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PubMed1987

Development of the spinal nerves in the lamprey: III. Spinal ganglia and dorsal roots in 26-day (13 mm) larvae.

Serial sections of the trunk and tail of 26-day (13 mm) larval lampreys were examined by light and electron microscopy. Trunk region: Spinal ganglia and ventral nerves are seen alternately along the spinal cord and the notochord in the trunk. Spinal ganglia are located medially in intermyotome spaces with intersegmental blood vessels and send "dorsal nerves" ventrally along the vessels. "Ventral nerves" are seen on the midmedial surface of each myotome. Fibers containing dense-cored vesicles occur in the dorsal root but not in the ventral root. Caudal region: In the caudal one-third of the tail the ventral nerves are formed earlier than spinal ganglia and dorsal nerves. The most caudal (primitive) ventral nerve (root) develops at the 12th myotome from the caudal end of the series of myotomes, the caudalmost ganglion being formed between the 15th and the 14th myotome in a 13-mm larval lamprey. The intimate association of dorsolateral outflow (DLO) fibers (Nakao and Ishizawa: J. Comp. Neurol. 256:356-368, '87b) with neural crest cells (DO cells of Nakao and Ishizawa; ibid.) strongly suggested that these fibers play an important role as the substrate for guiding the cells to form compact cell masses as primitive spinal ganglia. Two types of cell groups are progressively distinguished in primitive spinal ganglia during development. One of them has a light round nucleus with a prominent nucleolus and a large amount of the perinuclear cytoplasm that contains abundant free ribosomes, rough endoplasmic reticulum (ER), numerous Golgi apparatuses, and dense bodies. Cells of the other type are characterized by a dense, flattened nucleus with a small amount of perinuclear cytoplasm that extends as a thin cytoplasmic sheet to surround cells of the other type as a whole, the basal lamina surrounding the whole cell mass. The former type is interpreted as neural cells and the latter satellite cells of the ganglion. Central processes of ganglionic neural cells are assumed to enter the spinal cord along DLO fibers by using them as a substrate to establish the dorsal root. Intersegmental blood vessels develop later than spinal ganglia and peripheral processes extend along the vessels.

Animals↗

PubMed1994

Organization of N-methyl-D-aspartate glutamate receptor gene expression in the basal ganglia of the rat.

Glutamate is an important neurotransmitter in the circuitry of the basal ganglia. Of the four pharmacological classes of receptors that may mediate the actions of glutamate, the N-methyl-D-aspartate (NMDA) type is of particular interest insofar as it has been implicated in the neural processes underlying long-term synaptic plasticity as well as excitotoxic injury. NMDA ligand binding sites are abundant in the structures of the basal ganglia, and NMDA receptors have been linked to neuronal excitability, neuropeptide gene expression, and regulation of dopamine release in these regions. NMDA receptors are believed to be heterooligomers of subunits from two families: NMDAR1, encoded by a single gene but alternatively spliced to produce eight distinct isoforms (NMDAR1A-H), and NMDAR2, encoded by four separate genes (NMDAR2A-D). We have used in situ hybridization with a total of 13 oligonucleotide probes to examine the expression of these genes in the rat basal ganglia. NMDAR1 subunits are expressed throughout the basal ganglia as well as in the rest of the brain; however, the alternatively spliced amino-terminal region Insertion I is abundantly expressed only in the subthalamic nucleus and is not detectable in the neostriatum, globus pallidus, or substantia nigra pars compacta. In contrast, expression of the carboxy terminus segment Deletion I is prominent in the striatum but is not observed in other elements of the basal ganglia. NMDAR2 subunits also exhibit differential expression: NMDAR2B is abundant in the striatum, but NMDAR2A is present within the striatum only at low levels. NMDAR2C is present in the substantia nigra pars compacta only, while NMDAR2D exhibits an unusual distribution, with high levels of expression in the substantia nigra pars compacta, the subthalamic nucleus, the globus pallidus, and the ventral pallidum. Since each isoform of the NMDAR1 and NMDAR2 subunits can confer distinct properties on the resultant NMDA receptor, these data imply that there is a high degree of regional specialization in the properties of NMDA receptors within the basal ganglia.

Animals↗

PubMed2004

Hypothyroidism impairs long-term potentiation in sympathetic ganglia: electrophysiologic and molecular studies.

Electrophysiologic and molecular techniques were used to study the effect of adult-onset hypothyroidism on synaptic plasticity in the superior cervical sympathetic ganglion. Ganglia excised from adult thyroidectomized and sham-operated rats were subjected to a brief high-frequency stimulation of the preganglionic nerve to express long-term potentiation (gLTP). Western blotting was carried out to determine the protein levels of key signaling molecules that may be involved in the expression of gLTP. Input/output relationship in ganglia from hypothyroid rats indicated a normal basal synaptic transmission, whereas activity-dependent types of synaptic plasticity, posttetanic potentiation (PTP) and gLTP, were impaired. Immunoblot analysis showed that both calcium/calmodulin kinase II (CaMKII) and phosphorylated CaMKII (P-CaMKII) levels were reduced markedly in hypothyroid rat ganglia compared to those from euthyroid controls. Additionally, protein levels of nitric oxide synthase-1, heme oxygenase-2, calmodulin, protein kinase C (PKC), and calcineurin were also reduced in hypothyroid rat ganglia. The results indicate that abnormally low basal levels of signaling molecules may be responsible for hypothyroidism-induced impairment of gLTP in superior cervical ganglia. In addition, the results indicate that synaptic plasticity in sympathetic ganglia may involve a molecular sequence of events similar to that proposed for LTP in the hippocampus.

Animals↗

PubMed1992

Fine structure of presynaptic axonal terminals in sympathetic autonomic ganglia of aging and diabetic human subjects.

The neuropathologic changes that may underlie autonomic nervous system dysfunction in nondiabetic elderly human subjects or as a complication of diabetes have been systematically examined in sympathetic ganglia of a series of autopsied human subjects. As in animal models of aging and diabetes, enormously swollen terminal axons were found closely apposed to the perikarya of principal sympathetic neurons in prevertebral superior mesenteric sympathetic ganglia of aged and diabetic human subjects. Dystrophic axons consisted of two stereotyped forms: the first was composed of large numbers of misaligned aggregates of neurofilaments surrounded by variable numbers of small dense core vesicles; the second was characterized by large numbers of mitochondria, vacuoles, and dense and multivesicular bodies. The fine structural characteristics of neuroaxonal dystrophy, its predilection for prevertebral rather than paravertebral sympathetic ganglia, and the tendency for multiple dystrophic axons to cluster preferentially around selected neurons were identical in aged and diabetic human ganglia and were similar to changes seen in animal models of aging and diabetes. Neither diabetic nor aging ganglia demonstrated evidence of neuronal degeneration. Such structural changes may represent a degenerative influence of diabetes and aging on the normal remodeling of nerve terminals in autonomic ganglia, i.e., the continually ongoing process of turnover and replacement of axonal terminals. Similarity of lesions in human diabetes and aging suggests the possibility of pathogenetic mechanisms that are common to diabetes and the aging process. The substantial parallels between humans and animal models provide support for the validity of testing some proposed pathogenetic mechanisms directly in animal models.

Adolescent↗

PubMed2000

Basal ganglia output and cognition: evidence from anatomical, behavioral, and clinical studies.

The traditional view that the basal ganglia are simply involved in the control of movement has been challenged in recent years. Three lines of evidence indicate that the basal ganglia also are involved in nonmotor operations. First, the results of anatomical studies clearly indicate that the basal ganglia participate in multiple circuits or 'loops' with cognitive areas of the cerebral cortex. Second, the activity of neurons within selected portions of the basal ganglia is more related to cognitive or sensory operations than to motor functions. Finally, in some instances basal ganglia lesions cause primarily cognitive or sensory disturbances without gross motor impairments. In this report, we briefly review some of these data and present a new anatomical framework for understanding the basal ganglia contributions to nonmotor function.

Basal Ganglia↗

PubMed1995

Initial axial level-dependent differences in size of avian dorsal root ganglia are imposed by the sclerotome.

We have recently shown that there is very early variation in dorsal root ganglia (DRG) size based on their axial position. From the time of their condensation at Stage (St.) 20 (Embryonic Day 3), before the onset of apoptosis, the ganglia in brachial segments 14 and 15 are more than 80% larger on the average than those in cervical 5 and 6. This difference in volume is due to increased numbers of cells in the brachial DRG. In addition, the rostrocaudal length was found to be significantly greater for brachial ganglia, and the greater length of the brachial ganglia was found to be correlated with a greater length of brachial than cervical sclerotomes. It was therefore proposed that the difference in DRG size at the time of gangliogenesis is likely to arise from colonization by a larger initial number of neural crest cells of the longer adjacent rostral sclerotomes in brachial somites. In the present work, we have performed two types of experiments to test this hypothesis. First, we have performed heterotopic grafts of segmental plate mesoderm from cervical to brachial levels and vice versa. In all of these grafts, the sclerotomes developed with a rostrocaudal extent (length) corresponding to their level of origin in the donor embryo. DRG that formed in the grafted mesoderm attained a length appropriate to that of ganglia developing in segments of the axial level of the donor mesoderm, not that of the host. Second, we have estimated proliferation of DRG cells at St. 20 using HNK-1/bromodeoxyuridine double-stain immunocytochemistry. The percentage of cells in S-phase at both brachial and cervical levels of the neuraxis in newly formed ganglia was observed to be the same. These two lines of evidence strongly argue that the initial difference in size between DRG at different axial levels is not intrinsic, but rather is imposed by the mesodermal microenvironment in which they develop, as is the case for DRG segmentation. This is in contrast to what may occur in the hindbrain, where determination of rhombomere identity and neural crest segmentation are thought to be intrisic to the nervous system.

Animals↗

PubMed1993

Axonal regeneration from transplanted sympathetic ganglia is not impaired by age.

Changes occur with age in several areas of the nervous system, including autonomic ganglia and the target tissues of some sympathetic neurons where signs of neuronal degeneration have been shown in old age. In this study, we have employed an intraocular grafting technique to examine whether age changes occur in sympathetic neurons of the superior cervical (SCG) and stellate ganglia that might explain the reduced innervation of some of their target tissues in old age. Ganglia taken from young and old rats were implanted in oculo for 4 or 6 weeks in young hosts whose irises had been previously sympathetically denervated. The extent, pattern, and time course of reinnervation of the host iris was studied by catecholamine histochemistry followed by image analysis. We did not observe any difference in the pattern and time course of reinnervation between ganglia taken from young and old donors. If anything, the extent of reinnervation was greater in irises implanted with SCG taken from 25-month-old animals. Moreover, we did not observe any difference in ability to reinnervate the host iris between ganglia that normally project to the iris (SCG) and ganglia that normally do not project to the iris (stellate), regardless of the age of the donor animal. Our results suggest that sympathetic neurons from aged rats have unimpaired capability of regeneration and retain plasticity, as shown by their ability to reinnervate an inappropriate target. We hypothesize that the decreased innervation observed in some sympathetic targets in old age might be caused by changes in the target tissues themselves rather than being the result of degenerative changes in the neurons.

Aging↗

PubMed1988

Substance P- and vasoactive intestinal polypeptide (VIP)-immunoreactive nerve fibers in relation to ovarian postganglionic perikarya in para- and prevertebral ganglia: evidence from combined retrograde tracing and immunocytochemistry.

Retrograde neuronal tracing with the fluorescent dye True Blue and immunocytochemistry were utilized to examine postganglionic sympathetic neurons in para- and prevertebral ganglia projecting to the rat ovary. Perikarya in both ganglia were labeled with True Blue after application of the tracer to either the superior ovarian or ovarian plexus nerve. After application of True Blue to the superior ovarian nerve, 17% of the labeled cells in paravertebral ganglia were immunoreactive for vasoactive intestinal polypeptide. In contrast, after application of True Blue to the ovarian plexus nerve, approximately 1% of the labeled cells in paravertebral ganglia were immunoreactive for the same polypeptide. Some vasoactive intestinal polypeptide-immunoreactive perikarya in paravertebral ganglia were not labeled with True Blue. In some cases, substance P- and vasoactive intestinal polypeptide-immunoreactive fibers were closely apposed to True Blue-labeled perikarya in para- and prevertebral ganglia. Paravertebral vasoactive intestinal polypeptide-immunoreactive perikarya projecting to the ovary presumably participate directly in the control of various ovarian functions. Substance P- and vasoactive intestinal polypeptide-immunoreactive fibers closely apposed to perikarya projecting to the ovary may participate indirectly in the control of various ovarian functions by affecting the activity of ovarian postganglionic neurons.

Animals↗

PubMed1984

Dopamine-beta-hydroxylase-, neurotensin-, substance P-, vasoactive intestinal polypeptide- and enkephalin-immunohistochemistry of paravertebral and prevertebral ganglia in the cat.

Para- and prevertebral ganglia of the cat were investigated for immunoreactivity (IR) against neurotensin (NT), vasoactive intestinal polypeptide (VIP), substance P (SP) and enkephalin (ENK). Dopamine-beta-hydroxylase-(DBH)-IR was studied in consecutive sections to correlate the distribution of noradrenergic/adrenergic neurons with that of peptidergic nerve fibres and cells. In paravertebral (cervical and thoracic) ganglia, NT-IR or ENK-IR nerve fibres were seen in areas in which DBH-IR fibre networks also occurred. NT-IR varicosities were often in close contact with perikarya of principal ganglionic cells on which DBH-IR varicosities also terminated. Such an association was rarely seen between ENK-IR and DBH-IR fibre baskets. NT-IR and ENK-IR fibre baskets were not found to occur around the same principal ganglionic cell. The distribution of VIP-IR and SP-IR nerve fibres did not coincide with that of DBH-IR fibres. In prevertebral ganglia (celiac-superior mesenteric and inferior mesenteric) DBH-IR or VIP-IR varicosities surrounded the majority of principal ganglionic neurons. ENK-IR or SP-IR fibres were closely associated with only a minority of the neurons; NT-IR networks were rather sparse. Some principal neurons were approached by DBH-IR fibres and by different peptide-IR fibres. In paravertebral ganglia some principal ganglionic cells contained VIP-IR, a few of which were also surrounded by NT-IR varicosities. VIP-IR perikarya in prevertebral ganglia were extremely rare. No NT-IR, SP-IR or ENK-IR principal ganglionic cells were found. Glomus-like paraganglionic cell clusters in paravertebral and prevertebral ganglia exhibited DBH-IR cell bodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1976

Quantitative fluorescence studies of the effects of catecholamines and hydrocortisone on endogenous amine levels in neurones and small intensely fluorescent cells of embryonic chick sympathetic ganglia in vivo and in vitro.

Chick embryo lumbar sympathetic ganglia (11 day) cultured for three days and uncultured (in vivo) ganglia of comparable age were freeze-dried and processed by the formaldehyde-induced fluorescence technique for the demonstration of biogenic monoamines. The catecholamine levels within principal neurone cell bodies and small intensely fluorescent (SIF) cells were then examined in plastic sections of the in vivo and in vitro ganglia by a quantitative fluorescence method under various experimental conditions. Culture of ganglia for three days in the presence of hydrocortisone acetate (10 mug/ml) resulted in an increased SIF cells fluorescence (P less than 0.001 compared to control) and a green to yellow colour shift in the fluorophore of SIF cells. No detectable alteration in the fluorescence level of neurones was observed. When neurones after three days in culture were incubated for 1 h in exogenous catecholamines, a significant increase in fluorescence levels (interpreted as an increase in catecholamine content) occurred with noradrenaline (2 X 10(-6) M; 2 X 10(-5) M). SIF cells in ganglia removed directly from 14-day old chicks similarly took up noradrenaline and dopamine, and also adrenaline (2 X 10(-5) M). Morphological results are presented which indicate that the cellular appearances and architecture of cultured ganglion explants are very similar to those in comparable ganglia in vivo.

Animals↗

PubMed1980

Arm movement performance during reversible basal ganglia lesions in the monkey.

Arm motor performance of eight Cebus monkeys was examined during reversible cooling in the ventral lateral region of the putamen and globus pallidus (primarily the external segment), where neurons discharging during arm movements have been found (DeLong 1972). When attempting to hold a handle stationary during basal ganglia cooling, all monkeys developed flexion at the wrist and some developed a slow flexion drift of the arm at the elbow. The prominence of wrist flexion emphasizes that the basal ganglia may normally influence distal musculature. During basal ganglia cooling an increase in segmental stretch reflexes (15-30 ms) was sometimes observed following arm perturbations, but no consistent increase occurred in the later EMG responses (30-95 ms) in contrast to results obtained in Parkinsonian patients (Tatton and Lee 1975). No major changes were observed in the time of onset of the earliest EMG activity in the agonist muscle in a simple reaction time elbow movement task during basal ganglia cooling. Basal ganglia lesions produced major disorders in both flexion and extension movements including slowing of movements and rebound of the arm towards its initial position after onset of movement. These disorders were accompanied by an increase in tonic activity of both flexors and extensors while holding and by increased levels of cocontraction of agonists and antagonists during attempted movements. It is suggested that this basal ganglia disorder is due to a failure to achieve the correct balance of activity between agonists and antagonists that is appropriate for a particular motor act.

Animals↗

PubMed1995

Sympathoadrenal progenitors in embryonic chick sympathetic ganglia show distinct responses to glucocorticoid hormones.

The sympathoadrenal cell lineage originates from the neural crest and comprises the neurons of sympathetic ganglia, adrenal and extra-adrenal chromaffin cells, and the so-called small intensely fluorescent cells. In vitro studies using mammalian immature chromaffin cells, adrenal or sympathetic ganglionic progenitors, or ganglionic small intensely fluorescent cells, have suggested that glucocorticoid hormones are essential for inhibiting neuronal differentiation of sympathoadrenal progenitors and promoting the chromaffin cell phenotype. In avian systems, however, the distinct cellular phenotypes in this lineage and the molecular cues underlying their differentiation have not been fully explored. In the chick embryo, early sympathetic ganglion anlagen are populated by granule-containing cells that morphologically resemble small intensely fluorescent cells and chromaffin cell progenitors. These cells subsequently disappear from the ganglia, by death and by transition into fully differentiated sympathetic neurons, as indicated by the appearance of cells that are ultrastructurally intermediate between granule-containing cells and fully differentiated neurons (granule-containing cells in transition). In the present study, we show that treatment of cultured sympathetic cells dissociated from embryonic day (E) 7, 9, or 11 lumbar sympathetic ganglia with the glucocorticoid hormones hydrocortisone or corticosterone has neither an inhibitory nor an inductive effect on phenotypes of granule-containing cells or granule-containing cells in transition. In cell cultures of E15 ganglia, however, glucocorticoid treatment induces a granule-containing cell resembling the granule-containing phenotype. These results suggest that the early granule-containing cells and granule-containing cells in transition in chick sympathetic ganglia are not the counterparts of glucocorticoid-responsive mammalian small intensely fluorescent or chromaffin progenitor cells, despite their morphological similarity. However, E15 sympathetic ganglia apparently contain a glucocorticoid-responsive progenitor population that can differentiate into chromaffin-like cells. These progenitors seem to require a systemic or intraganglionic developmental signal or undergo a temporal switch that renders them susceptible to glucocorticoids.

Adrenal Medulla↗

PubMed1993

An analysis of dorsal root ganglia differentiation using three tissue culture systems.

The histogenesis of the dorsal root ganglia of chick embryos (ages 3 to 9 days) was followed in three different tissue culture systems. Organotypic explants included dorsal root ganglia connected to the lumbosacral segment of the spinal cord or isolated explants of the contralateral ganglia. Additionally, dissociated monolayer cultures of ganglia tissue were established. The gradual differentiation of progenitor neuroblasts into distinct populations of large ventrolateral and small dorsomedial neurons was observed in vivo and in vitro. Neurites developed after 3 days in the presence or absence of nerve growth factor in the medium. In contrast, autoradiographic analysis indicates that [3H]thymidine incorporation in neuronal cultures differed significantly from intact embryos. In vivo, the number of neuronal progenitor cells labeled with [3H]thymidine decreased in older embryos; in vitro, uptake of [3H]thymidine label was not observed in ganglionic progenitor cells regardless of the age of the donor embryo or the type of culture system. Lack of proliferation in ganglionic progenitor cells was not due to degeneration because vital staining and uptake of [3H]deoxyglucose indicated that neurons were metabolically active. Furthermore, the block in mitotic activity in vitro was limited to presumptive ganglionic neuronal cells. In the ependyma of the spinal cord segment connected to the dorsal root ganglia, neuronal progenitor cells were heavily labeled as were non-neuronal cells within both spinal cord and ganglia. Our results suggest that in vitro conditions can promote the differentiation of sensory neurons from early embryos (E3.5-4.5) without proliferation of progenitor cells.

Acetylcholinesterase↗

PubMed1985

Amino acid and protein metabolism in dorsal root ganglia of rabbits with experimental allergic neuritis.

Amino acid and protein metabolism has been studied in the dorsal root ganglia of rabbits with experimental allergic neuritis (EAN). The concentrations of a number of nonessential amino acids (glutamine, serine, aspartate, and glutamate) were reduced in the spinal ganglia of EAN animals without any comparable change in the blood plasma. The short-term influx of glycine and GABA was decreased in EAN animals, whereas that of histidine and valine was not altered. The prolonged accumulation of all the four amino acids was unchanged. These results suggest alterations in the cell metabolism of the dorsal root ganglia, rather than unspecific changes in cellular permeability. Furthermore, incorporation of tritiated valine, histidine, and glycine into proteins of EAN-ganglia in vitro was significantly increased. Autoradiography of the protein-bound [3H]-valine indicated alterations in the protein synthesis of the ganglion neurons: A decreased grain density was found in ganglion neurons of EAN animals. The increased grain densities in the affected ganglia were observed in macrophages, and possible in activated Schwann cells, over the demyelinated spots. The results suggest intraneuronal changes in the dorsal root ganglia of amino acid and protein metabolism, possibly in response to peripheral axonal injury and/or to nonspecific cytotoxic effect of active lymphocytes and macrophages.

Amino Acids↗

PubMed2004

Neural responses in multiple basal ganglia regions during spontaneous and treadmill locomotion tasks in rats.

To investigate the role of basal ganglia in locomotion, a multiple-channel, single-unit recording technique was used to record neural activity simultaneously in the dorsal lateral striatum (STR), globus pallidus (GP), subthalamic nucleus (STN) and substantia nigra pars reticulata (SNr) during spontaneous and treadmill locomotion tasks in freely moving rats. Active and quiescent phases appeared alternately in a spontaneous movement session that lasted 60 min. Principal component analysis of the ensemble neural activity from each region revealed a close correlation with spontaneous motor activity. Most of the neurons in these four basal ganglia areas increased their firing rates during the active phase. In the treadmill locomotion task, the firing rates of neurons in all recording areas, especially in the STN, increased significantly during locomotion. In addition, neural responses related to tone cue, initiation and termination of treadmill were observed in a subset of neurons in each basal ganglia region. Detailed video analysis revealed a limb movement related neural firing, predominantly in the STR and the GP, during treadmill walking. However, the proportion of neurons exhibiting limb movement related firing was significantly greater only in the STR. A few neurons in the STR (4.8%) and the GP (3.4%) discharged in an oscillatory pattern during treadmill walking, and the oscillatory frequency was similar to the frequency of the step cycle. This study demonstrates a variety of neural responses in the major basal ganglia regions during spontaneous and forced locomotion. General activation of all major basal ganglia regions during locomotion is more likely to provide a dynamic background for cortical signal processing rather than to directly control precise movements. Implications of these findings in the model of basal ganglia organization are discussed.

Action Potentials↗

PubMed2001

Lumbar spinal ganglia enhancement after gadolinium chelate administration: a radio-histological correlation.

The aim of the present study was to assess the frequency of enhancement of lumbar spinal ganglia after Gadolinium chelate injection in patients without radiculopathy, and to correlate the enhancement with histology. This study is based on the analysis of MR lumbar examinations conducted on 18 patients without radicular symptoms, or previous surgery of the lumbar spine, or disease of the nervous system. The patients were imaged with a 1.5 T unit. Sagittal images were first obtained with a T1-weighted turbo spin-echo. Axial and sagittal images were then obtained with a T1-weighted turbo spin-echo, fat-saturated sequence after Gadolinium intravenous injection from the T12/L1 to the L5/S1 level. All 180 spinal ganglia demonstrated an important and homogeneous enhancement after Gadolinium injection. Four spinal ganglia obtained by dissection from four different fresh cadavers were studied by light microscopy to determine the potential relationship between contrast enhancement and presence and topography of vessels within the spinal ganglia. Vessels were particularly abundant at the peripheral zone of the spinal ganglia. The post-contrast enhancement of the spinal ganglia after Gadolinium administration has to be known and may be explained by the microvasculature pattern.

Adult↗

PubMed2002

Functional anatomy of thalamus and basal ganglia.

THALAMUS: The human thalamus is a nuclear complex located in the diencephalon and comprising of four parts (the hypothalamus, the epythalamus, the ventral thalamus, and the dorsal thalamus). The thalamus is a relay centre subserving both sensory and motor mechanisms. Thalamic nuclei (50-60 nuclei) project to one or a few well-defined cortical areas. Multiple cortical areas receive afferents from a single thalamic nucleus and send back information to different thalamic nuclei. The corticofugal projection provides positive feedback to the "correct" input, while at the same time suppressing irrelevant information. Topographical organisation of the thalamic afferents and efferents is contralateral, and the lateralisation of the thalamic functions affects both sensory and motoric aspects. Symptoms of lesions located in the thalamus are closely related to the function of the areas involved. An infarction or haemorrhage thalamic lesion can develop somatosensory disturbances and/or central pain in the opposite hemibody, analgesic or purely algesic thalamic syndrome characterised by contralateral anaesthesia (or hypaesthesia), contralateral weakness, ataxia and, often, persistent spontaneous pain. BASAL GANGLIA: Basal ganglia form a major centre in the complex extrapyramidal motor system, as opposed to the pyramidal motor system (corticobulbar and corticospinal pathways). Basal ganglia are involved in many neuronal pathways having emotional, motivational, associative and cognitive functions as well. The striatum (caudate nucleus, putamen and nucleus accumbens) receive inputs from all cortical areas and, throughout the thalamus, project principally to frontal lobe areas (prefrontal, premotor and supplementary motor areas) which are concerned with motor planning. These circuits: (i) have an important regulatory influence on cortex, providing information for both automatic and voluntary motor responses to the pyramidal system; (ii) play a role in predicting future events, reinforcing wanted behaviour and suppressing unwanted behaviour, and (iii) are involved in shifting attentional sets and in both high-order processes of movement initiation and spatial working memory. Basal ganglia-thalamo-cortical circuits maintain somatotopic organisation of movement-related neurons throughout the circuit. These circuits reveal functional subdivisions of the oculomotor, prefrontal and cingulate circuits, which play an important role in attention, learning and potentiating behaviour-guiding rules. Involvement of the basal ganglia is related to involuntary and stereotyped movements or paucity of movements without involvement of voluntary motor functions, as in Parkinson's disease, Wilson's disease, progressive supranuclear palsy or Huntington's disease. The symptoms differ with the location of the lesion. The commonest disturbances in basal ganglia lesions are abulia (apathy with loss of initiative and of spontaneous thought and emotional responses) and dystonia, which become manifest as behavioural and motor disturbances, respectively.

Basal Ganglia↗

PubMed2006

Location and variability of epicardiac ganglia in human fetuses.

The aim of the study was to determine the morphology of epicardiac ganglia in human fetuses at different stages of their development as these ganglia are considered to be of a pivotal clinical importance. Twenty-one fetal hearts were investigated applying a technique of histochemistry for acetylcholinesterase to visualize the epicardiac neural ganglionated plexus with its subsequent stereoscopic examination on total organs. In all of the examined fetuses, epicardiac neural plexus with numerous ganglia was well recognizable and could be clearly differentiated into seven ganglionated subplexuses, topography and structural organization of which were typical for hearts of adult human. The largest ganglion number comprising 77% of all counted ganglia was identified on the dorsal atrial surface. Fetal epicardiac plexus in gestation period of 15-40 weeks contained 929 +/- 62 ganglia, but ganglion amount did vary substantially from heart to heart. In conclusion, this study implies that the human fetal epicardiac ganglia occupy their definitive location already at gestation period from 15 weeks and their number as well as distribution on heart surface presumably is not age dependent.

Fetal Heart↗