摘要:

AbstractThe regional and laminar distribution of the noradrenaline (NA) innervation in the adult rat cerebral cortex was quantified in radioautographs of semithin sections from whole hemisphere slices incubated with tritiated catecholamines and a monoamine oxidase inhibitor. Uptake‐labeled axonal varicosities (aggregates of silver grains) were counted with the help of a computerized image analyzer in seven cytoarchitectonic areas of the rostral half of the cortex: Cg3, rostral AID, Cg2, Fr1, Par1, caudal AID, and Pir (prepiriform) according to Zilles's nomenclature. Both dopamine (DA) and NA terminals were detected after incubation with [3H]DA and citalopram or with [3H]NA alone. In the presence of desipramine (DMI), DA terminals alone were demonstrated; the number of NA terminals was then obtained by subtraction from counts in adjacent slices incubated with or without DMI. These counts suggested that DA and NA varicosities were fully visualized only after labeling with their respective tritiated amine. Similar numbers of labeled NA varicosities as inferred after [3H]NA incubation with or without DMI were observed after [3H]NA incubation in the presence of benztropine (BZ). This indicated that NA terminals were then maximally detected to the exclusion of the DA ones, and the latter approach was adopted for the acquisition of normative data. Since the average diameter of the labeled NA varicosities was known from earlier measurements in electron microscope radioautographs, the initial counts of labeled sites/mm2of histological section could be expressed as numbers of varicosities/mm3of tissue following a double correction for incomplete detection at the chosen duration of radioautographic exposure and section thickness. The overall density of NA innervation was thus estimated at 1.2 million varicosities/mm3of tissue, with no statistically significant differences between the seven cortical areas examined. In every region, the number of NA terminals was the greatest in the molecular layer (1.5–2 times the density in the rest of cortex) and then progressively decreased in the underlying cortex, with a two‐ to threefold difference between upper and lower layers. These numerical data allowed an estimation to be made of the possible number of cortical NA varicosities per locus coeruleus nerve cell body of origin (at least 300,000), of their average number per cortical neuron (30–50), their actual incidence among all terminals in the cortex (1/1,000), their mean endogenous amine content per varicosity (0.22 fg), and the mean number of recognition sites for the uptake blocker DMI (4,500/varicosity). Further quantification of the cortical NA innervation in correlation with these and other measurable parameters of Na function under physiological or experimentally altered conditions should improve our understanding of the properties and role(s) of this monoamine in cerebral

ISSN:0092-7317    

DOI:10.1002/cne.902740302

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the ultrastructural basis for the immunoreactivity patterns in synaptic structures during development in layers I and II of the piriform cortex (PC) of rats. Antisera to cholecystokinin (CCK) and glutamic acid decarboxylase (GAD) were used at several different postnatal days (PN) and in adults to describe the distribution, characteristics, and relative frequency of labeled profiles–especially axons and terminals–with emphasis on details of the synaptic contacts. GAD‐positive terminals occur from PN 2 to adulthood but only form contacts in deeper sublayers (Ib and II) initially. Contacts increase in layer I after PN 6 and are reduced in layer II after PN 21 when the GAD‐labeled terminals and synapses take on adult features with flattened vesicles and symmetric contacts. CCK‐labeled terminals are present in deeper sublayers at PN 2 but are few and rarely form contacts. Both terminals and contacts increase between PN 2 and 9, taking on distinctive shapes and vesicle morphology by PN 13. At PN 21 and older, CCK terminals have mainly flattened vesicles and mostly form symmetric contacts onto dendrites and somata in deeper layers (Ib and II). Superficial sublayer Ia has very few CCK‐labeled synapses and axons. Thus immunoreactivity occurs in terminals prior to synapse formation; labeling of the presynaptic specializations precedes subsequent maturation; synaptic vesicle morphology and membrane specializations are similar for the vast majority of both CCK and GAD terminals; inhibitory (GABA) synapses are established sooner than the possibly excitatory CCK synapses; a deep to superficial gradient of synaptogenesis is associated with GAD‐positive terminals in the PC; and the labeling patterns may be related to critical developmental or synapto

ISSN:0092-7317    

DOI:10.1002/cne.902740303

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe purpose of this investigation was to study possible remodeling in synaptic structures of the piriform cortex (PC) of adult rats following neonatal deafferentation by removal of the olfactory bulb (OB) at birth. Emphasis was placed on possible qualitative changes in the ultrastructure and immunocytochemical localization of cholecystokinin (CCK, a possible excitatory neurotransmitter or modulator) and glutamic acid decarboxylase (GAD, precursor enzyme to the inhibitory transmitter GABA in axons, terminals, and synaptic complexes. Light microscopic results in normal adult material show that GAD‐positive terminals form a dense band subjacent to the lateral olfactory tract (LOT), become less dense in deeper Ib, and are rare in layer II. Following deafferentation, GAD‐positive terminals appear denser and more homogeneously distributed throughout layer I and are also more prevalent in layer II. Ultrastructural results of normals and controls indicate GAD‐positive terminals normally contain pleomorphic or flattened vesicles and form symmetric contacts onto dendritic shafts and branches throughout layer I. In deafferented layer I not only do there appear to be greater numbers of symmetric GAD‐positive contacts, but in contrast to normals, asymmetric contacts mainly onto spines are now present. Light microscopic results from deafferented material also show an apparent proliferation with spread or sprouting of CCK‐positive fibers or axonlike structures mainly into layer Ia, whereas these fibers are normally observed only in the LOT and are generally few in number. Also in normals the few CCK‐positive terminals in the area subjacent to the LOT contain flattened or pleomorphic vesicles and form symmetric contacts. Deafferentation results in CCK‐positive terminals throughout layer I with a greater frequency of synaptic contacts which now also include a few asymmetric contacts onto spines. The findings clearly show modifications in synaptic patterns of immunocyto‐chemical‐labeled terminals that might be compatible with the process of atypical reinnervation of deafferented postsynaptic sites and possible ingr

ISSN:0092-7317    

DOI:10.1002/cne.902740304

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA recent quantitative analysis of cat visual cortex has demonstrated that the numerical density (Nv) of symmetrical synaptic contacts formed by boutons containing flat vesicles (FS synapses) is nearly twice as large in animals raised in isolation (impoverished condition: IC) as in animals raised in a colony (enriched condition: EC). Although some FS synapses have been shown to be cholinergic there is evidence that many, indeed the vast majority, are GABAergic. In order to estimate whether the change in the Nvof FS contacts was accompanied by a change in the number of boutons containing GABA, we have incubated sections of tissue from both groups of animals in an antiserum for GAD. In spite of the large increase in the number of FS contacts in impoverished cortex, we saw no obvious change in the apparent amount of labelled GAD terninals. In retrospect we realized that though the amount of labelled GAD terminals might reasonably be expected to reflect the number of F‐boutons, it might not correspond so closely to the number of contacts formed by these boutons (which is what we had measured in the previous study): The richness of the environment could conceivably affect the number of contacts formed by the F‐boutons without affecting the number of boutons! We thus extended our study by estimating the number of F‐boutons in the two conditions.For the total cortical thickness, the Nvof F‐boutons is oniy 17% lower (P<.05) in enriched than in impoverished cats. The diameter of the boutons is 6% larger (P<.001) in the enriched cortex. Because the F‐boutons become fewer in number as they become larger in size, the total percentage volume occupied by these boutons does not change between the two experimental conditions. We conclude that this is the reason why there appears to be no change in the general amount of GAD label between the two groups of cats.More importantly, since the Nvof neurons is also 17% lower in enriched cortex, the number of F‐boutons per neuron (and presumably the total number of F‐boutons in the visual area) actually remains unchanged. In contrast, the previous study showed that the number of FS contacts per neuron is significantly decreased in enriched cortex. It follows that the number of contacts formed by each bouton must be altered. In the present study we demonstrate that there is an average of 2 contacts per F‐bouton in enriched and of 3 contacts per F‐bouton in impoverished visual cortex. Thus, the richness of the environment does not affect the number of F‐boutons per neuron but only the number of contacts established by each bouton. This clearly demonstrates the importance of the active zones in the cortical circuitry, at least for the GABAergic system.The more numerous contacts in the impoverished cortex are smaller, so that the computed average area if active zones per bouton is not significantly different between the two groups of animals. This is consistent with Changeux and Danch's suggestion that during learning there is aredistributionof receptiors in favor of synaptic contacts which are more frequently utilized. The effect of the richeness of the environment would thus be to restructure the inhibitory GABAergic system, rather than to change the amount of GABA or the numb

ISSN:0092-7317    

DOI:10.1002/cne.902740305

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe superior colliculus (SC) or optic tectum of mammals consists of seven layers, numbered I‐VII from superficial to deep, each of which has distinct connectivity patterns and electrophysiological response properties. The present study is devoted to a morphometrical analysis of neuronal diameters, densities, and numbers in different layers and regions of the SC of albino as well as pigmented rats in order to present a quantitative characterization of the collicular neuronal population involved in the different connectivities and functions of these compartments. The morphometric parameters were calculated from tracings of nuclei and cell bodies by means of Kontron‐Videoplan equipment and a Micro PDP 11/23 computer. The mean soma diameter per superior colliculus appears to be 12.0 μm, the average neuronal density 70 cells per 0.001 mm3, and the total number of neurons about 600,000. The mean soma diameter gradually increases from superficial to deep layers (i.e., from 10.0 to 14.0 μm). Cellular density is highest in layer III, the retinal afferent layer (90 cells per 0.001 mm3), and decreases both in more superficial layers (to about 80 in layer I) and deeper layers (to about 44 in layer VII). About 25% of all collicular neurons are situated in layer II whereas layer I contains the lowest percentage of cells (4%). Rostrally within each collicular layer, cellular volumes are about 25% larger than caudally. On the other hand, neuronal densities are rostrally about 38% lower than caudally in all layers except for layers VI and VII. We conclude that collicular neurons, in contrast to collicular axons, are not arranged in distinct layers or clusters but basically establish a random network with only gradual transitions. In this respect, no statistically significant differences were observed between albino and pigmented

ISSN:0092-7317    

DOI:10.1002/cne.902740306

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThere are three different descending projections from the bulbar gigantocellular tegmental field (BFTG) in the cat, as defined by intracellular recording and intracellular horseradish peroxidase (HRP) techniques. The first pathway arises from neurons which send axons to the contralateral medial longitudinal fasciculus (cMLF neurons); cMLF neurons show excitatory postsynaptic potentials (EPSPs) after stimulation of the ipsilateral pontine gigantocellular tegmental field (PFTG). Most cMLF neurons have large ellipsoid‐polygonal somata (mean, 56.8 μm), thick axons (average diameter, 3.09 μm), mostly non‐spiny dendrites and dendritic fields flattened in the anteroposterior direction. No cMLF neurons with axon collaterals in the BFTG are present in the data of this study. The second pathway arises from neurons which send axons to the ipsilateral MLF (iMLF neurons); iMLF neurons show EPSPs after stimulation of the ipsilateral PFTG. Most iMLF neurons have large ellipsoid‐polygonal somata (mean, 60.2 μm), thick axons (average diameter, 3.00 μm), mostly non‐spiny dendrites and dendritic fields that are only slightly flattened in the anteroposterior direction. As with cMLF neurons, no iMLF neurons with axon collaterals in the BFTG are present in the data of this study. The third pathway arises from neurons that send axons directly into the ipsilateral caudal bulbar reticular formation (iBRF neurons). Most iBRF neurons have smaller ellipsoid‐polygonal somata (mean, 38.6 μm), thinner axons (average diameter, 1.84 μm), mostly nonspiny dendrites, and dendritic fields that are flattened in the anteroposterior direction. In contrast to cMLF and iMLF neurons, axon collaterals are present in 73% of iBRF neurons. About half of iBRF neurons have bifurcated axon collaterals with both anterior and posterior projections, and in these neurons antidromic spike potentials are elicited by stimulation of the i

