摘要:

AbstractThe functional reorganization of cerebral cortex following peripheral deafferentation is associated with changes in a number of neurotransmitters and related molecules. Acetylcholine (ACh) enhances neuronal responsiveness and could play a role in activity‐dependent cortical plasticity. In this study, choline acetyltransferase (ChAT) immunohistochemistry was used to investigate ACh innervation of the primary somatosensory cortex in cats sustaining complete unilateral forearm and paw denervations. Survival times of 2–52 weeks were examined. The deafferented contralateral cortex was defined electrophysiologically, and quantitative estimates of ChAT‐immunoreactive fiber density were obtained from the forelimb and hindlimb sectors of area 3b in both hemispheres. In the 3b forelimb sector contralateral to the deafferentation, a decrease in density of ChAT‐positive fibers relative to the ipsilateral hemisphere was apparent at 2 weeks and most pronounced at 13 weeks, involving all cortical layers except layer I. There was no such decrease in the hindlimb sector, but the loss of ChAT immunoreactivity extended to sectors representing proximal forelimb and trunk. Changes in ChAT immunoreactivity were no longer found after 1 year of survival. This long‐lasting but reversible lowering of ChAT immunoreactivity could result from a loss of afferent activity in basalis neurons and/or trophic influences retrogradely exerted by cortex on these cells. Reduced ACh transmission might then contribute to the loss of gamma aminobutyric acid (GABA) inhibition in the deafferented cortex by decreasing the activation of inhibitory interneurons. The long‐term recovery of a normal ChAT immunoreactivity in cortex could be a consequence of its functional reorganization. © 1995 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903540302

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

年代:1995

数据来源: WILEY

摘要:

AbstractMultiunit recordings along mediolateral rows in the primary somatosensory cortex of the animals described by C. Avendafio, D. Umbriaco, R. W. Dykes, and L. Descarries (1995, J. Comp. Neurol. 354:321–332) provided information about the functional status of the regions in and near the deafferented cortex. Responses changed along this axis from normally organized receptive fields in the hindlimb representation through a transition zone of unusually small receptive fields into the clearly deafferented forelimb representation, where receptive fields were uncommon and often had unusual characteristics.The most abrupt change along this axis was the appearance of a repetitive, bursting discharge pattern in the multiunit activity near the border of the deprived cortex. The appearance of this pattern was used as a reference to describe differences between normal and deprived cortices. The nature of these differences evolved with time. Much of the deprived cortex lacked identifiable receptive fields for months after the nerve transections and, 1 year later, still only about half of the recording sites within the deprived region displayed organized receptive fields. Some sites within the deprived region lacking definable receptive fields could be excited at long latencies by somatic stimuli anywhere on the body. With time, regions of normal cortex near the border with the deprived zone became more involved in these processes. Spontaneous activity and thresholds also changed with time in both normal and deprived cortices.These electrophysiological responses occurred during a time when choline acetyltransferase staining was reduced in and around the deprived cortex (Avendaño et al., 1995); the effects of nerve transections were most pronounced between the 8th and 13th weeks, as was the reduction in immunostaining; however, although immunostaining had returned to normal levels at 1 year, many parts of the deprived cortex remained without new afferent drive, some being unresponsive to any somatic stimuli. © 1995 Wiley‐Liss

ISSN:0092-7317    

DOI:10.1002/cne.903540303

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe proportion of somatostatin‐containing dorsal root ganglion cells innervating the knee joint of the cat via the medial articular nerve was determined by using retrograde labeling with fast blue and immunohistochemistry. Immunoreactivity was found in 8.6% of labeled cell bodies. In colchicine‐treated ganglia, the proportion increased to 16.8%.Only small and intermediate‐sized perikarya showed somatostatin‐like immunoreactivity, indicating that this neuropeptide is synthesized predominantly in primary afferent units with unmyelinated sensory axons but may also be present in primary afferents with thinly myelinated sensory fibers. Colchicine treatment had no influence on the cell size distribution.Colocalization of somatostatin with substance P was determined by comparing the proportions of immunopositive dorsal root ganglion cells after incubation with antibodies against substance P or somatostatin or with a mixture of both. Substance P‐like immunoreactivity was found in 18.1% (untreated ganglia) and 19.6% (colchicine treated ganglia) of the labeled neurons. After incubation with a mixed antibody solution, 18.2% of joint afferents in untreated and 19.9% of the cells in colchicine‐treated ganglia were immunopositive. Comparing this result with the results obtained using somatostatin and substance P antibodies alone, one can calculate that both neuropeptides are colocalized in about 17% of the cat's knee joint afferents. About 3% of the neurons contain only substance P, whereas almost none of the neurons contain only somatostatin. Based on this fact, one can assume that both neuropeptides are coreleased in peripheral tissue as well as in the central nervous system. © 1995 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903540304

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

年代:1995

数据来源: WILEY

摘要:

AbstractFibroblast growth factor‐2 (FGF‐2; basic FGF) is widely distributed in the developing and adult brain and has numerous effects on cultured and lesioned neural cells. The physiological role of FGF‐2 in the unlesioned nervous system, however, is still not understood. We have studied the distribution of FGF‐2 in the developing, adult, and functionally impaired central auditory system of the rat using specific antibodies and peroxidase‐antiperoxidase immunocytochemistry. FGF‐2‐like immunoreactivity (FGF‐2‐IR) occurred in neuronal cell bodies and/or nerve fibers but was very rarely observed in glial cells. Several auditory brainstem nuclei, including the superior paraolivary nucleus, the medial superior olive, the lateral and ventral trapezoid nuclei, and the central nucleus, as well as the external cortex of the inferior colliculus, were entirely devoid of FGF‐2‐IR. In the dorsal cochlear nucleus, the lateral superior olive, and the nuclei of the lateral lemniscus, FGF‐2‐IR was not detectable in nerve cell bodies prior to adult age. Neurons in the medial geniculate body exhibited FGF‐2‐IR only transiently, from postnatal day (P) 5 until P16. Neurons in the medial nucleus of the trapezoid body were immunoreactive from P8 onwards. FGF‐2‐IR in anteroventral and posteroventral cochlear neurons disappeared at P14, i. e., at the onset of hearing, but immunoreactivity returned after P21. A transient expression of FGF‐2 around the time when hearing function commences was observed in the dorsal cortex of the inferior colliculus. Thus, regulation of neuronal FGF‐2‐IR in several, but not all, auditory, nuclei is related to the onset of hearing, in that IR disappears at that time or transiently appears. This suggests a causal link between the onset of hearing and FGF‐2 expression. In support of this notion, ototoxic treatment with gentamycin abolished FGF‐2‐IR in the P16 medial geniculate body but not in other auditory brainstem centers. Thus, FGF‐2 may be considered a regulator or indicator of the acquisition of functional activity and responsiveness to sensory stimuli in several areas

ISSN:0092-7317    

DOI:10.1002/cne.903540305

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

年代:1995

数据来源: WILEY

摘要:

AbstractLocal delivery of brain‐derived neurotrophic factor (BDNF) by genetically modified cells provides the unique opportunity to examine the effects of BDNF on adult dopaminergic and cholinergic neurons in vivo. Primary rat fibroblasts were genetically engineered to produce BDNF. Conditioned media from BDNF‐transduced fibroblasts supported embryonic chick dorsal root ganglion neurons as well as rat fetal mesencephalic neurons. BDNF‐transduced fibroblasts grafted to the rat brain survived and showed continued mRNA production for at least 2 weeks. The effects of BDNF‐transduced fibroblast grafts on the dopaminergic and cholinergic systems were then assessed. BDNF‐transduced fibroblasts grafted into the normal intact substantia nigra induced sprouting of tyrosine hydroxylase‐ and neurofilamentimmunoreactive fibers into the graft. Fibroblast grafts implanted into the normal intact striatum and midbrain as well as the 6‐hydroxydopamine‐lesioned brain did not induce sprouting of dopaminergic fibers; neither did they affect drug‐induced rotational behavior. BDNF‐transduced fibroblasts did, however, significantly increase the homovanillic acid/dopamine ratio when grafted into the normal midbrain. Following transection of the fimbriafornix, BDNF‐transduced fibroblasts grafted into the septum were unable to rescue the septal cholinergic population, as did nerve growth factor‐producing fibroblast grafts. Genetically modified fibroblast grafts may provide an effective, localized method of BDNF delivery in vivo to test biological effects of this factor on the central nervous system.

ISSN:0092-7317    

DOI:10.1002/cne.903540306

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe present study provides a description of the dendritic morphology and the dendritic domains of neurons in the lateral parabrachial nucleus (PB) of the rat. The cells were intracellularly stained in vitro with Lucifer yellow. A subpopulation of these cells was characterized beforehand as neurons projecting to the amygdaloid complex by retrograde transport with rhodamine beads.With respect to their dendritic arborization, different types of “spatially” organized PB neurons were discriminated. One major cell type in the external lateral PB (PBel) is characterized by long, elongated dendritic trees that are preferentially oriented parallel to the superior cerebellar peduncle. The majority of their dendrites appears to respect subnuclear boundaries, yet their distal dendrites often exceed the limits of the PBel to encroach upon adjacent subnuclei located dorsally and ventrolaterally to the PBel. Another prominent cell type in the PBel has fairly small and locally restricted dendritic trees that are also elongated, running with their main axis from ventrolateral to dorsomedial. The dendrites of the majority of these neurons apparently stay within the confines of the PBel. A distinct group of neurons is found in the ventral portion of the PBel. The majority of their dendrites is mediolaterally oriented and not confined to the PBelsubnucleus. In addition, we found a smaller number of neurons scattered within the lateral PB whose dendrites do not show a preferential orientation but travel across subnuclear boundaries into several different PB subnuclei.Our data show that the dendrites of a large proportion of neurons in the lateral PB either stay within the confines of a particular subnucleus or slightly extend across subnuclear limits. In any case, they appear to match with terminal territories of afferent axons and, thus, maintain the functional specificity of inputs by their relay through the PB. In contrast, PB neurons that extend their dendrites across subnuclear boundaries or known terminal territories are likely to receive inputs of different qualities from a variety of sources and therefore transmit a more general, integrated signal to the forebrain. © 1995 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903540307

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

年代:1995

数据来源: WILEY

摘要:

AbstractOdorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. Ca2+acceptors, such as calmodulin, may mediate between the change in intracellular calcium and the conductance mechanism underlying the initial electrical event. Ca2+acceptors also may participate in subsequent processing of olfactory information. The identification and characterization of these molecules, therefore, should provide important information about the complex signal transduction pathway involving calcium in olfaction as well as other sensory systems.The present study describes the distribution of six calcium‐binding proteins in the rat main olfactory epithelium during postnatal development to determine when different Ca2+acceptors can be detected and whether they segregate into different layers or p6 rtions of the epithelium. Calmodulin, calretinin, calbindin‐D28k, neurocalcin, and recoverin were detected immunohistochemically in olfactory receptors but not in basal cells. S‐100 immunoreactivity was restricted to glial cells primarily around the cribriform plate. During postnatal development (from P1 to P20), calmodulin, calretinin, calbindin‐D28k, and neurocalcin formed a gradient of immunoreactivity descending from the central to the lateral areas in the nasal cavity, whereas recoverin was expressed only in sporadic, mature receptors in the proximal region of the mucosa. At P20, the immunoreactivity pattern for each calcium‐binding protein was identical to the adult profile, indicating that the olfactory epithelium had reached maturity by this stage. Olfactory nerve fiber bundles displayed a differential staining pattern from P 1 until adulthood for calbindin‐D28k and calretinin (internal portions of bundles). Differential calmodulin immunoreactivity of olfactory nerves (large external portions of bundles) appeared at P10. The immunoreactivity of the nerve fiber bundles may reflect a further degree of organization relevant to odor discrimination. © 1995 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903540308

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe objectives of the present study were 1) to utilize Fos immunohistochemistry as a marker for neuronal activity in order to examine the population of neurons in the medulla that is engaged by activation of nociceptive peripheral afferents and 2) to determine whether catecholamine‐containing neurons in the medulla also express noxious heat‐evoked Fos‐like immunoreactivity. Noxious heating of the hindpaw evoked specific patterns of Fos‐like immunoreactivity in the medulla in regions known to be involved in both nociceptive processing and cardiovascular regulation. Noxious heating of the hindpaw significantly increased the mean number of neurons expressing Fos‐like immunoreactivity in the contralateral ventrolateral medulla. Increased numbers of Fos‐positive neurons also were observed in both the ipsilateral and the contralateral A1 catecholamine cell groups. Similarly, in the contralateral medullary dorsal reticular fields, noxious heating of the hindpaw significantly increased the mean number of neurons expressing Fos‐like immunoreactivity. In contrast, in the paramedian reticular nucleus, noxious heating of the hindpaw resulted in a significant decrease in the mean number of neurons expressing Fos‐like immunoreactivity. No significant differences in the mean numbers of neurons expressing Fos‐like immunoreactivity were noted in the A2, C1, or C2/C3 medullary catecholamine cell groups. These results suggest that noxious stimuli affect pools of neurons in the medulla with multiple physiological functions. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903540309

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn anamniote vertebrates the central region of the spinal cord has been implicated in its regeneration. This is a complex region and so as a first step in understanding its possible regenerative role we have examined the organization of the cells that contact the lumen of the spinal cord in two teleost fishes, eel and trout, using immunohistochemical procedures and light and electron microscopy.Cell bodies immunoreacting positively with antibodies for tyrosine hydroxylase and for dopamine were located at the ventral rim of the central canal, whereas cell bodies reacting for an antibody for gamma‐aminobutyric acid were more laterally located. None of the canal‐contacting cells were positively immunoreactive for choline acetyltransferase. All immunopositive cells have a similar morphology: the amphora‐shaped perikaryon is bipolar and has a single process that extends to the lumen of the canal, and another that branches and forms extensive lateral and ventral plexuses. Electron microscopic investigations of the ventral dopaminergic cells showed that the apical processes bear one or more cilia, which protrude into the canal lumen and which originate from within a superficial rosette of nonciliated processes. The ventral process was occasionally seen to form synapses; the cell body was also the target of synapses. © 1995 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903540310

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe development of A‐type horizontal cells (HC) was studied in the rabbit retina between embryonic day (E)24 and adulthood [the day of birth was called postnatal day (P)1 and corresponds to E31–32]. The cells were visualized by several methods 1) by immunolabeling with antibodies to neurofilament 70000 (NF‐70kD), 2) by immunolabeling with antibodies to a calcium binding protein (CaBP‐28kD), 3) by two different methods of silver impregnation, and (4) by histochemical demonstration of NADH‐diaphorase activity. Most methods labeled A‐type HC only in the dorsal retina; thus, our study is restricted to HC of this region. HC densities were determined at each developmental stage. The cells were drawn at scale, and size, quotient of symmetry, and topographical orientation of dendritic trees were studied by image analysis. The growth of HC dendritic fields was correlated with data on the postnatal local retinal expansion, which is known to be driven by the intraocular pressure (after cessation of retinal cell proliferation at P9). This expansion was evaluated in an earlier paper (Reichenbach et al. [1993]Vis. Neurosci. 10:479–498) by using local subpopulations of Müller cells as “markers” of distinct topographic regions of the retinae. After E24, when the final number of HC is established, we can discriminate three distinct developmental stages of A‐type HC. During the first stage, between E24 and E27, the young cells are often vertically oriented and may extend their first short dendrites within (the primordia of) both plexiform layers. The irregular HC mosaic at E24 shows a significant difference to all other stages. The second stage begins after birth when the dendritic trees of the cells are already restricted to the outer plexiform layer. Between P3 and P9, their dendritic trees enlarge more than the surrounding retinal tissue expands, and the coverage factor almost doubles from 2.5 to 4.4. The third stage occurs after P9 when the growth rate of dendritic tree areas corresponds to that of the local retinal tissue expansion caused by “passive stretching” of the postmitotic tissue, and the coverage factor remains constant. This is compatible with the view that mature synaptic connections of A‐type HC are mostly established after the first week of life and are then maintain

ISSN:0092-7317    

DOI:10.1002/cne.903540311

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

年代:1995

数据来源: WILEY