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A Parent

Publications and source records attributed to A Parent.

At least 109 records · Page 6Linked to original sources
PubMed1994

Multiple striatal representation in primate substantia nigra.

The pattern of arborization of the striatonigral fibers in the squirrel monkey (Saimiri sciureus) was studied with Phaseolus vulgaris-leucoagglutinin (PHA-L) and biocytin as anterograde tracers. Single, small injections of PHA-L or biocytin in either the caudate nucleus or the putamen give rise to at least four distinct, nonoverlapping but interconnected fiber plexuses that are distributed throughout the rostrocaudal extent of the substantia nigra pars reticulata (SNr) according to a strikingly precise and constant sequence. These plexuses, which comprise numerous fibers that closely entwine unlabeled dendrites of SNr neurons (woolly fibers), often lie at the base of dopaminergic cell columns of the substantia nigra pars compacta (SNc). Long and varicose fibers emerge dorsally from SNr plexuses and climb along the ventrally oriented dendrites of dopaminergic SNc neurons, as visualized with tyrosine hydroxylase immunohistochemistry. These fibers appear to contact en passant both dendrites and cell bodies of dopaminergic neurons belonging to the ventral tier of SNc. Anterograde double-labeling experiments involving small deposits of PHA-L and biocytin in adjacent areas of the caudate nucleus and the putamen reveal that neighboring striatonigral cell populations form two distinct sets of terminal plexuses that remain well segregated throughout SNr. Plexuses from the two sources interdigitate in some parts of SNr, but never intermix. Furthermore, the woolly fibers in these plexuses are composed exclusively of either PHA-L- or biocytin-labeled elements; none of them display both types of labeling. These results reveal that the striatonigral projection in primates is highly divergent and that the striatum has multiple representations at nigral levels. They also indicate that striatal information is conveyed to the substantia nigra in a highly ordered fashion through multiple segregated channels.

Animals↗
PubMed1994

Synaptic relationships between dopaminergic afferents and cortical or thalamic input in the sensorimotor territory of the striatum in monkey.

The cerebral cortex and the intralaminar thalamic nuclei are the major sources of excitatory glutamatergic afferents to the striatum, whereas the midbrain catecholaminergic neurones provide a dense intrastriatal plexus of dopamine-containing terminals. Evidence from various sources suggests that there is a functional interaction between the glutamate- and dopamine-containing terminals in the striatum. The aim of the present study was to determine the synaptic relationships between cortical or thalamic inputs and the dopaminergic afferents in the sensorimotor territory of the monkey striatum. To address this issue, anterograde tracing in combination with immunocytochemistry for tyrosine hydroxylase (TH) was carried out by light and electron microscopy. Squirrel monkeys received injections of biocytin in the primary motor and somatosensory cortical areas or injections of either Phaseolus vulgaris-leucoagglutinin (PHA-L) or biocytin in the centromedian nucleus (CM) of the thalamus. Sections that included the striatum were processed to visualize the anterograde tracers alone or in combination with TH immunoreactivity. The anterogradely labelled fibres from the cerebral cortex and CM display a band-like pattern and are exclusively confined to the postcommissural region of the putamen, whereas TH-immunoreactive axon terminals are homogeneously distributed throughout the entire extent of the striatum. Electron microscopic analysis revealed that the anterogradely labelled terminals from the cerebral cortex form asymmetric synapses almost exclusively with the heads of dendritic spines. The thalamic terminals also form asymmetric synapses, but in contrast to cortical fibres, predominantly with dendrites (67.4%) and less frequently with spines (32.6%). The TH-immunoreactive boutons are heterogeneous in morphology. The most common type (84% of the total population) forms symmetric synapses; of these the majority is in contact with dendritic shafts (72.1%), less with spines (22.5%) and few with perikarya (5.4%). In sections processed to reveal anterogradely labelled cortical fibres and TH-immunoreactive structures, individual spines of striatal neurones were found to receive convergent synaptic inputs from both cortical and TH-immunoreactive boutons. In contrast, anterogradely labelled thalamic terminals and TH-immunoreactive boutons were never seen to form convergent synaptic contacts on the same postsynaptic structure. These findings suggest that the dopaminergic afferents are located to subserve a more specific modulation of afferent cortical input than afferent thalamic input in the sensorimotor territory of the striatum in primates.

Animals↗
PubMed1994

Brainstem dopaminergic, cholinergic and serotoninergic afferents to the pallidum in the squirrel monkey.

The retrograde tracer cholera toxin B subunit (CTb) was used in combination with immunohistochemistry for tyrosine hydroxylase (TH), calbindin D-28k (CaBP), choline acetyltransferase (ChAT) and 5-hydroxytryptamine (5-HT) to determine the distribution and relative proportion of brainstem chemospecific neurons that project to the pallidum in the squirrel monkey (Saimiri sciureus). Large injections of CTb involving both pallidal segments produce numerous retrogradely labeled neurons in the substantia nigra (SN), the pedunculopontine tegmental nucleus (PPN) and the dorsal raphe nucleus (DR). Labeled neurons are distributed uniformly in SN with a slight numerical increase at the junction between the pars compacta (SNc) and the ventral tegmental area (VTA). Retrogradely labeled neurons abound also in PPN, principally in its pars dissipata, whereas other CTb-labeled cells are scattered throughout the rostrocaudal extent of DR. After CTb injection involving specifically the internal pallidal segment (GPi), the same pattern of cell distribution is found in SN, PPN and DR, except that the number of retrogradely labeled cells is lower than after large pallidal complex injections. Approximately 70% of all CTb-labeled neurons in SNc-VTA complex display TH immunoreactivity, whereas 20% are immunoreactive for CaBP. About 39% of all retrogradely labeled neurons in PPN are immunoreactive for ChAT, whereas approximately 38% of the labeled neurons in DR display 5-HT immunoreactivity. Following CTb injection in the external pallidal segment (GPe), the number of labeled cells is much smaller than after GPi injection. The majority of CTb-labeled cells in SNc-VTA complex are located in the lateral half of SNc and approximately 93% of these neurons display TH immunoreactivity compared to 10% that are immunoreactive for CaBP; very few CTb-labeled cells occur in PPN. Retrogradely labeled cells in DR are located more laterally than those that projects to the GPi and about 25% of them are immunoreactive for 5-HT. These results suggest that, in addition to their action at striatal and/or nigral levels, the brainstem dopaminergic, cholinergic and serotoninergic neurons influence the output of the primate basal ganglia by acting directly upon GPi neurons.

Afferent Pathways↗
PubMed1994

An interaction between inositol hexakisphosphate (IP6) and insulin-like growth factor II receptor binding sites in the rat brain.

Insulin-like growth factor II/mannose-6-phosphate (IGF II/Man-6-P) receptors participate in the trafficking of lysosomal enzymes and also in the transduction of the effects of the growth factor via transmembrane-anchored receptor protein. During ligand-induced endocytosis, this receptor interacts with clathrin-associated protein (AP-2) which can lead to their assembly and subsequent transport in coated vesicles to the lysosomes. Only recently has it been suggested that AP-2 itself may also act as one of the receptor sites for inositol hexakisphosphate (IP6). This evidence, together with autoradiographic data showing that [3H]IP6 binding sites in rat brain are similarly distributed to [125I] IGF II sites, led us to examine the possible interaction between IP6 and [125I]IGF II receptor binding sites using an autoradiographic approach. Our results indicate that IP6, at microM concentrations, competes for [125I]IGF II, but not [125I]IGF I or [125I]insulin binding sites in the rat brain. These results, in keeping with other evidence, suggest that IP6 may be able to regulate the [125I]IGF II receptor binding sites either directly or indirectly, possibly through clathrin-associated AP-2 sites.

Adaptor Proteins, Vesicular Transport↗
PubMed1994

Differential localization and pH dependency of phosphoinositide 1,4,5-IP3, 1,3,4,5-IP4 and IP6 receptors in rat and human brains.

It is well established that the inositol lipids mediate signal transduction in several cellular populations. Many neurotransmitters, hormones and growth factors act at plasma membrane receptors to induce the hydrolysis of phosphatidylinositols and hence the generation of various inositol phosphates (IP). The best known member of this family is 1,4,5-IP3, which is associated with the release of Ca2+ from intracellular pools. It has also been proposed that two others inositides, 1,3,4,5-IP4 and IP6, may be involved in Ca2+ homeostasis. In order to study the possible relevance of these various inositides in neuronal tissues, we have localized the respective receptors in rat and human brain under both acidic and basic pH conditions. In the hippocampal formation, [3H]1,3,4,5-IP4 binding sites are concentrated in the hilus and the molecular layer while a clearly different pattern of distribution is seen for [3H]1,4,5-IP3, its highest concentration of labelling being concentrated in the oriens and radiatum laminae. This contrasting profile of distribution is also observed in other brain areas such as the caudate-putamen, the septo-hippocampal area, and the molecular and granular layers of the cerebellum. Moreover, while highest amounts of specific [3H]1,4,5-IP3 binding are obtained at pH 8.5, the opposite is found for [3H]1,3,4,5-IP4, with high binding levels seen under acidic conditions. [3H]IP6 binding sites are broadly distributed with specific labelling concentrated in areas enriched with neuronal perikarya such as the granular cell layer of the dentate gyrus, the pyramidal cell layers of the hippocampus and the granular cell layer of the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Regulation of 1,4,5-IP3, 1,3,4,5-IP4 and IP6 binding sites following entorhinal cortex lesions in rat brain.

A lesion of the entorhinal cortex produces a loss of more than 80% of the synapses in the outer molecular layer of the hippocampus in the rat. However, this synaptic loss is transient. Beginning a few days after denervation, new synapses are formed, virtually replacing the lost inputs within two months. Synaptic remodelling induced by entorhinal cortex lesion is associated with specific modifications of various neurotransmitters, hormones and growth factors. Many of these substances act at membrane bound-receptors to induce the hydrolysis of phosphatidylinositols generating various inositol phosphates. Some of the key members of this family include inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate which are all associated with the maintenance Ca2+ homeostasis. To investigate the potential roles and/or alterations of inositol phosphates in entorhinal cortex lesions-induced neuronal plasticity, we quantified specific receptor sites for inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate using their respective tritiated ligands, at different periods post-lesion corresponding to the degenerative and subsequent reinnervation phases. [3H]inositol 1,4,5-trisphosphate binding sites are maximally increased (30%) between two and eight days post-lesion in the hippocampal formation on both sides of the lesion. In the cortex, [3H]inositol 1,4,5-trisphosphate binding increased also bilaterally following the lesion. Changes in [3H]inositol 1,3,4,5-tetrakisphosphate binding are delayed and reduced (20% increase) in magnitude compared to these seen for [3H]inositol 1,4,5-trisphosphate binding. The maximal peak in [3H]inositol 1,3,4,5-tetrakisphosphate binding is observed between eight and 14 days after the lesion in the hippocampal formation and the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Desmoplastic infantile gangliogliomas: an approach to therapy.

Desmoplastic infantile gangliogliomas are massive cystic tumors, typically occurring in the cerebral hemispheres of infants. They are remarkable pathologically for a prominent desmoplasia and, in some cases, for a cellular mitotically active component that can be readily interpreted as a malignant neoplasm. Four children less than 1 year of age were diagnosed with desmoplastic infantile gangliogliomas in the Pediatric Oncology Group infant brain tumor study (Protocol number 8633). All had been diagnosed by their respective institutions as having malignant tumors, i.e., Grade III astrocytoma, malignant meningioma, leptomeningeal fibrosarcoma, and gliosarcoma. All had increased intracranial pressure, and two had seizures. The tumors were extremely large, with one measuring 12 x 9 x 9 cm. None had evidence of metastatic disease. One patient had a gross total resection, and the other three had debulking procedures. All four children were treated with chemotherapy (cyclophosphamide, vincristine, cisplatinum, etoposide) for periods ranging from 12 to 24 months. Of those with postoperative measurable disease, one child had a complete response, one a partial response, and one had stable disease at the conclusion of chemotherapy. No child received radiation therapy. All children are alive with progression-free survivals after diagnosis of more than 36, 42, 48, and 60 months, respectively. Although desmoplastic infantile gangliomas are rare, recognition of this tumor type is essential because, despite their massive size and pathologically malignant appearance, they may have a relatively benign clinical course. If total surgical resection can be achieved, further therapy may not be indicated. In those patients in whom residual disease is present, chemotherapy appears to be an effective form of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Lung management with perfluorocarbon liquid ventilation improves pulmonary function and gas exchange during extracorporeal membrane oxygenation (ECMO).

We investigated whether pulmonary function and gas exchange would improve with liquid perfluorocarbon ventilation (LV) during ECMO for severe respiratory failure. Lung injury was induced in 11 young sheep 15.1 +/- 3.7 kg in weight utilizing right atrial injection of 0.07 cc/kg oleic acid followed by saline pulmonary lavage. When (A-a)DO2 > or = 600 mmHg and PaO2 < or = 50 mmHg with FiO2 = 1.0, ECMO was instituted. Animals were then ventilated with either standard ECMO "lung rest" gas ventilator settings (ECMO, n = 5) or with "total" liquid ventilation at standard ventilator device settings (LIQ-ECMO, n = 6) utilizing perflubron (perfluooctyl bromide, Liquivent; Alliance Pharmaceutical Corp.). After 3 hours on ECMO, pulmonary physiologic shunt decreased (ECMO = 88 +/- 11% vs LIQ-ECMO = 31 +/- 1%; p < .001) and pulmonary compliance increased (ECMO = 0.50 +/- 0.06 cc/cmH2O/kg vs. LIQ-ECMO = 1.04 +/- 0.19 cc/cmH2O/kg; p < .001). The ECMO flow rate required to maintain the PaO2 in the 50-80 mmHg range was decreased significantly (ECMO = 116 +/- 14 ml/kg/min vs. LIQ-ECMO = 14 +/- 5 ml/kg/min; p < .001). In this model requiring extracorporeal support for severe respiratory failure, lung management with liquid ventilation improves pulmonary function and gas exchange.

Animals↗
PubMed1994

Increased glutamate decarboxylase mRNA levels in the striatum and pallidum of MPTP-treated primates.

The mRNA levels encoding for the enzyme glutamate decarboxylase (GAD67) were measured by computerized image analysis after in situ hybridization histochemistry and radioautography in the striatum and pallidum of normal squirrel monkeys (Saimiri sciureus), or after treatment with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). All MPTP-injected monkeys exhibited profound motor deficits including akinesia. The dopaminergic innervation, as visualized and quantified on x-ray films after 3H-mazindol binding on tissue sections, was uniformly lost throughout the striatum of MPTP-treated monkeys. Brain sections processed with a probe synthesized from a feline or human GAD67 cDNA exhibited intense radioautographic labeling throughout the striatum. When measured on x-ray films, the intensity of GAD67 mRNA labeling was increased in the striatum of MPTP-treated versus control monkeys. Increased labeling reached statistical significance in the dorsolateral sector of the rostral putamen and throughout the putamen and the caudate at the caudal, postcommissural, level. Analysis of emulsion radioautographs demonstrated that the increase in GAD67 mRNA labeling in MPTP-treated monkeys occurred in individual neurons of the striatum. In the external and internal segments of the pallidum, numerous neurons labeled with the GAD67 cRNA probe were visualized on emulsion radioautographs. The intensity of GAD67 mRNA labeling in single neurons of both pallidal segments was increased in MPTP-treated versus control monkeys. Construction of the histograms of frequency distribution of labeling indicated that this increase occurred in a majority of labeled neurons. The present study demonstrates that GAD67 mRNA levels are significantly altered in the striatum and pallidum of parkinsonian monkeys. The preferential increase of GAD67 mRNA labeling in the dorsolateral putamen, which receives afferents from the sensorimotor cortex, provides further evidence of the involvement of GABAergic transmission in the expression of the motor deficits elicited after MPTP. In addition, increased GAD67 mRNA levels in the internal segment of the pallidum support the hypothesis of an increased activity of GABAergic neurons in the output structures of the basal ganglia in parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1994

Liquid ventilation provides uniform distribution of perfluorocarbon in the setting of respiratory failure.

BACKGROUND: We evaluated the effect of perfluorocarbon liquid ventilation (LV) on gas exchange and pulmonary function in the setting of respiratory failure and the distribution of the ventilating medium during LV when compared to gas ventilation (GV). METHODS: Ten sheep, 17.3 +/- 4.2 kg in weight, underwent oleic acid induction of lung injury followed by either GV (n = 5) or perfluorocarbon LV (n = 5). After 1 hour animals were killed, and chest computed tomographic (CT) imaging was performed. Average CT attenuation number was assessed as an indicator of the distribution of gas or perfluorocarbon in the dependent (posterior) and nondependent (anterior) zones of the lung (air = -1000; soft tissue = 0; perfluorocarbon = +2300 Hounsfield units [H]). RESULTS: Significant increases in PaO2 (LV = 298 +/- 76 mm Hg, GV = 43 +/- 18 mm Hg, p < 0.001), SvO2 (LV = 74% +/- 6%, GV = 32% +/- 18%, p < 0.01), and lung compliance (LV = 1.65 +/- 0.50 ml/cm H2O/kg, GV = 0.58 +/- 0.06 ml/cm H2O/kg, p < 0.01) were observed. Significant decreases in physiologic shunt (LV = 24% +/- 6%, GV = 62% +/- 14%, p < 0.01) were noted. CT attenuation data showed the presence of minimal gas ventilation in the dependent regions during GV although the nondependent regions remained well aerated (CT attention number during GV: ND = -654 +/- 160 H; D = -92 +/- 160 H, p < 0.0001). During LV, there was a fairly homogenous distribution of perfluorocarbon in the lungs (CT attenuation number during LV: D = 1071 +/- 330 Hounsfield units; ND = 1112 +/- 287 Hounsfield units; p = 0.240). Lung biopsy analysis in the LV animals was consistent with a reduction in intraalveolar hemorrhage, intraalveolar edema, and the inflammatory infiltrate. CONCLUSIONS: On the basis of the data, we conclude that in this lung injury model, (1) the distribution of the ventilating medium is uniform during LV when compared to GV, (2) LV improves gas exchange and pulmonary function, and (3) histologic evidence of lung injury is reduced after LV when compared to GV.

Animals↗
PubMed1993

[3H]phorbol ester binding sites and neuronal plasticity in the hippocampus following entorhinal cortex lesions.

Entorhinal cortex lesioning (ECL) produces a loss of more than 80% of the synapses in the outer molecular layer of the hippocampus. However, the loss of synapses is transient. Beginning a few days after denervation, new synapses are formed, virtually replacing the lost inputs within 2 months. Synaptic remodelling induced by ECL is associated with specific modifications of neurotransmitters, hormones and growth factors. Particularly, protein kinase C (PKC) plays important functional roles in receptor-mediated transmembrane signal transduction. PKC is also involved in various aspects of synaptic plasticity, such as cellular growth and differentiation. To investigate further the potential roles of PKC in synaptic plasticity observed in the ECL model, [3H]phorbol 12,13-dibutyrate ([3H]PDBu) binding, a putative marker of PKC, was examined at different times post-lesion. [3H]PDBu binding sites transiently decreased bilaterally at 2 and 8 days post-lesion (20%) in different laminae and sub-fields of the rostral hippocampus but returned to control values at 14 and 30 days post-lesion. In caudal portion of the hippocampus, [3H]PDBu binding was also decreased at 2 days post-lesion but only on the contralateral side. Interestingly, [3H]PDBu binding sites in the cortex increased by up to 30% in the contralateral side while no significant change was observed in the ipsilateral side at any time post-lesion. It is known that PKC can be regulated by different systems following alterations of neuronal and glial activity. We suggest that these could be involved in the response of PKC and [3H]PDBu binding sites following ECL. Moreover, PKC seemed to be modified in different brain areas in neuronal inputs from the entorhinal cortex and the subsequent reinnervation process.

Acetylcholinesterase↗
PubMed1993

Anatomical aspects of information processing in primate basal ganglia.

Recent studies with double-anterograde tract-tracing methods have shed new light on the organization of the basal ganglia circuitry in primates. This paper briefly reviews some of these findings and provides a personal interpretation of their possible functional significance. Emphasis is placed on the fact that the striatum and the subthalamic nucleus have multiple representations in the two major output structures of the basal ganglia, namely the internal segment of the globus pallidus and the substantia nigra pars reticulata. It is hypothesized that this multiple representation serves as a means of amplifying and diversifying the striatal and subthalamic influences upon thalamocortical neurons that is mediated through the globus pallidus and the substantia nigra. Furthermore, evidence for the highly ordered organization of the striatopallidal and subthalamopallidal projections, which converge onto single pallidal neurons according to different but highly specific patterns, is taken as an indication that the subthalamic nucleus uniformly excites a vast collection of pallidal neurons, whereas the striatum exerts a more specific inhibitory control upon selected subsets of subthalamically driven pallidal neurons.

Animals↗
PubMed1993

The heterogeneity of the mesostriatal dopaminergic system as revealed in normal and parkinsonian monkeys.

The present immunohistochemical study has shown that the mesostriatal DA system in primates is a highly heterogeneous entity composed of several subsystems displaying variable degrees of vulnerability to MPTP. These subsystems were shown to affect the expression of neuropeptide in the striatofugal neurons in a manner that varies according to the location of the cell bodies in the various striatal territories. Also, a distinct subset of DA neurons in the SN/VTA complex was found to specifically innervate GPi and to be relatively resistant to the neurotoxic effect of MPTP. Furthermore, DA neurons expressing calbindin were found to be much less severely affected than other DA neurons in the SN/VTA complex of PD monkeys. Therefore, in contrast to the situation in other neurodegenerative disorders, such as Alzheimer's and Huntington's diseases, calbindin can be used as a marker for a specific subpopulation of DA neurons that are less prone to degeneration in Parkinson's disease.

Animals↗
PubMed1992

Differential patterns of arborization of striatal and subthalamic fibers in the two pallidal segments in primates.

Double-anterograde tract-tracing experiments in the squirrel monkey (Saimiri sciureus) reveal that fibers from the striatum and the subthalamic nucleus converge onto the same neurons in both the external (GPe) and internal (GPi) segments of the globus pallidus. However, these two pallidal afferents arborize according to a different pattern in GPe and GPi. Whereas the striatal fibers closely entwined the distal dendrites of pallidal neurons in a similar fashion in both pallidal segments, the subthalamic fibers display a tight pericellular arrangement that is much more obvious in GPi than in GPe. This perisomatic arborization is similar to the pericellular contacts made by the GPe fibers terminating on GPi neurons. Such a resemblance suggests that these two types of afferents exert an opposite effect upon the cell body and proximal dendrites of GPi neurons. It also raises the possibility for striatal neurons to influence the same GPi neuron by acting directly on its distal dendrites and indirectly on its cell body via a relay in GPe.

Animals↗
PubMed1992

Calbindin D-28k and choline acetyltransferase are expressed by different neuronal populations in pedunculopontine nucleus but not in nucleus basalis in squirrel monkeys.

