摘要:

AbstractThe efferent connections of the lateral hypothalamic area (LHA) have been analyzed in a series of 30 rat brains with injections of3H‐amino acids into different parts of the area and the surrounding regions. Our findings indicate that all parts of the LHA contribute ascending and descending fibers to the medial forebrain bundle, and also project medially to certain of the adjoining hypothalamic nuclei. All levels of the LHA appear to send some fibers to a continuous group of structures that extends from the medial septal‐diagonal band complex rostrally, through the lateral preoptic and lateral hypothalamic areas to the mammillary complex and the ventral tegmental area caudally. In addition, it is evident that cells at different levels within the LHA may have differential projections. Thus, the anterior and lateral parts of the LHA also appear to project substantially to the anterior hypothalamic area, the ventromedial and dorsomedial hypothalamic nuclei, the parataenial and paraventricular nuclei of the thalamus, and the medial part of the lateral habenular nucleus. Similarly, cells in the tuberal and posterior parts of the LHA project to the central gray, the longest projections from the posterior region reaching as far caudally as the central tegmental field, the parabrachial nucleus, the locus coeruleus, and the superior central and dorsal nuclei of the raphe. Viewed as a whole, the LHA is therefore well‐suited to integrate inputs from the limbic system and brainstem and to relay them on the one hand to the medial zone of the hypothalamus and on the other to virtually every structure closely associated with the medical forebrain bundle and to the nuclei of origin of the major ascending monoaminergic sy

ISSN:0092-7317    

DOI:10.1002/cne.901830402

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe generation of lateral motor neurons (LMNs), interneurons and dorsal root ganglion (DRG) neurons of the cervical mouse spinal cord has been investigated by [3H]thymidine autoradiographic techniques. This investigation has two main objectives: (a) to determine on which embryonic days these three neuronal populations are born, and (b) to investigate the possibility that the neurons comprising early reflex circuits might be formed by a retrograde temporal sequencing of generation. LMNs are the first neurons generated in the cervical spinal cord. They arise between E8.8 and E11.5, and approximately 90% of these cells are born within a 36‐hour period between E9 and E10.5. The earliest time of origin for interneurons is on E9.5, and those cells which are generated between E9.5 and E10.5 cluster in two distinct regions of the adult spinal cord. One of these regions is the lateral portions of laminae IV through VI; this appears to be the location of many ipsilateral association neurons. DRG neurons begin to arise on E9.5 and their generation is completed by E14. There is a trend within the DRG population for large neurons to be born before small neurons. Those cells with diameters of 40 μm or greater reach their generation peak on E10.5, while those smaller than 40 μm arise in the greatest numbers on E12.The findings of other investigations have provided evidence for a retrograde sequence of synaptic closure in the formation of the early disynaptic forelimb reflex pathway. The temporal difference in synapse formation in the terminal fields of DRG and association neurons is discussed in terms of our observation that both of these populations appear to have similar generation times. We suggest that factors responsible for the delayed synaptic closure of DRG afferents include the greater distances and the degree of collateralization which these afferents must undergo in order to establish their terminal fields. Finally, we discuss the possibility that the temporal sequence of neuronal generation and factors involved with the growth of neurites combine to produce a retrograde sequence of synaptic closure in the early disynaptic forelimb reflex pathway of mouse spinal c

ISSN:0092-7317    

DOI:10.1002/cne.901830403

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

年代:1979

数据来源: WILEY

摘要:

AbstractRetinotectal topography, response properties of neurons in superior colliculus, and visual orienting behavior were studied in hamsters whose superior colliculi were innervated by one or the other of two types of anomalous ipsilateral projections.For the first type, an abnormally large uncrossed projection was created by monocular enucleation on the day of birth. This projection extended over the superficial part of the rostral half of the colliculus. The upper visual field was represented medially, and the lower visual field laterally, which corresponds to a normal projection. The rostrocaudal axis was disordered, but showed a slight tendency for nasal visual field to be represented rostrally and temporal field caudally; this tendency corresponds to an inversion of the normal ipsilateral projection, fitting instead the pattern of a contralateral projection.For the second type of anomalous ipsilateral projection, an abnormal intertectal decussation of optic tract fibers was created by neonatal ablation of the superficial layers of one superior colliculus and removal of the ipsilateral eye (Schneider, '73). Retinotectal topography observed in this recrossing projection was predominantly mirror‐symmetric to the normal contralateral projection; however, some distortions in retinotopic order were observed, including misplaced fields and local inversions of the mirror‐symmetric topography, and distortions of local magnification factor. Response properties of single units found medially in the left colliculus were similar to those found in normal colliculus. Units found more laterally were underresponsive, showing response decrements with repeated stimulation which is abnormal for units in the superficial gray, and many had abnormally large receptive fields. This physiological pattern was reflected in the pattern of errors made in visual orienting to small targets.It was concluded that polarity cues exist in the tectum sufficient to order the terminals of the retinotectal projection independent of the direction of fiber arrival or order in the optic tract as it enters the tectum. In addition, the functional competence of the abnormal recrossing retinotectal projection has been demonstrated by both electrophysiological and behavioral meth

ISSN:0092-7317    

DOI:10.1002/cne.901830404

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

年代:1979

数据来源: WILEY

摘要:

AbstractWe have examined the ultrastructure of the cell body of a vertebrate spinal neuron, the Rohon‐Beard cell ofXenopus laevis, at four stages during its development (Nieuwkoop and Faber stages: 22, 29/30, 37/38 and 42). At this time it has attained its electrical excitability and the action potential mechanism in the cell body is maturing through a sequence of stages in which the inward current is carried by Ca++(stages 20–25), later by Ca++and Na+(stages 25–40), and finally by Na+(stages 40–51) (Spitzer and Baccaglini, '976; Baccaglini and Spitzer, '77). There is a change in the abundance and distribution of the organelles in the perikaryon during this period, characteristic of other developing neurons. Mitochondria and Golgi apparatus become localized progressively more in the interior of the cells, and rough endoplasmic reticulum progressively more to the periphery where it often appears in orderly tiers parallel to the plasma membrane. The mitochondria contain dense intramitochondrial granules which are known in other cells to contain concentrations of divalent cations. The number of granules declines over the course of the developmental period studied.The presence of the intramitochondrial granules was examined quantitatively because electrophysiological data indicate that the amount of Ca++entering the cells in early stages should raise the internal Ca++concentration by several orders of magnitude, and that Ca++is rapidly sequestered (Baccaglini and Spitzer, '77). A minimum of 200 mitochondrial profiles from at least four Rohon‐Beard cells were scored for the presence of dense intramitochondrial granules at each stage studied. In stage 22 Rohon‐Beard cells 75 ± 5% (mean ± SD, n = 4) of the mitochondrial profiles scored contained granules; in stage 29/30, 56 ± 10% (n = 7); in stage 37/38, 3 ± 3% (n = 5); and in stage 42, 0.5 ± 0.25% (n = 4). Therefore, dense intramitochondrial granules, an indication of calcium accumulation in mitochondria, decrease in parallel with the loss of the Ca++component of the inward current of the action potential in Roh

ISSN:0092-7317    

DOI:10.1002/cne.901830405

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe efferent projections from nucleus caudalis of the spinal trigeminal complex in cats were studied with retrograde and anterograde axonal transport techniques combined with localization of recording sites in the thalamus and marginal zone of nucleus caudalis to innocuous skin cooling. Results showed brainstem projections from nucleus caudalis to rostral levels of the spinal trigeminal complex, to the ventral division of the principal trigeminal nucleus, the parabrachial nucleus, cranial motor nuclei 7 and 12, solitary complex, contralateral dorsal inferior olivary nucleus, portions of the lateral reticular formation, upper cervical spinal dorsal horn and, lateral cervical nucleus. Projections to the thalamus included: a dorsomedial region of VPM (bilaterally) and to the main part of VPM and PO contralaterally. Neuronal activity was recorded in the dorsomedial region of VPM to cooling the ipsilateral tongue. HRP injections in this thalamic region retrogradely labeled marginal neurons in nucleus caudalis. These results show that marginal neurons of nucleus caudalis provide a trigeminal equivalent of spinothalamic projections to the ventroposterior nucleus in cats.

ISSN:0092-7317    

DOI:10.1002/cne.901830406

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

年代:1979

数据来源: WILEY

摘要:

AbstractIndividual nerve fibers were traced on consecutive serial 1‐μm‐thick cross‐sections to determine their position of origin within the horizontal ampullary nerve trunk (HANT) and the site at which they penetrated the basilar lamina of the horizontal crista in the guitarfish,Rhinobatos productus. Of the 132 fibers successfully traced, 87.1% followed an anatomical projection pattern consistent with the dynamic response characteristics of the nerve fibers. That projection pattern was: from the peripheral HANT region to the ipsilateral slope; from the central HANT region to the crest; and from the intermediate HANT region both to the ipsilateral slope and the crest of the horizontal crista. The 12.9% of “error” fibers not following this projection pattern were also consistent with the functional neurophysiological data. The terms crista bulbus and crista angustarum were introduced to designate specific anatomical regions of the dumb‐bell shaped crist

ISSN:0092-7317    

DOI:10.1002/cne.901830407

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

年代:1979

数据来源: WILEY

摘要:

AbstractEfferent projections from the ventromedial nucleus of the hypothalamus (VMN) were traced using tritiated amino acid autoradiography in albino rats.Ascending fibers passed through the anterior hypothalamus. Labelled fibers and terminal fields were seen in the preoptic area, bed nucleus of the stria terminalis, substantia innominata, the anterior amygdaloid area, diagonal bands of Broca and lateral septum. Fibers also projected laterally from VMN and entered the supraoptic commissures and zona incerta. These lateral projections were responsible for the fibers observed in the cerebral peduncle, the amygdala, the thalamus and the reticular formation. Fibers descending in a medial position projected through the posterior hypothalamus and then swept dorsally to terminate in the mesencephalic and pontine central grey. A projection from VMN into the median eminence was noted. The overall patterns of projection from different parts of VMN were similar; differences that existed were primarily in the relative strengths of the different projections.The efferent projections from VMN are extensive, well organized, and would appear capable of supporting significant physiological actions on extra‐hypothalamic structure

ISSN:0092-7317    

DOI:10.1002/cne.901830408

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

年代:1979

数据来源: WILEY

摘要:

AbstractOptic axons from eyes transplanted to hindbrain and spinal cord (i.e., non‐optic areas) inXenopusembryos reproducibly follow a particular pair of continous tracts, theexternal sensory tractand theinternal sensory tract.The course of theexternal sensory tractmay coincide with the course of the general somatic afferent tracts (i.e., the ascending and descending tracts of nerve V, the tract of Lissauer, and the Rohon‐Beard cell tracts). The course of theinternal sensory tractparallels that of theexternal sensory tractbut runs more medially. Transplanted optic axons follow the same tracts regardless of where along the neural axis the axons have entered the CNS. What kind of developmental cues guide these optic axons? It is unlikely that the guidance cues are organized as spatial coordinates, rather it appears that the optic axons of these two tracts are guided along pre‐existing substrate routes. We have called these routessubstrate pathways. Substrate pathwaysmay be a device normally used for organizing fiber tracts in the developing nervous s

ISSN:0092-7317    

DOI:10.1002/cne.901830409

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe thalamic connectivity of areas 3b, 1 and 2 of the first somatic sensory cortex (SI) and of the adjacent areas 4, 3a and 5 has been studied in monkeys with anterograde and retrograde labeling techniques.Anteroposterior sectors of the SI cortex are represented in the thalamic ventrobasal complex by curved lamellae of thalamocortical relay cells extending through the dorso‐ventral and anteroposterior dimensions of the ventrobasal complex. Within such a lamella there are clustered aggregations of cells each projecting to a punctate zone of SI. Such cortical zones are less than 1 mm in circumference and are interpreted as comparable to the “columns” of electrophysiological studies. Each clustered aggregation in the ventrobasal complex is of limited mediolateral and dorsoventral extent but extends through much of the anteroposterior dimension of the ventrobasal complex. Punctate zones lying adjacent to one another in the mediolateral dimension of the SI cortex are connected with aggregations of cells lying in adjacent lamellae of the ventrobasal complex. Punctate zones lying anterior or posterior to one another in the anteroposterior dimension of SI are connected with aggregations of cells lying ventral or dorsal to one another in a lamella of the ventrobasal complex.Sectors of SI extending from posterior to anterior across areas 2 and 1 and others extending from posterior to anterior across area 3b, are each represented systematically across the full dorsal to ventral dimension of the ventrobasal complex. This implies at least two separate representations of the body surface: one in areas 2 and 1, and another in area 3b.Within a lamella of the ventrobasal complex, aggregations of cells projecting to areas 2 and 1 are mingled with those projecting to area 3b. Measurements of the sizes of retrogradely labeled cells in brains in which areas 2 and 1 or area 3b were separately injected showed no distinction between cells projecting to the three areas on the basis of size. Experiments combining retrograde cell degeneration due to ablation of area 3b with retrograde labeling after injection of areas 1 and 2 indicated little possibility of collateral projections to the three areas from the same cell.No part of SI, as defined by the most liberal anatomical criteria, is connected with any thalamic nucleus outside the confines of the ventrobasal complex (the caudal division of the ventroposterolateral nucleus and the large‐celled part of the ventroposteromedial nucleus) or of the intralaminar complex. Area 3a, as traditionally defined, has connectional relationships that strongly suggest it is a part of the motor cortex, area 4. However, short latency Group I evoked potentials could be elicited from a small part of area 3a lacking layer V giant cells and lying adjacent to area 3b. This part receives its thalamic input from the ventrobasal complex. The data indicate that area 4 is connected with the oral division of the ventroposterolateral nucleus and with the caudal nucleus of the ventral lateral complex. These cellular groupings, however, are only artificially separated and appear to form part of the same thalamic relay nucleus.Experiments on area 5 not only suggest that the posterior boundary of SI should be placed further posterior than is customary, but also suggest that area 5 can be divided into an anterior field related to the anterior nucleus of the pulvinar and a posterior field related to the lateral posterior

ISSN:0092-7317    

DOI:10.1002/cne.901830410

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

年代:1979

数据来源: WILEY

摘要:

AbstractA small group of selected optic fibers were surgically deflected from one tectum into the other, thus creating a novel additional projection originating from a small area of ipsilateral retina. The normal fibers to this “recipient” tectum were also severed so that both the deflected and the normal fibers regrew into this tectum at about the same time. The reinnervation pattern was analyzed by autoradiography and electrophysiologic mapping. Both techniques showed that the deflected fibers and the “normal” fibers failed to intermix. The deflected fibers typically formed several well‐defined patches of innervation in roughly the appropriate region of denervated recipient tectum. The normal fibers filled in the remaining uninnervated tectal areas and were completely or nearly completely excluded from the patches occupied by the deflected fibers. This segregation was often quite sharp having an apparent average overlap less than 25–50 μm. The electrophysiology indicated that the projections of both deflected and normal fibers were retinotopically organized but that the mapping by the normal fibers was compressed. This compression, an apparent consequence of being squeezed onto a smaller than normal region of tectum, was similar to that previously observed following ablations of part of the tectum. The negligible surgical damage in the present experiment, however, excludes the kind of cytochemical reorganization previously suggested to produce compression. The findings also provide evidence for a competitive type of interaction between

ISSN:0092-7317    

DOI:10.1002/cne.901830411

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

年代:1979

数据来源: WILEY