ISSN:0092-7317    

DOI:10.1002/cne.902740307

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe generation, migration, and morphogenesis of atypically oriented pyramidal neurons in the rat visual cortex were examined. In the mature cortex, these neurons were distributed through layers II–VI. Moreover, the atypically oriented pyramidal neurons in a particular layer tended to be oriented in a specific way; atypically oriented pyramidal neurons in layer II, layers III–VIa, and layer VIb were obliquely, radially, and obliquely oriented, respectively. Ultrastructurally, the somata of atypically oriented pyramidal neurons contained large euchromatic ovoid nuclei and cytoplasm that was replete with rough endoplasmic reticulum and Golgi apparatus. These somata formed only symmetric axosomatic synapses. Many atypically oriented pyramidal neurons projected axons into the white matter as demonstrated by a Golgi method and by a retrograde tract‐tracing technique; however, some of these pyramidal neurons in layers III–V had axons that ascended to layer I.By using a technique which combined retrograde tract tracing with [3H]thymidine autoradiography, it was determined that most atypically oriented pyramidal neurons in layers V and VIa, layer IV, and layer II were generated on gestational days (GD) 15–17, GD 17–19, and GD 20–21, respectively. Atypically oriented pyramidal neurons were identified during the period from postnatal day 0 (day of birth) to day 30. On day 0, obliquely oriented pyramidal neurons were distributed in the deep cortical plate, i.e., immature layer VI. On day 3, the youngest atypically oriented pyramidal neurons were radially oriented and were located in layer IV. Some obliquely oriented pyramidal neurons were present in layer II on day 6, but the greatest number and the most severely canted pyramidal neurons in layer II were evident on day 9. The orientations of the cell body and the apical dendrite did not change appreciably after migration was complete, except for those in layers V and VI with obliquely oriented cell bodies and radially oriented apical dendrites. The second and third postnatal weeks were marked by substantial morphological differentiation of all pyramidal neurons as noted by the lengthening and branching of dendrites and by the appearance of dendritic spines. By the fourth postnatal week, atypically oriented pyramidal neurons achieved their mature morphology.The generation, migration, and morphogenesis of atypically oriented pyramidal neurons proceed by an inside‐to‐outside sequence. This development is similar and concurrent with that of typically oriented

ISSN:0092-7317    

DOI:10.1002/cne.902740308

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractFetal striatal tissue grafts have been shown to partially reverse the biochemical and behavioral deficits induced by excitotoxic lesions. To determine if grafted striatal neurons contain neurochemical markers similar to those in neurons in the caudate nucleus and to establish the morphological characteristics and relative frequency of labeled neurons in the grafts, the localization of immunoreactive GABA and leucine‐enkephalin (ENK) and of NADPH‐diaphorase (NADPH‐d) activity was examined in fetal striatal grafts at the light and electron microscopic levels. Striatal tissue from 17‐day fetuses was grafted into the caudate nucleus of adult rats 1 week after intracaudate injections of either a low or high dose of quinolinic acid. At the light microscopic level, immunoreactive GABA and ENK and NADPH‐d‐positive neurons, processes, and punctate structures were present within adjacent sections of the same grafts. The frequency and morphological features of these labeled cell populations were similar in grafts placed into either minimally or extensively lesioned striata. Immunoreactive GABA and ENK neurons in the grafts constituted 28% and 13.5%, respectively, of the neuronal population of the graft and their mean diameters were 22 and 14% larger, respectively, than neostriatal neurons that contained the same chemical markers. NADPH‐d‐positive neurons in the grafts formed 3.5% of total grafted neurons and exhibited characteristics of neostriatal NADPH‐d‐containing aspiny cells, including medium‐sized somata, indented nuclei, and varicose dendrites.At the electron microscopic level most GABA‐positive neurons in the grafts contained indented nuclei and most immunoreactive ENK somata had unindented nuclei. Dendrites and dendritic spines with GABA or ENK immunoreactivity were present in the grafts where they were postsynaptic to unlabeled axons. Immunoreactive GABA and ENK axon terminals formed synapses with unlabeled neuronal profiles in the grafts. These findings demonstrate that fetal striatal grafts contain chemically defined neuronal populations that form synaptic connections within the graft and share some features with corresponding cell groups in the neostriatum. These results provide an anatomical basis for the graft‐induced recovery from behavioral and biochemical deficits caused by instrastriatal lesions

ISSN:0092-7317    

DOI:10.1002/cne.902740309

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe organization of the medial geniculate body and adjacent posterior thalamus of the Virginia opossum was studied in Nissl‐, Golgi‐, reduced silver, and myelin‐stained preparations. Our chief goals were to define the cytoarchitectonic subdivisions and boundaries in Nissl preparations and to reconcile these with those observed with the Golgi method and in experimental material, to present these results in an atlas of Nissl‐stained sections, and to compare the chief nuclear groups in the opossum and the cat medial geniculate body.In the opossum, theventral divisionconsists chiefly of the ventral nucleus. The ventral nucleus is divided into two main parts: thepars lateralisand thepars ovoidea, the former being relatively smaller in the oposum. The ventral nucleus of both species contains large principal neurons with bushy, tufted dendrites and smaller Golgi type II cells. However, the opossum has far fewer Golgi type II cells, and the texture of the neuropil is correspondingly different, although the primary ascending input from the midbrain arises from the central nucleus of the inferior colliculus in both species. Thedorsal divisionconsists of the dorsal nuclei, including the suprageniculate nucleus and the caudal part of the lateral posterior nucleus, the marginal zone, and the posterior limitans nucleus. These nuclei are identified in both species, although they are much smaller in the opossum. The neurons consist of medium‐size and small somata with a predominantly radiate mode of dendritic branching and a lower cell concentration than in the ventral division. In both species the afferent brain stem input comes from the inferior colliculus, the lateral tegmental area, the intercollicular tegmentum, and the superior colliculus. Themedial divisioncontains several types of cells, which are heterogeneous in form and size, most having radiating dendrites and a low cellular concentration. This division is especially smaller in the opossum, although comparable inputs arise from various auditory and non‐auditory sources in the midbrain and spinal cord in both species.A largeintralaminar complexof nuclei occurs in the opossum, which have a more extensive distribution than previously appreciated. They not only occupy the intramedullary laminae but form a shell around the medial geniculate nuclei and adjoining main sensory nuclei. The intralaminar complex includes the posterior limitans, posterior intralaminar, posterior, parafascicular, posterior parafascicular, central intralaminar, limitans, and central medial nuclei, and the marginal zone of the medial geniculate body. These predominantly radiate, poorly branched cells are similar in both species. However, the opossum intralaminar nuclei are much more conspicuous than those of the cat. While it is possible to subdivide this complex, their basic structural similarity and topograpgical continuity suggest that the intralaminar neurons constitute a fundamental architecctonic category. These neurons have differentiated during ontogeny and associated thalamic nuclei, which differ broadly in their connections and physiological properties.These findings imply: (1) tha the patterns of structural organization in the main thalamic sensory nuclei and in the associated nuclei are comparable in both species, (2) that the cortical and brain stem connections with thse nuclei are to be compared in both species, and (3) that despite these similarities, there may be interspecific differences in the cytological and perhaps the synaptic arrangement of partic

ISSN:0092-7317    

DOI:10.1002/cne.902740310

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractOne month after an in situ injection of kainic acid into the ventrobasal thalamic complex (VB), the lesioned area is totally depleted of neurons. The present study has been undertaken to determine the cytoarchitecture and connectivity of the nucleus constructed by fetal thalamic neurons implanted into the excitotoxically lesioned area.Adult rats received an injection of kainic acid inducing a total neuronal depletion of the right lateral thalamus (including both the nucleus reticularis thalami and the lateral portion of the ventrobasal complex). One month later, homotypic neurons were taken from the dorsal thalamic primordium of rat embryos (gestational age 15–16 days), dissociated, and injected into the lesioned area as a cell suspension. After 2–4‐month survival, the cytoarchitecture of the neonucleus formed by the grafted neurons within the previously neuron‐depleted area was analyzed. Additionally, connectivity was analyzed in seven rats in which dorsal column nuclei and/or cortical projections to the area were labeled anterogradely with either3H‐leucine or wheat‐germ agglutinin conjugated to HRP, and the animals were perfused and processed following various histological procedures (Nissl staining, autoradiographic processing, and histochemistry for visualization of peroxidase).Fetal neurons grew, differentiated, and progressively occupied the previously neuron‐depleted area of the adult host CNS. They organized themselves into a neonucleus with particular cytoarchitecural features including (1) the existence of two concentric zones–a central zone containing neurons and glial cells and a marginal zone only filled with a band of glial cells, (2) an increase in cellular density compared to the intact thalamus, (3) the grouping of neurons in spherical clusters, and (4) apparent polymorphism of neuronal somata. Lemniscal and corticothalamic afferents originating from the host were observed in the neonucleus when the fetal neurons had been implanted correctly into the lesioned area but not when they had been misplaced into either normal thalamic tissue or the internal capsule. The afferents labeled from either the dorsal column nuclei or the somatosensory cortex were, however, less dense in the neonucleus than in the normal thalamus.These results are discussed with regard to the normal cytoarchitecture and connectivity of the ventrobasal complex of t

ISSN:0092-7317    

DOI:10.1002/cne.902740311

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY