ISSN:0741-0581    

DOI:10.1002/jemt.1060150102

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

年代:1990

数据来源: WILEY

摘要:

AbstractCholinergic synapses can be identified in immunocytochemical preparations by the use of monoclonal antibodies and specific antisera to choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine (ACh) and a specific marker for cholinergic neurons. Electron microscopic studies demonstrate that the fibers and varicosities observed in light microscopic preparations of many brain regions are small‐diameter unmyelinated axons and vesicle‐containing boutons. The labeled boutons generally contain clear vesicles and one or more mitochondrial profiles. Many of these boutons form synaptic contacts, and the synapses are frequently of the symmetric type, displaying thin postsynaptic densities and relatively short contact zones. However, ChAT‐labeled synapses with asymmetric junctions are also observed, and their frequency varies among different brain regions. Unlabeled dendritic shafts are the most common postsynaptic elements in virtually all regions examined although other neuronal elements, including dendritic spines and neuronal somata, also receive some cholinergic innervation. ChAT‐labeled boutons form synaptic contacts with several different types of unlabeled neurons within the same brain region. Such findings are consistent with a generally diffuse pattern of cholinergic innervation in many parts of the central nervous system. Despite many similarities in the characteristics of ChAT‐labeled synapses, there appears to be some heterogeneity in the cholinergic innervation within as well as among brain regions. Differences are observed in the sizes of ChAT‐immunoreactive boutons, the types of synaptic contacts, and the predominant postsynaptic elements. Thus, the cholinergic system presents interesting challenges for future studies of the morphological organization and related function of cholinerg

ISSN:0741-0581    

DOI:10.1002/jemt.1060150103

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe monoamines dopamine, noradrenaline, adrenaline, and serotonin as well as the diamine histamine have a widespread distribution in the central nervous system within synaptic terminals and nonsynaptic varicosities. In certain regions of the central nervous system the monoamines are contained in varicosities that have no synaptic specialization associated with them, suggesting a possible neuromodulatory role for some of the monoamines. The majority of monoamine labelled structures are synaptic terminals which are characterized by the presence of small, clear vesicles (40–60 nm) and large, granular vesicles (70–120 nm) within the terminal. A third population of vesicles—small, granular vesicles—which are visible only after histochemical staining, are probably the equivalent of the small, clear vesicles present after either autoradiographic or immunohistochemical labelling. Most monoamine containing terminals contact dendrites and dendritic spines and, less frequently, neuronal somata and other axons. Both asymmetrical and symmetrical membrane specializations are associated with monoaminergic terminals; however, asymmetrical contacts are the most frequent type found. These ultrastructural results indicate that monoamine containing terminals and varicosities in general share many common morphological features, but still have diverse fu

ISSN:0741-0581    

DOI:10.1002/jemt.1060150104

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

年代:1990

数据来源: WILEY

摘要:

AbstractGABA is a known inhibitory neurotransmitter in the mammalian brain. The site of GABAergic synapses can be determined with immunocytochemical methods that localize either GABA or its synthesizing enzyme, glutamate decarboxylase (GAD). In general, GABAergic axon terminals contain pleomorphic synaptic vesicles and form symmetric synapses. However, a small number of GABAergic axon terminals in selected brain regions (spinal cord, cerebellum, superior colliculus, striatum, globus pallidus, inferior olive, and substantia nigra) form asymmetric synapses. GAD‐ and GABA‐immunoreactive processes that contain synaptic vesicles participate in every known morphological type of chemical synapse. These include axosomatic, axodendritic, axospinous, initial segment, axoaxonic, dendrodendritic, serial, reciprocal, and ribbon synapses. Although GABAergic synapses form a heterogeneous group, they most commonly form axosomatic, axodendritic, and initial segment synapses in the brain and spinal cord. These findings provide helpful guidelines for the identification of GABAergic synapses in future stud

ISSN:0741-0581    

DOI:10.1002/jemt.1060150105

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe ultrastructural localization of putative excitatory (glutamate, aspartate) and inhibitory (taurine, glycine) amino acid neurotransmitters is described in several selected rat brain regions. In general, axon terminal profiles immunoreactive for excitatory amino acids formed asymmetric synapses with non‐immunoreactive small diameter dendritic profiles or dendritic spines. In the cerebellum, both mossy fiber terminals and parallel fiber terminals were immunoreactive for glutamate and aspartate. In the hippocampus, mossy fiber terminals within the stratum lucidum of the CA3 region were immunoreactive for glutamate. Localization of glutamate and aspartate to cerebellar parallel and mossy fibers, as well as the identification of glutamate in hippocampal mossy fibers, is consistent with the excitatory nature of these fibers as described in previous physiological studies. Glutamate‐like immunoreactive terminals were also identified in subnucleus caudalis of the spinal trigeminal nucleus and in the dorsal horn of the spinal cord.Immunoreactive axon terminals for two putative inhibitory neurotransmitters, glycine and taurine, displayed a greater number of morphological variations in synaptic structure. In the cerebellum, taurine‐like immunoreactivity was present in both basket cell axon terminals which formed symmetric synapses with Purkinje cell neurons, and in a few mossy fiber terminals which formed asymmetric synapses with dendritic spines. In the area dentata of the hippocampus, taurine‐like immunoreactive profiles formed asymmetric synapses with dendritic elements. Glycine‐like immunoreactive terminals formed symmetric synapses with cell perikarya in both the ventral horn of the spinal cord and in the cochlear nuclei, and on axon terminals in the spinal trigeminal and cochlear nuclei. In contrast, some glycine‐like immunoreactive terminals formed asymmetric synapses with distal dendritic profiles in the spinal cord and spinal trigeminal nucleus. The localization of taurine to cerebellar basket cell axons and glycine to axon terminals that synapse on ventral horn motor neuron perikarya is consistent with the hypothesis that these amino acids are functioning as inhibitory neurotransmitters at these synapses. Taurine localization to cerebellar mossy fibers and to fibers in the molecular layer of the dentate gyrus may be more consistent with a proposed neuromodulator role

ISSN:0741-0581    

DOI:10.1002/jemt.1060150106

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

年代:1990

数据来源: WILEY

摘要:

AbstractA number of different neuropeptides have been described within presynaptic terminals at the ultrastructural level in the central nervous system. The majority of these neuropeptides share a common morphology with one another. Terminals containing neuropeptides have a population of small, clear vesicles associated with the active zone of the synapse and a lesser number of large, granular vesicles that are located at a distance from the active site of the synapse. It is believed that the large, granular vesicles act as a mechanism for the transport/storage of the neuropeptides, while the small, clear vesicles are thought to be acting as structures responsible for the release of the neurotransmitter/neuropeptide into the synaptic cleft. The neuropeptide containing terminals most often have asymmetrical junctions associated with their presynaptic membranes, although symmetrical junctions have been described with peptide containing terminals in a number of areas in the central nervous system. Neuropeptide containing terminals contact every part of the neuronal membrane; however, the majority of synaptic contacts involve portions of the dendritic shafts. Evidence is beginning to accumulate to indicate that for certain neuropeptides there is a specific spatial arrangement to their termination along the neuronal membrane.

ISSN:0741-0581    

DOI:10.1002/jemt.1060150107

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

年代:1990

数据来源: WILEY

摘要:

AbstractOver the last several years our knowledge of neurotransmitter receptors has increased dramatically as receptor types and subtypes have been identified through the development of selective antagonists, neuropharmacological studies, and radioactive ligand binding studies. At the same time major advances were made in the immunocytochemical localization of neurotransmitters and their related enzymes. However, only recently has immunocytochemistry been used to localize neurotransmitter receptors, and these studies have been limited. Four receptors have been localized in the CNS with immunocytochemistry: the nicotinic acetylcholine receptor, the beta‐adrenergic receptor, the GABA/benzodiazepine receptor, and the glycine receptor. Of these the glycine receptor has been the most thoroughly characterized. Glycine receptor immunoreactivity is highly concentrated at postsynaptic sites, and the distribution of immunoreactivity appears to correlate closely with glycinergic neurons. However, immunocytochemical studies done on other receptors suggest such a distribution may not always be the case. Some receptors may not be concentrated at postsynaptic sites, and receptor distribution may not always closely fit the distribution of the respective neurotransmitter. Work is rapidly progressing on the purification of other receptors and on the production of selective antibodies which will allow immunocytochemical studies which address these and other question

ISSN:0741-0581    

DOI:10.1002/jemt.1060150108

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

年代:1990

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060150109

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

年代:1990

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060150110

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

年代:1990

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060150111

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

年代:1990

数据来源: WILEY