摘要:

AbstractTo begin an investigation of the auditory pathways in the brainstem of the mustache bat, we examined the cytoarchitecture of the cochlear nuclei, superior olivary complex, nuclei of the lateral lemniscus, and inferior colliculus. Although all of these auditory centers are hypertrophied in this echolocating bat, only some areas have unusual cytoarchitectural features: (1) In the anterior part of the anteroventral cochlear nucleus we do not find the large spherical cells seen in other mammals; instead, very small spherical cells are found in this area. (2) In the posterior part of the anteroventral cochlear nucleus there is a region containing a homogeneous population of very large multipolar cells. (3) The medial superior olive is unusually large for an animal with a small head. (4) The most striking observations are seen in the lateral lemniscus. The ventral nucleus of the lateral lemniscus has a distinct columnar organization. The intermediate area of the lateral lemniscus contains a large and very distinct nucleus. Each of these cytoarchitectural features distinguishes the auditory system of this bat from that of other mammals. The results raise questions about whether or not there are unique subdivisions in the auditory pathways of echolocating bats. The results also identify these unusual nuclei as candidates to play a role in the special auditory functions related to echolocation.

ISSN:0092-7317    

DOI:10.1002/cne.902070102

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe origins of pathways to the inferior colliculus of the mustache bat were identified by retrograde transport of horseradish peroxidase (HRP). A specific goal of this study was to obtain evidence that would help determine whether the nuclei, shown in the previous paper to have unusual cytoarchitectural features, are unique to bats, or whether they are homologous to areas that are not well differentiated in other mammals. The auditory pathways in the lower brain stem ofPteronotusappear to conform to the same basic organization as in other mammals: After injection of HRP into one inferior colliculus, labeled cells are located contralaterally in the cochlear nucleus, ipsilaterally in the medial superior olive, bilaterally in the lateral superior olive, ipsilaterally in the ventral and intermediate nuclei of the lateral lemniscus, and bilaterally in the dorsal nucleus of the lateral lemniscus. These patterns of labeling provide a basis for understanding how the specialized auditory areas of the bat may be organized within a basic plan of mammalian auditory systems. In the anteroventral cochlear nucleus the unusually small spherical cells seem to be homologous to stellate cells in the anteroventral cochlear nucleus of the cat. In the superior olive, differences in patterns of labeled cells distinguish the medial from the lateral superior olive. In the lateral lemniscus the pattern of labeled cells shows clear differences between the two special parts, intermediate and ventral nuclei, as well as between these and the dorsal nucleus of the lateral lemniscus. The results are consistent with the hypothesis that the unusual auditory nuclei of the bat have homologues in mammals whose auditory systems are not specialized for echolocation.

ISSN:0092-7317    

DOI:10.1002/cne.902070103

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe photoreceptor terminals of newly eclosed female flies,Musca domestica, have been sampled in the first optic neuropile (or lamina) in one of two ways: first, in large number (n = 760) from single sections and second, from serial electron micrographs of the six terminals within each of three cartridges. Both sampling methods concur in assessing the number of synapses established with the two principal monopolar relay interneurons, L1 and L2, within each cartridge. Each receptor is calculated to be presynaptic at about 200 ± 40 (2 SE) synapses. This value considerably exceeds previous estimates, primarily because we took careful account of the appearance of synapses in different section planes. The number of these synapses correlates highly with the area of receptor terminal presynaptic membrane, so that each synapse is allotted, on average, about 1.6 μm2. The synapses are evenly graded in their distribution with an unexplained 23% decrease in both membrane perimeter and synapse number halfway along their receptor terminal's length. The numbers of synapses per receptor did not vary systematically within two horizontal (3 × 20 cartridge) strips of frontal, equatorial lamina sampled. Individual synapses are elongate tetrads (Burkhardt and Braitenberg, ′76) with two pairs of postsynaptic elements. The first pair is invariably contributed by the interneurons L1 and L2 (one each). The second pair comes either from the α processes of an amacrine cell or from a glial cell. In the distal lamina, however, L3 contributes one of the two postsynaptic processes, the second being αor glial. The overall ratio of postsynaptic involvement at distal synapses (α:glial:L3) is 55%, 20%, and 12% respectively, the remainder being unide

ISSN:0092-7317    

DOI:10.1002/cne.902070104

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

年代:1982

数据来源: WILEY

摘要:

AbstractAt the equator of the fly's eye, between dorsal and ventral eye halves, a systematic, natural addition of photoreceptor terminal input occurs at each of the fixed populations of uniquely identifiable postsynaptic interneurons in each cartridge of the first optic neuropile, or lamina. The equatorial cartridges are identical in composition except in having seven and eight receptor terminals (7R and 8R, respectively), compared with six elsewhere (6R cartridges). The effects of this augmented presynaptic input upon the frequency of the chief afferent class of photoreceptor tetrad synapse were studied compared with control data for 6R cartridges (Nicol and Meinertzhagen, ′82). The synapse population size and distribution within five depth levels of the lamina is, on average, approximately constant for all receptor terminals whether from 6R, 7R, or 8R cartridges. The overall determinant ofsynapse frequency is therefore presynaptic. Small (5–6%) average decreases in synapse frequency per receptor in 7R and 8R cartridges compared with 6R co‐vary with similar decreases in membrane area, each synapse occupying a patch of membrane of similar area in all cases. The tetradic postsynaptic composition of synapses was also similar in all cases. Because of the augmented synaptic input to the postsynaptic neurons, a morphometric analysis was undertaken of two (L1 and L2) which receive input as a pair from every synapse. There is the same dendrite number (about 180) in 8R L1/L2 as in 6R L1/L2 but they have different branching patterns, conforming to the different number and configuration of receptor terminals. Thus in an 8R cartridge each terminal is serviced by a comb of fewer dendrites, but each dendrite is longer, fatter, and services more synapses. The area of L1/L2 dendritic membrane exposed is increased, compared with 6R cartridges, in proportion with the number of synapses it participates at postsynaptically, so that all dendrites (6R and 8R) allocate the same mean area (about 0.55 μm2) of postsynaptic membrane per s

ISSN:0092-7317    

DOI:10.1002/cne.902070105

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe distribution of the cells of origin of the primate spinoreticular tract was determined following injections of horseradish peroxidase (HRP) into the pontomedullary reticular formation inMacaca fascicularis.Five animals received large bilateral injections which included the raphe nuclei and seven monkeys received smaller, unilateral injections. Sections sampled were from upper cervical levels, the cervical enlargement, upper and lower thoracic levels, and lumbosacral levels. The laminar distribution of spinoreticular cells in all spinal cord levels was comparable. More than half of the labeled cells were located ventromedially, in laminae VII and VIII. HRP‐labeled cells were also found in the dorsal horn, primarily in the lateral reticulated part of lamina V. Some cells were also found in laminae I and X. Spinoreticular cells in the lumbosacral spinal cord mainly projected to the contralateral brainstem. In the cervical enlargement, however, a bilateral distribution of cells was observed following unilateral injections of HRP. Most spinoreticular cells were multipolar neurons with extensive dendritic ramifications. The distribution of spinoreticular cells is similar to the distribution of spinal cord neurons that project to the medial thalamus, but different from that of spinal neurons projecting to the ventrobasal complex. The anatomical organization of the spinoreticular tract is consistent with a role for this pathway in nociceptio

ISSN:0092-7317    

DOI:10.1002/cne.902070106

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

年代:1982

数据来源: WILEY

摘要:

AbstractExtracellular recordings were made from 29 spinoreticular cells in the spinal cords of anesthetized monkeys. The cells were in either the cervicalor the lumbar enlargement, and they were identified by antidromic activation from the medial part of the pontomedullary reticular formation. More spinoreticular neurons were sampled in the cervical than in the lumbar cord. Most of the cells were contralateral to the side from which antidromic activation was observed, but a higher proportion of the spinoreticular neurons inthe cervical enlargement than in the lumbar enlargement was ipsilateral to the antidromic stimulus. Three cells in the lumbar cord were antidromicallyactivated not only from the reticular formation but also from the contralateral thalamus, confirming that some spinoreticular projections are formed by collaterals from spinothalamic cells. Most of the spinoreticular neurons were in the ventral horn in laminae VII and VIII, although a few were in laminae IV‐VI. Nearly half of the spinoreticular cells in the sample could not be activated by any form of peripheral stimulation tested. The other cells could be activated by stimulation of receptive fields that varied from small to large, that were sometimes bilateral regions of the skin or of deep tissues. Although some spinoreticular cells could be classified as low threshold or wide dynamic range, the largest proportion were high threshold, requiring noxious stimulation for their activation. Descending volleys resulting from stimulation in the reticular formation could often be shown to inhibit or to excite spinoreticular neurons. It can be concluded that at leastsome spinoreticular neurons may play a role in nociceptio

ISSN:0092-7317    

DOI:10.1002/cne.902070107

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe distribution and the orgins of substance P (SP)‐positive fibers in the papillae of the rat tongue were investigated by means of the indirect immunofluorescent method.Three types of papilla contain SP‐positive fibers, though the number ofthese fibers varies from papilla to papilla. The circumvallate papilla contains the greatest number of SP‐positive fibers, followed by the foliate papillae and the fungiform papillae; the filiform papillae lack SP‐positive fibers. The papillar SP‐positive fibers form dense bands in the lamina propria just beneath the epithelium. Some of the fibers enter the epithelium and the taste buds. It should be stressed that not every taste bud is provided with SP‐positive fibers: Only 95% of the taste buds in the foliate papillae, 70% of the taste buds in the fungiform papillae, and 40% of the taste buds in the circumvallate papillae contain detectable SP‐positive fibers. Unilateral section of the glossopharyngeal nerve resulted in a complete disappearance of SP‐positive fibers in the foliate papillae on the operated side, and a slight decrease in the circumvallate papillae on both sides. Bilateral section of the glossopharyngeal nerve resulted in a complete disappearance of SP‐positive fibers in the foliate and circumvallate papillae. Following unilateral section of the chorda tympani, SP‐positive fibers in the tastebuds of the fungiform papillae disappeared completely. In addition, unilateral neurotomy of the mandibular nerve resulted in a complete disappearance of SP‐positive fibers in the epithelium of the fungiform papillae. These facts strongly indicate that SP in the foliate and circumvallate papillae is supplied by the glossopharyngeal nerve, SP in the taste buds of the fungiform papillae by the chorda tympani, and SP in the epithelium of the fungiform papillae by the third division of

ISSN:0092-7317    

DOI:10.1002/cne.902070108

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

年代:1982

数据来源: WILEY

摘要:

AbstractAlthough androgens act on the primate central nervous system to modulate both endocrine functions and a number of limbic‐related behaviors, little is known about the anatomical location of the neurons which sequester these steroids in primates. To determine the prime location of these androgen‐concentrating neurons in the forebrain of the primate, we injected three castrated female rhesus monkeys in the femoral vein with 1 μg of 5α‐dihydro (1, 2, 4, 5, 6, 7‐3H) testosterone (3H‐DHT, 107 Ci/mmole) per kg of body weight. One of these animals also received an IV injection of 100 μg/kg body weight of unlabeled dihydrotestosterone (DHT) to serve as a control. One hour after the injection of3H‐DHT we rapidly exsanguinated each animal. The forebrain was sliced and blocks containing the amygdala, diencephalon, frontal pole, and hippocampus were frozen and stored in liquid nitrogen until processing. The tissue was then processed for autoradiography. A specific topographic pattern of nuclear concentration of DHT or one of its metabolites was obtained in neurons of the basal hypothalamus, preoptic region, amygdala, and hippocampus. This pattern was similar to that found in

ISSN:0092-7317    

DOI:10.1002/cne.902070109

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

年代:1982

数据来源: WILEY

摘要:

AbstractIt is estimated by means of electron microscopy that the optic nerve of the turtlePseudemys scripta eleganscontains 394,900 fibers of which approximately 80% are myelinated. The total fiber count agrees well withcounts obtained from electron microscopic studies on other turtle species. There are, however, differences among these species in the percentage of myelinated fibers in the optic nerve. The axon diameter distribution of the myelinated fibers (excluding myelin) has a mode at 0.87 μm while that of the unmyelinated fibers has a mode at 0.42 μm. Both distributions are unimodal and are of a similar form in all areas of the nerve sampled. The total fiber count reported here agrees well with previous reports of ganglion cell counts inPseudemysand the characteristics of the fiber distributions are comparable to those reported for nonreptilian vertebrate

ISSN:0092-7317    

DOI:10.1002/cne.902070110

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

年代:1982

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902070101

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

年代:1982

数据来源: WILEY