摘要:

AbstractPrevious molecular cloning studies have revealed that α‐bungarotoxin binding proteins present in the brain are members of the neuronal nicotinic acetylcholine receptor gene family. The α7 subunit is structurally related to the agonist binding subunits present in the central and peripheral nervous systems and, when expressed inXenopusoocytes, forms functional channels blockable by α‐bungarotoxin. In the present study, three different monoclonal antibodies raised against the α7 subunit were used to map its distribution throughout the central nervous system of the rat.Immunohistochemical localization revealed that the α7 subunit is expressed in most regions of the brain, being, overall, well correlated with previous “in situ” localization of α7 transcripts and α‐bungarotoxin autoradiographic binding studies. Particularly strong immuno‐reactivity was observed in several sensory and motor nuclei of the brainstem as well as the red nucleus. At the cellular level, α7 immunostaining was usually found both in somata and dendrites, whereas axonal and terminal labeling was not observed.The widespread distribution of the α7 subunit polypeptide is consistent with immunoprecipitation data demonstrating that it is a component of the predominant subtype of brain α‐bungarotoxin‐sensitive nicotinic receptor

ISSN:0092-7317    

DOI:10.1002/cne.903490302

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

年代:1994

数据来源: WILEY

摘要:

AbstractFerret retinal axons can be induced to innervate the medial geniculate nucleus (MGN) by a combination of brain lesions early in development. Our previous work suggests that the retinal ganglion cells responsible for this plasticity are W cells. The present study continues this work with a morphological investigation of normal retinal ganglion‐cell axons and retinal ganglioncell axons induced to arborize in the MGN. Retinal axons were bulk filled with horseradish peroxidase placed in the optic tract, and individual axons were serially reconstructed from sagittal sections. The control population consisted of fine‐caliber axons arborizing in the superior colliculus (SC) and in the ventral C laminae of the lateral geniculate nucleus (LGN) of normal ferrets. We also compared the axons in the MGN of lesioned ferrets to intracellularly filled X and Y axons from normal ferrets as reported by Roe et al. ([1989] J. Comp. Neurol. 288:208).We have found that the retino‐MGN axons in the lesioned ferrets do not resemble X or Y axons in normal ferrts in axon diameter, arbor volume, bouton number, or bouton density. However, they do resemble the fine‐caliber, presumed W axons arborizing in the C laminae of the LGN and in the SC of normal ferrets. Thus, this study, in combination with previous studies, suggests strongly that W retinal ganglion cells are responsible for the retinal input to the MGN in lesioned animals. In addition, we find that the retino‐MGN axons are of two types, branched and unbranched, which may correspond to different subtypes of retinal W cells. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903490303

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

年代:1994

数据来源: WILEY

摘要:

AbstractSpecific neonatal lesions in ferrets can induce retinal axons to project into the medial geniculate nucleus (MGN). In the accompanying paper (Pallas et al., this issue), we described the morphology of these retinal ganglion cell axons. Those results and others (Roe et al. [1993] J. Comp. Neurol. 334:263) suggest that these axons belong to the W class of retinal axons.In this paper, the retino‐MGN axons are compared with the normal inputs to the MGN from the brachium of the inferior colliculus (BIC). We first sought to determine further the extent to which a novel target might influence retinal axon arbor morphology. The second issue concerns retinal topography. Ferrets with retinal projections to the MGN have a two‐dimensional retinotopic map in the MGN and the primary auditory cortex rather than the one‐dimensional tonotopic map normally present (Roe et al. [1990] Science 250:818). To investigate whether there might be an anatomical substrate for a two‐dimensional retinotopic map in the MGN, we compared the space‐filling characteristics of the retino‐MGN axons with the IC‐MGN axons.Our results show that the branched retino‐MGN axons resemble normal retinal W axons much more closely than they resemble the normal inputs to MGN. In addition, most of the axon arbors from the BIC are elongated along the rostrocaudal (isofrequency) axis, whereas the branched retino‐MGN axons are more spatially restricted, suggesting an anatomical substrate for a retinotopic map in the MGN of the rewired ferrets. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903490304

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

年代:1994

数据来源: WILEY

摘要:

AbstractAs part of a continuing study of the development of the marsupial auditory system, auditory brainstem responses (ABR) were recorded and an ABR audiogram was constructed for five female Northern Quolls (Dasyurus hallucatus), which are nocturnal carnivores. The best frequency for hearing lies between 8 and 10 kHz, and at 50 dB SPL there is a range from about 0.5 to 40 kHz.Vocalizations of adult quolls and pouch‐young were recorded with a digital audio tape recorder, and the power spectra of representative calls were compared with the ABR audiogram. The common adult vocalization have most energy at the lower end of the hearing range, whereas frequencies that are dominant in the isolation calls of the pouch‐young lie close to the best frequency of hearing.Samples of nocturnal sounds of the habitat of the quoll were also recorded and analyzed. Power spectra have peak energy at frequencies between 2 and 5 kHz, with a smaller contribution above 10 kHz. The spectrum contains relatively little power at the best frequency of hearing.Measurements of the sound pressure level at the external ear canal as a function of stimulus frequency and location in space suggest that the directional amplifying properties of the pinna will operate most effectively on sound frequencies at the upper end of the quoll's hearing range, a region that may be important in prey detection.Comparisons are made with other mammalian nocturnal carnivores and with other marsupials. We speculate that, for nocturnal carnivores, one role of the low‐frequency part of the hearing range concerns the recognition of adult conspecifics, the mid‐frequency range is important for the detection of pouch‐young, and the upper range may be particularly concerned with prey/predator detect on. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903490305

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of neuregulin transcripts in rat brains was studied by both RNA blotting and in situ hybridization. Our data demonstrate that multiple neuregulin transcripts are expressed in neurons of the basal forebrain, the hippocampus, the diencephalon, the cerebellum, the brainstem, and the spinal cord. Developmental changes in the distribution of neuregulin transcripts were observed only in the cerebellum and the hippocampus. The intense neuregulin hybridization signals in the brainstem motor and sensory nuclei and the spinal motor neurons are suggestive of a functional involvement of neuregulins in motor and sensory systems. The expression of neuregulins in other parts of the brain also indicates that these factors are involved in a variety of central nervous system functions. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903490306

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

年代:1994

数据来源: WILEY

摘要:

AbstractTo understand its relationship to somatosensory areas in other species, we studied the rostral bank of the medial ansate sulcus in adult cats. Neurons in the shoulder and upper part of the sulcal wall responded to low‐threshold cutaneous stimuli much like neurons on the crown of the gyrus, whereas neurons in some deeper portions of the sulcus required more intense but innocuous somatic stimuli. Because we found much of the body surface re‐represented in this area, we suggest that, besides the representation in area 3b, there is another cutaneous representation of the hindlimb and trunk located on the gyral crown near the medial end of the medial ansate sulcus and of the forelimb and trunk within the medial ansate sulcus. Posterior to this second cutaneous representation, many parts of the body were also represented in regions activated by more intense stimuli and having a different cytoarchitecture, suggesting that they were part of another body representation.Area 3b and the shoulder of the gyrus were distinguished by relatively intense acetylcholinesterase staining of layers III and IV. In the wall of the sulcus, all layers except layer I were uniformly stained to a point where electrophysiological recordings showed the cortex to be unresponsive, whereupon the outer two‐thirds of layer I became very pale. Neurons activated by afferents from knee joints were found only in a small area; we did not find a mediolateral band serving joint afferents as is reported in primates. These data suggest that cat somatosensory cortex differs in some ways from primates but that it contains multiple representations of the body, as do most other mammals. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903490307

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe rabbit flocculus can be divided into five zones (zones 1, 2, 3, 4, and C2) with the use of acetylcholinesterase histochemistry. The projections of individual Purkinje cells in these zones to the vestibular and cerebellar nuclei were studied by using biocytin as an anterograde tracer. The zones were physiologically identified in terms of the Purkinje cell complex spike modulation occurring in response to optokinetic stimulation. In zones 1 and 3 neurons respond best to rotation about a horizontal axis that is close to perpendicular to the ipsilateral anterior semicircular canal, whereas in zones 2 and 4 neurons respond best to rotation about the vertical axis. Complex spike activity in zone C2 is unresponsive to optokinetic stimulation.Collectively, Purkinje cells of zone 1 projected to the ventral dentate nucleus, dorsal group y, and superior vestibular nucleus; Purkinje cells of zones 2 and 4 projected to the magnocellular and parvicellular parts of the medial vestibular nucleus; Purkinje cells of zone 3 projected to dorsal group y, ventral group y, and the superior vestibular nucleus; and Purkinje cells of zone C2 projected to the interposed posterior nucleus and dorsal group y. Some of the labeled Purkinje cell axons branched and innervated two nuclei. Branching axons from zone 1 either innervated both the ventral dentate nucleus and the superior vestibular nucleus or both dorsal group y and the superior vestibular nucleus. Branching axons from zones 2 and 4 innervated both the magnocellular and the parvicellular parts of the medial vestibular necleus. Branching axons from zone 3 innervated both dorsal group y and the superior vestibular nucleus, or both ventral group y and the superior vestibular nucleus. Branching axons from zone C2 innervated both the interposed posterior nucleus and dorsal group y.Some of the target nuclei of the floccular Purkinje cell axons (e. g., dorsal group y and interposed posterior nucleus) project to the part of the inferior olive that, in turn, projects to the corresponding floccular zone, thus completing a closed pathway consisting of the inferior olive, the cerebellar cortex, and the cerebellar and vestibular nuclei. Other target nuclei (e. g., superior vestibular nucleus and medial vestibular nucleus) do not project back to the olivary subnuclei that innervate the flocculus and are part of an open olivofloccular pathway. An individual Purkinje cell thus can innervate a nucleus in the closed pathway as well as a nucleus in the open pathway. To summarize, the present study illustrates that floccular Purkinje cells located in discrete zones are part of different pathways involved in the regulation of specific components of compensatory eye movements. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903490308

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe projections of Purkinje cells from zones in the ventral nodulus of pigmented rabbits were studied with the use of extracellulary injected biocytin as an anterograde tracer. The zones were physiologically identified according to the complex spike modulation of Purkinje cells in response to optokinetic stimulation. Purkinje cells in the most medialzone do not respond to optokinetic stimulation; they project to the fastigial nucleus, the perifastigial white matter, the periinterposed white matter, and the medial vestibular nucleus. In the adjacent zone, Purkinje cells respond best to optokinetic stimulation about the vertical axis; they project to the periinterposed white matter and the medial vestibular nucleus. Purkinje cells in the next zone respond best to optokinetic stimulation about an axis approximately perpendicular to the ipsilateral anterior canal; they project to the periinterposed white matter, dorsal group y, the superior vestibular nucleus, and the medial vestibular nucleus. In the most lateral zone, Purkinje cells respond best to optokinetic stimulation about the vertical axis; they project to the periinterposed white matter, dorsal group y, and the medial vestibular nucleus. The majority of axons gave off collaterals and innervated more than one nucleus. Often, three or four different areas received terminals from a single Purkinje cell axon. The zonal projection pattern of the ventral nodulus is compared to that of the flocculus, which, with respect to the visual climbing fiber afferents, has similar zones. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903490309

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

年代:1994

数据来源: WILEY

摘要:

AbstractPeripheral nerve crush induces novel projections from noradrenergic sympathetic neurons to sensory ganglia, and it has been suggested that these projections provide an anatomical substrate for chronic pain syndromes that occur after nerve injury. The present study demonstrates that novel sympathetic projections to sensory neurons are also induced in transgenic mice that overexpress nerve growth factor (NGF) in the skin. Specifically, a large proportion of trigeminal neurons in NGF transgenic mice were innervated by tyrosine hydroxylase (TH)‐positive pericellular arborizations that were seen only rarely in controls. Electron microscopic analysis of NGF transgenic mice revealed that trigeminal neurons were surrounded by numerous axonal varicosites containing synaptic specializations. Removal of the superior cervical ganglion abolished TH‐immunoreactive arborizations in the ipsilateral trigeminal ganglion confirming that these fibers were sympathetic axons. A two‐site enzymelinked immunosorbent assay revealed that transgenic ganglia contained a tenfold increase in NGF peptide compared to controls. However, reverse transcriptase polymerase chain reaction analysis showed no apparent expression of transgene mRNA in sensory ganglia, suggesting that the additional NGF was derived from increased NGF expression in the skin. These results indicate that NGF can induce novel sympathetic projections to sensory neurons in vivo and suggests a model in which increased NGF expression plays a role in the development of sympathetic hyperalgesia after nerve injury. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903490310

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

年代:1994

数据来源: WILEY

摘要:

AbstractLocal inflammation is associated with profound changes in the biochemistry and physiology of primary afferent nerve fibers and the central neurons responding to their signals. In some tissues, the neural changes accompanying inflammation include sprouting and cytochemical changes that are delayed several days after the initial injury. In the present stydiy, we have analyzed the effect of complete Freund's adjuvant (CFA)‐induced inflammation in the rat paw on clacitonin gene‐related peptide (CGRP) immunoreactivity (IR) in dorsal root ganglia and within tissue of the inflamed paw. We quantified the CGRP‐IR within the L1, L4, and L6ganglia, and in ankle, midpaw, joint and toe tissues.Analysis of the processed tissue revealed a significant increase in the percentage of CGRP‐positive cells within L4dorsal root ganglia ipsilateral to an inflamed hindpaw six days after administration of CFA. There was a parallel increase in the number and staining density of detectable CGRP‐immunoreactive fibers in periarticular and perivascular tissues of the inflamed digits and inflamed ankle. The other tissues of the paw, including epidermis and the regions surrounding the abceses, did not have detectable changes in CGRP‐immunoreactive fibers, despite tissue swelling and dystrophic changes in the foot that included loss of mast cell staining.These data demonstrate that local inflammation of the rat paw has delayed influences in the peripheral nervous system, in addition to a number of previoulsy characterized acute effects. The alterations of CGRP‐IR were focused around specific tissue types, such as joints and subdermal blood vessels, and absent from others, such as epidermis or in the areas surrounding abscesses. This suggests production of local factors within reactive tissues that selectively interact with nerve fibers to induce changes in CGRP‐IR within the fibers. © 1994

ISSN:0092-7317    

DOI:10.1002/cne.903490311

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

年代:1994

数据来源: WILEY