摘要:

AbstractC‐fosis a proto‐oncogene that is expressed within some neurons following depolarization. The protein product,c‐fosprotein, can be identified by immunohistochemical techniques. Therefore,c‐fosexpression might be used as a marker for neuronal activity throughout the neuraxis following peripheral stimulation. This study has analyzed patterns ofc‐fosexpression in both control and anesthetized animals and in anesthetized rats subjected to various forms of peripheral stimulation. Labeled cells were counted in the spinal cord, brainstem, hypothalamus, and thalamus. Littlec‐fosimmunoreactivity was found in control animals. Prolonged inhalational anesthesia increased the number of labeled cells at several brainstem sites. Noxious stimulation of anesthetized rats inducedc‐foswithin the neuraxis in patterns consistent with data obtained from electrophysiological studies and in additional locations for which few direct electrophysiological data are available, such as the ventrolateral medulla, the posterior hypothalamic nucleus, and the reuniens and paraventricular thalamic nuclei. Gentle mechanical stimulation was ineffective in inducingc‐fos‐like protein. The data suggest thatc‐foscan be used as a transynaptic marker for neuronal activity following noxious stimulation. However,c‐fosis expressed only in some kinds of neurons following peripheral stimulation, and it therefore may be an incomplete marker for nociresponsive activity. In addition, at least a few neurons expressc‐fosprotein in the absence of noxious stimulation. Experiments analyzingc‐fosexpression must be designed with care, as both extraneous stimuli and anesthetic de

ISSN:0092-7317    

DOI:10.1002/cne.902960402

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe projection from the dorsal lateral geniculate complex to the visual cortex inPseudemysandChrysemysturtles was examined by using the anterograde transport of horseradish peroxidase ((HRP)) in vitro and the retrograde transport of HRP in vivo.In vitro HRP injections into the lateral forebrain bundle were used to fill geniculocortical axons anterogradely, which were then analyzed in cortical wholemount preparations. Geniculocortical axons gain access to the visual cortex along its entire rostral‐caudal extent. They course in slightly curved trajectories for up to 2 mm from the lateral edge of the cortex through both the lateral (or pallial thickening) and medial parts of Desan's cortical area D2. Single axons are of fine caliber. They tend to cross each other and sometimes branch in the pallial thickening, but are generally unbranched in the medial part of D2. They bear small, fusiform varicosities at irregular intervals along their lengths. Although axons show small variations in the number of varicosities per 100 μm segment, no consistent variation in varicosity number as a function of distance could be detected. These results indicate that geniculocortical axons project to the visual cortex in an orderly pattern.The retrograde transport experiments provide some clue as to the significance of this pattern. Small, ionotophoretic injections of HRP in the visual cortex retrogradely labeled neurons in the dorsal lateral geniculate complex. Injections in the rostral visual cortex retrogradely labeled neurons in the caudal pole of the geniculate complex. Injections at progressively more caudal loci within the visual cortex labeled neurons at progressively more rostral loci within the geniculate complex. Thus, there is a representation of the rostral‐caudal axis of the geniculate complex along the caudal‐rostral axis of the visual cortex. Consistent with the anterograde transport experiments that showed individual geniculocortical axons coursing through both lateral and medial parts of the visual cortex, HRP injections restricted to the medial edge of the visual cortex retrogradely labeled neurons along the entire dorsal‐ventral axis of the geniculate complex at the appropriate rostral‐caudal position.The neurophysiological studies of Mazurskaya ('72:J. Evol. Biochem. Physiol. 8:550–555; '74:Neurosci. Behav. Physiol 7:311–318) indicate that neurons in the turtle visual cortex respond to a small, moving stimulus anywhere in visual space, implying a convergence of inputs from all points in visual space somewhere along the retinogeniculocortical pathway. The experiments reported here suggest a convergence in the geniculocortical projections of information along the vertical meridians, or azimuth lines, of visual space onto neurons lying along lateral to medial transects through the visual cortex. The cortex can, then, be viewed as a series of isoazimuth lamellae arranged in an orderly array along the rostral‐caudal axis of the hemisphere. This concept partially explains how the wide receptive fields described by Mazurskaya are elaborated, but does not account for the ability of a cortical neuron to respond to stimuli located at different horizonta

ISSN:0092-7317    

DOI:10.1002/cne.902960403

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe spatial pattern of projections within turtle visual cortex was studied by using focal injections of horseradish peroxidase into visual cortex in an in vitro wholebrain preparation. Injections anterogradely filled the axons of many layer 2 neurons, which could be followed for 200–500 μm from the injection sites. Axons were typically unbranched, relatively straight, and bore small varicosities at irregular intervals. They radiated from the injection sites in all directions, but showed some preference toward orientations along the lateral‐medial axis of the cortex. Earlier work ((Mulligan and Ulinski,'90)) had demonstrated that turtle visual cortex contains a series of isoazimuth lamellae, each representing an individual azimuth of visual space and oriented perpendicular to the rostral‐caudal axis of the cortex. The present study provides evidence for intrinsic projections both along isoazimuth lamellae and between adjacent lamellae. These projections may play roles in the elaboration of wide receptive fields of cortical n

ISSN:0092-7317    

DOI:10.1002/cne.902960404

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe somata of corticospinal neurons were labeled with horseradish peroxidase that had been applied to a hemisection of the spinal cord at the C1‐C2 junction in 22 species of mammals. After tetramethylbenzidine processing, with and without counterstaining with cresyl violet or neutral red, the labeled cells in systematic sets of sections throughout the cerebral cortex were plotted and counted. Several morphological features of the corticospinal cells were examined including their cell type, number, density, concentration, laminar distribution, and their distribution across the cortical surface.The results show that the labeled corticospinal neurons were invariably layer V pyramidal cells. However, in many mammals they were found to be stacked one above the other within layer V, sometimes many neurons deep. Despite the concentration of corticospinal neurons within layer V, many unlabeled neurons were also present within the layer throughout the extent of the labeled region.The results also indicate that at least two spatially distinct regions of neocortex originate corticospinal fibers in each of the animals in the sample. In addition to these two regions, a third segregated region is present in the cortex of primates and an apparently different third region is present in the cortex of Glires ((Rodentia and Lagomorpha)). The third region of corticospinal cortex in primates is located on the lateral surface of the cortex in prosimians and New World monkeys and is buried in the caudal bank of the inferior arcuate sulcus in Old World monkeys.The results also show a predominantly contralateral corticospinal tract in all but 4 of the 22 mammals in the sample. Although these 4 mammals are each members of the order Insectivora, a less modified member of the same order possessed the predominantly contralateral projection of most mammals, hence denying the notion that a predominantly ipsilateral tract is a characteristic of Insectivor

ISSN:0092-7317    

DOI:10.1002/cne.902960405

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn the companion paper to this one ((Nudo and Masterton:J. Comp. Neurol. 296:559–583. '90)), we have presented data indicating that in each of 22 mammals, there are either 2 or 3 separate regions of neocortex contributing corticospinal fibers. In this paper, we describe the variation in the absolute size of these cortical regions, the total amount of neocortex contributing corticospinal fibers ((CST cortex)), and the total amount of neocortex ((total cortex)) in each of the animals. We then use strict statistical tests to examine the relationships between these measures and several other quantitative measures or descriptions of the animals' size, ancestral heritage, motor prowess, and ecological adaptation.The results show that the absolute amout of CST cortex is more closely related to the total amount of neocortex than to any other quantitative measure available. The further variation—that is, the variation in the amount of CST cortex relative to total neocortex—appears to have been random over the inferred ancestral lineages of most animals in the sample, but seems to have been almost absent along the anthropoid lineage. Because this constancy in the relative amount of CST cortex over a very long period of anthropoid ancestry is apparently unusual if not unique among mammals, it may contain a clue to the special role of the corticospinal tract among primates.Finally, the distribution of the CST among the 3 cortical regions in primates was found to be more closely related to their particular mode of ecological adaptation than to their particular combination of digital dexterity and hand‐eye coord

ISSN:0092-7317    

DOI:10.1002/cne.902960406

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

年代:1990

数据来源: WILEY

摘要:

AbstractIntracellular recordings were obtained from pyramidal neurons in layer 5 of rat somatosensory and visual cortical slices maintained in vitro. When directly depolarized, one subclass of pyramidal neurons had the capacity to generate intrinsic burst discharges and another generated regular trains of single spikes. Burst responses were triggered in an all‐or‐none manner from depolarizing afterpotentials in most bursting neurons. Regular spiking cells responded to electrical stimulation of ascending afferents with a typical EPSP‐IPSP sequence, whereas IPSPs were hard to detect in bursting cells. Orthodromic activation of the latter evoked a prominent voltage‐dependent depolarization that could trigger a burst response. Intracellularly labelled bursting and regular spiking cells were located in layer 5b, but had distinctly different morphologies. Bursting neurons had a large pyramidal soma, a gradually emerging apical dendrite, and an extensile apical and basal dendritic tree. Their axonal collateral arborization was predominantly limited to layers 5/6. In contrast, regular spiking cells had a more rounded soma with abruptly emerging apical dendrite, a smaller dendritic arborization, and 2 to 8 ascending axonal collaterals that arborized widely in the supragranular layers. Both bursting and regular spiking cells had main axons that entered the subcortical white matter.These data show that some subgroups of pyramidal neurons within the deeper parts of layer 5 of rat cortex are morphologically and physiologically distinct and have different intracortical connections. Bursting cells presumably function to amplify and synchronize cortical outputs, whereas regular spiking output neurons provide excitatory feedback to neurons at all cortical levels and receive a more effective orthodromic inhibitory input. These data support the hypothesis that differences in gross neuronal structure, perhaps even the subtle differences that distinguish subclasses of neurons in a given lamina, are predictive of underlying differences in the type and distribution of ion channels in the nerve cell membrane and connections of cells within the cortical

ISSN:0092-7317    

DOI:10.1002/cne.902960407

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe cutaneus trunci muscle reflex in guinea pigs was studied with a combination of video analysis, electromyography, lesioning, and light microscopy. The muscle forms a bilateral, subdermal sheet over much of the trunk. Local contractions of the dorsal part of the muscle are produced in response to brief tactile or electrical stimulation of the skin and consist of a twitch centered 1–2 cm rostral of the stimulus site. The reflex receptive field covers most of the thoracic and lumbar dorsal surface. The sensory information is carried via segmental dorsal cutaneous nerves. Receptive fields of adjacent nerves overlap and form rectangular areas perpendicular to the midline, at thoracic levels. Motor innervation projects through the lateral thoracic nerves of the brachial plexus. The motoneurons are located near the cervical thoracic junction ((C7‐T1)). Lesions of the lower thoracic cord indicate that ascending sensory information is carried to the motor nuclei via the ventral half of the lateral funiculus. This pathway conveys information primarily from ipsilateral skin. There is a weaker input from contralateral skin, crossing at segmental levels. Electromyographic responses to brief electrical stimulation of lower thoracic skin occur usually as 10–12 msec bursts at latencies of 10–20 msec, and do not readily habituate or fatigue at stimulus frequencies below 10 Hz. The reflex persists under light pentobarbital anesthesia. This combination of characteristics makes the reflex useful for a variety of physiological and pathophysiological

ISSN:0092-7317    

DOI:10.1002/cne.902960408

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

年代:1990

数据来源: WILEY

摘要:

AbstractRight lateral hemisection of the lower thoracic spinal cord was performed in 216 adult guinea pigs. Animals that proved suitable for the study were divided into one control and two experimental groups. Experimental animals were implanted with intraperitoneal stimulators delivering regulated current of 35 or 50 μA through electrodes placed 1 cm rostral and caudal of the hemisection. The cathode was cranial to the lesion in one group (n= 67) and caudal in the other (n= 33). Control animals (n= 62) were implanted with sham stimulators and electrodes delivering no current. The functional status of the animals was measured by tactile stimulation of the back skin to elicit the cutaneus trunci muscle reflex, and by the vestibulospinal free‐fall response. The cutaneous response ipsilateral and caudal to the lesion was lost following hemisection and did not recover in any of the control animals or in animals with cathode caudal to the lesion. Recovery of the response was found in 9 of 67 animals in the cathode rostral group, between 56 and 139 days after injury. Toe spreading recovered spontaneously in 80–90% of animals in all groups. Of the possible mechanisms of skin reflex recovery, most current evidence points to regrowth of ascending nerve fibers in the lateral funiculus of the spinal cord local to the le

ISSN:0092-7317    

DOI:10.1002/cne.902960409

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new esterification‐silver approach to the directed staining of the dendritic trees of traumatized neurons is described. Stained neurons compare favorably to those labeled with silver chromate Golgi impregnations in the visualization of dendritic arbors. Cells in all parts of the brain, including the hypothalamus, hippocampus, cerebral cortex, cerebellum, striatum, spinal cord, thalamus, and olfactory bulb, can be detected after focal trauma to that region.Selection of neurons to be stained is made by increasing their affinity for silver with many different types of directed neuronal trauma, including micropipette wounds, pressure, surgical incision, chemical cytotoxicity, and impact trauma. Trauma to one area of the brain results in dendritic arbors staining only in the injured area; other areas of the brain are free of dendritic staining. Injury can be produced either in vivo or in vitro. In vitro injury to neurons allows a high degree of localization and facilitates the analysis of neuronal response to trauma in the absence of complicating factors such as blood flow and secondary injury.The selective affinity for silver staining in this approach is increased very rapidly, allowing detection of traumatized cells fixed minutes after injury. Brains of all mammals used appear to stain similarly, including the rat, mouse, pig, and human. Axons, although labeled less frequently than dendritic arbors, are induced to stain just as rapidly as dendrites.The ability to visualize a large part of the dendritic tree after trauma allows the segregation of neuronal subtypes on the basis of their differential response to injury. Subpopulations of cells in the same area of the brain appear to respond differently to trauma. Differential response of neurons to trauma can easily be detected. For instance, slight variations in trauma can be used to label selectively the major subpopulations of neurons in the hippocampus, including pyramidal cells, interneurons near the pyramidal cell layer, or granule cells. Similarly, neurons of the hypothalamic paraventricular and arcuate nuclei respond to compression trauma much more dramatically than other cell types in the same region of the hypothalamus. Hypothalamic neurons were studied extensively, particularly in regions that are difficult to routinely stain with Golgi impregnations, including the arcuate, paraventricular, supraoptic, and suprachiasmatic nuclei. Trauma to these areas was made in vitro after removal of the brain from the skull, allowing easy access to the ventral surface of the brain.The approach described here is useful for studying dendritic arbors throughout the nervous system, for addressing a number of questions relating to early cell injury and for detecting which neurons have been damaged in different models of neuronal function on the basis of selective cellular damage. The cellular basis for the specific labeling is common to a wide variety of neuronal insults, suggesting a commonality of mechanism for neuronal response to injury. We postulate that cytoskeletal changes induced by injury may be a cellular substrate for the esterification‐related silver label

ISSN:0092-7317    

DOI:10.1002/cne.902960410

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

年代:1990

数据来源: WILEY

摘要:

AbstractAfter spinal cord injury, endogenous peroxidatic‐like activity develops along the axis of the cord. At 2 weeks postinjury, this activity appears in cells whose processes are intimately associated with microvessels. The objectives of this study were to further characterize this response and to identify the cellular localization of endogenous peroxidatic‐like activity.After traumatic injury to the rat spinal cord, adjacent sections of spinal cord were processed in medium to visualize antiglial fibrillary acidic protein, endogenous peroxidatic activity, or cytochrome oxidase activity. In addition, certain sections, stained for endogenous peroxidatic‐like activity, were prepared for electron microscopy. To identify the nature of the activity, some sections were exposed to an incubation medium that included inhibitors of either catalase or heme protein activity.The distribution of prominent glial fibrillary acidic protein immunoreactivity in the dorsal columns corresponded to that of marked staining for endogenous peroxidatic‐like activity and cytochrome oxidase. At the ultrastructural level, endogenous peroxidatic‐like activity was identified in the cytoplasmic compartment of the astrocyte. This activity was abolished when potassium cyanide (an inhibitor of heme protein) was added to the incubation medium.Spinal cord injury elicited a pronounced cellular response along the axis of the cord that was characterized by enhanced staining for antiglial fibrillary acidic protein, cytochrome oxidase activity, and endogenous peroxidatic‐like activity. It is not clear whether pronounced cytochrome oxidase activity corresponded to astrocytes that also expressed prominent endogenous peroxidatic‐like activity. However, according to both light and ultrastructural findings, endogenous peroxidatic‐like activity was prominently associated with the astrocytic cytoplasm. The biochemical nature of the peroxidatic activity is unknown, but these results suggest that it is related to a heme‐c

ISSN:0092-7317    

DOI:10.1002/cne.902960411

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

年代:1990

数据来源: WILEY