe magnus (NRM) and the immediately adjacent reticular formation were studied in the macaque monkey following injections of the rostroventral medulla with 3H‐leucine and examination of the resultant labeled axons and terminals by light and electron microscopic autoradiography. Five monkeys had accurately placed injections, which resulted in fiber pathway labeling that coursed caudally, laterally, and dorsally to project to laminae I, II, and V of subnucleus caudalis of the trigeminal and then traveled in the dorsolateral funiculus of the cord and terminated in similar laminae of the spinal dorsal horn at cervical levels. The pathway was only lightly labeled caudal to the cervical enlargement and could not be readily discerned above background in the thoracic or lumbar cord.

Electron microscopy revealed that axons and terminals serving this system constitute a heterogeneous population. Large‐diameter myelinated axons (3–6‐μm diameter), small myelinated axons (0.75–3‐μm diameter), and clusters of nonmyelinated axons were labeled. Terminals in laminae I, II, and V contained mixtures of clear round and granular vesicles or clear pleomorphic and granular vesicles or formed the central element in synaptic glomeruli. The labeled profiles formed asymmetrical or symmetrical synapses on medium and small dendrites; labeled axosomatic synapses were not observed. In rare instances there were contacts between labeled profiles and vesicle‐containing structures, which were probably dendritic, but whether the NRM axon was pre‐ or postsynaptic to such structures could not be determined.

It was concluded that the NRM in the monkey is organized in a manner quite similar to that previously described in the cat. The wide variety of fiber types and synapti termials serving this system suggests that different classes of neurons participate in it, probably using several transmitter substances that result in varying postsynaptic effects on neurons located in the trigeminal complex and dorsal horn.
Microelectrode maps, myeloarchitecture, and cortical connections of three somatotopically organized representations of the body surface in the parietal cortex of squirrels
Authors: Krubitzer L. A. , Sesma M. A. , Kaas J. H.
Published: January 2005

Microelectrode mapping methods and anatomical procedures were combined in the same animals to reveal the cortical connections of three architectonically distinct representations of the body surface in the somatosensory cortex of grey squirrels. In individual experiments, microelectrode multiunit recordings were used to determine the somatotopic organization of regions of the cortex and to identify sites for injections of the anatomical tracer, wheat germ agglutinin conjugated to horseradish peroxidase. After the brains were perfused, the cortex was separated from the brainstem, flattened, and cut parallel to the flattened surface to facilitate comparisons of areal connection patterns, physiological data, and architectonic subdivisions.

Recordings in the primary (S‐I) and secondary (S‐II) somatosensory fields confirmed earlier descriptions of the somatotopic organization of these fields (Sur et al.: J. Comp. Neurol 179:425–450, '78; Nelson et al.: J. Comp. Neurol 184:473–490, '79). In addition, recordings in the cortex caudal to S‐I and ventral to S‐II revealed a third representation of the body surface in parietal cortex, the parietal ventral area (PV). Neurons in PV were responsive to light tactile stimulation of skin and hairs. Multiple unit receptive fields of neurons in PV were larger than those for neurons in S‐I but similar in size to those for neurons in S‐II. PV represented the contralateral body surface in a somatotopic manner that can be roughly characterized as an inverted “homunculus” with the limbs directed medially, the trunk located ventrally, and the face congruent with the representations of the upper lip and nose in S‐I. Neurons in some electrode penetrations in PV were also responsive to auditory clicks.

Microlesions placed at physiologically determined borders allowed all three somatic representations to be related to myeloarchitectonically defined fields. S‐I was architectonically distinct as a densely myelinated region. Within S‐I, a lightly myelinated oval of the cortex between the representation of the hand and face, the “unresponsive zone” (Sur et al.: J. Comp. Neurol 179:425‐450, '78), was an easily recognized landmark. S‐II and PV corresponded to less densely myelinated fields. Other subdivisions such as motor cortex, primary auditory cortex, and visual areas 17 and 18 were distinguished.
Cone synapses with Golgi‐stained bipolar cells that are morphologically similar to a center‐hyperpolarizing and a center‐depolarizing bipolar cell type in the turtle retina
Authors: Kolb Helga , Wang Hou Hua , Jones Jill
Published: January 2005

Two types of Golgi‐stained bipolar cells have been examined by light and electron microscopy to determine the ultrastructure of their synapses with photoreceptors and the spectral type of photoreceptor with which they connect in the retina of the turtle (Pseudemys scripta elegans). We have chosen bipolar cells that correspond in morphology to a center‐hyperpolarizing type (H‐bipolar) and a center‐depolarizing type (D‐bipolar) shown in Marchiafava and Weiler's paper (Proc. R. Soc. B 208:103‐113, '80).The latter authors recorded intracellular responses and marked their cells with the fluorescent dye Procion yellow, so that we have a clear picture of their morphology. These bipolars have been called B4 and B6, respectively, according to our recent classification scheme of Golgi‐stained cells. Serial section electron microscopy of two B4 bipolars shows that they made wide‐cleft, striated basal junctions with red and green cone pedicles. They connected to six or seven different cone pedicles. The three B6 bipolar cells studied made narrow‐cleft, semi‐invaginating basal junctions with cone pedicles. The dendrites of B6 bipolars did not become central elements at ribbon synapses ‐although they invaginated toward the synaptic ribbon. Serial section electron microscopy indicated that B6 bipolars contacted three to five cone pedicles also of a red or green cone type. We suggest that in the case of these two varieties of bipolar cell in turtle retina, sign‐conserving synapses with cones are wide‐cleft basal junctions while sign‐inverting synapses are narrow‐cleft, semi‐invaginating in morphology.
Changing role of forebrain astrocytes during development, regenerative failure, and induced regeneration upon transplantation
Authors: Smith George M. , Miller Robert H. , Silver Jerry
Published: January 2005

When the cerebral midline is lesioned in the embryo or neonate, the would‐be callosal axons form neuromas. We have shown that an untreated Millipore implant inserted between the neuromas in young acallosal animals can support the migration of immature astrocytes that, in turn, support the de novo growth of commissural axons between the hemispheres. Since callosal neuromas persist into adulthood, we asked whether a critical period exists after which reactive glia no longer promote axon growth. We found that a critical period does exist and have documented a variety of changes in reactive gliosis that, in part, may lead to the axon growth‐refractory state.

In acallosal mouse postnates given untreated implants on or prior to day 8, glial fibrillary acidic protein (GFAP)+, stellate‐shaped astrocytes migrated and attached to the implant by inserting foot processes into the pores of the filter. This form of gliotic response established an axon growth‐promoting substratum within 24–48 hours after implantation. During this critical stage there was no evidence of scar formation or necrosis at or around the implant surface. However, when acallosal mice were implanted on or later than postnatal day 14, extensive tissue degeneration occurred, and a mixed population of astrocytes and fibroblasts invaded the surface of the filter, producing a dense scar. Reactive cells within the scar did not promote axonal outgrowth.

To determine whether glia from neonates can influence the host environment and/or induce axonal regeneration in acallosal animals after the critical period, we harvested immature astrocytes on Millipore from critical‐period mouse forebrains and transplanted the glia‐coated prostheses into the brains of post‐critical‐period acallosal animals. Such transplants reduced glial scarring in the host, inhibited extensive bleeding and secondary necrosis, and promoted axonal regeneration.

Our studies suggest (1) that when controlled with a prosthesis, gliosis during the critical period is a beneficial process that can promote the reconstruction of malformed axon pathways; (2) that in older animals a variety of changes‐in reactive glia and the extracellular matrix may work together to hinder axon regeneration after the critical period; and (3) that axonal regeneration in the postcritical CNS may be stimulated by reintroducing an immature glial environment at the lesion site.
Competion and the dynamics of axon arbor growth in the cricket
Authors: Murphey R. K.
Published: January 2005

The growth of an identifiled axonal arborization in the cricket cercal sensory sytem was studied under conditions that vary the number of neighboring axonal arborizations. The cell stuided is one of a samll number of neurons that arborize bilaterally and is called the X‐neuron. Normally the axonal arborization of X is distributed roughly symmertrically about the midlen. Seven days after the birth of this neuron, as soon after its birth as it can be stained, the axonal arbor is more than half the normal size and it exhibits the normal degree of bilaterality. During the remaining 50 days of postermbryonic development, the arbor grows to its adult size, maintaning the bilateral distribution.

The relationship between the growth of this axonal arbor and the presence of absence of its neighbors was studied by the removal of one of the sensory appendages. The removal of a those neighbours near one half of the X‐neuron's arbor and causes a dramatic shift in the bilateral distribution of X's axonal processes; after treatment nearly all of the vaicosities were found in the deafferented region (Figs. 2, 6). Thus, neuron X responds to the loss of some to its neighbors by removing synaptic material from the area with normal neighbors and inserting additonal material in the region with fewer neighbors.

This effect is age dependent. Removal of neighbors early in life, during the initial period of synaptogenesis, causes a very rapid chang, while similar treatment later in life causes a much slower response (Fig. 7). Thus the flexilbility of the neuron is correlated with its growth rate; it is very flexible during its early, rapid growth phase and less flexible when the growth rate slows later in life.

This continuing flexibility of the axonal arbor could also be demonstrated by allowing the amputated cercus to regenerate (Figs. 8, 9). Under these conditons the growth of X's arbor returned toward the normal bilateral distribution. However, regenration of the neighboring arbors never restored the arbor to complete normality because a bias in the structure had already been imposed. In effect, regeneration arrested the chage but could not resverse it.

In breief, an identified sensory neuron's growth has been demonstrated to depend in part on the presence or absence of neighbors. This dependence extends throughout the life of the animal and fits the defination of a competitive interation.
Development of reticulospinal neurons of the zebrafish. II. Early axonal outgrowth and cell body position
Authors: Mendelson Bruce
Published: January 2005

The sequence of axonal outgrowth and the early cell body positions of identifiable types of reticulospinal (RS) neurons of the zebrafish (Brachydanio rerio) were determined in order to learn if differences in neuronal characterstics among specific cell types correlate with differences in the times at which the cells develop. The time of axonal outgrowth and the location of the cells in the developing embryo were determined by filling RS neurons retrogradely with horseradish peroxidase from their growing axons over a series of developmental stages.

Hindbrain cells developed in two distinct waves separated by about 10 hours. In the first wave, axons initiating growth at nearly the same time and from nearly the some location in the hindbrain diverged in their choice of an ipsilateral or contralateral pathway into the spinal cord. Individual types of RS neurons grew axons into the rostral spinal cord in a similar temporal sequence to that of their birthdays although the lag time between birthday and time of axonal outgrowth was variable (RS neuronal birthdays were reported in the previous paper, Mendelson: J. Comp. Neurol., 251:160–171 1986). All RS somata were initially observed along the ventral surface of the brain and were subsequently displaced dorsally. The displacement could be passive, due to growth of the ventral hindbrain, and could explain the previously observed dorsoventral differences in RS neuronal time of origin.
NADPH diaphorase histochemistry in the macaque striate cortex
Authors: Sandell Julie H.
Published: January 2005

The distribution of the enzyme dihydronicotinamide adenine dinucleotide phosphate (NADPH) diaphorase was examined in the striate cortex of the rhesus monkey. The pattern of activity in the neuropil matched that of cytochrome oxidase in adjacent sections and the enzymes were similarly modulated by monocular deprivation. Scattered individual cells were also intensely positive for NADPH diaphorase. Labelled cells were most common in the white matter and layers 2 and 3; they were least common inlayers 4 and 5. Diaphorase cells were morphologically diverse, but no pyramidal or spiny cells were labelled. Labelled cells often had multiple varicose processes, which extended laterally for over 1 mm. Although the function of this enzyme is unknown, the morphology and distribution of the diaphorasepositive cells resembles published reports of cortical cells containing somatostatin, avian pancreatic polypeptide, and neuropeptide Y‐like immunoreactivity, and NADPH diaphorase is colocalized with these substances in the rodent striatum (S.R. Vincent, O. Johansson, T. Hökfelt, L. Skirboll, R.P. Elde, L. Terenius, J. Kimmel, and M. Goldstein, J. Comp. Neurol. 217:252–263, '83).
Connections of the parahippocampal cortex in the cat. II. Subcortical afferents
Authors: Room Peter , Groenewegen Henk J.
Published: January 2005

The organization of subcortical inputs to the parahippocampal cortex, which in the present study in the cat is considered to comprise the entorhinal and perirhinal cortices, was studied by using retrograde and anterograde tracing techniques. The results of the retrograde tracer horseradish peroxidase (HRP), HRP conjugated with wheat germ agglutinine (WGA‐HRP), Fast Blue (FB) or Nuclear Yellow (NY) injections indicate that the entorhinal and perirhinal cortices receive inputs from the magnocellular basal forebrain and from distinct portions of the amygdaloid complex, the claustrum, and the thalamus. The two cortices are further projected upon by fibers from the supramamillary region of the hypothalamus, the ventral tegmental area of the mesencephalon, the dorsal raphe nucleus, the nucleus centralis superior, and the locus coeruleus. The entorhinal cortex, in addition, receives projections from the medial septum. As regards the projections from the amygdaloid complex, it was observed that the entorhinal cortex receives its heaviest input from the basolateral amygdaloid nucleus, whereas the perirhinal cortex receives a strong projection from the lateral nucleus and a weaker projection from the basomedial nucleus of the amygdala. Of the thalamic nuclei that project to the parahippocampal cortex, the nucleus reuniens is only connected with the entorhinal cortex, while fibers from the medial geniculate nucleus and the lateral posterior nucleus terminate in the perirhinal cortex. Injections of tritiated amino acid (3H‐leucine) were placed in the medial septum, the dorsal and ventral claustrum, the basolateral and basomedial amygdaloid nuclei, and the nucleus reuniens of the thalamus. The results of these experiments demonstrate that, with the exception of the claustrum, these subcortical areas project mainly to the superficial layers I‐III and the lamina dissecans of the parahippocampal cortex, and to a lesser degree to the deep layers V and VI.
Histaminergic neurons in the rat brain: Correlative immunocytochemistry, golgi impregnation, and electron microscopy
Authors: Wouterlood F. G. , Sauren Y. M. H. F. , Steinbusch H. W. M.
Published: January 2005

Histamine‐containing neurons were visualized in Vibratome‐sections of rat brain with the indirect peroxidase‐antiperoxidase immunocytochemical method of Sternberger (Immunocytochemistry, 2nd edition, New York: John Wiley and Sons, pp.1–354, '79) by utilizing a primary antibody directed against L‐histidine decarboxylase (HDC). Cell bodies of HDC‐immunoreactive neurons are located exclusively in the posterior hypothalamus: tuberal magnocellular nucleus (TM), caudal magnocellular nucleus (CM), and post‐mammillary magnocellular nucleus (PCM). With the light microscope, all the HDC‐immunoreactive neurons in CM and PCM and the majority of the HDC‐immunoreactive neurons in TM appear to be large neurons, with a short, thick dendrite emerging from each pole of the long axis of the oval perikaryon and one or more, thinner, nonpolar primary dendrites.

In the electron microscope, it can be seen that the immunoreaction product is diffusely dispersed in the cytoplasm. The ultrastructural features of all investigated (70) HDC‐immunoreactive neurons in the three nuclei, independent of their light microscopic characteristics, are remarkably similar: large, unindented, pale nucleus; a high proportion of cytoplasm to nucleus (with the exception of the medium‐sized HDC‐immunoreactive neurons in TM); large, perinuclear array of Golgi apparatus; numerous mitochondria; endoplasmic reticulum fragmented into numerous small cisterns; thick initial portions of the primary dendritic trunks; few axosomatic synaptic contacts.

Twenty‐one Golgi‐Kopsch‐impregnated neurons taken from CM, PCM, and TM were embedded in epoxy resin, serially sectioned, and investigated in the electron microscope. The ultrastructural characteristics typical of HDC‐immunoreactive neurons were observed in all three nuclei in neurons with large cell bodies tapering into two thick, sparsely spinous primary dendrites that subsequently dichotomize into very long (up to 100 μm), nontapering, aspinous secondary dendrites. In sections taken from the posterior hypothalamic area of rats prepared in a conventional way for electron microscopy, distinct populations of large cells can be observed in TM, CM, and PCM displaying the same set of ultrastructural characteristics as the HDC‐immunoreactive neurons.
Observations on the cerebellum of normal‐reeler mutant mouse chimera
Authors: Terashima Toshio , Inoue Kaoru , Inoue Yoshiro , Yokoyama Minesuke , Mikoshiba Katsuhiko
Published: January 2005

The normal‐reeler chimera mouse (+/+ ↔ rl/rl) provides an experimental system in which an analysis of the migration of immature neurons in the cerebellum can be accomplished. In the present study, five chimera mice were produced from embryos of the wild‐type control (C57Bl/6N) and the reeler mutant mouse (BALB/c) by the aggregation technique. The isozyme pattern of glucosephosphate isomerase (GPI) revealed that the brain tissue in the chimera contained both isozymes of the BALB/c (reeler) and C57Bl/6N (normal) strains, implying that internal mosaicism of the cerebellum truly existed. We found no abnormality in the cerebellum of the chimera mouse: the neuronal and glial subpopulations revealed no difference from those of the control. Such normalization of the cerebellum in the chimera suggests that the disturbance of neuronal migration in the reeler is attributable to an abnormal cell‐to‐cell interaction between migrating young neurons and the radial glial cells.
Cortical connections of the somatosensory fields of the lateral sulcus of macaques: Evidence for a corticolimbic pathway for touch
Authors: Friedman David P. , Murray Elisabeth A. , O'Neill J. Blanche , Mishkin Mortimer
Published: January 2005

The ipsilateral corticocortical connections of the somatosensory fields of the lateral sulcus of macaques were examined with both anterograde and retrograde axonal transport methods. In most cases, the field of interest was identified prior to the injection of the tracer substance by recording neuronal responses to somatic stimulation.

The results show that the second somatosensory area (S2) is reciprocally connected with the retroinsular area (Ri), area 7b, and the granular (Ig) and dysgranular (Id) insular fields. Ri is also reciprocally connected with Ig. Previously reported connections were confirmed between S2 and areas 3a, 3b, 1, and 2 and between area 5 and both area 7 and Ri. Moreover, the portions of Ig and Id that receive somatic inputs were shown to project to the amygdaloid complex. Id projects, in addition, to the perirhinal cortex, which supplies input to the hippocampal formation.

The corticocortical projections were found to have two distinct laminar patterns of termination. One is characterized by heavy terminations in layers IV and IIIb and the other by heavy terminations in layer I, but no terminations in layers IV and IIIb. These two patterns were typically found to be reciprocally related.

The results suggest that somatosensory information is processed by a series of cortical fields, including areas 3a, 3b, 1, 2, 5, 7b, S2, Ig, and Id. These fields have access to the amygdaloid complex and the hippocampal formation. Thus, a ventrally directed tactile processing pathway can be followed from S1 to the temporal lobe limbic structures via relays in S2 and the insula; this corticolimbic pathway may subserve tactile learning and memory.
Successive waves of differentiation of cutaneous afferents in rat mystacial skin
Authors: Munger Bryce L. , Rice Frank L.
Published: January 2005

The present study has traced the sequence of maturation of sensory receptors in the mystacial pad of postnatal rats. At birth the follicle‐sinus complexes (F‐SC) are well innervated by deep vibrissal nerves although the number of axons entering the sinus is less than that in the adult. The innervation of the F‐SC by the conus or superficial vibrissal nerves derived from skin nerves that form the superficial dermal nerve plexus is limited to the Merkel rete ridge collar at birth, and the innervation to the inner conical body is conspicuously absent. The inner conical body innervation begins to appear 3–4 days after birth and rapidly matures over the week. By 3 weeks of age the F‐SCs have a mature sensory innervation. At birth small guard hairs are present in the intervibrissal pelage and are associated with scant axons of the superficial dermal nerve plexus, but no mature sensory terminals are present. The sensory innervation of the intervening pelage begins to differentiate during the second week and mature piloneural complexes can be recognized by 3 weeks of age. Innervation to vellus hairs is still developing at 3–4 weeks of age. These maturational changes in peripheral sensory innervation correlate with gradual changes in the structure of barrels in the first somatosensory cortex (SI). Sequential waves of differentiation of sensory receptors appear to be a general feature of neural development.
Pattern in the laminar origin of corticocortical connections
Authors: Barbas H.
Published: January 2005

The laminar origin of cortical projections to the frontal cortex was studied in 17 adult rhesus monkeys with the use of the retrograde transport of horseradish peroxidase (HRP). The frontal regions injected with HRP extended from the posterior periarcuate region to the frontal pole. The architectonic boundaries of areas containing HRP‐labeled neurons were determined from matched sections stained for the visualization of cell bodies, myelin, or acetylcholinesterase. The results showed that the laminar origin of both nearby and distant corticocortical projections was correlated with the architectonic differentiation of the regions giving rise to the projecting afferent fibers. Frontally directed projections from limbic cortices, which show a redimentary laminar organization, emanated mainly from deep layers. On the other hand, projections from increasingly more differentiated cortices arose progressively from the upper (or superagranular) layers. This pattern was observed for projections originating along the axis of architectonic differentiation of the visual, somatosensory, auditory, motor, and preforntal cortical systems. Thus, as the cortical architecture within each system changes from limbic areas toward the primary cortices, the origin of frontally directed projections shifts from predominantly infragranular to predominantly superagranular layers.
Morphology and distribution of neurons in the retinal ganglion cell layer of the adult tammar wallaby—Macropus eugenii
Authors: Wong R. O. L. , Wye‐Dvorak J. , Henry G. H.
Published: January 2005

The morphology of the ganglion cell layer of the adult tammar wallaby has been examined from Nissl‐stained retinal flatmounts. From this material, neurons have been classed as ganglion cells or displaced amacrine cells according to the disposition of Nissl substance. A further subdivision of ganglion cells into a separate group of alphalike cells was assisted by determining the range of soma sizes in neurofibrillar‐stained flatmounts, a method which, in the cat, has revealed the presence of alpha cells. Isodensity contour maps prepared from the Nissl‐stained flatmounts show a well‐developed visual streak and an area centralis in the total neuronal population. A similar pattern was also found in the ganglion cells, thus confirming Tancred's (J. Comp. Neurol. 196:585–603, '81) finding, and, as well, in the alphalike ganglion cells and the displaced amacrine cells. The relative proportions of ganglion cells to displaced amacrines (GC:DA) were evaluated from isodensity profiles drawn along and vertical to the visual streak for the two cell types and also from maps showing the variation in the GC:DA ratio throughout the retina. A comparison with results published for other species shows that the visual streak development in the tammar wallaby is consistent with the expectations of the “terrain” theory and that, in its relative proportion of displaced amacrines, the tammar closely resembles the rabbit but contrasts sharply with the cat, which has half as many ganglion cells and three times as many displaced amacrines as the other two species.
Fasciculation in the early mouse trigeminal nerve is not ordered in relation to the emerging pattern of whisker follicles
Authors: Davies Alun M. , Lumsden Andrew G. S.
Published: January 2005

Detailed reconstructions of lengths of the embryonic mouse maxillary nerve were made from serial light and electron microscope sections to determine whether there is any correspondence between the arrangement of fasciculi in the developing nerve and the emerging pattern of whisker follicles on the snout. There was neither correspondence nor obvious pattern in the arrangement of fasciculi at either E11, when trigeminal nerve fibers first contact the presumptive whisker pad, or at E12, when the pattern of developing whisker follicles becomes apparent. Fasciculi merged and branched to form an intricate plexus. Furthermore, the ratio of the number of nerve fibers in one fasciculus to the number in another prior to their merger differed significantly from the ratio of fiber numbers in the two fasciculi after their separation, which indicates that nerve fibers are freely exchanged between fasciculi. Our findings suggest that the somatotopic representation of the whisker follicle pattern in the brainstem does not develop by nerve fiber growth augmenting an initially ordered pattern of fasciculi.
Structure of the olfactory bulb of the hedgeho (erinaceus europaeus): Description of cell types in the granular layer
Authors: López‐Mascaraque L. , De Carlos J. A. , Valverde F.
Published: January 2005

The cytoarchitecture of the olfactory bulb and the cell types in the granular layer of adult hedgehogs have been studied with the Golgi method. The mitral cell layer does not stand out as a monolayer as in most mammals; it is arranged as a diffuse stratum with mitral cells displaced into the external plexiform layer. The external plexiform layer is exceedingly thick and contains the branches of peripheral processes of granule cells and displaced mitral and tufted cells. The granular layer contains granule cells and varieties of short‐axon cells. Among granule cells a type of cell with an elaborate system of protrusions close to the cell body has been found. Four main varieties of short‐axon cells are described. These include cells with local or extended axons, according to the branching pattern of their axons inside the granular layer or extending into the external plexiform layer as well. Short‐axon cells were also classified as cells with smooth and spinous dendrites. A variety of cell with smooth dendrites and elaborate axonal system reaching the periglomerular zone is described. This type of cell has been found frequently in the olfactory bulb of the hedgehog. In comparison to several other mammals, short‐axon cells in the olfactory bulb of the hedgehog have been found to be particularly abundant and to have more complex axonal systems. It is suggested that some of them may represent inhibitory interneurons acting upon granule and periglomerular cells, playing an important role in the centrifugal pathway controlling the olfactory input.
Variability of axonal arborizations hides simple rules of construction: A topological study from HRP intracellular injections
Authors: Triller Antoine , Korn Henri
Published: January 2005

