摘要:

AbstractExperiments were carried out on cats to ascertain whether corticocortical neurones of somatosensory areas I (SI) and II (SII) could be labelled by retrograde axonal transport of D‐[3H]aspartate (D‐[3H]Asp). This tritiated enantiomer of the amino acid aspartate is (1) taken up selectively by axon terminals of neurones releasing aspartate and/or glutamate as excitatory neurotransmitter, (2) retrogradely transported and accumulated in perikarya, (3) not metabolized, and (4) visualized by autoradiography. A solution of D‐[3H]Asp was injected in eight cats in the trunk and forelimb zones of SI (two cats) or in the forelimb zone of SII (six cats). In order to compare the labelling patterns obtained with D‐[3H]Asp with those resulting after injection of a nonselective neuronal tracer, horseradish peroxidase (HRP) was delivered mixed with the radioactive tracer in seven of the eight cats. Furthermore, six additional animals received HRP injections in SI (three cats; trunk and forelimb zones) or SII (three cats; forelimb zone).D‐[3H]Asp retrograde labelling of perikarya was absent from the ipsilateral thalamus of all cats injected with the radioactive tracer but a dense terminal plexus of anterogradely labelled corticothalamic fibres from SI and SII was observed, overlapping the distribution area of thalamocortical neurones retrogradely labelled with HRP from the same areas. D‐[3H]Asp‐labelled neurones were present in ipsilateral SII (SII‐SI association neurones) in cats injected in SI, In these animals a bundle of radioactive fibres was observed in the rostral portion of the corpus callosum entering the contralateral hemisphere. There, neurones retrogradely labelled with silver grains were present in SI (SI‐SI callosal neurones). Association and callosal neurones labelled from SI showed a topographical distribution similar to that of neurones retrogradely labelled with HRP. The laminar patterns of corticocortical neurones labelled with D‐[3H]Asp or with HRP were also similar, with one exception. In the inner half of layer III, SII‐SI association neurones and SI‐SI callosal neurones labelled with the radioactive marker were much less numerous than those labelled with HRP.In cats injected in SII, D‐[3H]Asp retrogradely labelled cells were present in ipsilateral SI (SI‐SII association neurones). Their topographical and laminar distribution overlapped that of neurones labelled with HRP but, as in cats injected in SI, association neurones labelled with silver grains were unusually rare in the inner layer III. In spite of an intense D‐[3H]Asp labelling of fibres observed in the corpus callosum, no neurones retrogradely labelled with D‐[3H]Asp were found in the contralateral hemisphere.These results indicate that, except for the corticocortical neurones in the inner layer III, a large number of association and callosal neurones of SI and SII could be retrogradely labelled with D‐[3H]Asp. These neurones therefore are supposed to use the amino acids aspartate and/or glutamate

ISSN:0092-7317    

DOI:10.1002/cne.902630202

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe mustache bat,Pteronotus parnellii, depends on echolocation to navigate and capture prey. This adaptation is reflected in the large size and elaboration of brainstem auditory structures and in the minimal development of visual structures. The superior colliculus, usually associated with orienting the eyes, is nevertheless large and well developed inPteronotus.This observation raises the question of whether the superior colliculus in the echolocating bat has evolved to play a major role in auditory rather than visual orientation. The connections of the superior colliculus inPteronotuswere studied with the aid of anterograde and retrograde transport of wheat germ agglutinin conjugated to HRP. These results indicate that the superior colliculus ofPteronotusis composed almost entirely of the layers beneath stratum opticum. The retinal projection is restricted to a very thin zone just beneath the pial surface. Prominent afferent pathways originate in motor structures, particularly the substantia nigra and the deep nuclei of the cerebellum. Sensory input from the auditory system originates in three brainstem nuclei: the inferior colliculus, the anterolateral periolivary nucleus, and the dorsal nuclei of the lateral lemniscus. The projections from these auditory structures terminate mainly in the central tier of the deep layer. The most prominent efferent pathways are those to medial motor structures of the contralateral brainstem via the predorsal bundle and to the ipsilateral midbrain and pontine tegmentum via the lateral efferent bundle. Ascending projections to the diencephalon are mainly to the medial dorsal nucleus and zona incerta. Thus, the superior colliculus inPteronotuspossesses well‐developed anatomical connections that could mediate reflexes for orienting its ears, head, or body toward objects detected by echolocatio

ISSN:0092-7317    

DOI:10.1002/cne.902630203

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractElectrophysiological recordings were made from 187 single cells in the tammar wallaby (Macropus eugenii) dorsal lateral geniculate nucleus (LGNd). The results show that it is topographically organized such that the superior visual field is represented dorsally, the inferior field is represented ventrally, the nasal visual field is represented ventrally, and the temporal visual field is represented rostrally.The visual field of one eye ranges from −30° nasal to +179° temporal in azimuth and +73° superior to −49° inferior in elevation. Ganglion cells that had receptive field positions between −9° and +179° projected to the contralateral LGNd while the ganglion cells that projected to the ipsilateral LGNd had visual fields from 0 to +30°.The binocular visual field extends 60° in azimuth. This representation in the LGNd is expanded relative to the monocular representation. There is also an increased representation of the horizon in the temporal field corresponding to the visual streak of retinal ganglion cells. The binocular visual field is located where contralateral and ipsilateral laminae are shown to interdigitate by proline autoradiography.There are nine eye‐specific laminae in the LGNd. Four receive afferents from the contralateral eye and five receive afferents from the ipsilateral eye. The lines of isoelevation are perpendicular to the coronal plane of section while the lines of isoazimuth are nearly parallel to the coronal plane. The lines of projection representing one visual direction are inferred to be perpendicular to the tangent of curvature of the laminae as in the LGNd of other mammals.The majority of cells (85%) recorded had on‐ or off‐centre responses. On‐and off‐centre responses were not apparently segregated in the LGNd but segregation may not have been revealed by the single

ISSN:0092-7317    

DOI:10.1002/cne.902630204

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe anterograde transport of horseradish peroxidase following injections into the cervical, thoracic, or lumbosacral spinal cord was used to examine the organization of spinocervical tract terminations in the lateral cervical nucleus (LCN) of the cat. A somatotopic organization of the labeling originating from different spinal levels was observed in the mediolateral dimension. Cervical labeling generally occurred in the ventromedial portion and lumbosacral labeling in the dorsolateral portion of the LCN. Thoracic labeling occurred both in the middle and the most lateral edge of the nucleus. In all cases, labeling was distributed over most of the rostrocaudal extent of the LCN. In addition, distinct patches of labeling were present in the medialmost portion of the nucleus, regardless of the spinal level injected. These observations corroborate the topographical organization of the LCN described previously on the basis of physiological and retrograde labeling data, and support the identification of the medialmost part of the LCN as a distinct portion of the nucleus.Terminal labeling in the LCN always occurred in multiple, longitudinally distributed fields. The afferent input to each terminal field coursed in separate, loose bundles of fibers that descended from the superficial dorsolateral funiculus. Large injections resulted in more extensive, overlapping terminal fields. These observations indicate that collateral projections result in several discrete representations of a given portion of the skin over the longitudinal extent of the LCN, but that topographical relationships are longitudinally maintained. It is suggested that these multiple terminal fields are the anatomical correlate of the functionally selective convergence of spinocervical tract terminations, that has previously been postulated on physiological grounds to explain the generation of LCN receptive fields with homogenous receptor input within a somatotopic framework.

ISSN:0092-7317    

DOI:10.1002/cne.902630205

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe projection fields of spinocerebellar tracts arising from the cervical enlargement were studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in the cat.Following injections of WGA‐HRP into the C5–C8 or T1 segments, labeled terminals were seen in lobule I to sublobule Vf of the anterior lobe, and lobule VI, sublobule VIIb, lobules VIII and IX, the simple lobule, crus II, and the paramedian lobule of the posterior lobe. In the sagittal plane of sublobules Ib–Vf and sublobules VIf and VId, the labeled terminals were distributed mainly in the superficial two thirds of the apicobasal extent. The labeled terminals in the anterior lobe accounted for about 70% of the total labeled terminals; the great majority were in lobule IV (17–20%) and lobule V (40%). The labeled terminals in the posterior lobe accounted for 30% of the total labeled terminals; the majority were in sublobules VIf (11–15%) and VId (6%). In the mediolateral extent, more than 50% of the total labeled terminals in each lobule were concentrated within 1.0 mm from the midline (the vermis) and 70–80% within 2.0 mm from the midline (the vermis and the medial part of the intermediate regions). A smaller number were also present in the intermediate region. Cases with lateral cordotomies revealed that the projections were bilateral but predominantly ipsilateral to the cells of origin and that the quantity of the ipsilateral projection was 66.5–75% of the total in each of sublobules IVb, Va, and VIf, The projection to the paramedian lobule was also predominantly ipsilateral.Projection fields in the horizontal plane were reconstructed from a series of transverse sections through each lobule. In sublobules Va–VIf labeled terminals were distributed in three areas; area 1 located within 0.25 mm from the midline in zone Al of Voogd; area 2 located between 0.5 and 0.75 mm lateral to the midline in zones Al and A2; and area 3, which appeared to be located between 0.75 and 1.5 mm lateral to the midline in zones A2‐B. These areas extended longitudinally in the apical two thirds of the lobules.From the present and previous retrograde HRP studies it was suggested that the neuronal groups in the cervical enlargement (the medial lamina VI group and the central lamina VII group) project to lobules I–V of the anterior lobe and lobule VI, sublobule VIIb, and lobule VIII of the posterior lobe. They have strong projections to caudal lobules of the anterior lobe (lobules III–Va) and lobules facing the primary fissure (sublobules Vd–Vf an

ISSN:0092-7317    

DOI:10.1002/cne.902630206

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe organization of the olivocerebellar and corticonuclear relations for vermal lobules IX and X and the flocculus has been studied in the rat by using microinjections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP). This axonal tracer allowed us to study simultaneously the olivocortical connections (revealed by retrograde transport) and corticonuclear connections (revealed by anterograde transport) from a single injection in the cerebellar cortex.The results indicate that four modules can be distinguished, each of which consists of a region of cerebellar cortex receiving afferents from a single small region of the inferior olive (IO) and sending efferents to one or several portions of the cerebellar nuclei and/or vestibular nuclei.The first module includes a medial part of lobule X as well as all the flocculus. It receives afferents from the dorsal cap (dc) and sends efferents to the small cell (s) zone of the dentate nucleus as well as to the medial vestibular (VM) nucleus and subnucleus y.The second module includes a medial parasagittal region located in lobules IX and X. It receives afferents from the ventrolateral outgrowth (vlo) and/or beta nucleus (vlo+beta nucleus) and sends efferents principally to the ventrolateral part of fastigial nucleus and to the superior vestibular (VS), inferior vestibular (VI), and VM nuclei.The third module includes a lateral parasagittal region in lobules IX and X. It receives afferents from the dorsomedial cell column (dmcc) of 10 and sends efferents principally to the interpositus nucleus and subnucleus y.The fourth module includes the most lateral part of lobules IX and Xa. It receives afferents from the principal olive (PO) and sends efferents to the s zone of the dentate nucleus.These results are comparable to those obtained in the cat although a few differences are discusse

ISSN:0092-7317    

DOI:10.1002/cne.902630207

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe number of superior cervical ganglion (SCG) neurons does not differ for males and females on the day of birth, but by 15 days, after most of the normal neuron death has occurred, males have significantly more neurons than females. This difference persists in the adult. The present study was undertaken to determine whether the presence of afferent input to the SCG is required for the development of this sex difference.Bilateral transection of the cervical sympathetic trunk, which deafferents the SCG neurons, or a sham operation was performed on male and female Sprague Dawley rats on the day of birth. Numbers of neurons were counted in SCGs of animals sacrificed on either postnatal day 4 or 15, before or after normal development of the SCG sex difference.At 4 days, the number of SCG neurons in sham‐operated males and females were not different, but by 15 days, females had lost a significant number of neurons, whereas the males had not. Transection of the cervical sympathetic trunk led to a significant loss of over 6,000 SCG neurons by postnatal day 4 in both males and females. Whereas some of this loss is due to axotomy of caudally projecting SCG neurons, at least half of the neuron loss is due to removal of the afferent input, At 15 days, sham‐operated males had significantly more SCG neurons than did sham‐operated females, but the gender difference was not significant in animals with neonatally deafferented ganglia. Thus, the normal development of the gender difference in SCG neuron numbers requires an intact afferent

ISSN:0092-7317    

DOI:10.1002/cne.902630208

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe size and response magnitude of receptive fields were evaluated for cells in the rat cortical barrel‐field by using standard vibrissal deflections of 1.14°. Such stimuli fell within the plateau region of stimulus‐response curves. The responses of all neurones to all vibrissae within and surrounding centre‐receptive fields were analysed for probability and latency of response. It was found that cells in supragranular layers had small centre‐receptive fields (average 1.6 vibrissae) with small excitatory surrounds (1.5 vibrissae) while cells in the granular layers had small, powerful centre‐receptive fields (1.4) with moderately large excitatory surrounds (2.6). Neurones in infragranular layers possessed large but weak centre‐receptive fields (2.6) with large surrounds (3.5).Sixty‐four neurones in layer IV were studied, the precise locations of which were identified by using dye lesioning and cytochrome oxidase staining. There were no differences in receptive field size for cells within septa and barrel hollows, but the latter were twice as likely to produce two or more spikes per stimulus from the principal vibrissa (65% against 33%). Histological analysis showed that the principal vibrissa was synonymous with the appropriate vibrissa for the barrel on 86% (55 of 64) of occasions. A quantitative analysis of convergent input to three neighbouring barrels (E1, E2, and D1) showed considerable graded overlap of receptive field surrounds, although facial hair adjacent to the mystacial pad only influenced cells on the edge of the barrel‐field. Individual vibrissae exhibited significant divergent input to adjacent inappropriate barrels, being preferentially directed to distant septal rather than barrel hollow cells. An analysis of latencies showed that 40% of barrel hollow cells and 48% of barrel septal cells responded at short (30 ms), only 2% of inappropriate responses from barrel hollow cells and 13% from septal cells being of short latency. These results suggest that direct inputs largely project to appropriate barrels. The possibility that divergent inputs are generated by intracortical mecha

ISSN:0092-7317    

DOI:10.1002/cne.902630209

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe developmental changes of the fourth ventricular roof of the brain in mouse fetuses and neonates were observed by scanning and transmission electron microscopy with particular attention to the caudal portion where a median foramen might be formed during the fetal period. The fourth ventricular roof was continuously paved with a single layer of cuboidal or squamous neuroepithelial cells with poorly developed basement membrane until the 12th intrauterine day when the primitive choroid plexus appeared at the middle portion of the roof. With development of the choroid plexus, the roof caudal to the choroid plexus (membranous roof) became thinner, and it was mostly lined with a single layer of flat ependymal cells having cilia and microvilli and resting on a continuous basement membrane. These ependymal cells were connected with one another by a gap junction or an intermediate junction for the entire period examined, except at the 13th to 14th intrauterine days, during which the interependymal clefts were transiently widened up to 2 μm in width, in places, without disruption of the continuous basement membrane. Neither a median aperture nor wide intercellular pores were formed in the membranous roof during the fetal or neonatal term

ISSN:0092-7317    

DOI:10.1002/cne.902630210

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution pattern and the morphology of vasoactive intestinal polypeptide (VIP)‐ and cholecystokinin (CCK)‐like‐immunoreactive neurons were studied in the brain of the hedgehog and the sheep by means of the peroxidase‐antiperoxidase immunocytochemical method. A total of 34 hedgehogs and 26 sheep of both sexes were used. Fourteen hedgehogs and 13 sheep received an intracerebroventricular injection of colchicine that enhanced the immunostaining and revealed “new” immunoreactive cell bodies. VIP‐immunoreactive bipolar and multipolar neurons were observed in both species in the cerebral cortex, hippocampal formation, amygdaloid complex, hypothalamus, and central gray substance of the midbrain. CCK‐immunoreactive bipolar, bitufted, and multipolar neurons displayed a broader distribution in both mammals than VIP neurons and were found in the cerebral cortex, the hippocampal formation, the amygdaloid complex, the hypothalamus, the mesencephalon, and the pons.In the cortex, in both the hedgehog and the sheep, VIP neurons were located in all layers but were concentrated in layers II and III, with the majority being typical bipolar. CCK neurons were more numerous in the superficial layers (I‐III) but were found in the deep layers as well. They were bipolar, bitufted, or multipolar in morphology. From these neurons a small percentage, which were located almost exclusively in layers II and III of the visual cortex, exhibited also VIP immunoreactivity. Perikarya of such double‐labeled cells were ovoid or round in shape with one or two main processes emanating from each pole of the cell body and oriented perpendicularly to the pia. The coexistence of the two peptides within individual neurons of the cortex has not been reported in other species and its physiological significance is discussed in relation to the GABAergic ne

ISSN:0092-7317    

DOI:10.1002/cne.902630211

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY