bluuebunny/crossref_metadata_2025 huggingface dataset:
Demonstration of two separate descending noradrenergic pathways to the rat spinal cord: Evidence for an intragriseal trajectory of locus coeruleus axons in the superficial layers of the dorsal horn
Authors: Fritschy Jean‐Marc , Grzanna Reinhard
Published: January 2005

The rat spinal cord receives noradrenergic (NA) projections from the locus coeruleus (LC) and the A5 and A7 groups. In contradiction to previous statements about the distribution of descending NA axons, we have recently proposed that in the rat LC neurons project primarily to the dorsal horn and intermediate zone, whereas A5 and A7 neurons project to somatic motoneurons and the intermediolateral cell column. The aim of the present study was to determine the funicular course and terminal distribution of descending NA axons from the LC and from the A5 and A7 groups. The organization of the coeruleospinal projection was analyzed by using the anterograde tracer Phaseolus vulgaris leucoagglutinin in combination with dopaminehyphen;β‐hydroxylase immunohistochemistry. The trajectory of A5 and A7 axons was studied in spinal cord sections of rats following ablation of the coeruleospinal projection with the neurotoxin DSP‐4. To assess the relative contribution of the LC and the A5 and A7 groups to the NA innervation of the spinal cord, unilateral injections of the retrograde tracer True Blue were made at cervical, thoracic, and lumbar levels, and retrogradely labeled NA neurons were identified by dopamine‐β‐hydroxylase immunofluorescence.

The results of the anterograde tracing experiments confirm our previous findings that LC neurons project most heavily to the dorsal horn and intermediate zone. Analysis of horizontal sections revealed that LC axons descend the length of the spinal cord within layers I and II. In contrast to the intragriseal course of LC fibers, A5 and A7 axons travel in the ventral and dorsolateral funiculi and terminate in the ventral horn and the intermediolateral cell column. Retrograde transport studies indicate that the contribution of the A5 and A7 groups to the NA projection to the spinal cord is greater than that of the LC. We conclude that descending axons of the LC and A5 and A7 groups differ in their course and distribution within the spinal cord. The documentation of a definite topographic order in the bulbospinal NA projections suggests that the LC and the A5 and A7 groups have different functional capacities. The LC is in a position to influence the processing of sensory inputs, in particular nociceptive inputs, whereas A5 and A7 neurons are likely to influence motoneurons.
Correlation of monosynaptic field potentials evoked by single action potentials in single primary afferent axons and their bouton distributions in the dorsal horn
Authors: Koerber H. Richard , Mendell Lorne M. , Brown Paul B.
Published: January 2005

The relationship between structure and function of the projections of single identified primary cutaneous axons was investigated by recording cord dorsum potentials at 4 sites in response to electrical stimulation of the single axon and visualizing the boutons of the axon stained by intracellular injection of horseradish peroxidase. The rostrocaudal extent of boutons differed from fiber to fiber ranging from 4.14–11.50 mm; their location in the dorsal horn also varied in agreement with the known somatotopy of the presynaptic neuropil and dorsal horn neurons. Rostrocaudal distributions of cord dorsum potentials and boutons of individual fibers revealed good agreement. Cord dorsum potential amplitude and length of the spinal projection were positively correlated with number of boutons, but no correlation with bouton density was found. The spinal projection of afferents innervating slowly adapting type 1 mechanoreceptors exhibited a greater rostrocaudal extent (mean: 8.48 mm) than those innervating rapidly adapting mechanoreceptors (i. e., hair follicle and field receptors: mean: 5.87 mm). Although the mean total number of boutons was greater for axons with slowly adapting receptors (7,250/fiber) than for axons of rapidly adapting receptors (4,677/fiber), no differences in the longitudinal density of boutons (boutons/mm) were observed. Likewise, summed amplitudes of cord dorsum potentials at the 4 recording electrodes were larger for SA1 afferents than for those of field and hair follicle afferents. A major role for the number of boutons in determining these differences is supported by the finding that the calculated average contribution per bouton to cord dorsum potentials (expressed as an amplitude coefficient a) was similar for slowly and rapidly adapting afferents. No evidence was found for regions in which boutons did not contribute to the cord dorsum potential.
Fibre organization of the monkey's optic tract: II. Noncongruent representation of the two half‐retinae
Authors: Reese B. E. , Cowey A.
Published: January 2005

The representations of the two half‐retinae were examined in the monkey's optic tract. Intravitreal injections of tritiated amino acids were made to reveal the distributions of the crossed and uncrossed populations of optic axons, while localized implants of horseradish peroxidase (HRP) were made into different regions of the optic tract in order to examine the distributions and morphological types of retrogradely labelled cells at corresponding loci in the two half‐retinae.

Crossed and uncrossed optic axons are intermingled throughout most of the optic tract, but uncrossed axons are very sparse or absent along both the deep and superficial extremes of the tract. Implants of HRP into the deeper regions of the tract demonstrate that the crossed and uncrossed optic axons of the Pβ retinal ganglion cells are slightly out of binocular registration, with the uncrossed map being shifted to a slightly superficial location relative to the crossed map. The optic axons for the remaining cell classes, revealed by implants of HRP into the superficial portion of the tract, are much more conspicuously out of binocular registration (in particular, the Pβ optic axons); but in their cases, the uncrossed optic axons are shifted to deeper locations relative to the crossed optic axons. Further evidence that these optic axon classes are markedly out of binocular registration comes from the two optic tracts of a bilaterally destriated monkey, in which most of the Pβ optic axons have undergone a transneuronal retrograde degeneration. Following a uni‐ocular injection of tritiated amino acids, the distributions of the remaining crossed and uncrossed axonal labelling occupied different positions within the tract rather than being intermingled, with the uncrossed optic axons situated deep to the majority of crossed optic axons.

These results demonstrate that the optic chiasm does not combine binocularly corresponding optic axons of similar type. They also demonstrate that noncongruent field defects should be a common consequence of damage to the optic tract in humans.

If the fibre order in the mammalian optic tract arises as a consequence of the sequence of axonal addition during development, then differences in the relative times of genesis for nasal and temporal members of any cell class, and/or differences in the relative pathlengths between the eye and two optic tracts, may produce the fibre ordering described herein.
Schwann cell‐neuronal interactions in the rat involve nerve growth factor
Authors: Urschel Bethany A. , Hulsebosch Claire E.
Published: January 2005

To gain some insight into possible functions of nerve growth factor (NGF), we suppressed the endogenous levels of NGF in newborn rats by subcutaneous injections (3 μl/g body weight) of rabbit antibodies to purified mouse β‐NGF (ANTI‐NGF). Fiber and axonal areas and perimeters were measured for unmyelinated and myelinated sensory fibers in T9 dorsal roots (DR) in three groups of animals: (1) ANTI‐NGF treated littermates, (2) preimmune sera treated littermates (PREIMM), and (3) untreated littermates (UNTR). In some rats, fibers in ventral roots (VR) were measured and, in other rats, sensory processes in peripheral nerves (PN) were measured following radical ventral rhizotomy. The only outer area and perimeter measurements that were statistically different were those in the ventral root (P < 0.013 and P < 0.043, respectively). However, myelin thickness was significantly thinner in the dorsal roots of the ANTI‐NGF group than in the dorsal roots of the UNTR and PREIMM groups (P < 0.000009 and P < 10−6, respectively). Myelin thickness in the ventral roots of the ANTI‐NGF group was also statistically thinner than that in the UNTR group (P < 0.001). There were no statistically significant differences when comparing the UNTR group to the PREIMM group. In the peripheral nerves studied, there was no significant change in the myelin thicknesses between the ANTI‐NGF and UNTR groups of animals. These results indicate that Schwann cell‐neuronal interactions are altered by the inactivation of NGF, and that (1) the central processes of sensory fibers are affected and not the peripheral processes and (2) motor fiber myelination is altered. Therefore, we propose that NGF is not only a neurotrophic and neurotropic molecule but is also an important instructive molecule for the initiation and progress of normal myelination.
Identification of neurons producing long‐term potentiation in the cat motor cortex: Intracellular recordings and labeling
Authors: Keller Asaf , Iriki Atsushi , Asanuma Hiroshi
Published: January 2005

Intracellular, in vivo recordings were used to identify and subsequently to label neurons in the cat motor cortex in which long‐term potentiation (LTP) was induced. Thirty‐nine motor cortical neurons that produced excitatory postsynaptic potentials (EPSPs) in response to microstimulation in areas 1‐‐2 (SI) or in area 5a (SIII) were studied. Amplitudes of EPSPs produced in response to test stimulation (1 Hz) were recorded before and after tetanic stimulation (200 Hz, 20 seconds). In 25/39 cells (64%), EPSP amplitudes were significantly increased following the tetanic stimulation (65 ± 51% average increase), and remained at the potentiated level as long as stable recordings could be maintained (20 ± 18 minutes, maximum = 90 minutes). LTP was induced exclusively in cells that produced monosynpatic EPSPs in response to area 1‐‐2 or area 5a stimulation. Of the 39 analyzed cells, 13 were labeled by intracellular injections of 5% biocytin. Neurons in which LTP was induced included both pyramidal and nonpyramidal cells and were located exclusively in layers II or III of the motor cortex; cells in deeper cortical layers were not potentiated. These findings indicate that various corticocortical inputs can increase the efficacy of synaptic transmission in a subset of motor cortical neurons. We propose that this plasticity in synaptic transmission constitutes one of the bases of motor learning and memory.
Intraocular projections from the pterygopalatine ganglion in the cat
Authors: Kuchiiwa Satoshi
Published: January 2005

The intraocular projection of the cat pterygopalatine (sphenopalatine) ganglion was examined by using retrograde axoplasmic transport techniques in order to investigate the possibility of the involvement of the facial nerve in ocular parasympathetic innervation. Following an injection of horseradish peroxidase (HRP) or wheat germ agglutinin‐HRP into the eye, retrogradely labeled cells were observed in the ipsilateral pterygopalatine ganglion, principally in the caudal part. By dissection of silver‐impregnated, acetylcholinesterase‐ and cholinesterase‐stained orbital preparations, it was determined that two different nerve pathways link the pterygopalatine ganglion and the eye. One took a retrograde course to join the retro‐orbital plexus and then traveled forward accompanying the ciliary artery, the long ciliary nerve, the short ciliary nerve, and/or the optic nerve sheath. The other entered the orbit directly, fused with the ethmoidal nerve or the infratrochlear nerve in a retrograde fashion, and then turned forward along the long ciliary nerve to enter the eye. All these nerves arose from the caudal part of the ganglion. These results are discussed in relation to recent biochemical and histochemical data demonstrating the involvement of the facial nerve in the control of ocular blood flow and intraocular pressure.
Distribution of aromatase in the brain of the Japanese quail, ring dove, and zebra finch: An immunocytochemical study
Authors: Balthazart Jacques , Foidart Agnes , Surlemont Chantal , Vockel Angela , Harada Nobuhiro
Published: January 2005

An immunocytochemical peroxidase‐antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase‐containing cells in the brain of three avian species: the Japanese quail, the ring dove, and the zebra finch. In quail and dove, immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the medial preoptic area, in the septal area above the anterior commissure, in the ventromedial nucleus of the hypothalamus, and in rostral part of the infundibulum. Immunoreactivity was weaker in zebra finches, and no signal could therefore be detected in the ventromedial and tuberal hypothalamus. The positive material was localized in the perikarya and in adjacent cytoplasmic processes, including the full length of axons always leaving a clear unstained cell nucleus. These features could be observed in more detail on sections cut from perfused brains and stained with an alkaline phosphatase procedure. The distribution of aromatase immunoreactivity was similar in the three species although minor differences were observed in the preoptic area. The localization of labelled neurons coincided with the distribution of aromatase activity as studied by in vitro radioenzyme assays on brain nuclei dissected by the Palkovits punch method. There was one striking exception to this rule: no immunoreactivity was detected in the zebra finch telencephalon, while assays had shown the presence of an active enzyme in several nuclei such as the robustus archistriatalis, the hyperstriatum ventrale pars caudale, and the hippocampus and area parahippocampalis. The origins of this discrepancy and the functional role of the aromatase observed in the axons are discussed.
Morphological and physiological characterization of small multimodal ocellar interneurons in the American cockroach
Authors: Ohyama Takahiro , Toh Yoshihiro
Published: January 2005

The morphology and physiology of small multimodal ocellar interneurons (SM‐neurons) have been examined in the cockroach Periplaneta americana. The SM‐neuron is monopolar with its cell body in the tritocerebrum near the esophagus. In axon ascends to the protocerebrum and extends into the ocellar neuropil through the ocellar tract and the ocellar nerve. The axon sends a long collateral process towards the optic tract. The SM‐neuron responded with spike discharges to various sensory stimuli. The collateral and many side branches along the axon in the deutocerebrum appear to be input regions from those sensory afferents. Cereal stimulation triggered most effectively a train of spikes in the SM‐neuron: some of seven giant axons in the ventral nerve cord were involved in this pathway. Cereal stimulation also evoked depolarization in the large second order ocellar neurons (L‐neurons). A possible neural connection between SM‐neurons and L‐neurons was examined pharmacologically. Interaction of ocellar illumination and cereal stimulation in the L‐neuron was also examined. These data are discussed in relation to the ocellar function of cockroaches and in comparison with data obtained in other insects.
Topographically organized projections from the nucleus subceruleus to the hypoglossal nucleus in the rat: A light and electron microscopic study with complementary axonal transport techniques
Authors: Aldes Leonard D.
Published: January 2005

Projections from the nucleus subceruleus (nSC) to the hypoglossal nucleus (XII) were investigated with complementary retrograde and anterograde axonal transport techniques at the light and electron microscopic level in the rat. Injections of WGA‐HRP into XII resulted in labeling of neurons in and around the nSC. Labeled nSC neurons were few in number (<4 per 40–60 μm sections) and variable in size and shape. Most labeled nSC neurons were medium‐sized (X̄ = 16.89 μm), fusiform, triangular, or oval, with 3–4 dendrites typically oriented dorsomedially and ventrolaterally. These neurons were found throughout the rostrocaudal extent of the nSC but were most numerous medial, dorsomedial, and ventromedial to the motor trigeminal nucleus. Others were observed rostral to the motor trigeminal nucleus and ventral to the parabrachial nuclear complex.

Confirmation of retrograde results was obtained following injections of tritiated amino acids or WGA‐HRP into the nSC. This resulted in labeling throughout the rostrocaudal extent of XII mainly ipsilaterally. Labeled fibers descended the brainstem in the dorsolateral and, to a lesser extent, in the ventromedial component of Probst's tract. Fibers entered XII mainly rostrally along the lateral border of the nucleus. All regions of XII were recipients of nSC afferents, but the caudoventromedial quadrant contained the greatest density of terminal labeling.

Electron microscopic evaluation confirmed that nSC afferents synapsed on motoneurons in XII. Axon terminals containing WGA‐HRP reaction product were found contacting dendrites and somata, but primarily the former (81.3% versus 10.6%). Axodendritic terminals synapsed mainly on medium‐to‐small sized dendrites (<3 μm in diameter). The majority of labeled axodendritic terminals (90.1%) contained small, round, and clear synaptic vesicles (S‐type: 20–50 nm) and were associated with an asymmetric (60.6%), symmetric (11.4%), or no (18%) postsynaptic specialization. By contrast, most axosomatic terminals contained flattened vesicles (F‐type) and formed a symmetric or no postsynaptic specialization (75%). Large dense core vesicles (55–90 nm) were observed within a small proportion of all labeled axon terminals (1.3%).

The results from this study demonstrate that the nSC projects to XII, preferentially targets a specific subgrouping of protrusor motoneurons, and synapses on both somata and dendrites, although mainly on the latter. The implications of these data are discussed relative to tongue control.
Cochlear‐nucleus branches of thick (medial) olivocochlear fibers in the mouse: A cochaleotopic projection
Authors: Brown M. C. , Pierce S. , Berglund A. M.
Published: January 2005

Olivocochlear neurons have somata in the superior olivary complex and provide an efferent innervation to the cochlea. One subgroup of olivocochlear neurons, medial olivocochlear neurons, sends fibers to innervate the cochlear outer hair cells. En route to the cochlea, medial olivocochlear fibers give off branches to the ventral cochlear nucleus, the first auditory center of the brain. This study examines the cochlear‐nucleus branches of medial olivocochlear fibers, comparing those from fibers that innervate the cochlear base with those from fibers that innervate the cochlear apex. Basal fibers give off dorsal branches to the granule cell lamina and ventral branches to the auditory nerve root. Apical fibers give off few dorsal branches but many ventral branches that terminate rostrally to the nerve root. This cochleotopic mapping of medial olivocochlear branches corresponds in a general way to that of afferent fibers. Unlike afferent fibers, however, the branches terminate primarily along the edges of the cochlear nucleus. In the mouse, the particular edges of termination are (1) the medial border of the ventral cochlear nucleus where it meets the underlying vestibular nerve root, and (2) the border between the ventral cochlear nucleus and the granule cell lamina. Neurons and dendrites of these border regions may thus integrate efferent and afferent information in a frequency‐specific manner.
Effects of cortical and thalamic lesions upon primary afferent terminations, distributions of projection neurons, and the cytochrome oxidase pattern in the trigeminal brainstem complex
Authors: Chiaia Nicolas L. , Bennett‐Clarke Carol A. , Rhoades Robert W.
Published: January 2005

Early postnatal lesions of the primary somatosensory cortex alter the vibrissa‐related cytochrome oxidase (CO) pattern in nucleus principlis (PrV) of the rat's trigeminal (V) brainstem complex (Erzurumlu and Ebner, '88: Dev. Brain Res. 44:302–308). At present, the reason for this change is not clear. It may be that the corticotrigeminal projection is necessary for the maintenance of vibrissa‐related patterns in PrV. However, it is also possible that the loss of the normal pattern of CO activity reflects a change in the organization of brainstem cells resulting from transneuronal retrograde degeneration. In order to address this question, we made lesions of either the primary somatosensory cortex (S‐I) or ventrobasal thalamus (VB) in newborn rats and directly assayed distributions of V primary afferents by transganglionic transport of horseradish peroxidase and V‐thalamic neurons by retrograde transport of either fluorogold or true blue. Neonatal cortical and thalamic lesions produced no qualitative change in the distribution of primary afferent terminals in either PrV or V subnucleus interpolaris (SpI) beyond that which could be attributed to shrinkage of the brainstem resulting from retrograde degeneration. Most importantly, the “patchy” pattern of terminations observed in normal rats remained apparent in the brain‐damaged animals. The normal distribution of V‐thalamic neurons in PrV wasdisrupted by both cortical and thalamic lesions. These cells are normally patterned in a way that matches the distribution of primary afferent terminals and thus that of the mystacial vibrissae. This was not the case in the neonatally brain‐damaged rats. Taken together, these results are consistent with the conclusion that neonatal cortical and thalamic lesions disrupt the normal CO pattern in PrV primarily because of their effects upon the patterning of brainstem cells. The present findings demonstrate further that clustering of primary afferents does not require a normal complement of postsynaptic neurons.
Patterns of synaptic input on corticocortical and corticothalamic cells in the cat visual cortex. I. The cell body
Authors: Fariñas Isabel , DeFelipe Javier
Published: January 2005

Immunocytochemical and electron microscopic methods were used to examine the ultrastructure and synaptology of callosal and corticothalamic pyramidal cell somata in the cat visual cortex (area 17). Callosal and corticothalamic cells were labeled after injection of horseradish peroxidase (HRP) in the contralateral visual cortex or in the ipsilateral lateral geniculate nucleus. The synaptic relationship between each of the two populations of pyramidal cells and cells containing the inhibitory neurotransmitter γM‐aminobutyric acid (GABA) was examined at the light and electron microscope level using the combined techniques of retrograde transport of HRP and GABA immunocytochemistry. We found that callosal and corticothalamic cell somata have an ultrastructure and synaptology that distinguishes them from each other. Reconstructions from electron micrographs of serial sections revealed that the vast majority of synapses (89–96%) on the cell body of pyramidal cells were formed by GABAergic axon terminals, and that within each population of pyramidal cells there was variability in the number and density of axosomatic synapses. Callosal pyramidal cells received a greater number and higher density of axosomatic synapses than corticothalamic cells. These data suggest that callosal cells receive more inhibition than corticothalamic cells at the level of their somata.
Immunocytochemical localization of calretinin in the forebrain of the rat
Authors: Jacobowitz David M. , Winsky Lois
Published: January 2005

The distribution of the calcium binding protein calretinin (protein 10) was examined in the rat forebrain by immunohistochemistry. The main and accessory olfactory bulbs had immunoreactive label in granule, periglomerular, and mitral cells. Positive fibers were noted in the external plexiform and granule cell layers, glomeruli, and in the molecular layer of the anterior olfactory nucleus. The cerebral cortex contained calretinin label in nonpyramidal bipolar cells. Cells in the substantia nigra compacta and ventral tegmental area were also calretinin positive as were nigrostriatal and mesolimbic projections (caudate‐putamen, nucleus accumbens). In the hippocampus, interneurons were stained in all the subfields of the CA1‐CA4 regions. In the thalamus, many positive cells were observed in the periventricular, reticular, lateral habenula, and reunions nuclei. Calretinin immunoreactive cells were particularly abundant in the lateral mamillary and septofimbrial nuclei. Several fiber tracts were also revealed, i.e., the lateral olfactory tract, mamillothalamic tract, fasciculus retroflexus, optic tract, and stria medullaris. These results demonstrate a distinct distribution of calretinin within cell bodies and fibers.
Regional brain glucose metabolism is altered during rapid eye movement sleep in the cat: A preliminary study
Authors: Lydic R. , Baghdoyan H. A. , Hibbard L. , Bonyak E. V. , De Joseph M. R. , Hawkins R. A.
Published: January 2005

Glucose utilization was measured in 74 brain regions of the cat during states of wakefulness or rapid eye movement (REM) sleep. These data were obtained from intact, unanesthetized animals which were instrumented for objectively measuring states of consciousness. Through a chronically implanted intravenous catheter, the cats received 250 μCi of [6−14C]glucose during REM sleep (N = 3) or during wakefulness (N = 3). After spending ≈8 min in REM sleep or in quiet wakefulness, the cats were administered a lethal dose of barbiturate and the brains were removed and processed for autoradiography. The results revealed site‐specific changes in glucose metabolism during REM sleep. Significant alterations in glucose use occurred in the thalamus, the limbic system, and specific regions of the pontine reticular formation. These data demonstrate for the first time that during states comprised entirely of REM sleep there are anatomically specific changes in cerebral glucose metabolism. The majority of brain regions exhibiting REM sleep‐dependent changes in glucose metabolism either overlapped with regions known to contain cholinergic cell bodies, or with areas that receive prominent cholinergic input.
Similarities in the ultrastructural distribution of nerve growth factor receptor‐like immunoreactivity in cerebellar Purkinje cells of the neonatal and colchicine‐treated adult rat
Authors: Pioro Erik P. , Ribeiro‐Da‐Silva Alfredo , Cuello A. Claudio
Published: January 2005

The intracellular distribution of nerve growth factor receptor immunoreactivity was examined by electron microscopy in the cerebellum of adult and postnatal day 12 rats. The very faint immunostaining in Purkinje cells of naive adult animals was greatly amplified after colchicine treatment. Neonatal cerebellum, in contrast, contained prominent immunoreactivity in both Purkinje cells and germinal cells of the external granular layer. Intracellular distribution of the nerve growth factor receptor reaction product was very similar in Purkinje cells of both neonatal and colchicine‐treated adult animals. It was consistently present along the perikaryal cell membrane, in segments of the rough endoplasmic reticulum and Golgi complex. Numerous membrane‐bound aggregates of immunoreactive vesicles resembling multivesicular bodies (secondary lysosomes) were scattered throughout the cell soma, although less frequently in neonatal rats. Bulbous expansions along the proximal axons of colchicine‐treated Purkinje cells were filled with such immunoreactive multivesicular bodies. These cells also displayed evidence of nerve growth factor receptor internalization in the form of immunoreactive coated vesicles situated near the cell membrane. In addition to the staining in Purkinje cells, neonatal cerebellum contained high amounts of nerve growth factor receptor reaction product along the cell membrane of germinal cells in the external granular layer. Although Purkinje cells of naive adult animals possessed little or no cell membrane‐related nerve growth factor receptor immunoreactivity, reaction product was sometimes seen in cisternae of the rough endoplasmic reticulum and Golgi apparatus. These findings provide electron microscopic immunocytochemical evidence of nerve growth factor receptor synthesis, internalization, and catabolism in noncholinergic neurons of the central nervous system.
Morphological assessment of neuronal aggregates in the striatum of the rat
Authors: Paskevich P. A. , Evans H. K. , Domesick V. B.
Published: January 2005

Regional variations in cell‐packing density, culminating in the formation of cell clusters, is now a recognized morphological characteristic of the striatum that has been correlated, in some instances, with either regional histochemical variations or the distribution pattern of afferent fiber systems, or both. Within these cluster regions a further level of organization exists, in the form of discrete neuronal aggregates. The light microscopic morphology of these neurons and the nature of their intercellular contacts at the electron microscope level form the focus of this report. The neurons composing such aggregates are characterized by contiguous soma‐somatic or soma‐dendritic contact with extended regions of junctionlike symmetrical and consistent contacts where the distance between the cytoplasmic membranes of apposing neurons narrows to as close as 7 nm. Coated vesicles close to the contact areas are common. Three‐dimensional computer reconstructions of serial 1 μm sections through aggregates in either the caudatoputamen or nucleus accumbens reveal “chains” of contiguous cells that frequently involve as many as 60 neurons. These contiguous cell aggregates are discrete entities within the larger clusters or islands. It is postulated that the cellular aggregates may represent the fundamental level of striatal organization and may be local modules for intrinsic information processing, modifying extrinsic data processed through the biochemical compartmentalization of the striatum imparted by striosomes, neuropeptides, and dopaminergic, thalamic and cortical afferents.
Mitral cell‐to‐glomerulus connectivity: An HRP study of the orientation of mitral cell apical dendrites
Authors: Buonviso Nathalie , Chaput Michel A. , Scott John W.
Published: January 2005

It has been suggested that the principal output cells of the main olfactory bulb, the mitral cells, along with the glomerulus they enter, form an anatomical and functional column. To test the extent to which mitral cell somata lying close together in the mitral cell layer are connected to the same glomerulus, we reconstructed 267 mitral cells labeled by extracellular injections of horseradish peroxidase (HRP) in the external plexiform layer.

Results show that apical dendrites tilt rostrally from the somata to the glomeruli and this tilt is gradually greater as the somata are located more and more rostrally in the olfactory bulb. The apical dendrites of most mitral cells in the same region of the bulb are parallel. We analyzed the degree to which dendrites were parallel by measuring the difference in angle of all pairs of apical dendrites in each section, with the restriction that no cells were separated by more than 500 μm. About half of these pairs of dendrites differed in angle by 20° or less and were therefore said to be parallel. The degree of parallelism did not vary with the cell pair location or with intercell distance. Study of glomerular connections of pairs of mitral cells as a function of intercell distance revealed that 96% of mitral cells connected to the same glomerulus were separated by less than 120 μm, while 72% of cells connected to adjacent glomeruli and only 29% of cells connected to distant, i.e., nonadjacent, glomeruli were separated by less than 120 μm.

These results show that mitral cells whose somata lie close together in the mitral cell layer tend to connect the same glomerulus, thus forming anatomical columns. The fact that some mitral cell apical dendrites deviate greatly from this pattern (for example about 5% of mitral cells send their apical dendrite in an opposite direction from their neighbors) suggests at least two influences determining mitral cell‐glomerulus connections.
Quantitative study of the tectally projecting retinal ganglion cells in the adult frog. II. Cell survival and functional recovery after optic nerve transection
Authors: Singman Eric L. , Scalia Frank
Published: January 2005

It is known from previous work that ganglion cells disappear from the retina in significant numbers during optic nerve regeneration in the adult frog, In the present study, the population sine of surviving ganglion cells that have returned axon terminals to the correct tectal loci was estimated by counts of retrogradely labeled cells in retina‐flat‐mounts after tectal injections of HRP. Bilaterally symmetric injections were delivered to allow comparison of the normal and affected retinas. The frogs studied had regenerated the left optic nerve and had visually guided behaviors initiated by the recovered eye (see below). The proportion of tectally projecting ganglion cells in the normal retinas and in retinas of normal frogs studied in parallel ranged from 83–86% (Singman and Scalia: J. Comp. Neurol. 302: 792–809, 1991), In the affected retinas, the subpopulation of tectally projecting cells was reduced by 40–90% after regeneration, and the relative size of this subpopulation ranged from 67–86%.

The optic tectum was injected unilaterally in one specimen, on the side ipsilateral to the regenerated (left) optic nerve. The HRP‐labeled ganglion cells in the ipsilateral (left) retina accounted for only 0.8% of the surviving ganglion cells in this animal, whereas it was previously found that the ipsilateral tectally projecting ganglion cells normally amount to 0.9–2.3% (Singman and Scalia, op. cit.)

In frogs recovering from transection of the left optic nerve, the frequency, latency, and accuracy of the prey‐acquisition responses initiated by the recovering eye were compared with those initiated by the normal eye. Mealworms or lure dummies were used to stimulate prey acquisition. In one experiment, the stimuli were presented unilaterally in the monocular fields of frogs permitted to use both eyes. Prior to the fourteenth postoperative week, the affected eye initiated responses of abnormally long latency and low frequency. In contrast, responses initiated by the affected eye after 14 weeks appeared to be normal in all respects. In another experiment, the normal eye was sutured shut in some frogs recovering for at least 24 weeks and then the affected eye was retested. The affected eye was capable of consistently initiating brisk and accurate prey acquisition. In a final experiment, two stimuli were presented simultaneously in bilaterally symmetric regions of the monocular fields of frogs surviving at least 42 weeks. These fully recovered frogs showed no preference for using either the normal or the recovered eye. Despite severe loss of tectally projecting ganglion cells during optic nerve regeneration, frogs are capable of apparently normal visual responses in prey acquisition tests.
Reinnervation of cerebellar Purkinje cells by climbing fibres surviving a subtotal lesion of the inferior olive in the adult rat. I. Development of new collateral branches and terminal plexuses
Authors: Rossi F. , Wiklund L. , van der Want J. J. L. , Strata P.
Published: January 2005

Cerebellar climbing fibres react by collateral sprouting after subtotal lesions of the inferior olive, and the newly formed branches are able to reinnervate neighbouring denervated Purkinje cells. In the present paper, we used the Phaseolus vulgaris leucoagglutinin (PHA‐L) tracing technique to label the climbing fibres and study their plasticity in detail at the light microscopical level. The specific objectives were to study the time course and morphological aspects of their sprouting, to estimate their extent of growth, and to compare the newly formed terminal plexuses with normal climbing fibres.

Intraperitoneal injection of 3‐acetylpyridine induced degeneration of the majority of the olivary neurones, which terminate as climbing fibres in the cerebellar cortex. Regularly, small numbers of neurones survived in the inferior olive. In the cerebellar cortex scattered surviving climbing fibres were found, which were devoid of any sign of injury. Already 3 days after the lesion, surviving climbing fibres had emitted collateral branches, which elongated for some distance through the molecular layer and ended with a number of varicosities and very fine branchlets. By 7 days, it was possible to recognize new developing arbours which grew in the molecular layer with the same orientation as normal climbing fibres. At longer survival times, extensive terminal arbours had developed and double labelling experiments confirmed that they terminated around the proximal dendrites of Purkinje cells. The newly formed terminal plexuses resembled, in all essential aspects, normal climbing fibres. In addition, from 1 month onward, it was evident that every surviving climbing fibre was able to form several new terminal plexuses reinnervating a number of neighbouring Purkinje cells. The result of this process was the formation of large clusters of newly formed plexuses around the parental arborization. Quantitative estimates indicated that the domain of innervation of single surviving climbing fibres could be increased by more than six times.

It is concluded that climbing fibres surviving a subtotal olivary lesion are capable of extensive sprouting, axonal growth, and formation of new terminal plexuses, which resemble normal climbing fibres. Previous electrophysiological evidence indicates that this reinnervation is functional. The high specificity with which sprouting olivary axons reinnervate the proximal Purkinje cell dendrites suggests the existence of precise interactions between the growing fibres and their target. This example of “homotypic” collateral sprouting and reinnervation may thus provide a useful model for the study of nerve–target interactions.
Zebrin II immunoreactivity in the rat and in the weakly electric teleost Eigenmannia (gymnotiformes) reveals three modes of purkinje cell development
Authors: Lannoo Michael J. , Brochu Gino , Maler Leonard , Hawkes Richard
Published: January 2005

Monoclonal antibody (mab) anti‐zebrin II recognizes a single 36‐kD polypeptide in Purkinje cells in the rat and fish cerebellum. In the adult rat, zebrin II+ Purkinje cells form, in each hemicerebellum, seven parasagittal bands interposed by zebrin II− bands. We show that, in rats, immunoreactivity first appears caudally at postnatal day 5 and spreads; all Purkinje cells are labelled by postnatal day 12. Subsequently, immunoreactivity is selectively lost so that by day 18 the adult pattern of zebrin II+/− immunoreactive bands is created. This pattern indicates two types of Purkinje cells according to developmental trajectory, zebrin II−/+ and zebrin II−/+/−.

In the adult gymnotiform teleost Eigenmannia, Purkinje cells in the corpus cerebelli (CCb), lateral valvula cerebelli (VCbl), and eminentia granularis anterior (EGa) are zebrin II+ Purkinje cells in the eminentia granularis posterior (EGp) and medialis (EGm) and the medial valvula cerebelli (VCbm) are zebrin II−. Zebrin II antigenicity is first present at 6 days postspawning (P6) in the EGa and at P8 in the CCb. In the valvula, labelling does not appear until P29. Immunoreactivity in the CCb, VCbl, and the EGa persists in the adult, whereas in the VCbm Purkinje cells become zebrin II− before reaching adulthood. These developmental histories (zebrin II−/+ and zebrin II−/+/−) correspond to the patterns of Purkinje cell development in mammals. Additionally, Eigenmannia has a third class of Purkinje cells, in the EGp and EGm, that never express zebrin II immunoreactivity, indicating that zebrin II expression is not an obligatory feature of Purkinje cell development in all vertebrate.
Local circuit neurons of macaque monkey striate cortex: III. Neurons of laminae 4B, 4A, and 3B
Authors: Lund Jennifer S. , Yoshioka Takashi
Published: January 2005

We continue an investigation of the organization of local circuit neurons (largely inhibitory, GABAergic neurons, with smooth or sparsely spined dendrites) in the primary visual cortex of macaque monkey (Lund, '87: J. Comp. Neurol. 257:60–92; Lund et al., '88: J. Comp. Neurol. 276:1–29). This account covers local circuit neurons of layers 4B, 4A, and 3B; these three layers each receive different intrinsic second‐order relays of principal thalamic inputs as well as receiving primary thalamic inputs in the case of two of the three laminae (4A and 3B). The study shows the existence of a number of different local circuit neurons making interlaminar projections between 4B, 4A, and 3B; each provides specific cross links between different combinations of the three laminae. It is known that the functional properties recorded physiologically from layers 4B, 4A, and 3B differ from one another and so these anatomical cross links may allow for correlation between different attributes of visual stimuli, e.g., color or motion, while still enabling separate processing of these different attributes to proceed in each of the three layers and be passed on to extrastriate areas. Whereas no spine‐bearing neurons of layers 4B, 4A, or 3B provide “feedback” circuits to layer 4C (the source of their major intrinsic excitatory afferents), some of the local circuit neurons provide precisely structured axon feedback projections to divisions of 4C. The local circuit neurons also project to either lamina 5 or lamina 6, but not both and to superficial layers 3A, 2, and 1. Some local circuit neuron axon projections are of a dimension that would be confined to single functional clusters, e.g., cytochrome‐rich “blobs,” others reach out far enough to contact nearest neighbor “unlike” functional clusters, and yet others spread far enough to link repeating clusters of single function.
Parallel thalamic activation of the first and second somatosensory areas in prosimian primates and tree shrews
Authors: Garraghty P. E. , Florence S. L. , Tenhula W. N. , Kaas J. H.
Published: January 2005

In Tupaia belangeri and Galago senegalensis, microelectrode recordings immediately after ablation of the representation of the forelimb in the midportion of the first somatosensory area, S‐I, revealed that all parts of the second somatosensory area, S‐II, remained highly responsive to cutaneous stimuli. In this way, prosimian primates, close relatives of simian primates, and tree shrews differ markedly from monkeys in which S‐II is deactivated by comparable ablations, and resemble such mammals as cats and rabbits in which S‐II also remains highly responsive following ablations in S‐I. Thus, it appears that the generalized mammalian condition is that S‐I and S‐II are independently activated via parallel thalamocortical pathways. A dependence of S‐II on serial connections from the thalamus to the S‐I region and then to S‐II apparently evolved with the advent of anthropoid primates, and may be present only in monkeys and perhaps other higher primates.
The mossy cells of the fascia dentata: A comparative study of their fine structure and synaptic connections in rodents and primates
Authors: Frotscher Michael , Seress László , Schwerdtfeger Walter K. , Buhl Eberhard
Published: January 2005

In this study the fine structure and synaptic connections of mossy cells in the rat and monkey fascia dentata were analyzed. In order to study commissural connections of identified mossy cells in the rat, hilar neurons were retrogradely labeled by horseradish peroxidase (HRP) or Fast Blue (FB) injections into the contralateral hippocampus. Vibratome sections containing retrogradely HRP‐labeled hilar neurons were Golgi‐impregnated and gold‐toned. Hilar commissural neurons identified by contralateral FB injection were intracellularly labeled with Lucifer Yellow (LY). Lucifer Yellow staining was made electron‐dense by photoconversion thereby allowing for an electron microscopic analysis of the retrogradely labeled and intracellularly stained neurons. With these two different approaches, we succeeded in identifying rat mossy cells projecting to the contralateral hippocampus. Mossy cells in the fascia dentata of primates (Papio anubis, Macaca mulatto, Saimiri sciureus) were, like mossy cells of rats, either Golgi‐impregnated and gold‐toned or intracellularly injected with LY.

No major differences were found between mossy cells of rats and monkeys. The mossy cell dendrites originated from the two sides of an ovoid cell body and were mainly oriented parallel to the granule cell layer. In contrast to the rat, dendrites of mossy cells in the primate did not respect the granule cell layer and penetrated frequently into the molecular layer. The occurrence of excrescences on proximal dendrites was a characteristic feature of all mossy cells. These large spines were more complex in the primate than in the rat. In both rats and primates they formed numerous asymmetric synapses with large boutons of mossy fibers. Peripheral dendrites were covered with small, simple spines. Interestingly, these peripheral dendrites lacking excrescences also established asymmetric synapses with mossy fiber boutons as well as asymmetric and symmetric contacts with smaller terminals of unknown origin. These findings indicate that in both rats and primates the thorny excrescences are not the only target of the mossy terminals. While the proximal portions of the mossy cell dendrites appear to be exclusively contacted by the granule cells, a larger number of neuron types may converge on the distal dendrites. The axons of mossy cells, in both rats and primates, although incompletely stained with the present methods, were seen to ramify in‐the hilar region.

Our results demonstrate that, despite minor species differences, the mossy cells of the fascia dentata represent a cell type that is preserved in phylogenetically distant species.
Serotoninergic innervation of the ferret cerebral cortex. I. Adult pattern
Authors: Voigt Thomas , de Lima Ana Dolabela
Published: January 2005

We have investigated the serotoninergic innervation of the adult ferret cerebral cortex with immunohistochemical techniques. Distribution pattern of serotoninergic fibers in the ferret neocortex is characterized by a decrease in the density of fibers as one moves from the pial surface towards the white matter. Throughout the entire cerebral cortex, the serotoninergic fibers are very dense within the supragranular layers, especially within layer 1. In contrast, granular and infragranular layers exhibit only a sparse innervation. Although this general pattern of innervation is roughly the same in all cortical areas, significant variations in the fiber density are apparent in different regions. Areas 17, 1, 6, and 8 (primary visual cortex, presumptive somatosensory cortex, presumptive motor cortex, and prefrontal cortex, respectively) are described in more detail to illustrate the diversity of the serotoninergic innervation patterns. The density of innervation is highest in areas 1 and 6, intermediate in area 8, and lowest in area 17. It is noteworthy that while areas 1, 6, and 8 show a marked decrease in fiber density at the boundary between layer 3 and 4, the less strongly innervated area 17 shows a change in density in the transition from layer 2 to layer 3.

The types of fibers found within the ferret cortex are similar to those described in other mammalian species. The bulk of the innervation is made by very fine fusiform axons with small ovoid varicosities. In addition to this fiber type, axons with thick round varicosities and some smooth nonvaricose axons were found. The latter types occur in very small numbers within the supragranular layers and mostly in more anterior cortical regions. While the general innervation pattern and the fiber types are similar to those described in the cat cerebral cortex, the pericellular baskets found in the cat cortex (Mulligan and Törk, J Comp Neurol 270:86–110, 1988) are not seen in the ferret.