Intracellular staining with horseradish peroxidase (HRP) allows the analysis of the extent and diversity of axonal field, as the Golgi techniques did for dendritic fields. In this study, we have used such HRP injections to investigate possible rules of construction that underlie the variability in the observed morphological patterns of axons. The Mauthner cell of the teleost provides a suitable material for such a work since it receives inhibitory inputs from two distinct classes of cells that can be identified physiologically prior to their intracellular staining: those that contribute to a recurrent collateral network and those that are part of the commissural vestibuloves‐tibular pathway. The distribution of their terminal boutons over the M‐cell surface was quantified and their axonal arborizations were analyzed topologically with the help of a centripetal method of terminal ordering.

The results indicated (1) that both types of interneurons have qualitatively a similar distribution of boutons over this target, encompassing the soma, initial portions of the main dendrites, and the cap‐dendrites, and (2) that furthermore, the terminals have a tendency to form clusters, the proportion of which is relatively constant regardless of the total number of boutons established by a given afferent cell. In respect to their projection on the M‐cell, the two populations differ mainly in the number of established contacts, which averaged 44.1 ± 28.2 (n = 10) and 14.4 ± 11.3 (n = 43) for collateral and commissural interneurons, respectively. These differences reflect the variations in axonal arborizations. A topological analysis has revealed that (1) branching occurs mainly as bifurcations, whereas in contrast three or four segments issuing from a branch point are only occasionally observed at the level of the last segment; (2) for each cell, the distribution of boutons within orders is not random and rather follows an unimodal distribution, centered on the mean order (θ); (3) the terminals of each subset, or class, of neurons have their own pattern of distribution within orders; and finally (4) the mean order (θ) is linked to the number of terminal segments (nT) by the relation θ = 1.28 log2 nT. This parameter is of importance: it characterizes the axonal arborization and it allows one to predict the number of terminal segments of individual neurons. Similar analysis of camera lucida reconstruction of axonal arborizations of various cell types studied by other investigators suggests that this relation can be generalized.

Thus, although the axons of each class of neurons can be distinguished on the basis of their ramifications (or number of boutons), their arborizations might nevertheless result from common principles of construction, for which simple mathematical expressions have been found.
Neurotoxic action of kainic acid in the isolated toad and goldfish retina: I. Description of effects
Authors: Kleinschmidt Jochen , Zucker Charles L. , Yazulla Stephen
Published: January 2005

The neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). KA caused vacuolization of proximal and distal segments of horizontal cell dendrites in the OPL as well as perikaryal vacuolization and/or chromatin clumping in selected classes of neurons in the inner nuclear layer. Further, KA caused vacuolization and swelling in the inner plexiform layer. These effects were very similar in the retinae of goldfish and toad.

The extent of vacuolization in the OPL was graded with KA concentration and with length of incubation. For 15‐minute incubations, half‐maximal vacuolization was found at 10–20 μM KA. At 25 μM KA, OPL vacuolization was evident within 1–2 minutes of application of KA. In goldfish, but not in toad, rod‐connecting dendrites were less sensitive to KA than cone‐connecting dendrites.
Neurotoxic action of kainic acid in the isolated toad and goldfish retina: II. Mechanism of action
Authors: Kleinschmidt Jochen , Zucker Charles L. , Yazulla Stephen
Published: January 2005

The specificity and mechanism of the neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). Of 21 compounds tested as potential mimics of KA neurotoxicity in the OPL, only the enantiomers of glutamate and aspartate mimicked KA, inducing a low‐level neurotoxic effect at concentrations 5,000–10,000‐fold higher than concentrations of KA giving comparable effects. Further, of 22 compounds tested as potential blockers of KA neurotoxicity in the OPL, only D‐γ‐glutamylglycine, D,L‐α‐amino pimelic acid, sodium pentobarbital, D,L‐α‐amino adipic acid, L‐glutamate, and L‐aspartate blocked KA neurotoxicity (IC50 values of 0.1, 0.3, 0.3, 2, 5, and 15 mM, respectively). In ionic substitution experiments, KA‐induced vacuolization was found to require sodium and chloride ions but not calcium ions in the extracellular medium.

These findings support the hypothesis that KA combines with specific receptors in the membrane of susceptible neurons in the retinal OPL, leading to prolonged opening of membrane channels permeable to sodium and potassium ions. An accompanying equilibrating chloride influx may result in intracellular ion excess, leading to osmotic swelling and vacuolization. The membrane receptors involved in mediating the action of KA in the OPL are likely to be a class of postsynaptic or extrasynaptic glutamate receptor.
Olivocochlear neurons in the squirrel monkey brainstem
Authors: Thompson Glenn C. , Thompson Ann M.
Published: January 2005

Centrifugal projections from the brain to the cochlea have been well described in rodents and cats. In order to gain a better understanding of the general mammalian features of this efferent projection system—the olivocochlear (OC) system—we have begun to extend its description to other mammalian orders, particularly primates. This report describes the origin, cellular morphology, and cholinergic nature of OC neurons in squirrel monkey.

Olivocochlear neurons were identified after cochlear injection and subsequent retrograde transport of one of the tracers, horseradish peroxidase, True Blue, or Diamidino Yellow. One series of sections was processed to demonstrate the tracer and an adjacent series was processed to demonstrate acetylcholinesterase (AChE). In some cases, a series of sections was immunohistochemically processed to identify the presence of choline acetyltransferase (CAT), the synthesizing enzyme for acetylcholine.

Approximately 1,700–1,800 OC neurons were contained in five distinct regions surrounding the major nuclei of the superior olivary complex (SOC), namely: (1) dorsal to medial superior olive (MSO); (2) between MSO and lateral superior olive (LSO); (3) lateral to LSO; (4) medial to SOC; and (5) in the ventral nucleus of the trapezoid body (VTB). These neurons were larger in the regions dorsal to MSO, lateral to LSO, and within VTB; they tended to be smaller in the regions between MSO and LSO and medial to SOC. Neuronal shapes varied among regions and included oval, elongate, round, and multipolar cells. In further support of their cholinergic nature as implied by AChE reactivity, OC neurons also stained positively for the cholinergic marker, CAT.
Peptidergic innervation of insect reproductive tissue: The association of proctolin with oviduct visceral musculature
Authors: Lange Angela B. , Orchard Ian , Adams Michael E.
Published: January 2005

The visceral muscles of the oviducts of Locusta migratoria are sensitive to the pentapeptide proctolin (H‐Arg‐Tyr‐Leu‐Pro‐Thr‐OH). Amounts of proctolin as low as 2 fmol induce a tonic contraction that is dose‐dependent up to 200 fmol. By use of this bioassay we have quantified the amount of material showing proctolinlike bioactivity associated with the oviducts.

Reversed‐phase high performance liquid chromatography of tissue extracts indicates that material with proctolinlike bioactivity and co‐eluting with proctolin is present in the oviducts, the oviducal nerve, and the VIIth abdominal (penultimate) ganglion. The proctolin is present in areas of oviduct that receive extensive innervation. There is tenfold less proctolin in areas of oviduct that receive little or no innervation.

Proctolinlike immunoreactivity is present in axons of the oviducal nerve as well as in a number of cell bodies in the VIIth abdominal ganglion. Three of these neurons lie in a position similar to that of the previously described oviduct motoneurons. Neuropilar axons and processes, as well as axons in the median nerve, also show proctolinlike immunoreactivity.

The results indicate that proctolin, which has previously been identified as a neurotransmitter of insect hindgut visceral muscle, is also associated with visceral muscle of the reproductive system.
Distribution of noradrenaline in the brain of the teleost gasterosteus aculeatus L.: An immunohistochemical analysis
Authors: Ekström Peter , Reschke Maria , Steinbusch Harry , Van Veen Theo
Published: January 2005

The distribution of noradrenergic neurons in the brain of the threespined stickleback was demonstrated with the indirect peroxidase‐antiperoxidase (PAP) immunohistochemical method with antibodies against a noradrenaline‐bovine serum albumin conjugate. Noradrenergic neuronal somata were exclusively located in the isthmal area of the brain stem and in the lower medulla. Noradrenergic varicose axons innervate the reticular formation, motor nuclei, and interpeduncular nucleus of the brain stem, the hypothalamus and habenular nuclei, various parts of the area dorsalis telencephali (forebrain pallium), and the olfactory bulbs. Scattered noradrenergic axons were observed in the optic tectum and in various parts of the cerebellum. It is concluded that the isthmal cell group of the stickleback is, on topological and cytoarchitectonic grounds, equivalent to the ventral portion of the locus coeruleus/subcoeruleus area of amniotes, but that its efferent connections display features characteristic both of those originating in the locus coeruleus, and in the lateral tegmental cell groups of mammals.
Distribution of acetylcholinesterase in the hippocampal region of the rabbit: I. Entorhinal area, parasubiculum, and presubiculum
Authors: Geneser Finn A.
Published: January 2005

The distribution of acetylcholinesterase (AChE) was examined in three areas of the hippocampal region of adult rabbit, viz., the entorhinal area, the parasubiculum, and the presubiculum. AChE was demonstrated histochemically according to a modification of the Koelle copper thiocholine method. In each of the examined areas the pattern of AChE was distinctly stratified and corresponded extensively to fields and layers defined on the basis of cyto‐ and fibro‐architectonics. The enzyme activity was mainly present in the neuropil, but in addition, moderately to weakly stained nerve cell bodies were seen scattered in the entorhinal area and the presubiculum. Only a very small minority of the total number of neuronal somata showed an intense staining reaction for AChE.

Two subfields were discernible in the entorhinal area, these being termed pars medialis and pars lateralis. Pars medialis showed a distinctly stratified enzyme distribution, whereas stratification was less conspicuous in pars lateralis, especially at basal levels. The deep cortical layers (IV–VI) showed a similar distribution of AChE in all three areas—a medium‐stained layer IV, a weakly stained layer V, and a weakly to moderately stained layer VI. However, at more dorsal horizontal levels of pars medialis, heavily stained patches occurred in layer IV. In the entorhinal area, the superficial cortical layers (I–III) contained most enzyme activity in the superficial two‐thirds of layer I, the interstices between the stellate cell bodies in layer II, and the superficial part of layer III. In the parasubiculum, layers I–III formed a wedge‐shaped field with a very high content of AChE. The presubiculum was well stained in layers I and III, whereas the densely packed cell bodies of layer II were unstained.

The distribution of AChE in the rabbit was compared with that in the rat and guinea pig, previously described. The staining pattern is fundamentally similar in all three species, but certain clear differences exist.

Possible structural correlates to the AChE observed in the three areas are considered in detail, especially the relation to the distribution of afferent systems known from experimental studies in other animal species. Although a substantial amount of the enzyme is probably associated with the septohippocampal projection, at present it cannot be excluded that other fiber systems may account for some of the observed AChE.
Responses of rat dorsal horn neurons to natural stimulation and to iontophoretically applied norepinephrine
Authors: Howe James R. , Zieglgäunsberger Walter
Published: January 2005

Extracellular recordings were obtained of 177 neurons throughout the lumbar spinal dorsal horn of urethane‐ or halothane‐anesthetized rats. These neurons all responded to Iontophoretically applied L‐glutamate and their responses to natural stimulation of the ipsilateral hindlimb were characterized. Iontophoretically applied norepinephrine was tested on 94 of these neurons. Fifty‐one neurons were inhibited and 22 were excited. Norepinephrine produced a biphasic inhibitory/excitatory effect on nine neurons. Norepinephrine was exclusively inhibitory on superficial dorsal horn neurons that responded only to innocuous brush and touch and on neurons in the nucleus proprius that responded to brush, touch, and noxious skin pinch. Norepinephrine excited some superficial brush/touch/pinch neurons and produced short inhibitions that were followed by prolonged excitations of some nucleus proprius neurons that responded only to noxious skin pinch. Neurons in the base of the dorsal horn that responded to low‐threshold proprioceptive stimulation were excited by norepinephrine. Both the inhibitory and excitatory effects of norepinephrine were stereoselective, but they were not blocked by receptor subtype‐selective antagonists. Desensitization to norepinephrine occurred for 30% of the neurons.

This study demonstrates that the inhibitory effects of norepinephrine on rat dorsal horn neurons are not restricted to neurons that are responsive to noxious stimuli and that some of these neurons are primarily excited by norepinephrine. The excitatory effects of norepinephrine on low‐threshold proprioceptive neurons may contribute to norepinephrine's known enhancement of spinal flexor reflex activity.
Relationship between astrocytes, ganglion cells and vasculature of the retina
Authors: Stone Jonathan , Dreher Zofia
Published: January 2005

We have studied the distribution of astrocytes in the ganglion cell and nerve fibre layers of the retina in cat, rat, rabbit, and possum using antiserum and a monoclonal antibody against glial fibrillary acidic protein (GFAP) and our own monoclonal antibody against glial filaments. The distribution of retinal astrocytes appears to be strongly determined by the vasculature of the retina; astrocytes are absent from almost all the retina of the possum and from the avascular regions of the rabbit retina. In the cat and rabbit, retinal astrocytes also show a strong affinity for the bundles of ganglion cell axons found at the inner surface of the retina.

Retinal astrocytes do not invest the somas of ganglion cells, and even in areas of retina in which they are numerous, they are sharply confined to the layer of ganglion cell axons. It is suggested that retinal astrocytes are “immigrant” fibrous astrocytes that enter the retina with its vasculature.
A comparison of GABA‐ and GAD‐like immunoreactivity within the area postrema of the rat and cat
Authors: Newton Bruce W. , Maley Bruce E.
Published: January 2005

The immunohistochemical localization of gamma‐aminobutyric acid (GABA) was compared to that of glutamate decarboxylase (GAD) in the rat and cat area postrema with the aid of a polyclonal antibody produced in rabbits directed against GABA. In both the rat and cat, dense and very dense accumulations of GABA‐like immunoreactive (GABA‐LI) varicosities were present throughout the area postrema. GABA‐LI cell bodies were present in both species and were evenly distributed throughout the area postrema's extent. However, the rat area postrema contained more GABA‐LI cell bodies and varicosities than the cat area postrema. In the cat area postrema, a range of cell sizes were immunostained with the GABA antibody. The GAD antibody, however, failed to reveal cell bodies in the area postrema of the cat, thus indicating that the GABA polyclonal antibody may be a better indicator of GABA‐containing somata. Although the mechanism of action of GABA in the area postrema is not understood, it is possible that GABA may play a role in the different functions of the area postrema in emetic and nonemetic species.