Single- and double-immunostaining procedures were used to study the distribution of the acetylcholine synthesizing enzyme choline acetyltransferase (ChAT) and the calcium binding protein calbindin D-28k in the nucleus basalis of Meynert (nbM) and in the pedunculopontine nucleus (PPN) of the squirrel monkey (Saimiri sciureus). As expected from previous studies in other primates, including humans, the nbM in the squirrel monkey is enriched with large ChAT-immunoreactive neurons that form clusters in the substantia innominata. Some ChAT-positive neurons are also scattered more dorsally within the internal and external medullary laminae of the pallidal complex. A smaller number of calbindin-immunoreactive cells occur in the same locations and their mean cross-sectional somatic area (424 microns 2) is not significantly different from that of the ChAT-immunoreactive cells (450 microns 2). Furthermore, 60% of the ChAT-immunopositive cells in the nbM display calbindin immunoreactivity. Most of these double-immunoreactive neurons occur in the typical clusters of the nbM, whereas the large neurons scattered in between the clusters display ChAT immunoreactivity only. In the PPN, ChAT-positive neurons are scattered around and partly within the superior cerebellar peduncle and also form a dense cluster in the lateral portion of the mesopontine tegmentum. Calbindin-immunoreactive cells also abound around the superior cerebellar peduncle, but they are more sparsely distributed and cover a larger sector of the tegmentum than the ChAT-positive neurons. These calbindin-immunoreactive cells are significantly smaller (200 microns 2) than the ChAT-immunoreactive cells (471 microns 2) and no double-immunostained neurons are present in the PPN.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The striatopallidal projection displays a high degree of anatomical specificity in the primate.

The striatopallidal projection in the squirrel monkey (Saimiri sciureus) was studied with two highly sensitive anterograde tracers, the lectin Phaseolus vulgaris leucoagglutinin (PHA-L) and biocytin. After small PHA-L injections into various sectors of the striatum, the striatopallidal projection was found to display a very precise topographical organization. Fibers from the head of the caudate nucleus emerge as several distinct fascicles that penetrate the dorsal portion of the pallidum at various points along its rostrocaudal extent. Each fascicle arborizes into the dorsal third of the pallidum as dense plexuses composed of numerous fibers that closely entwined the dendrites of pallidal neurons, hence forming typical 'woolly' fiber arrangements. In contrast, fibers from the postcommissural putamen emerge as a few compact bundles that reach the pallidum through its lateral surface. In the pallidum, thin fibers detach themselves from these compact bundles, sweep caudally, and arborize in the form of narrow and elongated bands aligned parallel to the medullary laminae. Each band appears composed of numerous, thin and weakly varicose fibers that make only en passant type of contact with pallidal cell bodies rostrally, but form a dense field of woolly fibers caudally. In cases in which two PHA-L injections were made at two different rostrocaudal levels in the putamen, two rostrocaudally distant fields of woolly fibers, separated one another by thin varicose fibers, occur in each band. Furthermore, each PHA-L injection site in the striatum gives rise to at least two bands in each pallidal segment, indicating that the primate striatum has a dual representation at pallidal level. Finally, injections of PHA-L and biocytin into two small and mediolaterally adjacent areas of the postcommissural putamen lead to the formation of two clearly distinguishable sets of bands in each pallidal segment. Even though they lie very close to one another these two types of bands never really overlap. This experiment shows that, in contrast to previous beliefs, axons of striatal neurons from two small adjacent populations do not converge upon the same pallidal neurons but instead project to several distinct subsets of pallidal neurons. The findings of the present study reveal that the striatopallidal projection system in primates is highly ordered and displays a high degree of specificity with respect to its target sites in the pallidum. Different anatomical strategies are used to maximally exploit the relatively small pallidal space and ensure that the finely tuned corticostriatal information is not blurred as it flows through the funnel-shaped pallidum.

Animals↗