摘要:

AbstractDescending projections were studied in autoradiographically prepared material after injections of tritiated leucine in the pontine tegmentum of rats. Injections involving the medial pontine reticular formation resulted not only in labeling commissural fibers, the medial reticulospinal tract, and the dorsal cap of the inferior olive, but also, in two cases, in labeling a cerebellar projection that originated from a region near the midline and clearly dorsal to the nucleus reticularis tegmenti pontis. The labeled fibers passed ventrad in the midline to the pontine gray, then laterally through the gray and into the middle cerebellar peduncle to terminate as mossy fibers primarily in the flocculus, lobulus simplex, and Crus I of the ansiform lobule.Injections involving the mesencephalic nucleus of the trigeminal nerve (Vmes), resulted in labeling of Probst's tract, which descends in the dorsolateral reticular formation. Probst's tract gave off extensive terminal branches to the lateral medullary reticular formation and weaker projections to restricted portions of the descending trigeminal nucleus, the solitary nucleus, and the hypoglossal nucleus. In one case, fibers could be traced into the dorsal horn of the upper cervical cord.

ISSN:0092-7317    

DOI:10.1002/cne.902560402

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of putative cholinergic neurons in the brain of a cyprinid teleost was investigated by immunocytochemistry, with well‐characterized polyclonal antibodies to porcine choline acetyltransferase (ChAT), correlated with acetylcholinesterase (AChE) histochemistry. AChE‐positive neurons were more numerous than GhAT‐immunoreactive (ChAT‐IR) neurons. Regions with ChAT‐IR neurons generally also contained AChE‐positive ones, but regions with AChE‐positive neurons often did not contain (or contained only small numbers of) ChAT‐IR neurons. ChAT‐IR neurons were located in the brainstem cranial nerve motor nuclei, in the brainstem reticular formation, in the nucleus laterals valvulae and an adjacent subnucleus “a,” in the nucleus isthmi, and in the stratum griseum periventriculare of the tectum opticum. All neurons in these areas were AChE positive. ChAT‐IR neurons were also observed within the boundaries of the nucleus sensibilis nervi trigemini and the n. descendens nervi trigemini. The periventricular hypothalamus and the paraventricular organ, the pineal organ, and (possibly) the nucleus suprachiasmaticus also contained ChAT‐IR neurons. In these areas, AChE activity was either low or located mainly in neurons other than the ChAT‐IR ones. A small population of ChAT‐IR neurons was observed in area ventralis telencephali pars lateralis. This was the only telencephalic ChAT‐IR cell group. Furthermore, some previously unrecognized cell groups were observed. A small number of ChAT‐IR neurons, located on the dorsal aspect of the fasciculus longitudinalis medialis (caudal to n. raphe dorsalis), emitted axons that passed caudally along the raphe midline and innervated some of the large reticular neurons. Another group of ChAT‐IR neurons was observed caudal to the thalamic nucleus centralis posterior and was tentatively designed n. tractus rotundus, on the basis of the neuronal morphology. The almost Golgilike staining of some of the ChAT‐IR cell groups permitted the identification of their efferent connections and

ISSN:0092-7317    

DOI:10.1002/cne.902560403

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

Abstract1An electron microscopic study has been made of chemical synapses that develop between identified nerve cells isolated from the CNS of the leech and maintained in culture. Structures resembling synapses were observed in pairs of Retzius cells and P sensory cells at which chemical transmission had been demonstrated by recording with microelectrodes. Vesicle recycling was shown by following the uptake of extracellular markers after stimulation.2The membrane separation between the presynaptic Retzius cell (which is known to liberate serotonin) and the postsynaptic P cell was wider in synaptic than in extrasynaptic regions. The Retzius cell contained clusters of clear vesicles apposed to thickenings of the presynaptic membrane. These clear vesicle clusters were capped by a layer of dense core vesicles that did not contact the presynaptic membrane thickenings. Subsynaptic cisternae were found in the postsynaptic cell opposite the presynaptic membrane thickenings. Occasional slight postsynaptic membrane thickenings were seen. Extracellular material was observed within the synaptic cleft.3Similar synaptic structures developed between pairs of Retzius cells in culture; even a single Retzius cell was able to form autapses upon itself.4Structures resembling transmitter release sites were found in Retzius cells at a distance from any postsynaptic membranes. These are presumed to be locations for the diffuse release of transmitter.5Presynaptic structures resembling release sites were never observed in P cells apposed to Retzius cells.6Antibody to serotonin (5‐HT) labelled with colloidal gold showed serotonin to be localized in the dense core vesicles in Retzius cells.7Stimulation of pairs of Retzius and P cells by raised concentrations of K+ resulted in uptake of extracellular markers. Only Retzius cells became labelled. Ferritin was found in cisternae, in dense core vesicles, and in clear vesicles. HRP was found in cisternae and in clear vesicles. Colloidal gold was taken up by coated vesicles and was occasionally found in both clear and dense core vesicles. The uptake of extracellular markers following stimulation was blocked by high Mg ++.8These results show that structures develop between pairs of cells at which chemical transmission develops and that transmitter release leads to turnover of dense core and clear vesicle

ISSN:0092-7317    

DOI:10.1002/cne.902560404

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractCells in the dorsal motor vagal nucleus (DMVN) of the adult guinea pig were counted at different times after unilateral cervical section of the vagus nerve. The counts were made from serial 30 μm coronal sections throughout the DMVN in normal and operated animals. There are three types of cells in the DMVN of guinea pig: medium‐sized motoneurons that are retrogradely filled by HRP from the site of the vagotomy, small neurons, and glial cells. An interesting observation was a change in distribution of cells in the DMVN with age in unoperated guinea pigs.Following vagotomy degeneration was seen only in the motoneurons. Disappearance of motoneurons was slow and only 27% were present after 1 year. During that time the decrease in the total number of motoneurons was exponential with a time constant of 8.6 months, but degeneration in different parts of the nucleus was not uniform. Thirty‐four percent of motoneurons in the caudal area of DMVN disappeared in the first month after vagotomy, while the rostral area was almost unchanged. The rostral area, however, showed rapid degeneration between 3 and 6 months after vagotomy. The central part of the nucleus degenerated at a constant rate between those of the rostral and caudal regions. At the end of 1 year, cell loss in all parts of the nucleus was approximately equal.Surviving motoneurons showed morphological changes: rounding of the soma, continuous reduction of the cell volume, and shrinkage of the nucleus. Occasional abnormal forms showing vacuolization or invaginated nuclei were seen. Calculations show that the process of degeneration lasts 25 days on the average.The marked degeneration found in dorsal vagal motoneurons, in contrast to recovery from axotomy in somatic motoneurons, is similar to that found in intrinsic neurons of the central nervous system. The slow and continuous time course of disappearance of motoneurons after vagotomy, however, is exceptional. It is reasonable to postulate that the increased vulnerability of these motoneurons may be sufficient to result in degeneration in response to what are normally nonpathological metabolic dem

ISSN:0092-7317    

DOI:10.1002/cne.902560405

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAfferent connections of the anterior thalamic nuclei (ATN) are classically thought to originate in the mammillary body and limbic cortex. This study explores nonlimbic sources of ATN afferents by using retrograde transport of horseradish peroxidase (HUP) to ascertain the relative contribution of these connections. Spread of HRP into adjacent regions was prevented either by removing the overlying cortex or by injecting through permanently implanted cannulas.The main sources of nonlimbic ATN afferents are the pretectum and central gray. Pretectal neurons were HRP‐labeled primarily in the contralateral medial pretectal nucleus with a smaller number in the ipsilateral posterior pretectal nucleus. In the central gray, labeled cells were concentrated ipsilaterally in the laterodorsal tegmental nucleus. Additional projections to ATN originate in the reticular and ventral lateral geniculate nuclei of the thalamus, raphe nuclei, peripontine tegmental nucleus, and locus coeruleus.The association of ATN afferents with muscarinic receptors was also explored by means ofin vitroreceptor autoradiography with the muscarinic ligands propylbenzilylcholine mustard (PrBCM) and pirenzepine (PZ) in normal rats and rats with ablations. Ibotenic acid injections into ATN were used to destroy intrinsic neurons while leaving afferent fibers intact. Whereas such ablations produced statistically significant decreases in PrBCM binding in the anterior dorsal (AD, −45%) and anterior ventral, magnocellular part (AVm, −51%) nuclei, binding in the anterior ventral, parvicellular part (AVp) and anterior medial (AM) nuclei was not significantly decreased. Furthermore, PZ binding in normal rat ATN was significantly less (−72%) than PrBCM binding. These results suggest that a major proportion of muscarinic binding is associated with presynaptic elements.Ibotenic acid ablations of the mammillary body reduced PrBCM binding in ATN whereas lesions in cingulate cortex and laterodorsal tegmental nucleus had no effect. Compared to sham lesion controls, mammillary body lesions resulted in statistically significant decreases in binding bilaterally in AD (−15%), AVm (−19%), and AM (−20%).In conclusion, ATN receive afferents from several nonlimbic regions. Of these inputs, the pretectum may be the primary route through which sensory information reaches ATN. In addition, cholinergic input may modulate activity in projections from the mammillary body to ATN through presynaptic muscari

ISSN:0092-7317    

DOI:10.1002/cne.902560406

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractWe investigated the influence of different subcortical structures on the survival of specific populations of occipital cortex neurons developingin vitro.Explants of embryonic day 14–15 (E14–15) rat cortex were cultured for 5 days with explants of either diencephalon or optic tectum or another occipital cortex explant. Stereological analysis of the explants revealed that after 5 daysin vitro(5 DIV) all the cortical explants contained equal proportions of healthy neurons, glia, neuropil, and degenerating profiles, regardless of the culturing conditions. In order to determine if different neuronal populations survived preferentially in the cortical explants as a result of the presence of potential target or afferent structures, we used HRP filling and3H‐thymidine labeling techniques. Specific differences in the morphology of the cells and their time of origin are found in the cortical explants. In the cortical explants cocultured with diencephalon (Cx+D) the cortical cells that survive tend to be round with small cross‐sectional areas and have few neurites. These cells are generated late in the culturing period. The surviving cortical neurons in the cortex plus tectum (Cx + T) cultures are larger‐many with a pyramidal‐shaped soma and several neurites. These cells are generated earlierin vitro. The cortex cultured with other cortex (Cx+Cx) gives values intermediate to the Cx+D and Cx+T cultures. The results of these experiments suggest that there are diffusible trophic factors that arise from subcortical structures that selectively support the survival of neuron populations in the developin

ISSN:0092-7317    

DOI:10.1002/cne.902560407

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe specificity of trophic interactions in the rat visual system is investigatedin vivoby using a combination of tissue culture and CNS transplantation methods. In a companion paper (Repka and Cunningham: '87) we showed that explants of embryonic day 14 (E14) occipital cortex are biased to contain different cortical cell populations depending on whether the explants develop in culture with diencephalon or with optic tectum. In this study we transplanted these precultured cortical explants into the cavity created by a lesion of the occipital cortex in newborn rats and then measured the neuron‐occupied volume and the numbers of thymidine‐labeled cells in the surviving ipsilateral dorsal lateral geniculate nucleus (dLGN) of the host rats. The results were compared to (1) animals with lesions but no transplants, (2) animals with transplants of E14 cortical tissue that had not been precultured, and (3) animals with cerebellar transplants that had been similarly precultured either with other cerebellar tissue or with diencephalon. At 5 days postlesion, both the largest dLGN volume and the greatest number of labeled dLGN neurons survive in animals with cortical transplants precultured with diencephalon or other cortex. The surviving dLGN neurons that are rescued by these transplants are generated on E15 or E16, a period that corresponds to the latter part of geniculate neurogenesis. Relatively few cells generated on E14 survive in any group of animals. Furthermore, animals with all types of cortical transplants have significantly larger volumes of surviving dLGN than animals with either leisons only or cerebellar transplants. However, by 9 days postlesion, the dLGN has almost completely disappeared in all groups of rats, indicating that the effect of the transplants is temporary. The results demonstrate that cortical transplants can protect host neurons in particular stages of development from degeneration after a cortical lesion and suggest that a particular population of later‐generated cortical cells is responsible for this effect. Since many of these later‐generated cells may represent neurons that are the natural targets of dLGN neurons, the results suggest a high degree of neurotrophic specificity duringin vivodevelopment of the rat visual

ISSN:0092-7317    

DOI:10.1002/cne.902560408

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe cortical projection to the lateral reticular nucleus (LRN) was explored in monkeys prepared for autoradiography and horseradish peroxidase (HRP) histochemistry. An unambiguous projection was revealed only in cases with injections of the precentral forelimb and hindlimb areas. The forelimb area projection occupied centromedial segments, the hindlimb area projection occupied ventrolateral segments of the LRN with very little overlap. Some sparse labeling was also seen with injections of the supplementary motor area (SMA), but only when the lectin‐bound tracer HRP was injected and not when autoradiography was used. Retrogradely labeled cortical cells occupied a larger cortical area in one case with injection of free HRP into the LRN. Since the additional expanse of cortex, however, was not examined in anterograde cases, and since the injected marker substance had diffused to neighboring structures, the significance of the labeled cells outside the precentral motor cortex is questionable. There was no evidence for a projection from the precentral face area with either anterograde tracing method. The corticoreticular projection was bilateral and only slightly more marked contralateral to the injection. The labeling was largely confined to the magnocellular division with minor amounts in the parvicellular division (especially in the hindlimb cases). The subtrigeminal portion was spared in all cases. It is concluded that the LRN constitutes another somatotopically organized precerebellar nucleus relaying signals from the motor cortex to the cerebellum. Compared with the corticopontocerebellar parthway in monkeys, however, the LRN is only a minor component of the corticocerebellar transmission syste

ISSN:0092-7317    

DOI:10.1002/cne.902560409

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe aim of this study was to extend the anatomical study of the cortico‐reticular organization in the monkey by means of microelectrophysiological techniques. Considering the relatively modest projection (see companion paper, Wiesendanger and Wiesendanger, '87), it was surprising to see that over 70% of the investigated LRN neurons were influenced from at least one cortical stimulation site. Many neurons responded, however, with long latencies suggesting an indirect transmission line. In line with the anatomical tracing study, most short‐latency responses were obtained from the motor cortex. Postcentral cortex and the SMA were, in general, less effective sites for evoking responses in the LRN. LRN neurons with similar cortical inputs tended to be clustered together suggesting that the corticoreticular projection is discretely organized with an “intermingled somatotopy.” The majority of the 87 tested LRN neurons were not reactive to any peripheral stimulus (33%) or responded only to nociceptive peripheral stimulation (31%). Very large receptive fields were seen in 8% of the units. However, a significant proportion of LRN neurons (10%) had restricted receptive fields and reacted to gentle cutaneous stimuli, and others (17%) responded to discrete passive rotations of one or more joints. There was often a somatotopical correspondence between the peripheral and the cortical inputs. It is concluded that the LRN in monkeys is under the influence of the motor cortex, which, however, may be exerted to a major extent via indirect pathways. The electrophysiological data suggest a discrete rather than a diffuse relationship with

ISSN:0092-7317    

DOI:10.1002/cne.902560410

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of nerves containing immunoreactivity for substance P (SP), vasoactive intestinal polypeptide (VIP), leucine‐enkephalin (LENK), and gastrin‐releasing polypeptide (GRP) in the margin of the reticulo‐omasal orifice, omasum, and omasal pillar of calves and cows was studied by immunohistochemistry. The general distribution of nerves was determined by means of neuron‐specific enolase (NSE) antiserum and then compared to the distribution of immunoreactive (IR) nerves stained for the four peptides.Marked differences in the distribution of immunoreactive nerves were associated with age and the segment examined. SP‐IR fibers were abundant in the musculature of the ungulate papillae at the reticulo‐omasal orifice and in the smooth muscle of the omasal leaves, moderately dense in the omasal pillar, and low in density in the inner muscle layer of the reticuio‐omasal orifice and in the muscle of the omasal wall. In order of decreasing abundance, the cell bodies of SP‐IR nerves were found at the reticulo‐omasal orifice, in the omasal wall, and in the omasal pillar. LENK‐IR fibers, though less abundant, showed a pattern of distribution that was similar to that of SP‐IR fibers. Nerve cell bodies showing weak immunoreactivity for LENK were detected rarely. Abundant VIP‐IR fibers were present in the inner muscle layer of the reticulo‐omasal orifice and in the omasal wall, while moderate numbers were seen in the omasal pillar: they were low in density in the ungulate papillae and omasal leaves. Cell bodies of VIP‐IR nerves decreased in number through the omasum, reticulo‐omasal orifice, and omasal pillar. The distribution of GRP‐IR nerve fibers was similar to that of VTP‐IR fibers, although GRP‐IR fibers were less abundant. Nerve cell bodies showing weak immunoreactivity for GRP were detected rarely. The individual distribution of peptide‐IR nerves was similar in the calf and cow, but immunoreactive nerves were far more abundant in the calf. The present study provides valuable information for discussion of the possible role of nerves

ISSN:0092-7317    

DOI:10.1002/cne.902560411

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY