摘要:

AbstractThe mystacial pad of the ferret has an elaborate sensory innervation provided by three types of terminal nerves that arise from the infrorbital branch of the trigeminal nerve. Deep and superficial vibrissal nerves innervate nearly exclusive targets in the large follicle–sinus complexes (F‐SCs) at the base of each tactile vibrissa. Dermal plexus nerves innervate the fur between the vibrissae. Each type of nerve provides a similar variety of sensory endings, albeit to different targets. In this study, Winkelmann and Sevier‐Munger reduced silver techniques revealed that most of the endings differntiate postnatally in an overlapping sequence like that observed previously in the rat. Afferents from the deep vibrissal nerves begin to differentiate first, followed successively by those from superficial vibrissal nerves and the dermal plexus. Within each type of nerve, Merkel endings begin to differentiate first, followed successively by lanceolate endings and circumferential endings. In the ferret, the differentiation of the intervibrissal fur and its innervation is slightly delayed but substantially overlaps the development of the vibrissal innervation, whereas in the rat it occurs almost entirely later. There was no evidence of a transient exuberant or misplaced innervation or other secondary remodeling. Differentiating afferents and endings are located only in the sites normally seen in the adult, suggesting a high degree of afferent‐target specificity. In the ferret, innervation is virtually lacking in one target—the inner conical body of the F‐SCs, which is densely innervated in the rat. This lack was due to a failure of innervation to develop rather than to a secondary elimination of a transient innervation. © 1993 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903330302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractFunctional studies of the development of the corpus callosum in the cat have shown that an intact callosum during postnatal month 1 is necessary for normal visual development. In vivo tracing techniques have not provided enough information on corpus callosum connectivity to fully evaluate the evidence for a morphological mechanism for the functional effects of neonatal callosum section. However, lipophilic in vitro membrane tracers permit a more detailed search for such evidence because the entire limit of many cells can be labeled simulatanously. To investigate the morphological basis for the observed functional results in cats, the corpus callosum was labeled in vitro with the carbocyanine dye, DiI. Crystals of DiI were placed in the midsagittal callosum in tissue from 2 to 277‐day‐old cats. Tissue was coronally sectioned 3–22 months later. Sections were photographed and reconstructed to show the overall distribution of corpus callosum projections, as well as the locations of individual corpus callosum axons and their presumed terminals.The distribution of corpus callosum projections, examined in cortical areas 17–19, 7, and posterior medial lateral suprasylvian cortex, changes significantly during development. During postnatal week 1, callosal axons extend throughout these cortical areas to layer I. Numerous varicosities on callosal axons are located en passant and at axon terminals in layer I. During postnatal week 2, the density of callosal projections is reduced in all cortical areas, although many axons still extend to layer I. By postnatal month 2, the callosal axons extending to layer I are predominantly near the border with adjacent cortical areas; in the nonborder regions of these areas, many axons extend to layer VI while a much smaller number of axons extend to layers II–V. By postnatal month 3, the callosal projections to supragranular layers are almost exclusively restricted to cytoarchitectonic border regions; in the remaining regions, including medial area 17, there are occasional axons extending to the supragranular layers and only a moderate number of axons extending to infragranular layers.Thus, a substantial number of elaborately formed transitory corpus callosum axons, distributed throughout visual cortex, exist for several weeks during postnatal development; in area 17, these axons are found in central through peripheral visual field representations. The transitory callosal axons appear to have axon terminals in layer I as well as en passant terminals while extending through layers II–VI. If some of these terminals were to form synapses, there would be extensive opportunities for the corpus callosum to provide input to layers I–VI throughout visual cortex during the period of development in which cortical microcircuitry is being established. © 1993 W

ISSN:0092-7317    

DOI:10.1002/cne.903330303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractLocalization of oxytocin‐ and vasopressin‐binding sites has so far been studied in the rat brain by means of film autoradiographs. The disposal of iodinated ligands with high specificity has allowed us to develop histoautoradiography on emulsion‐coated sections and to reinvestigate on a microscopic scale the distribution of these sites in the telencephalon (septum, striatopallidal system, amygdala and hippocampus). This technique showed that oxytocin and vasopressin labelling presented distinct distributions and coincided with delimited zones, corresponding to anatomical subdivisions defined on cytoarchitectural and immunocytochemical bases. Vasopressin sites were seen in the dorsal and intermediate parts of the lateral septum and the juxtacapsular nucleus of the bed nucleus of the stria terminalis. Oxytocin sites were located in the ventral and intermediate parts of the lateral septum, the oval and the principal nuclei of the bed nucleus of the stria terminalis and the septofimbrial nucleus. In the striatopallidal system, vasopressin sites were found in the accumbens nucleus and the fundus striati, whereas oxytocin sites were in the accumbens nucleus, the head, and the posterolateral parts of the caudate‐putamen, the striatal cell bridges, and the olfactory tubercle. In the amygdala, vasopressin sites were not found, but oxytocin sites were located in the central, medial, and basomedial nuclei. In the hippocampus, vasopressin sites were located in the dentate gyrus (polymorph and molecular layers), and oxytocin sites, in the subiculum (molecular and pyramidal layers) and in the field CA1 of Ammon's horn (lacunosum moleculare and pyramidal layers). The localization of the binding sites at the microscopic level permitted us to reinvestigate whether or not correlation existed in a same area between innervation, electrophysiological effects, and presence of binding sites. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903330304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe cat superior colliculus (SC) receives a dense cholinergic input from three brainstem nuclei, the pedunculopontine tegmental nucleus, the lateral dorsal tegmental nucleus, and the parabigeminal nucleus (PBG). The tegmental inputs project densely to the intermediate gray layer (IGL) and sparsely to the superficial layers. The PBG input probably projects only to the superficial layers. In the present study, the morphology of choline acetyltransferase (ChAT)‐immunoreactive axons and synaptic endings in the superficial and deep layers of the SC was examined by light and electron microscopy to determine whether these cholinergic afferents form different types of synapses in the superifical and deep layers.Two types of fibers were found within the zonal (ZL) and upper superficial gray layers (SGL): small diameter fibers with few varicosities and larger diameter fibers with numerous varicosities. Quantitative analysis demonstrated a bimodal distribution of axon diameters, with one peak at approximately 0.3–0.5 μm and the other at 0.9–1.0 μm. On the other hand, ChAT‐immunoreactive fibers in the IGL were almost all small and formed discrete patches within the IGL.Two types of ChAT‐immunoreactive synaptic profiles were observed within the ZL and upper SGL using the electron microscope. The first type consisted of small terminals containing predominantly round synaptic vesicles and forming asymmetric synaptic contacts, mostly on dendrites. The second type was comprised of varicose profiles that also contained round synaptic vesicles. Their synaptic contacts were always symmetric in profile. ChAT‐immunoreactive terminals in the IGL patches contained round or pleomorphic synaptic vescles, and the postsynaptic densities varied from symmetric to asymmetric, including intermediate forms. However, no large varicose profiles were observed.This study suggests that cholinergic fibers include at least two differnt synaptic morphologies: small terminals with asymmetric thickenings and large varicose profiles with symmetric terminals. The large varicose profile in the superficial layers is absent in the IGL. This result suggests that the cholinergic inputs that innervate the superficial layers and the patches in the IGL of the cat SC differ in their synaptic organization and possibly also in their physiological actions. © 1993 W

ISSN:0092-7317    

DOI:10.1002/cne.903330305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractInsulin‐like growth factors I and II (IGF I and IGF II) and insulin itself, which are structurally related polypeptides, play an important role in regulating brain growth and development as well as in the maintenance of its normal functions during adulthood. In order to provide a substrate for the better understanding of the roles of these growth factors, we have investigated the anatomical distribution as well as the variation in the density of [125I]IGF I, [125I]IGF II, and [125I]insulin receptor binding sites in developing and adult rat brain by in vitro quantitative autoradiography. The distributional profile of [125I]IGF I, [125I]IGF II, and [125I]insulin receptor binding sites showed a widespread but selective regional localization throughout the brain at all stages of development. The neuroanatomic regions which exhibited relatively high density of binding sites with each of these radioligands include the olfactory bulb, cortex, hippocampus, choroid plexus, and cerebellum. However, in any given region, receptor binding sites for IGF I, IGF II, or insulin are concentrated in anatomically distinct areas. In the cerebellum, for example, [125I]IGF II receptor binding sites are concentrated in the granular cell layer, [125I]insulin binding sites are localized primarily in the molecular layer, whereas [125I]IGF I receptor binding sites are noted in relatively high amounts in granular as well as molecular cell layers. The apparent density of sites recognized by each radioligand also undergoes remarkable variation in most brain nuclei, being relatively high either during late embryonic (i.e., IGF I and IGF II) or early postnatal (i.e., insulin) stages and then declining gradually to adult levels around the third week of postnatal development. These results, taken together, suggest that each receptor‐ligand system is regulated differently during development and thus may have different roles in the process of cellular growth, differentiation, and maintenance of the nervous system. Furthermore, the localization of [125I]IGF I, [125I]IGF II, and [125I]insulin receptor binding sites over a wide variety of physiologically distinct brain regions suggests possible involvement of these growth factors in a variety of functions associated with specific neuronal pathways. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903330306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractCadherins are a family of cell surface molecules mediating calcium‐dependent cell–cell adhesion in a variety of tissues. More than a dozen cadherins are expressed in the vertebrate brain. To obtain insight into the biological significance of this diversity in cadherin expression, we mapped the expression of N‐and R‐cadherin in the brain of the developing chicken embryo (days 2–19 of incubation) by immunohistochemical and in situ hybridizaiton techniques.Whereas the expression of N‐ and R‐cadherin is relatively uniform or weak in early (about 2–5 days of incubation) and late development (15 days of incubation to hatching stage), these two molecules are differentially expressed in specific nuclei and fiber tracts between days 6–11 of incubation. For example, in the mes‐ and diencephalon, one of the tectofugal pathways and its target nuclei, here called the tecto‐pretecto‐rotundal system, express N‐cadherin. R‐cadherin is expressed by a different tectofugal system, the tectoisthmic pathway. The other tectofugal systems express neither N‐ nor R‐cadherin. In addition, a small number of other mes‐ and diencephalic nuclei express N‐ or R‐cadherin. On the basis of these results and experimental evidence from other studies, we speculate that the two cadherins are involved in the formation and segregation of particular functional systems within the vertebrate central nervous system (CNS) by regulating the formation of nuclei, and the pathfinding and/or the selective fasciculation of neurites.Apart from neuronal elements, a variety of vascular and ependymal structures also express N‐cadherin or R‐cadherin, e.g., the parenchymal blood vessels, the choroid plexus, the floor and roof plates, and the ventricular lining. These findings suggest that the two cadherins play a variety of roles during the development of neuronal and nonneuronal epithelial structures throughou

ISSN:0092-7317    

DOI:10.1002/cne.903330307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractRegional distribution of gene expression of the axonal growth‐associated protein, GAP‐43, was studied in adult rat brains by in situ hybridization autoradiography to determine the features of mature neuronal populations that synthesize GAP‐43 protein. Such synthesis appears to correlate with axonal growth during maturation and regrowth after axotomy. In most adult neurons, the sharp decline in GAP‐43 gene expression implies a reduced capacity for axonal growth. Neurons capable of extending axonal knobs in the absence of injury may indicate a “plasticity” underlying dynamic processes of interaction between neurons and their synaptic targets.Antisense and sense (control) riboprobes were used on serial sections in the three principal axes, and the magnitude of hybridization signal was examined to determine regional patterns. GAP‐43 mRNA levels are pronounced in diverse neuronal groups including the locus coeruleus, raphé nn., dopaminergic nigral and ventral tegmental nn., mitral cells, hippocampal CA3, inferior olivary n., vagal motor n. and other parasympathetic preganglionic neurons, select thalamic midline and intralaminar nn., several specific nn. of the hypothalamus and basal forebrain, the granular layer of cerebellar cortex, the infragranular neocortex, and the granular olfactory paleocortex; there is substantial range in the magnitude of expression. Regions revealing minimal signal include most thalamic sensory relay nuclei, the granule neurons of the olfactory bulb and dentate gyrus, and the caudate and putamen.Possible concomitants of GAP‐43 expression include regulation of ion flux and neurotrans‐mitter release. Those neurons with long, extensively dispersed and numerous synaptic connections display the strongest signals and may possess the greatest propensity forcontinuous growthand turnover of their axon terminals, in contrast to short‐axon and specific projection neurons exhibiting minimal levels. These data may enable inferring which populations display normal or experimentally induced axonal growth. ©

ISSN:0092-7317    

DOI:10.1002/cne.903330308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThere is increasing evidence that the various types of hippocampal nonpyramidal neurons control the principal cells in different ways. In the present study a type of spiny nonpyramidal cell in stratum lucidum of rat hippocampal region CA3 was studied by Golgi impregnation. Three Golgi‐impregnated and gold‐toned neurons of this type were further analyzed by electron microscopy and postembedding immunocytochemistry. The dendrites of these bipolar neurons seemed to be restricted to stratum lucidum and ran parallel with the mossy fibers that terminate in this layer. A characteristic feature of this neuron is the presence of long, thin spines on both cell body and dendrites. Although these dendrites were exposed to a large number of mossy fibers, no thorny excrescences were formed which are characteristic postsynaptic elements of CA3 pyramidal neurons for synaptic contact with the mossy fibers. Semithin sections of Golgi‐impregnated and gold‐toned stratum lucidum cells displayed immunoreactivity of the cell body region for glutamate but not for GABA.A fine‐structural analysis of gold‐toned sections revealed a large cell body with numerous cytoplasmic organelles and an indented nucleus. Numerous asymmetric synapses were found on dendritic shafts as well as on the long, thin somatic and dendritic spines. Usually, several presynaptic boutons contacted a single spine. The majority of these asymmetric spine synapses were probably of mossy fiber origin, although no giant mossy fiber synapses were formed. The long spines were contacted by much smaller en passant synapses of preterminal axons. In contrast, giant mossy fiber boutons were found presynaptic to dendritic shafts and cell bodies of these cells.Our morphological analysis of a glutamate‐immunoreactive, GABA‐negative type of non‐pyramidal neuron that receives convergent mossy fiber input suggests that the impulse flow within the “trisynaptic pathway” is more complex than previously assumed.

ISSN:0092-7317    

DOI:10.1002/cne.903330309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe delayed Wallerian degeneration which occurs in the C57BL/Ola mouse is associated with impaired motor axon regeneration. Following sciatic nerve crush, recovery of the sciatic functional index was delayed and incomplete when compared with recovery in C57BL/6J mice. After facial nerve crush, recovery of whisker movement in Ola mice was also delayed, and there was a prolonged period of partial recovery, not seen in 6J mice. Regeneration rate of the motor axons was measured by the axonal transport technique in sciatic nerve and was approximately 0.7 mm/d for Ola mice, and 4.0 mm/d for 6J mice. Combining these results from our previous work, we conclude that regeneration of both sensory and motor axons is imparired when Wallerian degeneration does not follow its usual time course after injury. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903330310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractBy immunocytochemical and immunohistochemical methods, FMRFamide‐like immunoreactivity (FLI) was localized to many neurons and processes in theAscarisnervous system, including the head, tail, and lateral lines. Some of these cells were identified; they included sensory neurons, interneurons, and motor neurons. FLI was also present in the pharyngeal neurons and in their varicosities near the surface of the pharynx. By HPLC analysis of extract, only a subset of the FMRFamide‐like peptides (FLPs) expressed inAscarisheads, and heads from which the pharynx had been removed, were expressed in the pharynx. Furthermore, FLPs appeared to be differentially expressed in female heads and tails and male heads and tails. Acetone and acid methanol differentially extracted subforms of FLI fromAscarisheads and fromC. elegans. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903330311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY