Rat intralaminar thalamic nuclei projections to the globus pallidus: a biotinylated dextran amine anterograde tracing study

The topographical organization and ultrastructural features of the intralaminar thalamic nuclei (ITN) projections to the globus pallidus (GP) were studied using the biotinylated dextran amine (BDA) anterograde tracing method in the rat. To assess the functional association of BDA injection sites in the ITN, the known topographical organization of the ITN-neostriatal (Str) projections and calcium binding protein (CaBP) immunostaining patterns of the Str and GP were used. BDA injection in the lateral part of the lateral parafascicular nucleus and the caudal part of the central lateral nucleus labeled fibers and boutons mainly in the dorsolateral sensorimotor territory of the Str and the middle territories of the GP. BDA injection in the medial part of the lateral parafascicular nucleus and the central lateral nucleus labeled mainly the middle association territory of the Str and the border and the caudomedial territories of the GP. BDA injection in the medial parafascicular nucleus and the central medial nucleus labeled mainly the medial limbic territory of the Str. The medial parafascicular nucleus projected to the medial-most region of the GP, while the central medial nucleus projection to the GP was very sparse. Electron microscopic observations indicated that BDA-labeled boutons form asymmetric synapses mainly on 0.5-2.0 microm diameter dendritic shafts in the GP. The boutons were small but had a relatively long active zone. The present observations together with the known topographical organization of striatopallidal projections indicated that the ITN-GP projections were topographically organized in parallel to the ITN-Str projections. Thus, each part of the ITN projecting to the sensorimotor, the association, and the limbic territories of the Str also projects to the corresponding functional territories of the GP.     

Organization of the projections of a circumventricular organ: the area postrema in the rat

The projections of the rat area postrema were analysed using anterograde and retrograde axonal transport techniques. Discrete injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the area postrema produced anterograde labeling in specific medullary and pontine nuclei. In the medulla, anterograde labeling was present in the internal solitary zone and dorsal division of the medial solitary nucleus, both of which also contained a small number of retrogradely labeled perikarya. Prominent projections to the dorsal motor nucleus of the vagus were seen only if the WGA-HRP injections in the area postrema invaded dorsal solitary nuclei. In the pons, anterograde labeling was present in the parabrachial nuclei, the dorsolateral tegmental nucleus, and the pericentral division of the dorsal tegmental nucleus. By far the major pontine projection was to the dorsolateral region of the middle one-third of the rostrocaudal extent of the parabrachial nuclei. Retrograde fluorescent tracing studies indicated that most area postrema neurons take part in this parabrachial projection. The area postrema projection to the parabrachial nuclei was bilaterally distributed, whereas that from the dorsal solitary nuclei was primarily ipsilateral. The external solitary zone, immediately subadjacent to the area postrema, neither received area postrema projections nor participated in the projections to the parabrachial nuclei. Fluorescent retrograde double labeling studies confirmed the bilateral nature of the area postrema projection to the parabrachial nuclei. In addition, because no doubly labeled neurons were observed it appears that individual area postrema neurons project to either side but not both sides of the dorsal pons. Thus, numerous neuronal pathways exist for the transfer of blood-borne information (that cannot cross the blood-brain barrier) from the area postrema to other brain regions.     

Thalamic innervation of striatal and subthalamic neurons projecting to the rat entopeduncular nucleus

The present study analyses the anatomical arrangement of the projections linking the Wistar rat parafascicular thalamic nucleus (PF) and basal ganglia structures, such as the striatum and the subthalamic nucleus (STN), by using neuroanatomical tract-tracing techniques. Both the thalamostriatal and the striato-entopeduncular projections were topographically organized, and several areas of overlap between identified circuits were noticed, sustaining the existence of up to three separated channels within the Nauta-Mehler loop. Thalamic afferents arising from dorsolateral PF territories are in register with striatofugal neurons located in dorsolateral striatal areas, which in turn project to dorsolateral regions of the entopeduncular nucleus (ENT). Medial ENT regions are innervated by striatal neurons located within medial striatal territories, these neurons being the target for thalamic afferents coming from medial PF areas. Finally, afferents from neurons located in ventrolateral PF areas approached striatal neurons in ventral and lateral striatal territories, which in turn project towards ventral and lateral ENT regions. Efferent STN neurons projecting to ENT were found to be the apparent postsynaptic target for thalamo-subthalamic axons. The thalamo-subthalamic projection was also topographically organized. Medial, central and lateral STN territories are innervated by thalamic neurons located within medial, ventrolateral and dorsolateral PF areas, respectively. Thus, each individual PF subregion projects in a segregated fashion to specific parts of the striato-entopeduncular and subthalamo-entopeduncular systems. These circuits enabled the caudal intralaminar nuclei to modulate basal ganglia output.     

Dopaminergic cell group A8 in the monkey: anatomical organization and projections to the striatum.

The first part of the study was a quantitative analysis of the distribution of A8 neurons compared with that of A9 and A10 neurons by means of tyrosine hydroxylase and calbindin-D(28K) immunohistochemistry and image analysis in monkeys. Then the striatal projection of A8 neurons was studied using retrograde and anterograde tracing methods. It was compared with that originating in cell groups A9 and A10 by performing injections of the retrograde tracer wheat germ agglutinin conjugated to horseradish peroxidase into different regions of the striatum. Ten percent of all mesencephalic dopaminergic neurons are located in cell group A8. This cell group, along with A10 and the dorsal part of A9, constitutes the dorsal tier, which accounts for 28% of mesencephalic dopaminergic neurons. Double-staining experiments showed that the neurons located in the dorsal tier were calbindin positive, whereas those from the ventral tier were not. In terms of anatomical projection, the dorsal tier mainly projects to the ventral part of the associative striatum, with preferential projections of A8 neurons to the ventrocaudal putamen, of A10 neurons to the nucleus accumbens, and of dorsal A9 neurons to both. Conversely, the main targets of the ventral tier of mesencephalic neurons (ventral part of A9) are the sensorimotor putamen and the associative caudate nucleus. In conclusion, each mesencephalic cell group projects primarily to one specific striatal region but also participates, albeit to a lesser extent, in the innervation of all the remaining striatal parts.     

Calcium-binding proteins, parvalbumin- and calbindin-D 28k-immunoreactive neurons in the rat spinal cord and dorsal root ganglia: a light and electron microscopic study

The distribution of two calcium-binding proteins, parvalbumin (PV) and calbindin-D 28K (CaBP), was studied by the peroxidase-anti-peroxidase immunohistochemical method at the light and electron microscopic level in the rat spinal cord and dorsal root ganglia. The possible coexistence of these two proteins was also investigated. PV-positive neurons were revealed in all layers of the spinal cord, except lamina I, which was devoid of labelling. Most of the PV-positive cells were found in the inner layer of lamina II, lamina III, internal basilar nucleus, central gray region, and at the dorsomedial and ventromedial aspects of the lateral motor column in the ventral horn. Neuronal processes intensely stained for PV sharply delineated inner lamina II. With the electron microscope most of them appeared to be dendrites, but vesicle containing profiles were also found in a smaller number. CaBP-positive neurons appeared to be dispersed all over the spinal gray matter. The great majority of them were found in laminae I, II, IV; the central gray region; the intermediolateral nucleus; and in the ventral horn just medial to the lateral motor column. Laminae I and II were densely packed with CaBP-positive punctate profiles that proved to be dendrites and axons in the electron microscope. A portion of labelled neurons in lamina IV and on the ventromedial aspect of the lateral motor column in the ventral horn disclosed both PV- and CaBP-immunoreactivity. All of the funiculi of the spinal white matter contained a large number of fibres immunopositive for both PV and CaBP. The highest density of CaBP-positive fibres was found in the dorsolateral funiculus, which was also densely packed with PV-positive fibres. PV-positive fibres were even more numerous in the dorsal part of the dorsal funiculus. The territory of the gracile funiculus in the brachial cord and that of the pyramidal tract in its whole extent were devoid of labelled fibres. In the thoracic cord, the dorsal nucleus of Clarke received a large number of PV-positive fibres. Dorsal root ganglia displayed both PV- and CaBP-immunopositivity. The cell diameter distribution histogram of PV-positive neurons disclosed two peaks--one at 35 microns and the other at 50 microns. CaBP-positive cells in the dorsal root ganglia corresponded to subgroups of small and large neurons with mean diameters of 25 microns and 45 microns, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)     

Distribution of parvalbumin immunoreactivity in the rat septal area

The distribution of parvalbumin (PV)-containing neurons and processes in the septal area of the rat brain was studied using a monoclonal antibody and the avidin-biotin immunoperoxidase method. PV-immunoreactive neurons were mainly located in the medial septum/diagonal band complex and in the horizontal limb of the diagonal band of Broca, showing a high density of heavily immunostained neurons and fibers. Nonimmunoreactive cells surrounded by PV-positive cells and processes were observed in the same region, but no pericellular basket-like arrangements were found. On the contrary, the dorsal, intermediate, and ventral nuclei of the lateral septum were practically devoid of PV-positive neurons and processes. Thus, in these nuclei only a very low density of isolated neurons was labeled; these were specially scattered in the ventrolateral septal nucleus and in the dorsolateral septal nucleus just below the corpus callosum. Delicate PV-positive axonal plexuses were also observed in the dorsal and intermediate nuclei of the lateral septum. The immunopositive neurons displayed very different sizes and morphologies among the various septal nuclei and inside each of them, indicating that they do not belong to a single morphological class of neurons. Finally, the distribution of PV in the rat septal area is not directly related to cholinergic and GABAergic septal neurons.     

Separate populations of neurons in the rostral ventromedial medulla project to the spinal cord and to the dorsolateral pons in the rat

Activation of neurons in the rostral ventromedial medulla (RVM) directly modulates spinal nociceptive transmission by projections to the spinal cord dorsal horn and indirectly by projections to neurons in the dorsolateral pons (DLP) that project to the spinal cord dorsal horn. However, it is not known whether the same neurons in the RVM produce both direct and indirect modulation of nociception. Deposits of the retrograde tracers Fluoro-Gold (FG) in the spinal cord dorsal horn and DiI in the DLP were used to determine whether the same RVM neurons project to both of these regions. Only 0.9+/-0.1% of RVM neurons retrogradely labeled with Fluoro-Gold from the spinal cord were also labeled with DiI placed in the DLP. In addition, spinally projecting RVM neurons were significantly larger than RVM neurons that project to the DLP. Finally, spinally projecting neurons were found predominantly on the midline and within the RVM; neurons that project to the DLP had a wider distribution and were present both within and outside of the RVM. Thus, separate and morphologically distinct populations of RVM neurons appear to modulate nociception by direct and indirect descending pathways.     

Calbindin D-28k as a marker for the associative cortical territory of the striatum in macaque

An immunohistochemical study was made to investigate the topographic distribution of calbindin D-28k in relation to the associative and sensorimotor cortical territories in the macaque. An intense calbindin-staining was found in the caudate nucleus and ventromedial putamen, i.e., in the associative striatum. In contrast, only a weak immunoreaction was found in the dorsolateral, sensorimotor, putamen. Calbindin immunoreactivity thus appears as a specific marker for the associative striatum.     

Cerebellar corticonuclear and corticovestibular fibers from the posterior lobe of the albino rat, with comments on zones

The topographic organization of cerebellar cortical efferent fibers from the posterior lobe of the albino rat was studied by silver impregnation methods. The corticonuclear fibers from the vermis of the posterior lobe project to the caudomedial and middle parts of the medial cerebellar nucleus (MN) with medio-lateral localization; fibers from the medial portion of the vermis project to the caudomedial part of the MN (MNcm) and those from the lateral portion project to the middle part of the MN (MNm). Corticovestibular fibers originate in the caudal vermis lateral to the area projecting to the MNcm and MNm, and terminate in the dorsal part of the lateral vestibular nucleus (LVN). The origins of corticonuclear fibers to the dorsolateral protuberance of the MN (MNdlp), the posterior interpositus nucleus (PIN) and the anterior interpositus nucleus (AIN) are located latero-medially in the intermediate cortex. Fibers from the area adjacent to the vermis and rostral to the prepyramidal fissure project to the MNdlp, while those from the area lateral to the origin of the corticovestibular fibers and caudal to the fissure project to the medial AIN. Together, these areas comprise a medial portion of the intermediate cortex. Corticonuclear fibers to the PIN and lateral AIN originate from the lateral portion of the intermediate cortex. The corticonuclear fibers to the dorsolateral hump and lateral nucleus originate from the medial and lateral portions of the lateral cortex, respectively.     

Differential subcellular localization of forward and feedback interareal inputs to parvalbumin expressing GABAergic neurons in rat visual cortex

In rat visual cortex, forward and feedback interareal pathways innervate both pyramidal and gamma-aminobutyric acid (GABA)ergic (Johnson and Burkhalter [1996] J. Comp. Neurol. 368:383-398). GABAergic neurons consist of different cell types of which the largest group expresses parvalbumin (PV; Gonchar and Burkhalter [1997] Cereb. Cortex 4:347-358). Here, we report that PV neurons in layers 2/3 are synaptic targets of forward and feedback projections between area 17 and the lateromedial area (LM) of rat visual cortex. In both forward and feedback pathways, approximately 90% of axon terminals in layer 2/3 labeled by tracing with biotinylated dextran amine formed synapses with PV-negative profiles. In both pathways, most of these profiles resembled dendritic spines. Although there were no differences in the innervation of PV-negative targets, the two pathways differed in the innervation of PV-positive neurons. In each pathway, approximately 10% of terminals formed synapses with PV-positive profiles. However, in the forward pathway, the size of the contacted PV-positive profiles was larger than in the feedback pathway. Moreover, in the forward pathway, axon terminals on PV-positive profiles were larger, contained more mitochondria and docked synaptic vesicles than feedback synapses on PV neurons. Our results show that PV neurons provide a major target for area 17 <-> LM forward and feedback pathways terminating in upper layers. In each pathway, the proportion of axons contacting PV neurons is similar. However, both pathways differ in the subcellular localization and morphology of synapses on PV neurons. These asymmetries may contribute to the inequality in the strength of disynaptic inhibition evoked by forward and feedback inputs (Shao and Burkhalter [1996] J. Neurosci. 16:7353-7365).     

A Golgi analysis of the primate globus pallidus. III. Spatial organization of the striato-pallidal complex

An atlas of transverse sections of the globus pallidus and striatum was established in macaque with reference to ventricular coordinates. The three-dimensional geometry of the striato-pallidal complex was investigated by means of sagittal and horizontal reconstructions. Both a personal case studied with autoradiography and data from literature were used to analyze the distribution of cortical axons into the striatum. One may distinguish two striatal territories: one, somatotopically arranged, sensorimotor territory extending over the major part of the putamen; and the other, an associative territory, comprising the caudate nucleus and antero-medial and postero-inferior parts of the putamen. The striato-pallido-nigral bundle was studied using Golgi, Perls, and Fink-Heimer techniques. The bundle is described in four parts: prepallidal (subdivided into caudato-pallidal and putamino-pallidal subparts), transpallidal, pallido-nigral, and nigral. The tracing of the limit between the caudate (associative) and putaminal (essentially sensorimotor) territories shows that the two components are of roughly the same size in the pallidum. The data were compared with geometry and orientation of the dendritic arborizations of large pallidal neurons analyzed in Yelnik et al. ('84). Each pallidal dendritic disc is able to receive axons from a wide region of the striatum. This leads to a convergence on pallidal neurons of striatal axons from different striatal somatotopic strips and from the sensorimotor and associative territories. This is an indication that the globus pallidus may have an integrative role.     

The globus pallidus receives a projection from the parafascicular nucleus in the rat

Study of the afferents of the rat globus pallidus (GP) with Fluoro-gold, a retrograde tracer, revealed retrogradely labeled neurons in the ipsilateral parafascicular nucleus of the thalamus (PF), a previously undescribed afferent of the rat GP. We used the anterograde tracer, Phaseolus vulgaris-leucoagglutinin (PHA-L), to confirm and extend our findings. After injections of PHA-L in the PF, labeled fibers with varicosities and terminal specializations were observed in the ipsilateral GP. The topographical organization of the projection is such that lateral and ventral PF neurons project preferentially to respective parts of the GP, and medial PF neurons project primarily to the ventral GP. There were very few labeled fibers seen in the dorsal or medial GP. The presently described projection from the PF to the GP provides an additional route for the PF to influence basal ganglia circuitry.     

Organization of thalamic afferents to anterior dorsal ventricular ridge in turtles. II. Properties of the rotundo-dorsal map

This study describes some properties of the map of nucleus rotundus onto dorsal area of anterior dorsal ventricular ridge (ADVR) in emydid turtles by correlating results of anterograde and retrograde tracing experiments with observations from Golgi- and myelin-stained brains. An earlier paper (Balaban and Ulinski, '81) demonstrated that this projection is restricted to zone 4 of dorsal area of ADVR. This paper indicates that the rotundal pathway is organized such that longitudinally aligned groups of neurons in nucleus rotundus project to longitudinal regions in zone 4 of dorsal area. The projection field spans the dorsoventral (or concentric) dimension of zone 4 at each transverse level. Comparisons of experimental and Golgi preparations suggest that each rotundal neuron projects, via collaterals, to the entire rostrocaudal extent of rotundorecipient zone 4. Individual terminal branches span the dorsoventral dimension of zone 4 and are confined within both sagittal and transvere planes. Lesion experiments suggest that collaterals of a single rotundal axon are also distributed over at least one-third to one-half of the superficial-deep dimension of zone 4. This is also reflected in the observation that neurons from disjoint dorsal, dorsolateral and medial rotundal loci project to overlapping, concentric regions of dorsal area. Both this prominent concentric component of terminal branches and the extensive overlap of projections of neurons at distinct rotundal loci preclude the possibility of a topographic representation of either dorsoventral or mediolateral rotundal axes in zone 4 of dorsal area.     

Thalamo-telencephalic connections: new insights on the cortical organization in reptiles

Tracer injections into the dorsal tier of the lacertilian dorsal thalamus revealed an extensive innervation of the cerebral cortex. The medial cortex, the dorsomedial cortex, and the medial part of the dorsal cortex received a bilateral projection, whereas the lateral part of dorsal cortex and the dorsal part of the lateral cortex received only an ipsilateral thalamic projection. Thalamocortical fibers were found superficially in all cortical regions, but in the dorsal part of the lateral cortex, varicose axons within the cellular layer were also observed. The bilateral thalamocortical projection originates from a cell population located throughout the dorsolateral anterior nucleus, whereas the ipsilateral input originates mainly from a rostral neuronal subpopulation of the nucleus. This feature suggests that the dorsolateral anterior nucleus consists of various parts with different projections. The dorsal subdivision of the lateral cortex displayed hodological and topological (radial glia processes) features of a dorsal pallium derivative. After tracer injections into the dorsal cortex of lizards, we found long descending projections that reached the striatum, the diencephalic basal plate, and the mesencephalic tegmentum, which suggests that it may represent a sensorimotor cortex.     

Projections to the spinal cord from medullary somatosensory relay nuclei.

Descending projections to the spinal card from the dorsal column nuclei were studied in the cat, rat and monkey with the retrograde horseradish peroxidase (HRP) technique, and in the cat with the autoradiographic anterograde axonal transport technique. Retrogradely labeled neurons were seen in the dorsal column nuclei after HRP injections at all levels of the spinal cord and additionally in the magnocellular division of the spinal caudalis nucleus of the trigeminal nerve after injections into cervical spinal segments in all three species. HRP-positive neurons were predominantly located along the middle of the rostro-caudal axis of the dorsal column nuclei and amongst the fusiform, triangular and polygonal cells that surround, especially ventrally, the cell nest zone containing thalamic relay neurons. The labeled neurons are densely concentrated in those portions of the dorsal column nuclei where most corticofugal and non-primary afferent projections terminate and where the terminal distribution of primary afferent fibers is overlapping and diffuse. Previous studies have shown that most neurons in this middle and ventral region do not project to the thalamus or cerebellum. The majority of the cells in the dorsal column nuclei with descending axons or axon collaterals project by way of the ipsilateral dorsal columns, but some fibers project into the dorsolateral funiculus; the descending trigeminal fibers course in the dorsolateral funiculus. The terminal fields for these fibers in the cervical spinal cord include the lateral cervical nucleus, laminae IV and V, and possibly lamina I. These results indicate that the dorsal column nuclei may contribute to a feedback mechanism regulating the flow of sensory information ascending along other somatosensory spinal pathways.     

The distribution of neocortical projection neurons in the locus coeruleus

The present study was conducted to examine the spatial organization of locus coeruleus (LC) neurons that project to rat cerebral cortex. Long-Evans hooded rats received unilateral pressure injections of horseradish peroxidase (HRP) in either frontal (n = 6) or sensorimotor (n = 11) or occipital (n = 7) cortex to determine the intranuclear location of LC neurons which project to specific neocortical regions. Coronal and sagittal sections (40-100 micron) through the LC were examined by light microscopy after carrying out the tetramethyl benzidine reaction and staining with neutral red. The locations of retrogradely labeled cells were recorded on a three-dimensional biological coordinate system maintained by a computer linked to the light microscope. LC neurons labeled from cerebrocortical injections of HRP were primarily located in the ipsilateral and to a lesser extent (fewer than 5% of total labeled cells) in the contralateral nucleus. Coeruleocortical projection neurons were concentrated in the caudal three-fifths of the dorsal division of the ipsilateral LC. Within this portion of the nucleus, HRP-filled neurons were distributed so that individual groups of cells projecting to occipital or sensorimotor or frontal cortex were coarsely aligned in a dorsal to ventral array, respectively. Moreover, in the sagittal plane of the nucleus the pattern of labeling was spatially graded so that the subset of neurons projecting to the occipital cortex was displaced more caudally in the LC than the groups of cells sending axons to sensorimotor or frontal cortex. Only the frontal area of the cortex received a projection from both dorsal and ventral divisions of the ipsilateral LC. Computer-assisted analysis of the data further suggested that neocortical projection neurons in the dorsal LC are loosely organized into two groups which run rostrocaudally through the core of the caudal nucleus. The zone of labeling resulting from injections confined to the neocortical gray matter overlapped with but was not coextensive with that observed following injections into the caudate, hippocampus, and cerebellum. These results suggest that partially overlapping subsets of LC cells might independently influence separate populations of neurons within noradrenergic terminal fields of the neocortex.     

胃肠道伤害性刺激引起大鼠孤束核与中脑导水管周围灰质神经元表达FOS

为研究中脑导水管周围灰质（PAG）与孤束核（NTS）内脏伤害性信息传递和调控之间的相互关系，采用免疫荧光组织化学方法结合荧光金（FG）逆行追踪技术，观察了大鼠NTS和PAG之间相互投射神经元在给予胃肠道伤害性刺激后的FOS表达情况。给胃肠道以1％多聚甲醛的伤害性刺激后，FOS阳性细胞主要出现于中尾段NTS的内侧亚核；在PAG内，则主要出现于足段PAG的腹外侧区。将FG微量注射于PAG后，再给予动物刺激，发现NTS内部分FG逆行标记细胞同时为FOS阳性，它们主要分布于中尾段NTS的内侧亚核，双标细胞占FG标记细胞的十分之一左右。同上，将FG注射于中尾段NTS后再施予伤害性刺激，在PAG内发现有FOS阳性的FG道标细胞，它们集中分布于尾段PAG的腹外侧区，双标细胞约占FG标记细胞的五分之一。此外，在中缝背核内也发现有一定数且的双标细胞。本文结果提示PAG可能对NTS内内脏伤害性信息的传递具有调控作用。     

Monkey globus pallidus external segment neurons projecting to the neostriatum.

Experiments were performed to assess the number and parvalbumin (PV) immunoreactivity of neurons participating in the pallidostriatal projection in macaque monkeys. Injection of WGA-HRP into the right caudate nucleus and the left putamen of a Macaca mulatta and a M. fuscata labeled a large number of the globus pallidus external segment (GPe) neurons. Counting neurons labeled with WGA-HRP and those stained with neuronal markers indicated that approximately 30% of GPe neurons project to neostriatum. Approximately 2/3 of the pallidostriatal neurons are PV-immunoreactive. This study revealed that a significant number of primate GPe PV immunoreactive neurons project to the neostriatum, and suggest that the pallidostriatal projection should be taken into account in the analysis of functional roles of the basal ganglia circuitry.