摘要:

AbstractGlutamate is an important neurotransmitter in the circuitry of the basal ganglia. Of the four pharmacological classes of receptors that many 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, encode by four separate genes (NMDAR2A–D).We have used in situ hydridization 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. © 1994 W

ISSN:0092-7317    

DOI:10.1002/cne.903430102

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe electron microscopic autoradiographic tracing method has been used to examine the morphology and postsynaptic relationships of five projections (retina, cortical area 17, superior colliculus (tectal), parabigeminal nucleus, and pretectum) to the dorsal lateral geniculate nucleus of the greater bush babygalago crassicaudatus.Retinal terminals have been examined in the contralaterally innervated layer of each of the three matched pairs [parvi‐(X‐cell), magno‐ (Y‐‐cell), and koniocellular (small, W‐cell)] of geniculate layers. These terminals are large and contain pale mitochondria and round vesicles (RLPs). RLPs are presynaptic to juxtasomatic regions of parvi‐and magnocellular neurons. In contrast, RLPs innervate more distal regions of konicellular neurons.Labeled cortical, tectal, and parabigeminal terminals are relatively small and contain round vesicles na dark mitochondria. Cortical terminals in each of the three representative layers are presynaptic to small diameter dendrites. No convergence of cortical and retinal terminals has been seen in any layer. Labeled tectal and parabigminal terminals are found primarily in the koniocellular layers, but the latter are also seen in all other layers. Tectal and parabigeminal terminals have been observed converging with retinal terminals on dendrites of some koniocellular neurons.Labeled pretectogeniculate terminals contain densely packed pleomorphic vesicles, dark mitochondria, and a dark cytoplasmic matric. These terminals, which are present in each of the representative layers, are presynaptic to conventional dendrites and profiles containing loosely despersed pleomorphic vesicles and a pale cytoplasmic matrix. © 1994 W

ISSN:0092-7317    

DOI:10.1002/cne.903430103

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious studies concluded that parrots and oscine songbirds, two taxa that have independently evolved the ability to learn vocalizations, possess similar neural circuits for vocal control. These investigations suggested, however, that the vocal control systems of parrots and songbirds may also differ in several respects. Most importantly, auditory inputs to the vocal control system derive from Field L in songbirds, but this area does not appear to project to the vocal control system in parrots. The principal aims in the present study were, therefore, to determine (1) exactly how similar the vocal control system in budgerigars is to that in songbirds and (2) whether the vocal control system in budgerigars receives auditory inputes from areas other than Field L.Biotinylated and fluorescently labeled dextrans were injected into five telencephalic nuclei of the vocal control system in budgerigars and into the physiologically identified auditory portions of the frontal neostriatum and nucleus basalis. The results indicate that the forebrain voca; control system in budgerigars is only superficially similar to that in songbirds. Many of the vocal control nuclei differ between the two taxa in both cytoarchitecture and connections. The nuclei in budgerigars that are comparable to those of the accessory loop of the vocal control system in songbirds, for example, do not form an accessory loop in budgerigars. The vocal control systems in the two taxa differ most significantly in the source of their auditory inputs. In songbirds, auditory information is conveyed to the vocal control system via Field L, whereas, in budgerigars, the auditory inputs to the vocal control system derive from nucleus basalis and the frontal neostratum. A phylogenetic analysis suggests that the midbrain and medullary vocal control pathways are homologous across all birds, but that most of the vocal control circuits in the forebrain have probably evolved independently in parrots and songbirds. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903430104

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractAcetylcholine or vasoactive intestinal peptide (VIP)nerve terminals closely related to intracortical blood vessels have previously been reported. Recent physiological evidence indicates that these central neuronal systems are involved in the fine control of local cerebral blood flow. In the present study, the intimate associations between choline acetyltransferase (ChAT) and VIP azon terminals and intracortical microvessels were characterized by light (LM) and electron microscopic (EM) immunocytochemistry. In semithin sections, LM analysis of the distribution of ChAT‐and VIP‐immunostained puncta juxtaposed to small intraparenchymal blood vessels demonstrated that neither type of terminal was enriched or improverished around microvessels within the cerebral cortex. At the EM level, most ChAT‐ or VIP ‐Immunolabelled elements located within a 3μm perimeter around vessel walls were axon terminals. These perivascular terminals were associated primarily with capillaries but also, to a lesser extent, with microarterioles. Even thought ChAT and VIP terminals were frequently found in the immediate vicinity (≤0.25 μm) of microvessels, they almost never contacted the outer basal lamina, usually abutting onto perivascular astroglial leaflets. There were no membrane specializations at the site of contact between ChAT or VIP terminals and perivascular astroglia. In all cortical areas examined, the average size of VIP‐Immunolabelled varicosities (0.56 ± 0.04 μm2) was significantly larger than that of their ChAT counterparts (0.32 ± 0.02 μm2;P<0.001). Perivascular VIP terminals were more frequently engaged in synaptic contact than those immunostained for ChAT, which rarely exhibited a synaptic junction even in serial thin sections. Neither VIP nor ChAT immunostaining was ever observed in endothelial cells.These results suggest that both acetylcholine and VIP exert their effects on intracortical microvessels through indirect, paracrine mechanisms. The marked difference in synaptic incidence and average size between both types of perivascular terminals indicates that these two vasoactive agents are primarily located in distinct neuronal populations. Further, our results show that the astrocytic glia is the major direct target for both ChAT and VIP perivascular terminals and suggest that neuronal/glial/vascular interactions are a key element in the neurogenic control of the intracortical microcirculation. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903430105

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPeptide histidine‐isoleucine (PHI) is a regulatory peptide, synthesized as part of the same propeptide that includes also vasoactive intestinal peptide (VIP). The present study describes the distribution of PHI‐immunoreactive nerve fibers in the sheep pineal organ and compares their location with the distribution of VIP‐immunoreactive fibers in both normal and superior cervical ganglionectomized sheep in order to elucidate the origin of the PHI/VIP immunoreactive nerve fibers. Several PHI‐immunoreactive nerve fibers were present in the meninges and in the pineal capsule. Numerous positive nerve fibers entered the pineal gland and travelled within connective tissue spaces. Individual PHI‐positive nerve fibers were either smooth, without specialization, or varicose. Generally VIP‐ and PHI‐immunoreactive fibers were located close to connective septa and blood vessels. However, many PHIergic and VIPergic fibers possessing varicosities of variable sizes were also disperesed between pinealocytes. The distribution, density, and morphology of PHI‐ and VIP‐immunoreactive fibers in the sheep pineal gland were similar. In superior cervical ganglionectomized animals, intrapineal VIP‐ and PHI‐ immunoreactive nerve fibers were present with the same density as in control animals. In agreement, the concentration of immunoreactive VIP and PHI did not change after ganglionectomy. No VIP‐ and PHI‐immunoreactive cell bodies were observed in the superior cervical ganglia. Thus this study shows that the intrapineal VIP‐ and PHI‐immunoreactive nerve fibers do not originate from the sympathetic superior cervical gan

ISSN:0092-7317    

DOI:10.1002/cne.903430106

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe anatomical distribution of substance P‐like immunoreactivity across the subnuclear divisions of the nucleus of the solitary tract has been examined in the human medulla oblongata. A differential distribution of neurons, fibers, and terminals was observed throughout the ten subnuclear divisions of this nucleus. Substance P‐like immunoreactive neurons were observed most frequently in the nucleus gelationsus, with moderate numbers in the medial, intermediate subnuclei and very few in the commissural, ventral, dorsal, and dorsolateral subnuclei. The paracommissural, ventrolateral, and interstitial subnuclei did not contain substance P‐like‐immunoreactive neurons. These neurons were typically bipolar and moderate‐sized to large, except for the neurons in the nucleus gelatinosus, which were substantially smaller. The highest densities of fibres and terminals were observed in the gelatinosus, medical, and intermediate nuclei, with moderate densities in the paracommissural and dorsal subnuclei. Sparse substance P‐like‐immunoreactive fibres and terminals were seen in the ventral and interstitial nuclei as well as within the solitary tract. The dorsolateral nucleus was characterized by a light distribution of fibres and terminals, except for a dense aggregation along its lateralmost border. A prominent innervation of pigmented neurons by substance P‐like‐immunoreactive terminals and fibres was also observed in the dorsolateral nucleus. The results reveal that the subnuclear complexity of the nucleus of the solitary tract is richly reflected by its differential pattern of substance P‐like‐immunoreactive structures.

ISSN:0092-7317    

DOI:10.1002/cne.903430107

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe present study examined the postnatal development of the radial glib in the rabbit superior colliculus during the first 40 postnatal days. An antivimentin monoclonal antibody and the carbocyanine fluorescent tracer DiI were used in order to investigate the development of laminar connectivity in the superior colliculus. We focused our study on the superficial gray layer, the intermediate layer, and the deep layers of the superior colliculus, the periaqueductal gray matter (PAGM), and the medial intercollicular region.Vimentin‐positive structures of glial lineage consisted of (1) the main radial system, which in the newborn rabbit was made up of wavy fibers that ran from the aqueduct to the glial surface, where they terminated in end‐feet. At postnatal day 15, these fibers diminished to 100–200 μm long wavy tracts, which emanated from the aqueduct, and to a few straight or arched fragments in the superficial gray layer; (2) The median ventricular formation, which extends from mesencephalic aqueduct to the intercollicular sulcus, was characterized by a series of ascending, vimentin‐positive fibers, some of large caliber, which persisted until postnatal day 40; (3) the tangential fiber system, which was made up of fibers that diverged from the median ventricular formation and of a number of short tracts running perpendicular to the periaqueductal radial fibers; these structures may provide support for migrating subpopulations of neurons; (4) immature and mature‐like protoplasmic and fibrous astrocytes, which appeared during the second postnatal week. Thereafter, the number of vimentin‐positive astrocytes decreased sharply. Our findings generally support earlier descriptions of the radial glib, except for the persistence, in superficial layers of the superior colliculus, of straight and curved fragments of fibers, which may participate in the organization of visual afferents at this level. © 1994 Wi

ISSN:0092-7317    

DOI:10.1002/cne.903430108

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractBrain aromatase has been considered to be an important clue in elucidating the actions of androgen on brain sexual differentiation. Using highly specific anti‐P450arom antiserum, the regional and subcellular distributions were immunohistochemically evaluated in the preoptic, strial, and amygdaloid regions of developing rat brains. Aromatase‐immunoreactive (AROM‐I) neurons were classified into three groups. The first, in which immunostaining occurs only during certain pre‐ or neonatal days (E16–P2), included the anterior medial preoptic nucleus, the periventricular preoptic nucleus, neurons associated with the strial part of the preoptic area, and the rostral portion of the medial preoptic nucleus. The second is a striking AROM‐I cell group in the “medial preopticoamygdaloid neuronal arc,” which extends from the medial preoptic nucleus to the principal nucleus of the bed nucleus of the stria terminals and the posterodorsal part of the medial amygdaloid nucleus. The AROM‐I neurons appeared by E16, reaching a peak in staining intensity between E18 and P2 and diminishing after the perinatal stage. After P14, a third group of AROM‐I neurons emerged in the lateral septal nucleus, the oval nucleus of the bed nucleus of the stria terminalis, and the central amygdaloid nucleus. The second group was thought to be the major aromatization center in developing rat brains, while the center might partly shift to the third group of neurons after the late infantile stage. The distribution and developmental patterns were basically similar in males and females, suggesting that the neonatally prominent aromatase is not induced by male‐specific androgen surges occurring around birth. On immunoelectron microscopy, subneuronal aromatase was predominantly localized on the nuclear membrane and endoplasmic reticulum, which appeared to be appropriate for the efficient conversion of androgen into estrogen just prior to blinding to the nuclear receptors.

ISSN:0092-7317    

DOI:10.1002/cne.903430109

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSome human blood group antigens are expressed by rodent epithelial cells at different stages of differentiation. Since adult taste cells are continually replaced throughout life, we investigated the expression of the H, B, A and Lewisbblood group determinants by cells of the rat fungiform, foliate and vallate papilae. We employed antibodies against the trisaccharide structures of the H, B, and A blood group antigens and against the Lewisbblood group epitope in studies of normal and denervated taste buds. The antibody against the H antigen reacted with the majority of cells in all taste buds and with cells in the spinous layer of the tongue epithelium. The B antigen was expressed by the majority of taste cells but not by other epithelial cells. The expression of the A antigen was significantly less in the fungiform taste buds than in the vallate or foliate taste buds. The A antigen was also abundantly expressed in the acini of the lingual salivary glands. The Lewisbepitope was expressed by a subset of cells in taste buds of the fungiform, foliate and vallate papillae. Taste buds are trophically dependent upon gustatory nerve innervation. Transection of the chorda tympani or the IXth nerve resulted in the loss of expression of these molecules from the gustatory epithelium, indicating that they are expressed only on differentiated taste cell. The blood group antigens are lactoseries carbohydrates; they are differentially expressed in developing cochlear hair cells and olfactory neurons and may play roles in cell‐cell recognition, adhesion, and other interactions important in the developing nervous system. They could have similar functions in the taste and olfactory systems, where the receptors are continually renewed and new synapses between the receptors and their neural targets continually form. © 1994 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903430110

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe rat is now the model of choice for many studies of motor function. However, little quantitative information on the structure of rat motoneurons is available. In conjunction with efforts to define the physiologic and anatomic substates of operantly conditioned plasticity in the spinal cord, 13 physiologically identified triceps surae motoneurons in the rat lumbar spinal cord were labeled intracellularly with horseradish peroxidase and completely reconstructed and measured with a computer‐based neuron‐tracing system.Somata were all located in the ventral horn of lumbar segments 4–5, had and average diameter of 35 μm, and had 6–12 dendrites. Dendrites remified throughout the ventral horn and also penetrated the white matter. Their spread was greater in the rostocaudal and dorsoventral directions (1.53 ± 0.24 mm and 1.35 ±0.23 mm, respectively) than in the mediolateral direction (0.85 ± 0.14 mm). Regardless of soma location, dendritic fields usually extended throughout the ipsilateral coronal cross‐section of the ventral horn.As a result, the ventral or lateral extent of the field was correlated strongly with the soma's distance from the ventral or lateral border, respectively, of the ventral horn. Furthermore, although soma locations in the coronal plane varied widely, the centers of the dendritic fields tended to cluster near the center of the ventral horn. Dendrites constituted 96.2–98.4% (mean ± SD = 97.3 ± 0.7%) of the total neuronal surface area. Each of the 104 dendrites studies had an average of 13 branch points and 27 segments. First‐order segment diameters ranged from 1.4 to 11.7 μm (mean ±SD = 5.3 ± 2.1 μm). Total dendritic length, surface area, volume, number of dendritic segments, and maximum segment order were correlated strongly with diameter of the first‐order segment. Proceeding distally between branch points, the mean decrease in dendritic diameter (i. e., tapering) ± the standard deviation was 22 ± 8% of the proximal diameter. The average ratio ± the standard deviation of the sum of the average diameters of each daughter segment raised to the 1.5 power to the average diameter of the parent segment raised to the 1.5 power (i. e., Rall's ratio; Rall, 1959) was 0.87 ± 0.08.In comparison with cat α‐motoneurons, rat motoneurons had smaller soma diameters, fewer dendrites, smaller total surface areas, and shorter total dendritic lengths. However, the number of terminations per dendrite was similar in the two species, so that rat motoneurons had more terminations per unit dendritic length. This greater branching density indicates that the dendritic fields of rat motoneurons are more compact and their branching structures are more densely packed that those of cat mot

ISSN:0092-7317    

DOI:10.1002/cne.903430111

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY