摘要:

AbstractDopamine‐immunoreactive neurons were revealed in lobster embryos, larvae, and postlarvae, and staining patterns were compared to neuronal labeling in the juvenile lobster nervous system (Cournil et al. [1994] J. Comp. Neurol.344:455–469). Dopamine immunoreactivity is first detected by midembryonic life in 35–40 neuroi somata located anteriorly in brain and subesophageal ganglion. When the lobsters assume a benthic life during the first postlarval stage, an average of 58 cell bodies are labeled. The acquisition of dopamine in lobster neurons is a protracted event spanning embryonic, larval, and postlarval life and finally reaching the full complement of roughly 100 neurons in juvenile stages.Some of the dopaminergic neurons previously identified in the mature nervous system, such as the paired Br cells, L cells, and mandibular cells, are labeled in embryos and persist throughout development. In contrast, other neurons stain transiently for dopamine during the developmental period, but, by the adult stage, these neurons are no longer immunoreactive. Such transiently labeled neurons project to the foregut, the thoracic dorsal muscles, the neurohormonal pericardial plexus, and the pericardial pouches. It is proposed that these neurons are alive and functioning in adult lobster but that dopamine levels have been abolished, proving that neurotransmitter status is a dynamic, changing process. © Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903620102

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe three dimensional organization of the dendritic trees of pyramidal cells in the rat hippocampus was investigated using intracellular injection of horseradish peroxidase in thein vitrohippocampal slice preparation and computer‐aided reconstruction. The total dendritic length, dendritic length in each of the hippocampal laminae, and the number of dendritic branches were measured in 20 CAl pyramidal cells, 7 neurons in CA2 and 20 CA3 pyramidal cells. The total dendritic length of CA3 pyramidal cells varied in a consistent fashion depending on their position within the field. Cells located close to the dentate gyrus had the smallest dendritic trees which averaged 9,300 μm in total length. Cells in the distal part of CA3 (near CA2) had the largest dendritic trees, averaging 15,800 μm. The CA2 field contained cells which resembled CA3 pyramidal cells in most respects except for the absence of thorny excrescences on their proximal dendrites. There were also smaller pyramidal cells that resembled CAl neurons. CAl pyramidal cells tended to be more homogeneous. Pyramidal neurons throughout the transverse extent of CAl had a total dendritic length on the order of 13,500 μm. The quantitative analysis of the laminar distribution of dendrites demonstrated that the stratum oriens and stratum radiatum contained significant portions of the pyramidal cell dendritic trees. In CA3, for example, 42–51% of the total dendritic length was located in stratum oriens; about 34% of the dendritic tree was located in stratum radiatum. The amount of dendritic length in stratum lacunosum‐moleculare of CA3 varied depending on the location of the cell. Many CA3 cells located within the limbs of the dentate gyrus, for example, had no dendrites extending into stratum lacunosum‐moleculare whereas those located distally in CA3 had about the same percentage of their dendritic tree in stratum lacunosum‐moleculare as in stratum radiatum. In CAl, nearly half of the dendritic length was located in stratum radiatum, 34% was in stratum oriens and 18% was in stratum lacunosum‐moleculare. These studies identified distinctive dendritic branching patterns, in the stratum radiatum and stratum lacunosum moleculare, which clearly distinguished CA3 from CAl neurons. ©

ISSN:0092-7317    

DOI:10.1002/cne.903620103

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractProjections from the claustrum (Cl) and the thalamic anterior intralaminar nuclei (MN) to different representations within the primary somatosensory (S1) and visual (V1) areas were studied using the multiple retrograde fluorescent tracing technique. The injected cortical regions were identified electrophysiologically. Retrograde labeling in Cl reveals two different projection patterns. The first pattern is characterized by a clear topographic organization and is composed of two parts. The somatosensory Cl shows a dorsoventral progression of cells projecting to the hindpaw, forepaw, and face representations of S1. The visual Cl has cells projecting to the vertical meridian representation of V1 surrounded dorsally by neurons projecting to the representation of retinal periphery. A second pattern of Cl projections is composed of neurons that are distributed diffusely through the nucleus. In both somatosensory and visual sectors, these intermingle with the topographically projecting cells. Neurons retrogradely labeled from cortical injections are always present in the AIN. In the central medial nucleus, the segregation of modality is evident: The visual‐projecting sector is dorsal, and the somatosensory is ventral. Projections from the central lateral nucleus display detectable somatotopic and retinotopic organization: Individual regions are preferentially connected with specific representations of S1 or V1. In the paracentral nucleus, no clear regional preferences are detectable. Also performed were comparisons of the proportions of neurons projecting to different sensory representations. Projections to V1 from both AIN and Cl are biased towards the retinal periphery representation. S1 projection preference is for the forepaw representation in Cl and for the hindpaw in the AIN. The quantitative analysis of multiply labeled cells reveals that, compared to Cl, the AIN contains a higher proportion of neurons branching between different representations of S1 or V1. The concept of topographic vs. diffuse projecting systems is reviewed and discussed, and functional implications of quantitative analysis are considered. © Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903620104

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe N‐methyl‐D‐aspartate (NMDA)‐type glutamate receptor in the basolateral amygdala (BLA) has been implicated in activity‐dependent plasticity important for cortically evoked acquisition of fear‐potentiated startle response. We examined the ultrastructural immunoperoxidase labeling of the R1 subunit of the NMDA receptor in the BLA of adult rats to determine the potential cellular and subcellular sites mediating the effects generated by NMDA activation. The localization was compared with that seen in the bed nucleus of the stria terminalis (BNST), the major efferent pathway from the central nucleus of the amygdala, which has a more pronounced involvement in autonomic function. Electron microscopy established that in the BLA, 68. 4% (n=177) of the profiles showing NMDAR1–like immunoreactivity (NMDAR1–LI) were dendrites, and 19. 8% were distal tips of astrocytic processes. In contrast, profiles containing NMDAR1–LI (n=262) in the BNST were more equally distributed between dendrites (37. 4%) and axons (38. 2%). The subcellular localization of NMDAR1 immunoreactivity was, however, similar in both regions. Our findings provide the first ultrastructural evidence that glutamate may prominently act through NMDAR1 receptors to elicit postsynaptic actions on intrinsic neurons in the BLA and BNST. The results also indicate that, in the BLA, the NMDAR1 receptor plays an important role in astrocytic function, whereas the receptor is more preferentially a presynaptic modulator in axons which terminate in or pass through the BNST.

ISSN:0092-7317    

DOI:10.1002/cne.903620105

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAnatomical and physiological studies indicate that the amino acid L‐glutamate is the excitatory transmitter in sensory afferent pathways to the amygdala and in intraamygdala circuits involving the lateral and basal nuclei. The regional, cellular, and subcellular immunocytochemical localizations of N‐methyl‐D‐aspartate (NMDA) and L‐α‐amino‐3–hydroxy‐5–methyl‐ 4–isoxazole propionate (AMPA), two major classes of glutamate receptors, were examined in these areas of the amygdala. A monoclonal antibody and a polyclonal antiserum directed against the R1 subunit of the NMDA receptor were used. Each immunoreagent produced distinct distributions of perikaryal and neuropilar staining. Dendritic immunoreactivity was localized primarily to asymmetric (excitatory) synaptic junctions, mostly on spines, consistent with the conventional view of the organization and function of NMDA receptors. Whereas the anti‐NMDAR1 antiserum produced sparse presynaptic axon terminal labeling and extensive glial labeling, the anti‐NMDAR1 antibody labeled considerably fewer glia and many more presynaptic axon terminals. Labeled presynaptic terminals formed asymmetric and symmetric synapses, suggesting presynaptic regulation of both excitatory and inhibitory transmission. Immunoreactivity for different subunits of the AMPA receptor (GluR1, GluR2/3, and GluR4) was uniquely distributed across neuronal populations, and some receptor subunits were specific to certain cell types. Immunoreactivity for GluR1 and Glu2/3 was predominately localized to dendritic shafts and was more extensive than that of GluR4 due to heavy labeling of proximal portions of dendrites. The distribution of GluR4 immunoreactivity was similar to NMDAR1: GluR4 was seen in presynaptic terminals, glia, and dendrites and was primarily localized to spines. The presynaptic localization of GluR4 in the absence of GluR2 suggests glutamate. mediated modulation of presynaptic Ca++concentrations. These data add to our understanding of the morphological basis of pre‐ and postsynaptic transmission mechanisms and synaptic plasticity in t

ISSN:0092-7317    

DOI:10.1002/cne.903620106

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe neurochemical characteristics of the neuronal subsets that furnish different types of corticocortical connections have been only partially determined. In recent years, several cytoskeletal proteins have emerged as reliable markers to distinguish subsets of pyramidal neurons in the cerebral cortex of primates. In particular, previous studies using an antibody to nonphosphorylated neurofilament protein (SMI‐32) have revealed a consistent degree of regional and laminar specificity in the distribution of a subpopulation of pyramidal cells in the primate cerebral cortex. The density of neurofilament protein‐immunoreactive neurons was shown to vary across corticocortical pathways in macaque monkeys. In the present study, we have used the antibody SMI‐32 to examine further and to quantify the distribution of a subset of corticocortically projecting neurons in a series of long ipsilateral corticocortical pathways in comparison to short corticocortical, commissural, and limbic connections. The results demonstrate that the long association pathways interconnecting the frontal, parietal, and temporal neocortex have a high representation of neurofilament protein‐enriched pyramidal neurons (45–90%), whereas short corticocortical, callosal, and limbic pathways are characterized by much lower numbers of such neurons (4–35%). These data suggest that different types of corticocortical connections have differential representation of highly specific neuronal subsets that share common neurochemical characteristics, thereby determining regional and laminar cortical patterns of morphological and molecular heterogeneity. These differences in neuronal neurochernical phenotype among corticocortical circuits may have considerable influence on cortical processing and may be directly related to the type of integrative function subserved by each cortical pathway. Finally, it is worth noting that neurofilainent protein‐immunoreactive neurons are dramatically affected in the course of Alzheimer's disease. The present results support the hypothesis that neurofilament protein may be crucially linked to the development of selective neuronal vulnerability and subsequent disruption of corticocortical pathways that lead to the severe impairment of cognitive function commonly observed in age‐related dementing disorders. ©

ISSN:0092-7317    

DOI:10.1002/cne.903620107

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe metabotropic glutamate receptor mGluR5 is a G‐protein coupled receptor that plays a key role in release of Ca2+from internal stores via inositol triphosphate mobilization. Western and Northern blot analyses revealed a greatly enhanced expression of mGluR5 in rats during early stages of hypothalamic development compared with the adult. This enhanced developmental expression provides an explanation for the dramatic physiological response of developing neurons to metabotropic glutamate receptor activation and supports the argument that metabotropic glutamate receptors may play an important role in hypothalamic development. During development, expression of the mGluR5 gene was reduced, not only in the hypothalamus but also in other regions of the brain. A differential decrease in mGluR5 protein was found in different brain regions with Western blot analysis. The hypothalamus showed a sixfold decrease in mGluR5 with dovelopment, whereas the cortex showed only a threefold decrease.Immunocytochemistzy with an afflnity‐purified antibody against a peptide deduced from the cloned mGluR5 gene revealed selective expression in some regions in the adult hypothalamus. In the adult and developing (postnatal day 10) brain, immunoreactive neurons were found in the suprachiasmatic nucleus, preoptic area, lateral hypothalamus, and mammillary region, areas where the related metabotropic glutamate receptor mGluR1 is also found. In contrast, the ventromedial nucleus, an area critically involved in the regulation of food intake and metabolic balances, showed strong mGluR5 immunoreactivity but no mGluR1 immunoreactivity. Little or no mGluR5 staining was found in the neurosecretory neurons of the paraventricular, supraoptic, and arcuate nuclei. Ultrastructurally, mGluR5 was associated with the cytoplasmic face of the plasmalemma on hypothalamic dendrites, dendritic spines, and neuronal perikarya in the adult. The strongest immunoreactivity was found in patches on the membrane, sometimes associated with the postsynaptic side of synapses and sometimes associated with nonsynaptic dendritic or perikaryal membrane. Intense immunostaining was found on some astrocyte processes surrounding synaptic complexes containing asymmetrical synapses. These astrocytes would be in an ideal position to receive excitatory signals from glutamatergic axons. Unlike the punctate appearance of immunolabeling on neuronal membranes, astrocytes showed continuous staining along the plasma membrane. © Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903620108

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903620101

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY