摘要:

AbstractThe prepacemaker nucleus (PPN) in the midbrain of gymnotiform electric fish projects to the pacemaker nucleus (PN) in the medulla and modulates its rhythmic discharges in the context of social electric communication. Anterograde labeling of PPN axons with HRP and ultrastructural studies of their terminations in the PN have shown that PPN neurons form synaptic contacts with both types of neurons in the PN, pacemaker cells, and relay cells.

ISSN:0092-7317    

DOI:10.1002/cne.902840202

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

年代:1989

数据来源: WILEY

摘要:

AbstractSeven Japanese monkeys (Macaca fuscata) were used to investigate the fiber pathways of the optic nerve. Optic nerve fibers and retinal ganglion cells were retrogradely labeled by iontophoretic injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) into electrophysiologically defined positions of the lateral geniculate nucleus (LGN). By gross anatomical observation, the optic nerve usually had one distinct bend, which flexed dorsally 3‐4 mm from the eyeball, and occasionally another ventrally directed bend was found just behind the eyeball. In the optic nerve head, fibers from the various retinal areas were arranged in a wedge according to the fiber trajectory on the retinal surface. For about a 3 mm distance from the disc, fibers rapidly spread out radially. Subsequently, rather than scattering dorsoventrally, they progressed to the chiasm with a gradual increase in the degree of mediolateral (nasotemporal) scatter. The degree of the scatter was different depending on the retinal site from which the axons originated. Fibers from the peripheral retina spread out widely for a few millimeters behind the eyeball. Thereafter the scatter was rather limited until the chiasm. On the other hand, the scatter of fibers from the foveal and parafoveal areas progressed gradually through the nerve. The present study also suggests that the difference in scatter depends on the types of cells of origin. Fibers from large ganglion cells displayed more extensive scatter than fibers from medium‐sized cells. In spite of the extensive scatter of fibers, two clear segregations were found; one was a dorsoventral segregation, which was displayed by both central and peripheral retinal fibers, and the other was a center‐peripheral segregation in which the fibers from the nasal central (papillomacular) retina were located almost exclusively in the central part of the optic nerve surrounded by peripheral retinal fibers. However, the temporal central retinal fibers were located in the lateral periphery of the nerve, and they overlapped significantly with fibers from the temporal peripheral retina. Furthermore, a broad intermingling was found between nasal and temporal peripheral retinal fibers owing to their mediolateral scatter. Thus, the present findings based on more precise anatomical techniques indicate that the classical notion of the retinal quadrant topography in the monkey optic nerve probably is suspect. In addition, the “rotation” of the fiber arrangement was not d

ISSN:0092-7317    

DOI:10.1002/cne.902840203

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

年代:1989

数据来源: WILEY

摘要:

AbstractAlthough it is well known that magnocellular cholinergic basal forebrain neurons are trophically responsive to nerve growth factor (NGF) and contain NGF receptors (NGFr), the exact distribution of forebrain NGFr‐immunoreactive neurons and the degree to which cholinergic neurons are colocalized with them have remained in question. In this study we employed a very sensitive double‐labelling method and examined in the same tissue section the distribution and cellular features of NGFr‐positive and choline acetyltransferase (ChAT)‐immunolabelled neurons within the rat basal forebrain. Throughout this region the majority of magnocellular basal forebrain neurons were immunoreactive for both NGFr and ChAT. However, a small percentage of neurons in the ventral portion of the vertical limb of the diagonal band of Broca were immunoreactive only for NGFr, whereas a larger population of magnocellular neurons in the substantia innominata exhibited only ChAT immunoreactivity. No NGFr‐immunoreactive cells were found associated with ChAT‐positive neurons in the striatum, neocortex, or hippocampus, and no single‐labelled NGFr‐immunoreactive neurons were found outside the basal forebrain area, except for a large number of positive‐labelled cells along the ventricular walls of the third ventricle.In addition to its function in maintaining the normal integrity of the basal forebrain and cholinergic, peripheral sympathetic, and neural‐crest‐derived sensory neurons, NGF may also have a role in the growth of these neurons after damage to the nervous system. To examine this postulate the hippocampus was denervated of its septal input and examined 8 weeks later. Two populations of neurons were found to have undergone collateral sprouting—namely, the midline magnocellular cholinergic neurons of the dorsal hippocampus and the sympathetic noradrenergic neurons of the superior cervical ganglion. Both of these neuronal populations also stained strongly for NGFr. In contrast, the small intrinsic cholinergic neurons of the hippocampus exhibited neither sprouting response nor staining for NGFr. In view of these results, we suggest that the differing sprouting responses demonstrated by these three neuronal populations may be due to their responsiveness to NGF, as indicated by the presence or a

ISSN:0092-7317    

DOI:10.1002/cne.902840204

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe fine structure of the afferent synapses on the Mauthner cell of larvalXenopus laevishas been studied as a first step toward comparing the fine structure of the afferent synaptic apparatus before and after metamorphosis. There are various types of afferent endings on this cell, some of which are confined to specific cellular regions, while others are distributed over most of the large surface of the neuron. Four different main types of endings have been observed: club endings, round‐vesicle end bulbs, flattened‐vesicle end bulbs and spiral fibers endings. While the myelinated club endings and the spiral fibers endings are located at the distal end of the lateral dendrite and in the axon cap, respectively, the end bulbs are widely distributed over the whole cell. A further type of ending has been observed, although rarely, on the Mauthner cell soma and dendrites: end bulbs characterized by an unusually dense presynaptic substance. Results obtained in the present research suggest that, as in fish, different endings on the anuran Mauthner neuron correspond to different synaptic inputs. The possible origin of some of these inputs is discus

ISSN:0092-7317    

DOI:10.1002/cne.902840205

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

年代:1989

数据来源: WILEY

摘要:

AbstractNewborn animals recover from neurological injury to a greater extent than adults in spite of the greater vulnerability of developing neurons to retrograde or transneuronal degeneration (Kennard, '42; Goldman, '74; Prendergast and Stelzner, '76; Bregman and Goldberger, '82, '83). The cellular mechanisms underlying this “infant lesion effect” are incompletely understood (Bregman and Goldberger, '82). The dorsal root ganglion (DRG) is an excellent model in which to compare the developing and adult nervous system with respect to the effects of axotomy on cell survival and cellular function. We studied the survival of L5 DRG neurons after section‐ligation of the sciatic nerve of adult and neonatal rats and used qualitative and quantitative immunocytochemical methods to examine changes in intraspinal substance P immunoreactivity (SPIR). Retrograde transport of wheatgerm agglutinin‐horseradish (WGA‐HRP) peroxidase applied to the sciatic nerve of adult or neonatal rats demonstrated that 70% of the neurons in the normal L5 DRG project into the sciatic nerve at the site of transection. In adults 20% of all L5 DRG neurons died between 10 and 60 days postoperative; in newborns 50% of the neurons died between 5 and 10 days. These results indicate that 30% of axotomized neurons in adults and 75% in neonates die after sciatic nerve section and that neuron loss is both more rapid and more extensive in neonates. No cell death was observed in the L5 DRG of neonates after dorsal rhizotomy, thus suggesting that at this stage of development the survival of DRG neurons depends on the peripheral but not the central process.SPIR in laminae I and II of both adult and newborn operates decreased and then recovered, but the time course and extent of the recovery differ. In adults SPIR was depleted in the medial portion of the L5 segment ipsilateral to surgery by 10 days postoperative and remained depleted for at least 2 months. By 1 year partial recovery occurred, but remained incomplete even at the longest survival time studied (15 months). SPIR, which is present in the dorsal horn at birth, was diminished in ipsilateral laminae I and II by 4 days after nerve section on the day of birth. Between 30 days and 60 days, the density of SPIR in the dorsal horn ipsilateral to surgery became virtually indistinguishable from that on the contralateral, intact side, suggesting a more rapid and complete recovery than in adults. The area occupied by SPIR staining remained smaller than that seen on the unoperated side, thus suggesting incomplete or abnormal development of the terminal field in the deafferented dorsal horn.Recutting the sciatic nerve after SPIR recovery depleted the recovered SPIR in both adults and neonates, indicating that in both groups recovery was largely due to DRG neurons that had survived initial transection of their axons. The results indicate that in developing animals 25% of the normal numbers of DRG neurons that survive sciatic nerve section can restore the normal pattern and density of the substance P (SP)projection to the dorsal horn. Immature DRG neurons, therefore, appear to be more likely to die after axotomy, yet those that survive are capable of robust anatomical and biochemical reorganization in comparison to axotomized mature

ISSN:0092-7317    

DOI:10.1002/cne.902840206

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe present work seeks to determine if axons to an amphibian muscle are segregated in nerve trunks between the spinal cord and muscle according to their primary nerve destination or their topographical projection in the muscle. The distribution of axons to different compartments and subcompartments of the amphibian (Bufo marinus) glutaeus muscle has been determined in transverse sections of spinal and limb nerves after retrogradely labelling the axons with horseradish peroxidase. Glutaeus axons were dispersed widely through spinal nerves 8 and 9 but loosely gathered together in one quadrant of the sciatic nerve after passing through the lumbar plexus. Glutaeus axons became tightly clustered to the exclusion of other axons along the length of the triceps femoris nerve after it divides from the sciatic nerve. Furthermore, axons destined for one of the two glutaeus primary nerve branches segregate from those of the other branch at the level of the triceps femoris nerve before the glutaeus nerve forms. On the other hand, motoneurones that subserve a primary branch are not segregated, but are found throughout the rostrocaudal extent of the glutaeus motoneurone pool.Injection of horseradish peroxidase under the epimysium of either the ventral or the dorsal surfaces of the glutaeus muscle labelled motoneurones preferentially in either the rostral or caudal part of the motoneurone pool, respectively. This confirms studies that have shown a topographical projection from the spinal motoneurone pool onto the glutaeus muscle. However, there was no segregation of dorsally projecting axons in the glutaeus and primary nerve branches. Thus, glutaeus axons segregate according to their muscle compartmental projections well before entering the muscle, but they show no organization in nerves with respect to their topographical projections within a compartment.

ISSN:0092-7317    

DOI:10.1002/cne.902840207

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

年代:1989

数据来源: WILEY

摘要:

AbstractVocalization, the nonverbal production of sound, can be elicited in many vertebrates by stimulation in several regions of the limbic system but most easily in the caudal periaqueductal gray (PAG). This study shows that a specific cell group in the lateral part of the caudal PAG and in the tegmentum just lateral to it projects bilaterally to the nucleus retroambiguus (NRA) in the caudal medulla oblongata. Similar but much weaker projections are derived from the dorsal PAG. Neurons in the NRA in turn project via a contralateral pathway through the ventral funiculus of the spinal cord to motoneuronal cell groups, innervating intercostal and abdominal muscles. These projections are stronger on the contralateral side, although at lower thoracic and upper lumbar levels, many fibers recross to terminate in the ipsilateral motoneuronal cell groups. In the brainstem NRA neurons project to the motoneuronal cell groups innervating mouth‐opening and perioral muscles as well as to motoneurons innervating the pharynx, soft palate, and tongue, and probably to the larynx. All these muscles are active in vocalization. The present anatomical results, combined with the physiological results of others, indicate that the projections from PAG via NRA to vocalization motoneurons from the final common pathway in vocalization. The role of this pathway in the total framework of emotional behavior is discusse

ISSN:0092-7317    

DOI:10.1002/cne.902840208

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe blind mole ratSpalax ehrenbergiis a subterranean rodent that shows striking behavioral, structural, and physiological adaptations to fossorial life including highly degenerated eyes and optic nerves and a behavioral audiogram that indicates high specialization for low‐frequency hearing. A 2‐deoxyglucose functional mapping of acoustically activated structures, in conjunction with Nissl/Klüver‐Barrera‐stained material, revealed a typical mammalian auditory pathway with some indications for specialized low‐frequency hearing such as a poorly differentiated lateral nucleus and a well‐developed medial nucleus in the superior olive complex. The most striking finding was a marked 2‐deoxyglucose labeling of the dorsal lateral geniculate body and of cortical regions that correspond to visual areas in sighted rodents. The results render the blind mole rat a good model system for studying natural neural plasticity and intermodal compensation. In this report, we confine ourselves to the subcortical levels. The cortical level will be dealt comprehensively in a f

ISSN:0092-7317    

DOI:10.1002/cne.902840209

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

年代:1989

数据来源: WILEY

摘要:

AbstractA new and remarkable type of amacrine cell has been identified in the primate retina. Application of the vital dye acridine orange to macaque retinas maintained in vitro produced a stable fluorescence in the somata of apparently all retinal neurons in both the inner nuclear and ganglion cell layers. Large somata (∼15‐20 μm diam) were also consistently observed in the approximate center of the inner plexiform layer (IPL). Intracellular injections of horseradish peroxidase (HRP) made under direct microscopic control showed that the cells in the middle of the IPL constitute a single, morphologically distinct amacrine cell subpopulation. An unusual and characteristic feature of this cell type is the presence of multiple axons that arise from the dendritic tree and project beyond it to form a second, morphologically distinct arborization within the IPL; these cells have thus been referred to as axon‐bearing amacrine cells.The dendritic tree of the axon‐bearing amacrine cell is highly branched (∼40‐50 terminal dendrites) and broadly stratified, spanning the central 50% of the IPL so that the soma is situated between the outermost and innermost branches. Dendritic field size increases from ∼200 μm in diameter within 2 mm of the fovea to ∼500 μm in the retinal periphery. HRP injections of groups of neighboring cells revealed a regular intercell spacing (∼200‐300 μm in the retinal periphery), suggesting that dendritic territories uniformly cover the retina.One to four axons originate from the proximal dendrites as thin (<0.5 μm). smooth processes. The axons increase in diameter (∼1‐2 μm) as they course beyond the dendritic field and bifurcate once or twice into secondary branches. These branches give rise to a number of thin, bouton‐bearing collaterals that extend radially from the dendritic tree for1‐3 mm without much further branching. The result is a sparsely branched and widely spreading axonal tree that concentrically surrounds the smaller, more highly branched dendritic tree. The axonal tree is narrowly stratified over the central 0‐20% of the IPL; it is approximately ten times the diameter of the dendritic tree, resulting in a 100 times greater coverage factor.The clear division of an amacrine cell's processes into distinct dendritic and axonal components has recently been observed in other, morphologically distinct amacrine cell types of the cat and monkey retina and therefore represents a property common to a number of functionally distinct cell types. It is hypothesized that the axon‐bearing amacrine cells, like classical neurons, use action potentials to transmit signals over long distances in the IPL and, on the basis of previous immunohistochemical results, contain

ISSN:0092-7317    

DOI:10.1002/cne.902840210

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe distribution of somatostatin‐like immunoreactivity was studied in the macaque monkey (Macaca fascicularis) by using primary antisera that recognize somatostatin‐28 (S309) or somatostatin‐281‐12(S320). Somatostatin‐immunoreactive neuronal cell bodies were observed in all amygdaloid nuclei and cortical regions. The density of labeled cells varied substantially, however, both within and across the various amygdaloid subdivisions. The highest densities of labeled neurons were observed in layer III of the periamygdaloid cortex, in layers II and III of the medial nucleus, in the magnocellular division of the accessory basal nucleus, and in the medial portion of the lateral nucleus. Many labeled cells were also consistently observed in the caudoventral portion of the lateral division of the central nucleus. Labeled cells were heterogeneous in size and shape ranging from small and spherical to large and multipolar. The density of somatostatin‐immunoreactive fibers also varied greatly from region to region and was often inversely related to the density of immunoreactive cells. Highest densities of immunoreactive fibers were observed in the periamygdaloid cortex, medial nucleus, parvicellular division of the accessory basal nucleus, paralaminar nucleus, ventrolateral portion of the lateral nucleus, parvicellular division of the basal nucleus, and the lateral division of the central nucleus. Fibers and terminals in the central nucleus had a coarsely varicose appearance and this pattern of staining was continuous along the trajectory of the central nucleus projection to the bed nucleus of the stria terminalis. The large, immunoreactive varicosities located in this area often appeared to outline dendritic or vascular profiles within the substantia innominata. The lowest levels of somatostatin‐immunoreactive fibers were observed in the magnocellular division of the basal nucleus and in the ventromedial portion of the accessory

ISSN:0092-7317    

DOI:10.1002/cne.902840211

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

年代:1989

数据来源: WILEY