摘要:

AbstractA population of cortical neurons contains the opioid peptide dynorphin; the laminar distribution of these neurons in the adult cerebral cortex and their patterns of development are not well known. We have utilized in situ hybridization techniques to localize prodynorphin mRNA‐containing neurons. Rats aged from embryonic day (E) 15 through postnatal day (P) 90 were used. Prenatal animals did not show any labeling in the cerebral cortex. By P4, prodynorphin was expressed in a small number of cortical neurons for the first time. The autoradiographic signal was restricted to perikarya. In the frontoparietal cortex, labeled neurons first appeared in layer V and the upper part of layer VI. Subsequently, from P11 onward, the band expanded in an “inside‐out” sequence to include layers IV through II. In the posterior cingulate cortex and in the insular and perirhinal cortices, prodinorphin mRNA containing‐neurons were located preferentially in layer V. In all cortical areas analyzed, a progressive increase in the packing density of neurons expressing prodynorphin mRNA was observed until P14; it decreased slightly t

ISSN:0092-7317    

DOI:10.1002/cne.903000302

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe intraocular projection of the cat pterygopalatine (sphenopalatine) ganglion was examined by using retrograde axoplasmic transport techniques in order to investigate the possibility of the involvement of the facial nerve in ocular parasympathetic innervation. Following an injection of horseradish peroxidase (HRP) or wheat germ agglutinin‐HRP into the eye, retrogradely labeled cells were observed in the ipsilateral pterygopalatine ganglion, principally in the caudal part. By dissection of silver‐impregnated, acetylcholinesterase‐ and cholinesterase‐stained orbital preparations, it was determined that two different nerve pathways link the pterygopalatine ganglion and the eye. One took a retrograde course to join the retro‐orbital plexus and then traveled forward accompanying the ciliary artery, the long ciliary nerve, the short ciliary nerve, and/or the optic nerve sheath. The other entered the orbit directly, fused with the ethmoidal nerve or the infratrochlear nerve in a retrograde fashion, and then turned forward along the long ciliary nerve to enter the eye. All these nerves arose from the caudal part of the ganglion. These results are discussed in relation to recent biochemical and histochemical data demonstrating the involvement of the facial nerve in the control of ocular blood flow and intraocular

ISSN:0092-7317    

DOI:10.1002/cne.903000303

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractVarious populations of retinal and brain neurons display different degrees of sensitivity to the toxic effects of excitatory amino acid agonists. To further define this phenomenon, the effects of intravitreal injections of kainic acid, N‐methyl‐D‐aspartate (NMDA), quinolinic acid, and ibotenic acid on NADPH‐diaphorase (NADPHd) reactive cells of the rabbit retina were examined. In normal rabbit retinas, NADPHd histochemistry selectively stains two populations of cells at the inner margin of the inner plexiform layer: large densely staining (Type I) and more numerous, smaller and lightly staining (Type II) cells. All of the toxins studied destroy both cell types at high doses. Kainic acid, however, at low doses destroys Type I cells but selectively spares Type II cells. NMDA injections result in a more complex and less consistent pattern of cell loss; overall, the Type I cells are perhaps slightly resistant to this agent as compared to Type II cells. The Type I neurons in this respect are analogous to striatal NADPHd‐reactive neurons, which have, at most, a slight relative resistance to NMDA neurotoxicity.The excitotoxin lesions reduce the complexity of the fiber plexus in the inner plexiform layer and thereby reveal anatomic features of surviving NADPHd reactive neurons that are not apparent in normal retinas. In particular, each Type I cell gives off several fine, straight, beaded processes that emanate from dendrites and run several millimeters in the inner plexiform layer. These processes are presumably involved in long‐distance interactions within the retina. Excitotoxin lesions may provide a generally useful anatomic tool for elucidating morphological features of neurons stained by histochemical and immunohistochemi

ISSN:0092-7317    

DOI:10.1002/cne.903000304

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractIn mammalian visual pathways, information is carried in parallel channels from the retina through the visual thalamus to visual cortex. The cat's visual pathway comprises at least three major channels that begin with the X, Y, and W ganglion cells in the retina. In the dorsal lateral geniculate nucleus (LGN) of the thalamus, neurons in the X, Y, and W channels receive input from their retinal counterparts and can be discriminated from one another on the basis of their anatomical and physiological properties.The search for molecular properties that might correlate with anatomically or physiologically defined classes of neuron has been a major area of research in recent years. Monoclonal antibody Cat‐301 recognizes a neuronal surface‐associated proteoglycan in many areas of the mammalian central nervous system. In the cat LGN Cat‐301 immunoreactivity is restricted to a subset of neurons. We show here that the distribution, size, morphology, and cortical projection pattern of Cat‐301‐positive LGN neurons match those previously described for Y‐cells. Taken together with our previous studies of the development of immunoreactivity and the sensitivity of Cat‐301 staining to visual deprivation, these studies suggest that Cat‐301 specifically recognizes Y‐cells in the cat‐LGN. These results indicate that neurons within a physiologically and anatomically denned cell class share a molecular property. They further suggest that differences in molecular traits may reflect, and possibly subserve, differences in anatomical and physiologi

ISSN:0092-7317    

DOI:10.1002/cne.903000305

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractAnatomical and electrophysiological experiments were performed on cats to investigate the pattern of divergence and convergence in the association projections from the first (SI) to the second (SII) somatic sensory cortex and to ascertain whether diverging and converging fibre components from SI have receptive fields (RFs) matching those of target neurons in SII. In the first group of six cats, a single deposit of horseradish peroxidase (HRP) was iontophoretically placed (2–4 μAfor 20 minutes) into an electrophysiologically identified site of the SII map: the digit (3 cats), forepaw (2 cats), and arm (1 cat) zones. The forelimb representation in ipsilateral SI was subsequently explored with microelectrodes and RFs from small clusters of neurons systematically mapped. Planar maps of this area were reconstructed with the aid of a computer from serial sections, to correlate on the tangential plane the topographical distribution of retrogradely labelled association neurons with the physiological map of the forelimb. Since diverging projections were observed from a zone of SI to multiple zones of SII, double‐labelling experiments were carried out in a second group of three cats, in which two retrograde fluorescent dyes (diamidino yellow and fast blue) were injected by pressure into two different sites of the SII map, to ascertain whether SI sends diverging projections by branching axons.HRP injections in SII retrogradely labelled a discrete number of association neurons in SI. Their distribution area was several tens of times wider than that covered by the injection site. This suggests that a remarkable amount of divergence and convergence exists in the association projections from SI to SII. Despite the substantial difference in the extent of the injected and labelled areas, RFs of afferent and target neurons corresponded closely. Injections covering a small region within a single digit zone of SII labelled neurons throughout the entire representation of the same digit in SI, while neurons labelled in somatotopically inappropriate zones were rare. RFs mapped from several sites of the labelled region in SI were individually smaller than the RF mapped from the injection site in SII, but the overall size of afferent RFs encompassed that of target neurons. Divergence and convergence in the SI projections to SII zones representing more proximal portions of the forelimb may be even greater since HRP injections in the forepaw and arm zones of SII labelled a number of neurons also in the digit zone of SI, providing the RFs mapped from the injection sites were sufficiently wide to include the digits. Double‐labelling experiments showed that these long‐range diverging projections and those from the same digit zone of SI to the somatotopically matched zone of SII contain rare branched axons. Divergence and convergence in the SI projections to SII of cats might subtend a mechanism to overcome RF size disparity between the two somatosensory areas and to ensure a virtually complete matching of sensory information between afferent and target

ISSN:0092-7317    

DOI:10.1002/cne.903000306

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe avian wulst, a laminated “bulge” in the dorsal telencephalon, contains several distinct regions. The posterolateral portion (visual wulst) has been proposed to be an avian equivalent of the mammalian striate cortex. The present study examines specific neurotransmitters and neuropeptides within the visual wulst by immunohistochemical techniques. Antisera and monoclonal antibodies against choline acetyltransferase (ChAT), nicotinic acetylcholine receptor (nAChR), tyrosine hydroxylase (TH), serotonin (5‐HT), glutamic acid decarboxylase (GAD), gammaaminobutyric acid A receptor (GABAAR), cholecystokinin (CCK), substance P (SP), leucine‐enkephalin (L‐ENK), neurotensin (NT), neuropeptide Y (NPY), somatostatin (SRIF), corticotropin‐releasing factor (CRF), and vasoactive intestinal polypeptide (VIP) were used. Somata and neuropil displaying specific immunoreactivity were generally distributed in accordance with the laminar cytoarchitectonic organization of the wulst. The superficial layer of the wulst, the hyperstriatum accessorium, contained the highest densities of TH‐, 5‐HT‐, SP‐, NPY‐, SRIF‐, CRF‐, and VIP‐positive neuropil in the wulst, whereas the highest density of CCK‐ and NT‐staining was found in the deepest layer of the wulst, the hyperstriatum dorsale, In addition to the traditionally defined four laminae of the wulst, the immunoreactive staining revealed several subregions within each lamina. The most dorsolateral portion of the wulst contained the highest densities of ChAT‐ and L‐ENK‐stained fibers in the wulst, as well as moderately dense staining of neuropil for 5‐HT‐, TH‐, SP‐, and CCK‐like immunoreactivity. The nACh‐Rimmunoreactivity was faint and distributed rather uniformly throughout the wulst. The results suggest that the wulst consists of multiple regional variations within layers comparable to laminar variations found within different c

ISSN:0092-7317    

DOI:10.1002/cne.903000307

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe capacity of the central terminals of primary afferents to sprout into denervated areas of neonatal spinal cord and the morphology of any novel terminals has been investigated. In rats which had undergone sciatic nerve section on the day of birth, 12 of 18 physiologically characterized intact saphenous hair follicle afferents (HFAs) were labelled intra‐axonally with horseradish peroxidase (HRP) were shown to sprout up to 2,000 m̈m into the deafferented sciatic terminal field. The morphology of these sprouts depended on which area of the sciatic nerve territory was invaded by the afferent sprouts. Six HFAs sprouted into areas normally innervated by glabrous skin afferents and the morphology of the collateral sprouts in this region resembled that of rapidly adapting (RA) afferents. The other six saphenous HFAs had sprouted into sciatic “hairy” skin areas and the morphology of these sprouts, although abnormal, was flame shaped.In rats whose sural, saphenous, and superficial peroneal nerves were cut at birth, 4 of 7 single HRP labelled RA afferents had central terminals that had sprouted into regions of cord normally devoted to “hairy” input. These showed clear signs of HFA morphology despite their peripheral receptive fields remaining in the glabrous skin.The results show collateral sprouting of single cutaneous sensory afferent axons into adjacent inappropriate central target regions following neonatal deafferentation. Such plasticity may provide some compensation following neonatal injury. The morphology of the sprouted terminals is appropriate to the new target area rather than to its functional class and is also independent of the peripheral receptive field location providing an example of central rather than peripheral control over afferent growt

ISSN:0092-7317    

DOI:10.1002/cne.903000308

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractWe examined the regenerating electroreceptors of the weakly electric fishSternopygusby light and electron microscopy to search for possible structural correlates of known physiological changes that occur during regeneration (Zakon:J. Neurosci. 6(11): 3297–3308, 1986) and to compare them with developing electroreceptors in larval fish (Vischer: Brain Behav. Evol.33:223–236). Nine days after removal of a patch of cheek skin, new skin had filled the wound and undifferentiated precursor cell clusters were located in the epidermis just above the dermis. Nerve fibers were present near most, but not all, cell clusters. A few recognizable tuberous and ampullary precursor organs were seen at this time. Tuberous organs were composed of a group of large cells surrounded by smaller cells without a lumen and showed the beginning of a cellular plug. Ampullary organs appeared as a ball of cells with a small lumen opening into a nascent canal. Degenerating cells were found within organs, and sometimes entire organs degenerated. These were not innervated.By 2 weeks the large cells of the tuberous organ were developing into sensory cells, while the smaller cells were forming the capsule wall and the underlying basal cells. The characteristic tuberous organ canal filled with loosely packed epidermal cells was evident. The sensory cells of the ampullary organs were visible within the epithelial layer at the base of the lumen, and the large synaptic discs were beginning to form. The sensory cells and postsynaptic terminals contained numerous vesicles. The presynaptic vesicles, which appear in normal receptor cells, remained throughout regeneration and presumably underlie transmitter release. The postsynaptic vesicles appeared transiently in large numbers but declined to adult values by 4 weeks. We presume that these may serve a trophic role. By 3 weeks, organs generally appeared mature and began dividing into daughter organs. The formation of individual receptor organs during regeneration is similar to that observed in development.Receptor organs continued dividing until the appropriate number of organs per afferent was reached for the size of the fish. Although the organization of the receptors appeared generally normal, there were a few anomalies. Some afferents sent sprouts into the epidermis, and, as a result of such sprouting, some of these afferents innervated multiple organs over a greater distance than normal. This was first seen early in regeneration and persisted for as long as 5 months. In addition, as many as 20% of all tuberous units were innervated by two axons, which is significantly more than normal. Within a doubly innervated organ, each sensory cell was innervated by only one of the afferents. These anomalous innervation patterns may be the result of regenerating afferents attempting to establish rapidly their correct innervation of a number of sensory organs. To explain the degeneration of the receptor cells as well as the anomolous innervation patterns, we propose that (1) receptor organ formation occurs not through the transformation of epithelial cells, but of a limited number of precursor cells (basal cells?), into organs; (2) once formed, these organs are critically dependent on innervation for their survival; and (3) competition between afferents in dually innervated organs occurs at the level of the single sensory c

ISSN:0092-7317    

DOI:10.1002/cne.903000309

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractCentrifugal fibers to the retinas of chick embryos and hatched chicks have been examined and traced following staining by diffusion along their axonal membranes of the carbocyanine dye DiI in fixed tissue.In the older embryos and hatched chicks, the report of Dogiel (Arch. Mikrosk. Anat.44:622–648, 1895) has been confirmed that there are two very different morphological types of centrifugal fiber. Therestricted typeends as a relatively thick fiber, lacking varicosities, that runs for a short distance in the most sclerad level of the inner plexiform layer before terminating in a pericellular nest overlying the flask‐shaped body of a single amacrine cell. Thin filaments occasionally leave the pericellular net, apparently to terminate on adjacent cells. Thewidespread typealso runs in the most sclerad level of the inner plexiform layer, but it is thin, varicose, and highly branched, and its terminal arbor may span more than 1 mm, remaining at the same level. Both types of terminal arbor issue from parent axons in the optic fiber layer of the retina. A single parent axon gives either a single terminal fiber of the restricted type or several terminals of the widespread type, but never a mixture of the two. It is argued that the restricted and widespread types originate respectively from the neurons of the contralateral isthmo‐optic nucleus and from the “ectopic” neurons scattered outside the isthmo‐optic nucleus.In development, the centrifugal fibers reach the retina between E9 and E10 and initially run radially in the optic fiber layer, parallel to the retinofugal fibers but avoiding the dorsal retina. They dive into the inner plexiform layer at about E12. By E13, the terminal arbors are forming, and the widespread and restricted types can already be distinguished. The widespread type continues to increase its territory until about E18, and then appears to remain stable, whereas the restricted type attains its maximum ramification between E13 and E15 and then contracts. Prior to the retraction, the terminal territories of the restricted type fibers overlap, which may provide the anatomical basis for the interaxonal competition that apparently contributes to neuronal death in the isthmo‐optic nucleus between E13 and E16. Axons of ganglion cells exhibit transient side branches between E11 and E13; these never reach as deep as the level where the centrifug

ISSN:0092-7317    

DOI:10.1002/cne.903000310

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe times of origin (birthdays) of sensory and motor neurons that innervate the triceps brachii muscles of the bullfrog (Rana catesbeiana) were determined to learn whether neurons innervating a specific target are generated at a particular developmental time.3H‐thymidine (3H‐TdR) was made available continuously throughout a specific developmental period. All neurons that innervated the triceps muscle in juvenile frogs (identified by filling cells retrogradely with HRP) were generated prior to metamorphosis. Triceps motoneurons were all postmitotic by early limb bud stage V. Triceps sensory neurons were generated over a protracted period of larval development, from stage V through early pre‐metamorphic stage XV. Most large triceps sensory neurons were generated before the majority of the small cells. However, there was considerable overlap in the times of origin of the two populations; both large and small cells were generated at all stages of sensory neurogenesis. There was thus no strict relationship between sensory soma size and birthdate. Late‐generated sensory neurons tended to be located in clusters within ganglia, whereas HRP‐filled triceps neurons were not. These3H‐labeled clusters may represent clones of neurons which would indicate that late stage neuroblasts give rise to neurons that supply different peripheral targets. The time course of triceps neuronal generation paralleled that of all other brachial sensory neurons implying that the time of last cell division does not in itself determine either the target a neuron will innervate or the sensory modality to which it w

ISSN:0092-7317    

DOI:10.1002/cne.903000311

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY