摘要:

AbstractPrevious studies suggest that the principal cells of the medial nucleus of the trapezoid body (MNTB) give rise to the projection from MNTB to the lateral superior olivary nucleus (LSO) of the same side, where they mediate rapid inhibitory effects of contralateral sound stimulation. In the present study, we explored certain morphological features of this connection as well as several other projections of the MNTB by using anterograde and retrograde axonal tracing methods. Following injections of tritiated leucine into MNTB, labeled axons reached LSO by passing ventral to, dorsal to, and through the medial superior olivary nucleus, and gave rise to labeling around the somata and proximal dendrites of LSO fusiform cells. As measured in autoradiograms of 2 μm plastic sections, these axons had a modal diameter of 5–6 μ. Terminal labeling, tentatively attributed to principal cell axons, was also seen in the ventral nucleus of the lateral lemniscus (VNLL) and the dorsomedial and ventromedial periolivary nuclei. HRP injections into the LSO and the VNLL showed that the prinicpal cell projected to both of these nuclei and revealed a topographic arrangement of the projection to the LSO which is consistent with tonotopic maps determined electrophysiologically. Control HRP injections demonstrated that other minor projections of the MNTB arose from minor cell populations in this nucleus. The findings provide a morphological correlate of certain physiological findings and suggest a wider role for the MNTB in the ascending auditory system than previously has been suppo

ISSN:0092-7317    

DOI:10.1002/cne.902380302

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe neuronal population of area 17 of rat visual cortex has been examined by using tissue from brains fixed by perfusion. The tissue was osmicated and embedded in plastic so that the same neurons could be examined by both light and electron microscopy. In these preparations area 17 was 1.49 mm thick and by stereological procedures it was calculated that there are about 120,000 neurons beneath 1 mm2of cortical surface. If one assumes area 17 in each hemisphere of the rat to occupy between 7.1 and 9.4 mm2of cortical surface, then in each hemisphere the area contains between 850,000 and 1,128,000 neurons. Of these neurons 85% are pyramidal cells and 15% are nonpyramidal cells. About one‐third of the nonpyramidal cells occur in layers I and VIb, both of which contain only this kind of neuron. The remaining two‐thirds of the nonpyramidal cells are in layers II‐VIa. Within these layers it has been possible to differentiate bipolar cells from other types of nonpyramidal cells and in each of these two nonpyramidal cell groups to recognize both small and large neurons. The greatest concentration of nonpyramidal cells occurs in layer II/III. To confirm the validity of the stereologically derived data direct counts were made of the medium and large pyramidal cells in la

ISSN:0092-7317    

DOI:10.1002/cne.902380303

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

年代:1985

数据来源: WILEY

摘要:

AbstractMotoneurons in the turtle lumbar spinal cord were injected with HRP by electrophoresis after being electrophysiologically identified as innervating a muscle belonging to a functional group. The distribution of dendrites was studied in transverse reconstructions of 45 motoneurons, including motoneurons identified as innervating knee extensor muscles, eight motoneurons innervating hip retractor and knee flexor muscles, 14 motoneurons innervating ankle and/or toe extensors and 12 motoneurons innervating ankle and/or toe flexor muscles.The dorsal dendritic tree of motoneurons innervating distally positioned musculature (ankle and/or toe extensors and flexors) was observed to contain significantly less terminal dendritic branches compared to the dorsal dendritic trees of motoneurons innervating proximally situated (hip and knee) muscles.The distribution of dendrites within the white matter was studied by measuring the total projected length of the dendritic branches within empirically defined sectors in the transverse plane. This kind of analysis also revealed differences between the dorsal dendrites of motoneurons innervating distally and proximally positioned muscles conforming to the counts of terminal dendritic branches. It is suggested that these apparent differences in the size of the dorsal dendrite may be related to the number of synapses made by primary afferents.In the white matter, the highest dendritic density for all four groups of mononeurons was found within the central part of the lateral funiculus. However, only in the ventral funiculus could slight indications be found that the dendritic density of functionally different motoneuron groups may bear some relation to the locations of the terminations of the descending pathways known to establish monosynaptic contacts with lumbar mononeurons.

ISSN:0092-7317    

DOI:10.1002/cne.902380304

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

年代:1985

数据来源: WILEY

摘要:

AbstractMonoclonal antibodies to choline acetyltransferase (ChAT) were used in an immunocytochemical study to characterize putative cholinergic neurons and synaptic junctions in rat caudate‐putamen. Light microscopy (LM) revealed that ChAT‐positive neurons are distributed throughout the striatum. These cells have large oval or multipolar somata, and exhibit three to four primary dendrites that branch and extend long distances. Quantitative analysis of counterstained preparations indicated that ChAT‐positive neurons constitute 1.7% of the total neuronal population. Electron microscopy (EM) of immunoreactive neurons initially studied by LM revealed somata characterized by deeply invaginated nuclei and by abundant amounts of organelle‐rich cytoplasm. Surfaces of ChAT‐positive neurons are frequently smooth, but occasional somatic protrusions and dendritic spines occur. Although infrequently observed, axons of ChAT‐positive neurons branch, receive synapses, and become myelinated. Unlabeled boutons make both symmetrical and asymmetrical synapses with ChAT‐positive somata and proximal dendrites, but are more numerous on distal dendrites. In addition, some unlabeled terminals form asymmetrical synapses with ChAT‐positive somata and dendrites that are distinguished by prominent subsynaptic dense bodies. Light microscopy demonstrated a dense distribution of ChAT‐positive fibers and punctate structures in the striatum, and these structures appear to correlate, respectively, with labeled preterminal axons and presynaptic boutons identified by EM. ChAT‐positive boutons contain pleomorphic vesicles, and make symmetrical synapses primarily with unlabeled dendritic shafts. Furthermore, they establish synaptic contacts with somata, dendrites and axon initial segments of unlabeled neurons that ultrastructurally resemble medium spiny neurons. These observations, together with the results of other investigations, suggest that medium spiny GABAergic projection neurons receive a cholinergic innervation that is probably derived from ChAT‐positive striatal cells. The results of this study also indicate that cholinergic neurons within caudate‐putamen belong to a single population of cells that have large somata and extensive sparsely spined dendrites. Such neurons, in combination with dense concentrations of ChAT‐positive fibers and terminals, are the likely basis for the large amounts of ChAT and acetylcholine detected biochemical

ISSN:0092-7317    

DOI:10.1002/cne.902380305

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

年代:1985

数据来源: WILEY

摘要:

AbstractA study of the efferent projections of the entorhinal area in the guinea pig, by using anterograde (autoradiographic tracing of tritiated amino acids) and retrograde(fluorochrome tracing) methods, revealed the following projections: (1) tononhippocampal cortices: retrosplenial cortex (area 29), cingulate cortex (areas 23, 24), prelimbic cortex (area 32), infralimbic cortex (area 25), perirhinal cortex (areas 35, 36), prepyriform cortex (area 51B), and insular cortex (areas 13–16). All received direct projection; (2) to subcortical targets', distinct terminations were observed in the lateral thalamic nucleus, the striatum, and the accumbens nucleus.In retrograde experiments, the cells giving rise to the projections to the hippocampus were found to He in layers II and III, those projecting to the nonhippocampal cortical regions to originate in layer IV, and those projecting to the striatum and the accumbens to lie in layers V and VI.Many of the efferent projections to the cerebral cortical regions are associated with reciprocal projections from these regions to the superficial layers (I–III) of the entorhinal cortex. The entorhinal efferent projections generally terminate ipsilaterally. A weak termination is, however, present at the contralateral side. The efferent projections of the entorhinal area represent a route for important caudally directed, nonfornical hippocampal out

ISSN:0092-7317    

DOI:10.1002/cne.902380306

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe morphology of neurons in the subthalamic nucleus (STN) of the lesser bushbaby (Galago senegalensis) is described in coronal brain sections processed by Golgi‐ and Nissl‐staining techniques. Quantitative and statistical methods are used to evaluate (1) soma size and shape, (2) dendritic field size, shape, and branch frequency, (3) the number of dendritic and somatic spines per neuron, and (4) neuron location within the STN. Principal components analysis of these variables suggests that three classes of neurons are present. Two of these classes are considered to be projection cells, referred to as elongate‐fusiform and radiate neurons, respectively. Elongate fusiform neurons have somata and dendritic fields which are large in diameter, extremely fusiform in shape, and give rise to few appendages. Somata and dendritic fields of radiate neurons are smaller in diameter, more rounded in shape, and support more spines than the elongate‐fusiform neurons. The third class of cells inGalagoSTN is tentatively identified as consisting of interneurons on the basis of small soma and dendritic field size, thin and varicose dendritic morphology, and the presence of multilobulated dendritic app

ISSN:0092-7317    

DOI:10.1002/cne.902380307

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.

ISSN:0092-7317    

DOI:10.1002/cne.902380308

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

年代:1985

数据来源: WILEY

摘要:

AbstractImmunoreactive luteinizing hormone‐releasing hormone (LHRH) was first detected at 15 days of gestation in ganglion cells associated with the peripheral, intracranial, and central parts of the nervus terminalis of the rat. LHRH was not detected in any other structure of the central nervous system at this age.In the 17‐day‐old fetal rat, 62% of the total LHRH‐reactive neuronal population was found in ganglion cells of the nervus terminalis. At this same age, immunoreactive beta‐luteinizing hormone (β‐LH) was first seen in gonadotropes of the anterior pituitary gland.At 19 days of gestation, 31% of the total number of LHRH‐reactive neurons observed in the rat brain was found in the nervus terminalis, and immunoreactive processes were first seen in the organum vasculosum of the lamina terminalis and in the median eminence.Our data indicate that from 15 to 19 days of gestation the nervus terminalis is a principal source of LHRH in the fetal rat. Presence of the decapeptide in the nervus terminalis prior to appearance of β‐LH in the anterior pituitary suggests a possible role for LHRH in this system on maturation of the gonadotropes and differentiation of the brain‐pit

ISSN:0092-7317    

DOI:10.1002/cne.902380309

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe present study tests the hypothesis that there are numerous unmyelinated primary afferent fibers in cat posterior funiculi. The animals have unilateral dorsal rhizotomies from L6 to Ca3. One week later the axons of both S2 dorsal funiculi are counted. The data indicate that there are approximately 22,500 myelinated and 8,500 unmyelinated axons on the unoperated side and 11,000 myelinated and 3,900 unmyelinated axons on the operated side. On this basis we suggest that 51% of the myelinated and 54% of the unmyelinated axons in cat dorsal funiculi arise from dorsal root ganglion cells and thus are primary afferent axons. If this is correct, then 71% of the primary afferent axons in the cat dorsal funiculus are myelinated and 29% are unmyelinated. The function of this large group of previously unsuspected fine sensory axons remains to be determined.

ISSN:0092-7317    

DOI:10.1002/cne.902380310

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

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902380301

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

年代:1985

数据来源: WILEY