Dextran Amine (dextran + amine)

Distribution by Scientific Domains

Kinds of Dextran Amine

  • biotinylated dextran amine

  • Selected Abstracts

    GABAergic projections from the hippocampus to the retrosplenial cortex in the rat

    Toshio Miyashita
    Abstract The retrosplenial cortex (RS) in rats has been implicated in a wide range of behaviors, including spatial navigation and memory. Relevant to this, the RS is closely interconnected with the hippocampus by multiple direct and indirect routes. Here, by injecting the retrograde tracer cholera toxin subunit B conjugated with Alexa488 (CTB-Alexa488) in the granular retrosplenial cortex (GRS), we demonstrate a moderately dense non-pyramidal projection from CA1. Neurons are in several layers, but mainly (about 65%) at the border of the stratum radiatum (SR) and stratum lacunosum moleculare (SLM). In particular, by double-labeling with GAD67 or ,-aminobutyric acid (GABA), we establish that these neurons are GABAergic. Further immunocytochemical screening for calcium-binding proteins, somatostatin (SS) or cholecystokinin (CCK) failed to identify additional neurochemical subgroups; but a small subset (about 14%) is positive for the m2 muscarinic acetylcholine receptor (M2R). Terminations target layer 1 of the GRS, as shown by biotinylated dextran amine (BDA) injections into CA1 and confirmed by a very superficial injection of CTB-Alexa488 in GRS. The superficial injection shows that there is a sparse GABAergic projection from the subiculum to layer 1 of the GRS, in addition to the dense excitatory connections to layer 3. The role of these dual inhibitory,excitatory pathways , within the subiculum, and in parallel from CA1 and the subiculum , remains to be determined, but may be related to synchronized oscillatory activity in the hippocampal complex and GRS, or to the generation of rhythmic activity within the GRS. [source]

    Topographical projection from the superior colliculus to the nucleus of the brachium of the inferior colliculus in the ferret: convergence of visual and auditory information

    Timothy P. Doubell
    Abstract The normal maturation of the auditory space map in the deeper layers of the ferret superior colliculus (SC) depends on signals provided by the superficial visual layers, but it is unknown where or how these signals influence the developing auditory responses. Here we report that tracer injections in the superficial layers label axons with en passant and terminal boutons, both in the deeper layers of the SC and in their primary source of auditory input, the nucleus of the brachium of the inferior colliculus (nBIC). Electron microscopy confirmed that biocytin-labelled SC axons form axodendritic synapses on nBIC neurons. Injections of biotinylated dextran amine in the nBIC resulted in anterograde labelling in the deeper layers of the SC, as well as retrogradely labelled superficial and deep SC neurons, whose distribution varied systematically with the rostrocaudal placement of the injection sites in the nBIC. Topographical order in the projection from the SC to the ipsilateral nBIC was confirmed using fluorescent microspheres. We demonstrated the existence of functional SC-nBIC connections by making whole-cell current-clamp recordings from young ferret slices. Both monosynaptic and polysynaptic EPSPs were generated by electrical stimulation of either the superficial or deep SC layers. In addition to unimodal auditory units, both visual and bimodal visual,auditory units were recorded in the nBIC in vivo and their incidence was higher in juvenile ferrets than in adults. The SC-nBIC circuit provides a potential means by which visual and other sensory or premotor signals may be delivered to the nBIC to calibrate the representation of auditory space. [source]

    Organization of connections of the basal and accessory basal nuclei in the monkey amygdala

    Eva Bonda
    Abstract PLEASE NOTE: Expression of Concern (EJN, 12:11, p4153) The present study investigated the intrinsic connections of the basal and accessory basal nuclei of the Macaca fascicularis monkey by means of the anterograde tracers Phaseolus vulgaris-leucoagglutinin (PHA-L) and biotinylated dextran amine (BDA). Analysis of the intranuclear connections of the basal nucleus indicates that there are five modules: dorsal, intermediate, ventral lateral, ventral medial and periamygdaloid sulcal cortex. The dorsal division projects to the intermediate division. Laterally, the intermediate division projects to the ventral lateral division and dorsal parts of the ventral medial division. Ventrally, the ventral lateral division projects to the ventral medial division and periamygdaloid sulcal cortex, which appears to constitute a medial extension of the basal nucleus onto the cortical surface of the amygdala. Medially, the ventral medial division projects to the intermediate and dorsal divisions. Thus, the connections between these modules form functional microcolumns within the nucleus with distinct patterns of information flow that are dorsal to ventral laterally, lateral to medial ventrally, and ventral to dorsal medially. Observations on the intranuclear connections of the accessory basal nucleus suggest that they are organized into two relatively distinct domains: the dorsal division projects to the ventral division and the ventral division projects primarily to the ventromedial division. Projections to other amygdaloid areas originate in select divisions of the basal and accessory basal nuclei, and are topographically distributed. The organization of intrinsic connections of the basal nuclei correlates with specific amygdalo-cortical connections and suggests that extensive convergence of information takes place within the amygdala, which potentially influences activity at both the temporal and parietal pathways and hippocampal fields. [source]

    Precise matching of olivo-cortical divergence and cortico-nuclear convergence between somatotopically corresponding areas in the medial C1 and medial C3 zones of the paravermal cerebellum

    R. Apps
    Abstract The paravermal cerebellar cortex contains three spatially separate zones (the C1, C3 and Y zones) which form a functionally coupled system involved in the control of voluntary limb movements. A series of ,modules' has been postulated, each defined by a set of olivary neurons with similar receptive fields, the cortical microzones innervated by these neurons and the group of deep cerebellar nuclear neurons upon which the microzones converge. A key feature of this modular organization is a correspondence between cortical input and output, irrespective of the zonal identity of the microzone. This was tested directly using a combined electrophysiological and bi-directional tracer technique in barbiturate-anaesthetized cats. During an initial operation, small injections of a mix of retrograde and anterograde tracer material (red beads combined with Fluoro-Ruby or green beads combined with biotinylated dextran amine or Fluoro-Emerald) were made into areas of the medial C1 and medial C3 zones in cerebellar lobule V characterized by olivo-cerebellar input from the ventral forelimb. The inferior olive and the deep cerebellar nuclei were then scrutinized for retrogradely labelled cells and anterogradely labelled axon terminals, respectively. For individual experiments, the degree of C1,C3 zone terminal field overlap in the nucleus interpositus anterior was plotted as a function of either the regional overlap of single-labelled cells or the proportion of double-labelled cells in the dorsal accessory olive. The results were highly positively correlated, indicating that cortico-nuclear convergence between parts of the two zones is in close proportion to the corresponding olivo-cerebellar divergence, entirely consistent with the modular hypothesis. [source]

    Cortical efferents of the perirhinal, postrhinal, and entorhinal cortices of the rat

    HIPPOCAMPUS, Issue 12 2009
    Kara L. Agster
    Abstract We investigated the cortical efferents of the parahippocampal region by placing injections of the anterograde tracers, Phaseolus vulgaris -leuccoagglutinin, and biotinylated dextran amine, throughout the perirhinal (PER), postrhinal (POR), and entorhinal cortices of the rat brain. The resulting density of labeled fibers was evaluated in 25 subregions of the piriform, frontal, insular, temporal, cingulate, parietal, and occipital areas. The locations of labeled terminal fibers differed substantially depending on whether the location of the injection site was in PER area 35, PER area 36, POR, or the lateral or the medial entorhinal (LEA and MEA). The differences were greater for sensory regions. For example, the POR efferents preferentially target visual and spatial regions, whereas the PER efferents target all sensory modalities. The cortical efferents of each region largely reciprocate the cortical afferents, though the degree of reciprocity varied across originating and target regions. The laminar pattern of terminal fibers was consistent with the notion that the efferents are feedback projections. The density and amount of labeled fibers also differed substantially depending on the regional location of injection sites. PER area 36 and POR give rise to a greater number of heavy projections, followed by PER area 35. LEA also gives rise to widespread cortical efferents, arising mainly from a narrow band of cortex adjacent to the PER. In contrast, the remainder of the LEA and the MEA provides only weak efferents to cortical regions. Prior work has shown that nonspatial and spatial information is transmitted to the hippocampus via the PER-LEA and POR-MEA pathways, respectively. Our findings suggest that the return projections follow the same pathways, though perhaps with less segregration. 2009 Wiley-Liss, Inc. [source]

    Evidence that serotonin reuptake modulators increase the density of serotonin innervation in the forebrain

    Lijun Zhou
    Abstract The mechanism of action of commonly used antidepressants remains an issue of debate. In the experiments reported here we studied the effects of three representative compounds, the selective serotonin reuptake inhibitor fluoxetine, the selective serotonin reuptake enhancer tianeptine and the selective norepinephrine reuptake inhibitor desipramine on the structure of central serotonin pathways after a 4-week administration. We found that the serotonin modulators fluoxetine and tianeptine, but not desipramine, increase the density of 5-HT and serotonin transporter (SERT)-immunoreactive axons in the neocortical layer IV and certain forebrain limbic areas, such as piriform cortex and the shell region of nucleus accumbens. These changes were noted in the absence of a significant effect of serotonin antidepressants on the expression of tryptophan hydroxylase (TPH-2), i.e. the rate-limiting enzyme for 5-HT biosynthesis and of SERT at the mRNA level. In addition, we found that anterogradely filled terminal axons from injections of biotinylated dextran amine into the dorsal raphe showed significantly more branching in animals treated with fluoxetine compared with animals treated with liposyn vehicle. Our findings suggest that antidepressants may exert very selective structural effects on their cognate monoamine systems in normal animals and raise the possibility that neurotrophic mechanisms may play a role in their clinical efficacy. [source]

    Poster Sessions CP04: Axonal Growth and Transport

    L. Zhou
    Neurotrophins support neuronal survival and axonal regeneration after injury. To test whether local expression of Neurotrophin-3 (NT-3) would elicit axonal regeneration we lesioned the corticospinal tract (CST) at the level of the hindbrain and measured the number of axons that would grow from the unlesioned CST to the contralateral side where NT-3 was over expressed at the lumbar level of the spinal cord. An adenoviral vector that carried the rat NT-3 gene and the NGF signal peptide driven by the EF1, promoter (Adv.EF-NT-3) was used. This model enabled us to test the effects of NT-3 on axonal regeneration without confounding injury processes. Biotinylated dextran amine (BDA) was injected into the rat cortex on unlesioned side to mark CST axons 10 days postlesion. Adenoviral vectors (1 109 pfu, Adv.EF-NT-3 or Adv.EF-LacZ) were delivered to lumbar spinal cord by retrograde transport from the sciatic nerve 4 days later. Histological examination 3 weeks later revealed that more BDA-labelled axons had grown from the unlesioned CST to the denervated side at the lumbar level. Morphometric measurements showed that a significantly larger number of BDA-labelled CST axons (p < 0.001) were present in the animals that were treated with Adv.EF-NT-3 than those treated with Adv.EF-LacZ. These data demonstrate that local expression of NT-3 will support axonal regeneration in the injured spinal cord without adverse effects and suggest that gene delivery of neurotrophins may be an effective strategy for nervous system repair after injury. Acknowledgements:, Funded by NIH Grant NS35280 and by Mission Connect of the TIRR Foundation. [source]

    Changes in the connections of the main olfactory bulb after mitral cell selective neurodegeneration

    Javier S. Recio
    Abstract The connections of the main olfactory bulb (OB) of the mouse were studied with iontophoretic injections of biotinylated dextran amine. To sort efferences from mitral cells and tufted cells, the Purkinje cell degeneration (PCD) mouse was used. This mutant animal undergoes a specific neurodegeneration of mitral cells, whereas tufted cells do not degenerate. The unilateral tracer injections used were small and confined largely to the OB of both PCD and control mice at P120. Seven days after tracer injection, the efferences from the OB and the centrifugal afferences from secondary olfactory structures to it were studied. Although there is a large overlap of their target fields, mitral cell axons innervated more caudal regions of the olfactory cortex than tufted cell axons, thus providing definitive evidence of the differential projections of olfactory output neurons. Additionally, an important increase in retrogradely-labeled neurons was detected in the ipsilateral anterior olfactory nucleus of the mutant animals. This was not observed in any other secondary olfactory structure, suggesting a strengthening of the centrifugal input to the OB from that central area after mitral cell loss. Moreover, we recorded a complete loss of bilaterality in the olfactory connections of the PCD mice due to degeneration of the anterior commissure. These results point to an important reorganization of this essential olfactory circuit between the anterior olfactory nucleus and the OB, and hint at a transsynaptic level of plasticity not considered previously in literature. 2007 Wiley-Liss, Inc. [source]

    Guanosine-Induced Synaptogenesis in the Adult Brain In Vivo

    Inmaculada Gerrikagoitia
    Abstract Astrocytes release factors like cholesterol, apoE, and pleiotropic molecules that influence synaptogenesis in the central nervous system. In vitro studies have shown that guanosine elicits the production and further release of these synaptogenic factors. To demonstrate that such astrocytic factors are synaptogenic in vivo, osmotic pumps were implanted in primary visual cortex (VC) of Sprague-Dawley rats to deliver guanosine. Simultaneous injection of dextran amine as an anterograde tracer at the same site where the osmotic pumps were implanted enabled the morphology of the fibers emerging from the VC to be visualized as well. The guanosine-treated efferent connections from these animals showed a significant increase in the number and size of synaptic boutons along the efferent fibers when compared with controls. A similar increase in the number and size of synaptic boutons was also detected when the cortico,cortical connection to the lateral secondary visual area was studied in more detail. The ensuing morphological changes to the synapses did not show a clear preference for any particular type or site of the axonal branches that integrates this cortical connection. Moreover, the distribution of boutons along the fibers was clearly stochastic according to their size. Thus, guanosine administration appears to open up the possibility of manipulating connections to compensate for total or partial denervation. Anat Rec, 292:1968,1975, 2009. 2009 Wiley-Liss, Inc. [source]

    Comparison of the ultrastructure of cortical and retinal terminals in the rat superior colliculus

    Kamran Boka
    Abstract We compared the ultrastructure and synaptic targets of terminals of cortical or retinal origin in the stratum griseum superficiale and stratum opticum of the rat superior colliculus. Following injections of biotinylated dextran amine into cortical area 17, corticotectal axons were labeled by anterograde transport. Corticotectal axons were of relatively small caliber with infrequent small varicosities. At the ultrastructural level, corticotectal terminals were observed to be small profiles (0.44 0.27 ,m2) that contained densely packed round vesicles. In tissue stained for gamma amino butyric acid (GABA) using postembedding immunocytochemical techniques, corticotectal terminals were found to contact small (0.51 0.69 ,m2) non-GABAergic dendrites and spines (93%) and a few small GABAergic dendrites (7%). In the same tissue, retinotectal terminals, identified by their distinctive pale mitochondria, were observed to be larger than corticotectal terminals (3.34 1.79 ,m2). In comparison to corticotectal terminals, retinotectal terminals contacted larger (1.59 1.70 ,m2) non-GABAergic dendrites and spines (73%) and a larger proportion of GABAergic profiles (27%) of relatively large size (2.17 1.49 ,m2), most of which were vesicle-filled (71%). Our results suggest that cortical and retinal terminals target different dendritic compartments within the neuropil of the superficial layers of the superior colliculus. Anat Rec Part A, 288A:850,858, 2006. 2006 Wiley-Liss, Inc. [source]

    Axonal branching patterns of nucleus accumbens neurons in the rat

    Anushree Tripathi
    Abstract The patterns of axonal collateralization of nucleus accumbens (Acb) projection neurons were investigated in the rat by means of single-axon tracing techniques using the anterograde tracer biotinylated dextran amine. Seventy-three axons were fully traced, originating from either the core (AcbC) or shell (AcbSh) compartment, as assessed by differential calbindin D28k-immunoreactivity. Axons from AcbC and AcbSh showed a substantial segregation in their targets; target areas were either exclusively or preferentially innervated from AcbC or AcbSh. Axon collaterals in the subthalamic nucleus were found at higher than expected frequencies; moreover, these originated exclusively in the dorsal AcbC. Intercompartmental collaterals were observed from ventral AcbC axons into AcbSh, and likewise, interconnections at pallidal and mesencephalic levels were also observed, although mostly from AcbC axons toward AcbSh targets, possibly supporting crosstalk between the two subcircuits at several levels. Cell somata giving rise to short-range accumbal axons, projecting to the ventral pallidum (VP), were spatially intermingled with others, giving rise to long-range axons that innervated VP and more caudal targets. This anatomical organization parallels that of the dorsal striatum and provides the basis for possible dual direct and indirect actions from a single axon on either individual or small sets of neurons. J. Comp. Neurol. 518:4649,4673, 2010. 2010 Wiley-Liss, Inc. [source]

    Connections of eye-saccade-related areas within mesencephalic reticular formation with the optic tectum in goldfish

    Maria A. Luque
    Abstract Physiological studies demonstrate that separate sites within the mesencephalic reticular formation (MRF) can evoke eye saccades with different preferred directions. Furthermore, anatomical research suggests that a tectoreticulotectal circuit organized in accordance with the tectal eye movement map is present. However, whether the reticulotectal projection shifts with the gaze map present in the MRF is unknown. We explored this question in goldfish, by injecting biotin dextran amine within MRF sites that evoked upward, downward, oblique, and horizontal eye saccades. Then, we analyzed the labeling in the optic tectum. The main findings can be summarized as follows. 1) The MRF and the optic tectum were connected by separate axons of the tectobulbar tract. 2) The MRF was reciprocally connected mainly with the ipsilateral tectal lobe, but also with the contralateral one. 3) The MRF received projections chiefly from neurons located within intermediate and deep tectal layers. In addition, the MRF projections terminated primarily within the intermediate tectal layer. 4) The distribution of labeled neurons in the tectum shifted with the different MRF sites in a manner consistent with the tectal motor map. The area containing these cells was targeted by a high-density reticulotectal projection. In addition to this high-density topographic projection, there was a low-density one spread throughout the tectum. 5) Occasionally, boutons were observed adjacent to tectal labeled neurons. We conclude that the organization of the reticulotectal circuit is consistent with the functional topography of the MRF and that the MRF participates in a tectoreticulotectal feedback circuit. J. Comp. Neurol. 500:6,19, 2007. 2006 Wiley-Liss, Inc. [source]

    Central projections of the saccular and utricular nerves in macaques

    Shawn D. Newlands
    Abstract The central projections of the utricular and saccular nerve in macaques were examined using transganglionic labeling of vestibular afferent neurons. In these experiments, biotinylated dextran amine was injected directly into the saccular or utricular neuroepithelium of fascicularis (Macaca fascicularis) or rhesus (Macaca mulatta) monkeys. Two to 5 weeks later, the animals were killed and the peripheral vestibular sensory organs, brainstem, and cerebellum were collected for analysis. The principal brainstem areas of saccular nerve termination were lateral, particularly the spinal vestibular nucleus, the lateral portion of the superior vestibular nucleus, ventral nucleus y, the external cuneate nucleus, and cell group l. The principal cerebellar projection was to the uvula with a less dense projection to the nodulus. Principle brainstem areas of termination of the utricular nerve were the lateral/dorsal medial vestibular nucleus, ventral and lateral portions of the superior vestibular nucleus, and rostral portion of the spinal vestibular nucleus. In the cerebellum, a strong projection was observed to the nodulus and weak projections were present in the flocculus, ventral paraflocculus, bilateral fastigial nuclei, and uvula. Although there is extensive overlap of saccular and utricular projections, saccular inputs to the lateral portions of the vestibular nuclear complex suggest that saccular afferents contribute to the vestibulospinal system. In contrast, the utricular nerve projects more rostrally into areas of known concentration of vestibulo-ocular related cells. Although sparse, the projections of the utricle to the flocculus/ventral paraflocculus suggest a potential convergence with floccular projection inputs from the vestibular brainstem that have been implicated in vestibulo-ocular motor learning. J. Comp. Neurol. 466:31,47, 2003. 2003 Wiley-Liss, Inc. [source]

    Structure of intraglomerular dendritic tufts of mitral cells and their contacts with olfactory nerve terminals and calbindin-immunoreactive type 2 periglomerular neurons

    Katsuko Kosaka
    Abstract Intraglomerular dendritic tufts of Golgi-impregnated and biotinylated dextran amine (BDA)-labeled mitral cells in the rat main olfactory bulb were analyzed in detail. In particular, the relationships of BDA-labeled tufts with olfactory nerve (ON) terminals and processes of calbindin D-28K-immunoreactive (CB-IR) cells were investigated with confocal laser-scanning light microscopic (CLSM) and electron microscopic (EM) analyses. CB-IR cells were type 2 periglomerular cells that restricted their processes in the ON-free (non-ON) zone of the glomerulus and received few synapses from ON terminals. The mitral tufts varied in complexity, but individual branches were rather simple, smooth processes that bore some branchlets and spines and extended more or less in a straight line or a gentle curve rather than winding tortuously within glomeruli as though they did not consider the compartmental organization, which consisted of ON and non-ON zones that interdigitated in a complex manner with one another. Conventional EM analysis revealed that both thin and thick, presumed proximal branches of mitral/tufted cell dendritic tufts received asymmetrical synapses from ON terminals. Correlated CLSM-EM analysis confirmed direct contacts between the BDA- and CB-labeled processes detected in the CLSM examinations, and synapses were recognized at some of those sites. Furthermore, ON terminals and CB-IR processes were distributed on both proximal and distal dendritic branches in a more or less mosaic pattern. These findings revealed that, on the mitral dendritic tufts, ON terminals and processes of type 2 periglomerular neurons were not clearly segregated proximodistally but, rather, were arranged in a mosaic pattern, which may be important in fine tuning the output from individual glomeruli. J. Comp. Neurol. 440:219,235, 2001. 2001 Wiley-Liss, Inc. [source]

    Forebrain projections to the hypothalamus are topographically organized in anurans: conservative traits as compared with amniotes

    Nerea Moreno
    Abstract The organization of the forebrain in amphibians (anamniotes) is currently being re-evaluated in terms of evolution and several evidences have corroborated numerous traits shared by amphibians and amniotes, such as the organization of the basal ganglia and the amygdaloid complex. In the present study we have analysed the organization of forebrain afferent systems to the hypothalamus of the frog Rana perezi. In vivo and in vitro tract-tracing techniques with dextran amines and immunohistochemistry for localizing nitric oxide synthase (NOS) in a series of single or combined experiments were used as NOS labelling reveals hypothalamic afferents arising from the lateral amygdala and the combination allowed analysis of the relationship between fibers of different origins in the same section. The results showed a large segregation of afferents in the hypothalamic region depending on their site of origin in the forebrain. Four highly topographically organized prosencephalic tracts reaching the anuran hypothalamus were observed: (i) the medial forebrain bundle, from the medial pallium and septal complex; (ii) the caudal branch of the stria terminalis formed by fibers arising in the lateral and medial amygdala; (iii) part of the lateral forebrain bundle with fibers from the central amygdala and (iv) the dorsal thalamo-hypothalamic tract. Fibers coursing in each tract reach the hypothalamus and terminate in distinct fields. The resemblance in pattern of forebrain-hypothalamic organization between amphibians and amniotes suggests that this feature represents an important trait conserved in the evolution of all tetrapods and therefore essential for the hypothalamic function. [source]

    Immunohistochemical and hodological characterization of calbindin-D28k-containing neurons in the spinal cord of the turtle, Pseudemys scripta elegans

    Ruth Morona
    Abstract Neurons and fibers containing the calcium-binding protein calbindin-D28k (CB) were studied by immunohistochemical techniques in the spinal cord of adult and juvenile turtles, Pseudemys scripta elegans. Abundant cell bodies and fibers immunoreactive for CB were widely and distinctly distributed throughout the spinal cord. Most neurons and fibers were labeled in the superficial dorsal horn, but numerous cells were also located in the intermediate gray and ventral horn. In the dorsal horn, most CB-containing cells were located in close relation to the synaptic fields formed by primary afferents, which were not labeled for CB. Double immunohistofluorescence demonstrated distinct cell populations in the dorsal horn labeled only for CB or nitric oxide synthase, whereas in the dorsal part of the ventral horn colocalization of nitric oxide synthase was found in about 6% of the CB-immunoreactive cells in this region. Choline acetyltransferase immunohistochemistry revealed that only about 2% of the neurons in the dorsal part of the ventral horn colocalized CB, whereas motoneurons were not CB-immunoreactive. The involvement of CB-containing neurons in ascending spinal projections to the thalamus, tegmentum, and reticular formation was demonstrated combining the retrograde transport of dextran amines and immunohistochemistry. Similar experiments demonstrated supraspinal projections from CB-containing cells mainly located in the reticular formation but also in the thalamus and the vestibular nucleus. The revealed organization of the neurons and fibers containing CB in the spinal cord of the turtle shares distribution and developmental features, colocalization with other neuronal markers, and connectivity with other tetrapods and, in particular with mammals. Microsc. Res. Tech., 2007. 2007 Wiley-Liss, Inc. [source]

    Preservation of segmental hindbrain organization in adult frogs

    Hans Straka
    Abstract To test for possible retention of early segmental patterning throughout development, the cranial nerve efferent nuclei in adult ranid frogs were quantitatively mapped and compared with the segmental organization of these nuclei in larvae. Cranial nerve roots IV,X were labeled in larvae with fluorescent dextran amines. Each cranial nerve efferent nucleus resided in a characteristic segmental position within the clearly visible larval hindbrain rhombomeres (r). Trochlear motoneurons were located in r0, trigeminal motoneurons in r2,r3, facial branchiomotor and vestibuloacoustic efferent neurons in r4, abducens and facial parasympathetic neurons in r5, glossopharyngeal motoneurons in r6, and vagal efferent neurons in r7,r8 and rostral spinal cord. In adult frogs, biocytin labeling of cranial nerve roots IV,XII and spinal ventral root 2 in various combinations on both sides of the brain revealed precisely the same rostrocaudal sequence of efferent nuclei relative to each other as observed in larvae. This indicates that no longitudinal migratory rearrangement of hindbrain efferent neurons occurs. Although rhombomeres are not visible in adults, a segmental map of adult cranial nerve efferent nuclei can be inferred from the strict retention of the larval hindbrain pattern. Precise measurements of the borders of adjacent efferent nuclei within a coordinate system based on external landmarks were used to create a quantitative adult segmental map that mirrors the organization of the larval rhombomeric framework. Plotting morphologically and physiologically identified hindbrain neurons onto this map allows the physiological properties of adult hindbrain neurons to be linked with the underlying genetically specified segmental framework. J. Comp. Neurol. 494:228,245, 2006. 2005 Wiley-Liss, Inc. [source]

    Localization and connectivity of the lateral amygdala in anuran amphibians

    Nerea Moreno
    Abstract On the basis of chemoarchitecture and gene expression patterns in the amphibian amygdaloid complex, new subdivisions have been proposed and compared with their counterparts in amniotes. Thus, a portion of the ventral pallium of anurans has been tentatively named "lateral amygdala" (LA) and compared with the basolateral complex of mammals. To strengthen the putative homology, we have analyzed the pattern of afferent and efferent connections of the LA in the anurans Rana perezi and Xenopus laevis. Tract-tracing techniques with dextran amines were used under in vivo and in vitro conditions. The results showed important connections with the main olfactory bulb, via the lateral olfactory tract. In addition, abundant intratelencephalic connections, via the rostral branch of the stria terminalis, were revealed, involving mainly the basal ganglia, septal nuclei, bed nucleus of the stria terminalis, and especially other amygdaloid nuclei. Nontelencephalic connections were found from the dorsal thalamus and parabrachial area and, in particular, from the hypothalamus through the caudal branch of the stria terminalis. All these results strongly suggest that the LA in anurans is a multimodal area in the ventral pallium that shares many hodological features with the amygdaloid ventropallial derivatives of the basolateral complex of amniotes. J. Comp. Neurol. 479:130,148, 2004. 2004 Wiley-Liss, Inc. [source]