摘要:

AbstractThe location in time and space of the terminal mitoses of type I and type II sensory hair cells (HCI and HCII) of the developing crista ampullaris in rat lateral semicircular canal and macula utriculi was determined by radioautographs of specimens exposed to tritiated thymidine from the 13th to the 20th day of gestation. Qualitative analysis and statistical treatment of the percentages of labeled HCI and HCII show that the terminal mitoses occur first in the macula utriculi with a maximum percentage of the 14th day of gestation, for the HCI, and on the 15th day of gestation, for the HCII. In the lateral crista, the maximum percentage of labeled HCI occurs on the 17th and 18th day of gestation and on the 19th day of gestation for the HCII. A spatial distribution of this labeling activity is also described: the older cells are located at the top of the crista and at the level of the striola of the macula utriculi while the younger cells are found at the bottom of the crista and on the sides of the utricle. A study of the vestibular receptors in the fetuses shows that synaptic contacts already exist on the 18th day of gestation in the macula utriculi at the level of the striola and on the 19th day at the top of the crista; the cells situated on the periphery are still immature. The first hair cells to undergo their terminal mitoses are, therefore, connected first. These results also suggest that the two types of cells are genetically programmed and that the HCI start functioning first during the development of the labyrinth.

ISSN:0092-7317    

DOI:10.1002/cne.902060102

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractAlthough the rat tail flick reflex (TFR) is widely used to study neural mechanisms of analgesia, its underlying anatomy has not been systematically studied. In the present study axonal transport of horseradish peroxidase (HRP) was used to trace the efferent and afferent connections of the TFR. The extensor caudae medialis (ECM), extensor caudae lateralis (ECL), and abductor caudae dorsalis (ACD) were identified as tail flick muscles and injected with HRP. Labeled motor neurons were found in lumbar segments L4–L6, sacral segments S1–S4, and coccygeal segments Co1–Co2; ECL injections also labeled cells in Co3. Motor neurons were concentrated at levels L5‐S2 for ECM, at levels S2‐Co2 for ECL, and at levels L5‐Co1 for ACD.To label the terminals of tail flick afferents, the dorsolateral tail nerve (DLTN) and the ventrolateral tail nerve (VLTN) which innervate the skin of the tail were cut and exposed to HRP. Application of HRP to either DLTN or VLTN labeled afferent terminals in S4, Co1, Co2, and Co3. For DLTN, the greatest density of afferent label was observed in the lateral half of laminae I and II of the dorsal horn. In contrast, labeled afferents from VLTN were concentrated in the medial half of laminae I–II. With longer survival times afferent terminals were also labeled in S3, and in the ventral horn of segments L6‐S2. Bilateral dorsal rhizotomies at levels S3‐Co3 were necessary and sufficient to abolish the tail flick. This corroborated the results from the anatomical studies.Although tail flick motor neurons were present in ten spinal segments, L4‐Co3, tail flick afferents were concentrated caudally in segments S3‐Co3. Thus, in addition to segmental connections, the TFR requires an ascending propriospinal connection from coccygeal and caudal sacral dorsal horn to S1, S2, and to the lumbar enlargement. The intense labeling from tail afferents found in the substantia gelatinosa (SG) is consistent with pharmacological, anatomical, and physiological studies implicating the SG as an important site for inhibition of the tail flick reflex by opiates and by

ISSN:0092-7317    

DOI:10.1002/cne.902060103

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe afferent projections from the brainstem to the mediodorsal thalamic nucleus (MD) were studied in the cat, by means of retrograde transport of horseradish peroxidase. A topographical arrangement of these projections is described. The medial part of MD is the area of the nucleus which receives fewer afferents from the brainstem. After injections in this part, labeled neurons were observed mainly in the interpeduncular nucleus, the ventral tegmental area and the substantia nigra. After injections of HRP in the intermediate part of the MD, labeled cells were seen mainly in the interpeduncular nucleus, substantia nigra, dorsal and centralis superior raphe nuclei, dorsal tegmental nucleus, and coeruleus complex. Less conspicuous was the number of labeled cells in the central gray and the dorsolateral portion of the tegmentum of the mesencephalon and pons. After injections in the lateral part of MD, labeled neurons were observed mainly in the deep layers of the superior colliculus, central gray, the oral paramedian pontine reticular tegmentum, and the interpeduncular nucleus. Labeled cells were also observed in the substantia nigra, locus coeruleus, dorsal tegmental nucleus, cuneiform area, and the mesencephalic reticular formation. These findings show the MD as a thalamic link of three different groups of brainstem structures projecting to different cortical areas with different functional significance.

ISSN:0092-7317    

DOI:10.1002/cne.902060104

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe cortical projection of the nucleus submedius (Sm) was studied in the cat with the autoradiographic and horseradish peroxidase (HRP) methods. The results indicate that Sm projects topographically on to layer 3 of a distinct agranular cortical field that occupies the posterolateral gyrus proreus, the adjacent fundus of the rhinal sulcus, and the postero‐ventral portion of the medial wall of the presylvian sulcus. This cortical field is denoted the ventrolateral orbital cortex (VLO), consonant with previous nomenclature in the rat (Krettek and Price, '77a). The more ventral part (VLOβ) is cytoarchitectonically distinct from the dorsal part (VLOα); the former receives input from the anterior part of Sm (Sma), while the latter receives superficial layer 1 of VLO probably also arises from Sm, and there may be an input to layers 5 and 6. The corticothalamic projection from VLO to Sm reciprocates the ipsilateral thalamocortical projection and also has a moderate contralateral component. A dense, subpial layer 1 input to VLO arises from cells of the ventromedial nucleus (VM) subjacent to Sm. The present experiments also indicate that clusters of cells in VM probably provide input to layer 3 of the cortex in the fundus of the presylvian sulcus, as well as area 6aβ in the lateral wall of the presylvian sulcus and the ventral bank of the cruciate sulcus. Results from the HRP experiments additionally indicate that VLOβ and the anteroventral (Smv) portion of VLOα are reciprocally connected with the ventral agranular insular cortex and the cingulate cortex, ipsilaterally, while the posterodorsal (Smd) portion of VLOα is instead connected with specific portions of the somatosensory cortical areas bilaterally. All portions of VLOα appear to project to the ventrolateral periaqueductal gray.In light of the recent suggestion that (Smd) is involved with nociception (Craig and Burton, '81), the present results suggest that the related portion of VLOα may serve as a cortical representation for noxiou

ISSN:0092-7317    

DOI:10.1002/cne.902060105

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper is the first of a projected series of studies on the strcture and composition of the medial forebrain bundle (MFB) of the rat and the relations of this fiber system to its bed nucleus, the lateral hypothalamic area. The first part of the paper comprises an extensive review of literature on the MFB from its discovery by Ganser in 1882 to the present. This review serves as the basis for an evalution of our present‐day knowledge of the organization of the MFB, which is presented in the second part of this paper. Despite the wealth of information available on the origins and sites of termination of the axons that constitute the MFB, surprisingly little attention has been given to the bundle itself, to its topographic boundaries, its fiber composition, or to the spatial arrangement of its constituent components. These features of the MFB as it extends through the lateral preoptic and lateral hypothalamic areas have been analyzed in normal Klüver‐Barrera‐ and Bodian‐stained material. From this analysis, a detailed atlas of the MFB and some of the surrounding structures has been prepared. This atlas, which forms the third section of this paper, illustrates the appearance and organization of the MFB at ten equidistant levels through the lateral preoptic and lateral hypothalamic c

ISSN:0092-7317    

DOI:10.1002/cne.902060106

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe medial forebrain bundle (MFB) is a complex fiber system that courses through and partly arises and partly terminates within the lateral preoptic and lateral hypothalamic areas. It consists mainly of thin fibers and may be comprised of as many as 50 descending and ascending components of varying lengths and of different origins and/or destinations (Nieuwenhuys et al., 1982). With the aid of an an atlas of the MFB and the surrounding brain areas in the rat presented in the preceding paper (Nieuwenhuys et al.,1982), the position and topographic relationships of some 21 components of the bundle have been analyzed in detail, in brains that had been prepared for autoradiography following injections of tritiated amino acids into a number of structures that are known to contribute fibers to the MFB. From this analysis it is clear that most of the labeled components occupy specific and rather constant positions within the MFB. For example, theascendingcomponents are largely confined to the dorsal half of the bundle; those arising from the medial preoptic area and the various hypothalamic nuclei are distributed rather diffusely over much of the MFB; and thedescendingcomponents that arise from the olfactory tubercle and the magnocellular preoptic nucleus are confined to restricted parts of the bundle. These findings indicate that the neurons which occupy different parts of the lateral hypothalamic area probably receive distinctive inputs, and to a first approximation these are likely to be determined principally by their position within the MFB.

ISSN:0092-7317    

DOI:10.1002/cne.902060107

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902060101

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY