bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic organization of GABAergic neurons in the mouse SmI cortex
Authors: Keller Asaf , White Edward L. 
Published: January 2005

AbstractImmunocytochemical methods were used to examine GABAergic neurons in the barrel region of the mouse primary somatosensory cortex. GABAergic neurons occur in all layers of the barrel cortex but are more concentrated in the upper portion of layers II/III and in layers IV and VI. Nine cells in layer IV were examined with the electron microscope, and portions of their dendrites were reconstructed from serial thin sections. These cells are of the nonspiny, multipolar or bitufted varieties, and some of them have beaded dendrites. The labeled cell bodies and their reconstructed dendrites were postsynaptic at asymmetrical synapses with thalamocortical axon terminals labeled by lesion‐induced degeneration and with unlabeled axon terminals. Each cell also received symmetrical synapses from GABAergic axon terminals and from unlabeled axon terminals. Our results indicate that GABAergic cell bodies and processes receive synapses from thalamocortical axon terminals but that different cells display marked differences in the proportion of thalamocortical and other synapses they receive. These results indicate that GABAergic cells form a heterogeneous population with respect to their morphologies and patterns of synaptic inputs. The synaptic sequences revealed here for GABAergic neurons represent an anatomical substrate for various inhibitory processes known to occur within the cerebral cortex.
Dependence of cytochrome oxidase activity in the rat lateral geniculate nucleus on retinal innervation
Authors: Land Peter W. 
Published: January 2005

AbstractPatterns of cytochrome oxidase (CO) activity were examined histochemically in the dorsal lateral geniculate nucleus (LGNd) and retina of pigmented rats. CO staining was not uniform and was distributed in a pattern similar to that of retinal afferents. Portions of the LGNd receiving an exclusively crossed projection were moderately reactive whereas regions receiving an uncrossed or overlapping crossed and uncrossed projection were darkly reactive. The dependence of oxidative metabolic activity in the LGNd on retinal innervation was verified in animals with unilateral enucleation. In adults, chronic monocular enucleation led to a decrease in CO staining in portions of the LGNd deprived of retinal input; in animals enucleated at birth, normal patterns of CO reactivity failed to develop and both LGNd had a more uniform pattern of moderate CO staining.Most neurons in the ganglion cell layer of the retina were moderately reactive for CO. However, there were approximately 3,000 darkly reactive cells, most of which appear to be ganglion cells. The darkly reactive cells were more numerous in the peripheral temporal retina. The laminar pattern of CO staining in the retina was similar to that described previously for carnivores and primates. The most reactive laminae were the inner and outer plexiform layers and the photoreceptor inner segments. Within the inner plexiform layer, sublamina a was more darkly stained than sublamina b. These results suggest that the physiological properties of crossed and uncrossed visual pathways in rats are functionally dissimilar at the level of both the retina and the LGNd.
Distribution of acetylcholinesterase in the hippocampal region of the rabbit: III. The dentate area
Authors: Geneser Finn A. 
Published: January 2005

AbstractThe distribution of acetylcholinesterase (AChE) in the dentate area, a part of the hippocampal region, of the adult rabbit was described. A modification of the Koelle copper thiocholine method was used for the histochemical demonstration of AChE. The dentate area contained high amounts of this enzyme, distributed in a well‐defined stratified pattern. Thus, in the molecular layer seven distinct and differently stained layers were observed at most septotemporal levels. The granular cell bodies were entirely devoid of AChE, but stained precipitate occurred between the cell bodies, in particular in the superficial half of the granular cell layer. In the hilus, five layers of alternating stronger and weaker activity were recognizable. In the molecular layer and the granular cell layer, almost all activity was restricted to the neuropil, whereas a great number of intensely stained cell bodies were observed in the hilus.Criteria for the delimitation of the dentate area, as defined by Blackstad, are discussed in view of the concepts of Cajal and Lorente de Nó and in relation to more recent hodological and histochemical data. The results obtained in the present report compare well with the concept of a layered rabbit hilus, the cytoarchitecture of this being representative of one group of animals including the guinea pig, monkey, and humans and differing from the nonlayered hilus found in, for example, the rat and mouse.The distribution of AChE in the rabbit was compared with that in the rat and guinea pig, described previously. Very striking differences in the staining pattern of the molecular layer were observed, whereas the granular cell layer had a virtually identical appearance. The stratified pattern observed in the rabbit hilus corresponds to the distribution profile of the enzyme in the guinea pig, but contrasts with the rather diffuse distribution in the rat. This variation in the staining pattern of the hilus, however, mainly reflects the differences in cytomorphology between the rabbit and guinea pig on the one hand and the rat on the other, rather than being representative of a true species difference.The possible correlation of the AChE observed in the rabbit dentate area with cyto‐ and fibroarchitecture, in particular the terminal fields of fiber systems known from experimental investigations, is discussed in detail.The possibility that some of the AChE observed in the hippocampal region could be involved in the hydrolysis of a number of neuropeptides, in particular substance P and enkephalin, is considered.
The GABAergic neurons and axon terminals in the lateralis medialis‐suprageniculate nuclear complex of the cat: GABA‐immunocytochemical and WGA‐HRP studies by light and electron microscopy
Authors: Norita Masao , Katoh Yoshimitsu 
Published: January 2005

AbstractIn order to get more detailed information on the neural circuit of the lateralis medialis‐suprageniculate nuclear (LM‐Sg) complex of the cat, the GABAergic innervation of this complex was studied by GABA immunohistochemical techniques. Small immunoreactive cells were found throughout the LM‐Sg complex. On the basis of their ultrastructural features, these GABAergic cells were identified as Golgi type II interneurons. The neuropil of this nucleus displayed a conspicuous granular immunoreactivity. Ultra‐structurally, the immunoreactive neural profiles in the neuropil were identified as the presynaptic dendrites of interneurons, myelinated axons, or axon terminals. The GABAergic‐dendritic profiles, containing pleomorphic synaptic vesicles, were involved in synaptic glomeruli. Additionally, GABAergic axon terminals containing pleomorphic synaptic vesicles formed symmetric axodendritic synaptic contacts mainly in the extraglomerular neuropil. They appeared to correspond to either axon terminals from the thalamic reticular nucleus (TRN) or the axon terminals of interneurons.The projections from the TRN to the LM‐Sg complex were studied by using wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP). Following injection of WGA‐HRP into the LM‐Sg complex, a number of retrogradely labeled cells were observed in the TRN. The connections between the TEN and the LM‐Sg complex appeared to be topographically organized, the dorsal TRN being connected mainly with the dorsomedial portion of the LM‐Sg complex, and the ventral TRN being connected chiefly with the ventrolateral portion of the LM‐Sg complex. Following injection of the tracer into the TRN. ultrastructural examination of anterograde labeling in the LM‐Sg complex revealed that labeled terminals contain pleomorphic vesicles and make symmetric synaptic contacts mainly with small to medium‐sized dendrites. The labeled terminals were not involved in synaptic glomeruli.The present results provide anatomic support for the contention that the projection cells of the LM‐Sg complex may be inhibited by both the TRN axons and interneurons, probably through the mediation of GABA.
Fetal tectal or cortical tissue transplanted into brachial lesion cavities in rats: Influence on the regrowth of host retinal axons
Authors: Harvey Alan R. , Gan Seng Khee , Pauken Janice M. 
Published: January 2005

AbstractFetal neural tissue was transplanted into suction lesions of the left brachium and pretectal region in young rats. Tectal tissue was grafted into 6–18‐day‐old rats and cortical tissue was transplanted into 17–20‐day‐old animals. The aim was to determine whether grafts could potentiate the regrowth of damaged retinal axons and, as a consequence, stimulate the axons to reenter their host target, the superior colliculus (SC).Fifteen to 581 days after transplantation, host retinal projections were traced by injecting the right eye with horseradish peroxidase (HRP). Parallel series of frozen brain sections were stained for HRP histochemistry, acetylcholinesterase, Nissl, or neurofibrils. At all ages studied, grafts survived and grew within the wound cavity; survival was better in the older animals. Most cortical grafts and a small number of tectal grafts filled the wound cavity and formed complete tissue bridges across the lesion. The majority of tectal grafts were attached to one or the other side of the lesion and were connected to the opposite lesion face by glial and connective tissue membranes that formed over the lesion site.In many animals that received tectal transplants, host retinal axons were traced growing into the grafts. Regenerating axons innervated specific, localized areas within the grafts, and it appeared that the axons retained the ability to recognize their appropriate target cells within the graft neuropil. Comparable ingrowth into cortical grafts was not observed. Optic axons were occasionally seen reentering the superficial layers of the host SC; however; compared to fetal tectal grafts, the density of host SC innervation was sparse. The implications of these data are discussed with regard to the possible use of fetal neural tissue grafts as reconstructive tissue bridges in the mammalian central nervous system.
Central projections of the mesencephalic nucleus of the fifth nerve: An autoradiographic study
Authors: Luschei Erich S. 
Published: January 2005

AbstractProjections of cells of the mesencephalic nucleus of the fifth nerve (Mes V) to brainstem structures in the cat were studied by labelling Mes V cells with tritiated leucine. Before the leucine injections were made, however, large kainic acid lesions were produced in the vicinity of Mes V cells because these neurons are resistant to being killed or injured by this neurotoxin. Thus Mes V cells were selectively labelled by the leucine even though they are scattered among many other neurons.Leucine injections near Mes V cells located in the mesencephalon, which are primarily the somata of jaw muscle spindle afferent fibers, produced essentially the same pattern of terminal labelling as injections near a caudally located group of Mew V cells that includes the somata of many tooth mechanoreceptive afferents. Labelling was dense above the trigeminal motor nucleus in the nucleus supratrigeminalis and in the most medial portion of the principal trigeminal sensory nucleus. A scattering of labelled axons and diffuse label was seen along the length of the tract of Probst, which follows the medial border of the descending trigeminal sensory nucleus as far caudally as the dorsal motor nucleus of the vagus.Labelling within most of the trigeminal motor nucleus, which is known to receive direct synaptic input from Mes V cells, was very light. The only reasonably dense region of label was confined to a small dorsolateral portion of the motor nucleus.Although Mes V has generally been supposed to be involved with jaw control in a direct, reflexive manner, the extensive projections to nucleus supratrigeminalis and parts of the trigeminal sensory system draw attention to the potential proprioceptive sensory contribution of Mes V.
Subcortical connections of the superior colliculus in the mustache bat, Pteronotus parnellii
Authors: Covey E. , Hall W. C. , Kobler J. B. 
Published: January 2005

AbstractThe mustache bat, Pteronotus parnellii, depends on echolocation to navigate and capture prey. This adaptation is reflected in the large size and elaboration of brainstem auditory structures and in the minimal development of visual structures. The superior colliculus, usually associated with orienting the eyes, is nevertheless large and well developed in Pteronotus. This observation raises the question of whether the superior colliculus in the echolocating bat has evolved to play a major role in auditory rather than visual orientation. The connections of the superior colliculus in Pteronotus were studied with the aid of anterograde and retrograde transport of wheat germ agglutinin conjugated to HRP. These results indicate that the superior colliculus of Pteronotus is composed almost entirely of the layers beneath stratum opticum. The retinal projection is restricted to a very thin zone just beneath the pial surface. Prominent afferent pathways originate in motor structures, particularly the substantia nigra and the deep nuclei of the cerebellum. Sensory input from the auditory system originates in three brainstem nuclei: the inferior colliculus, the anterolateral periolivary nucleus, and the dorsal nuclei of the lateral lemniscus. The projections from these auditory structures terminate mainly in the central tier of the deep layer. The most prominent efferent pathways are those to medial motor structures of the contralateral brainstem via the predorsal bundle and to the ipsilateral midbrain and pontine tegmentum via the lateral efferent bundle. Ascending projections to the diencephalon are mainly to the medial dorsal nucleus and zona incerta. Thus, the superior colliculus in Pteronotus possesses well‐developed anatomical connections that could mediate reflexes for orienting its ears, head, or body toward objects detected by echolocation.
Regional distribution of cholecystokinin receptors in primate cerebral cortex determined by in vitro receptor autoradiography
Authors: Kritzer M. F. , Innis R. B. , Goldman‐Rakic P. S. 
Published: January 2005

AbstractCholecystokinin (CCK) is a putative peptide neurotransmitter present in high concentration in the cerebral cortex. By using techniques of in vitro receptor autoradiography, CCK binding sites in primate cortex were labeled with 125I‐Bolton‐Hunter‐labeled CCK‐33 (the 33‐amino‐acid C‐terminal peptide) and 3H‐CCK‐8 (the C‐terminal octapeptide). Biochemical studies performed on homogenized and slide‐mounted tissue sections showed that the two ligands labeled a high‐affinity, apparently single, saturable site.Autoradiography revealed that binding sites labeled by both ligands were anatomically indistinguishable and were distributed in two basic patterns. A faint and diffuse label characterized portions of medial prefrontal cortex, premotor and motor cortices, the superior parietal lobule, and the temporal pole. In other cortical areas the pattern of binding was layer‐specific i.e., binding sites were concentrated within particular cortical layers and were superimposed upon the background of diffuse label. Layer‐specific label was found in the prefrontal cortex, anterior and posterior cingulate gyrus, somatosensory cortex, inferior parietal lobule, retrosplenial cortex, insula, temporal lobe cortices, and in the primary visual and adjacent visual association cortices.The areal and laminar localization of layer‐specific CCK binding sites consistently coincided with the cortical projections of thalamic nuclei. In prefrontal cortex, CCK binding sites were present in layers III and IV, precisely paralleling the terminal fields of thalamocortical projections from the mediodorsal and medial pulvinar nucleus of the thalamus. In somatosensory cortex, the pattern of CCK binding in layer IV coincided with thalamic inputs arising from the ventrobasal complex, while in the posterior cingulate gyrus, insular cortex, and retrosplenial cortex, layer IV and lower III binding mirrored the laminar distribution of cortical afferents of the medial pulvinar. CCK binding in layers IVa, IVc alpha, IVc beta, and VI of primary visual cortex corresponded to the terminal field disposition of lateral geniculate neurons, whereas in adjacent visual association cortex, binding in layers III, IV, and VI faithfully followed the cortical distribution of projections from the inferior and lateral divisions of the pulvinar nucleus of the thalamus.We interpret the diffusely labeled binding sites in primate cortex as being associated with the intrinsic system of CCK‐containing interneurons that are distributed throughout all layers and areas of the cortex. The stratified binding sites, however, appear to be associated with specific extrinsic peptidergic projections. The anatomical coincidence of layer‐specific CCK binding sited and thalamocortical terminal fields suggests that certain thalamocortical projection fibres either contain CCK or interact with CCK. containing systems.
Different origins of cochlear efferents in some bat species, rats, and guinea pigs
Authors: Aschoff Andreas , Ostwald Joachim 
Published: January 2005

AbstractThe origin of olivocochlear efferents was studied in the rat, the guinea pig, and the bats Rhinolophus, Rhinopoma, Tadarida, and Phylostomus by retrograde labeling with HRP and the fluorescent dye fast blue. In all species with the exception of Rhinolophus rouxi two types of cochlear efferents could be found: small neurons located in the lateral superior olive (LSO) and larger ones located bilaterally in the periolivary region. In bats and rats small olivocochlear neurons (OCN) were found only in the ipsilateral LSO. In guinea pigs some small OCN were found also in the contralateral LSO. Large OCN were found in all animals except Rhinolophus. They were organized in a horseshoelike nucleus that extended in a rostrocaudal direction and bent rostrally around the medial superior olive (MSO). This nucleus contains several periolivary nuclei described separately by other authors.In Rhinol rouxi somata of all olivocochlear efferents are concentrated in a single nucleus between the MSO and LSO, which we therefore call the nucleus olivocochlearis. This nucleus stains for acetylcholinesterase. We consider its neurons to be similar to small OCN, because they are small, associated with the LSO, and only ipsilaterally labeled. This fits well with the fact that Rhinolophus lacks an efferent innervation of outer hair cells (Bishop: Ph.D. Thesis, University of North Carolina, Chapel Hill, '86; Bruns and Schmieszek: Hear. Res. 3: 27–43, '80), which are normally innervated by large OCN (Guinan et al: J. Comp. Neurol. 221: 358–370, '83).
Ultrastructural identification of synaptic terminals from the axon of type 3 interneurons in the cat lateral geniculate nucleus
Authors: Montero V. M. 
Published: January 2005

AbstractSynaptic terminals from the axons of type 3 neurons in the A‐laminae of the cat LGN impregnated with the Golgi gold‐toning procedure were examined at light and electron microscopic levels. The axons were identified by their somatic origin, thin diameter, and, in one of these cells, by dense undercoating beneath the axolemma, which is a known characteristic of the axon initial segment. The axon of one of the analyzed cells was profusely branched and extended throughout most of lamina A within the dendritic domains of the cell, and both types of processes were oriented along projection lines in LGN. This suggests that the dendrites and axons of type 3 cells receive inputs and exert effects, of probably inhibitory nature, within restricted retinotopic regions of LGN. The vast majority of the axon terminals of these cells were distributed in series along axonal branches. In one of the type 3 cells, however, a dense cluster of terminals arising from a secondary axonal branch was observed. Ultrastructurally, the analyzed synaptic terminals of the type 3 cells contained flattened or pleomorphic synaptic vesicles, dark mitochondria, and established synapses that appeared to be of symmetrical type when the membranes were perpendicularly cut. On the basis of these characteristics these terminals are classified as F boutons, following Guillery's (Z. Zellforsch. 96: 1–38, '69), nomenclature. The postsynaptic elements to the axon terminals were dendrites of small to medium size, which received “en passant” synaptic contacts in extraglomerular regions of the geniculate neuropil by the terminals distributed in series. The axon terminals located in clusters, however, made synapses with dendrites in glomerular regions of the neuropil, where they were not seen postsynaptic to retinal or other types of terminals. This is in contrast to the postsynaptic nature of F2 boutons in the same glomeruli, which have been identified as dendritic appendages of the GABA positive type 3 neurons in the cat LGN (Montero: J. Comp. Neurol 254: 223–245, '86). On the other hand, the axonal F terminals differ from F1 boutons in terms of synaptic relations and ultrastructure, since the latter have been shown to be presynaptic to F2s and sonata and to contain crowded populations of flat synaptic vesicles which give them a characteristic dark appearance. Terminals equivalent to F1 boutons have been shown to originate from perigeniculate cells in the rat LGN. From these observations it is suggested that the geniculate GABAergic interneurons support two morphologically and functionally different types of inhibitory terminals synapsing the dendrites of relay cells: the dendritic F2 terminals that in microcircuits are under the influence of retinal, cortical, perigeniculate, and cholinergic terminals from the midbrain, and the axonal F boutons, which would convey to the postsynaptic relay cell the unaltered output of these interneurons.
Cytoarchitecture of the avian ventral lateral geniculate nucleus
Authors: Guiloff Gloria D. , Maturana Humberto R. , Varela Francisco J. 
Published: January 2005

AbstractThe avian thalamic ventral lateral geniculate nucleus (GLv) was studied by light microscopic techniques in order to understand its anatomy, neuronal composition, and the nature of its retinal and tectal afferents. The avian GLv is of considerable interest because physiological experiments show that it is the brain structure with the highest percentage of color‐opponent responses (Maturana and Varela, '82).We used adult pigeons and quail for the present study. With Nissl techniques a predominance of medium‐size neurons (58%) constitute the GLv. The shape, size, and orientation of the different neurons is highly variable throughout the GLv. With the Golgi methods, 5 classes of neurons are distinguished: I and IV (large), II (medium‐size), III and V (small). Some class IV large neurons have bifurcated axons; no axons were distinguished on the small neurons. Optic fibers penetrating the GLv are often collateral branches of retinal axons that continue elsewhere. Fink‐Heimer methods show that retinal axon terminals end around large and medium‐size neurons and also reach the internal lamina of the GLv. HRP tracing shows that the large and medium‐size neurons of the GLv project to the optic tectum.On the basis of comparisons between the cytoarchitecture of the GLv described here and the physiological findings previously reported (Maturana and Varela, '82; Pateromichelakis, '79), we suggest that: (1) large GLv neurons are the color‐opponent units, (2) medium‐size neurons are the movement‐sensitive units, and (3) small neurons are either interneurons (local circuit neurons), or they might project to the area pretectalis or to some other GLv projection region not yet described.