摘要:

AbstractStudies of the trophic activities of brain‐derived neurotrophic factor and neurotrophin‐3 indicate that both molecules support the survival of a number of different embryonic cell types in culture. We have shown that mRNAs for brain‐derived neurotrophic factor and neurotrophin‐3 are localized to specific ventral mesencephalic regions containing dopaminergic cell bodies, including the substantia nigra and ventral tegmental area. In the present study, in situ hybridization with35S‐labeled cRNA probes for the neurotrophin mRNAs was combined with neurotoxin lesions or with immunocytochemistry for the catecholamine‐synthesizing enzyme tyrosine hydroxylase to determine whether the dopaminergic neurons, themselves, synthesize the neurotrophins in adult rat midbrain. Following unilateral destruction of the midbrain dopamine cells with 6‐hydroxydopamine, a substantial, but incomplete, depletion of brain‐derived neurotrophic factor and neurotrophin‐3 mRNA‐containing cells was observed in the ipsilateral substantia nigra pars compacta and ventral tegmental area. In other rats, combined in situ hybridization and tyrosine hydroxylase immunocytochemistry demonstrated that the vast majority of the neurotrophin mRNA‐containing neurons in the substantia nigra and ventral tegmental area were tyrosine hydroxylase immunoreactive. Of the total population of tyrosine hydroxylase‐positive cells, double‐labeled neurons constituted 25–50% in the ventral tegmental area and 10–30% in the substantia nigra pars compacta, with the proportion being greater in medial pars compacta. In addition, tyrosine hydroxylase/neurotrophin mRNA coexistence was observed in neurons in other mesencephalic regions including the retrorubral field, interfascicular nucleus, rostral and central linear nuclei, dorsal raphe nucleus, and supramammillary region. The present results demonstrate brain‐derived neurotrophic factor and neurotrophin‐3 expression by adult midbrain dopamine neurons and support the suggestion that these neurotrophins influence dopamine neurons via autocrine or paracrine mechanisms. These data raise the additional possibility that inappropriate expression of the neurotrophins by dopaminergic neurons could contribute to the neuropathology of disease states such as Parkinson's disease and schi

ISSN:0092-7317    

DOI:10.1002/cne.903420302

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe neuropeptides myomodulin, small cardioactive peptide (SCP), and buccalin are widely distributed in the phylum Mollusca and have important physiological functions. Here, we describe the detailed distribution of each class of peptide in the central nervous system (CNS) of the snailLymnaea stagnalisby the use of immunocytochemical techniques combined with dye‐marking of electrophysiologically identified neurons. We report the isolation and structural characterization of aLymnaeamyomodulin, PMSMLRLamide, identical to myomodulin A ofAplysia californica. Myomodulin immunoreactivity was localized in all 11 ganglia, in their connectives, and in peripheral nerves. In many cases, myomodulin immunoreactivity appeared localized in neuronal clusters expressing FMRFamide‐like peptides, but also in a large number of additional neurons. Double‐labelling experiments demonstrated myomodulin immunoreactivity in the visceral white interneuron, involved in regulation of cardiorespiration. SCP‐like immunoreactivity also appeared in all ganglia, and double‐labelling experiments revealed that in many locations it was specifically associated with clusters expressing distinct exons of the FMRFamide gene that are differentially expressed in the CNS. Characterization of the two types of SCP‐antisera used in this study, however, suggested that they cross‐reacted with both FMRFamide and N‐terminally extended FMRFamide‐like peptides. Selective preadsorption with these cross‐reacting peptides resulted in elimination of the widespread staining and retention of bona fide SCP immunoreactivity in the buccal and pedal ganglia only. Buccalin immunoreactivity was limited to the buccal and pedal ganglia. It did not coincide with the distribution of either myomodulin or SCP. Most immunoreactive clusters were found in the pedal ganglia. ©

ISSN:0092-7317    

DOI:10.1002/cne.903420303

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper investigates the distribution of four classes of neuropeptides, myomodulin, small cardioactive peptide (SCP), buccalin, and FMRFamide, in central neurons forming the network that underlies feeding behavior in the snailLymnaea stagnalis. Intracellular dye‐marking and immunocytochemical analysis, using antisera to the different classes of peptides, were applied to identified neurons of all three levels of the hierarchy of the circuitry: modulatory interneurons (cerebral giant cells, CGC; slow oscillator, SO), central pattern generator (CPG) interneurons (N1, N2, N3), motoneurons (B1–B10), and their peripheral target organs. Myomodulin immunoreactivity was detected in the CGC interneurons, in the SO, and in ventral N2‐type CPG interneurons. Several large buccal motoneurons, the paired B1, B2, B3, B7, and neurons located in the dorsal posterior area (putative B4 cluster types) were also myomodulin immunoreactive. Target organs of buccal motoneurons, the buccal mass, salivary glands, and oesophagus contained myomodulin‐immunopositive fibers. SCP appeared in N2‐type interneurons and was found colocalized with myomodulin in the B1 and B2 motoneurons. SCP‐containing neurons in the B4 cluster area were also detected. The buccal mass and salivary glands exhibited SCP‐immunoreactive fibers. Buccalin immunoreactivity was scarce in the buccal ganglia and was identified only in N1‐type interneurons and three pairs of dorsal posterior neurons. In the periphery, immunoreactive fibers were localized in the oesophagus only. None of the buccal neuronal types examined revealed immunoreactivity to SEQPDVDDYLRDVVLQSEEPLY (“SEEPLY”), a peptide encoded in the FMRFamide precursor protein ofLymnaea. SEEPLY immunoreactivity was confined to a pair of novel ventral neurons with projections to the laterobuccal nerve innervating the buccal mass. Immunoreactive fibers were also traced in this organ. ©

ISSN:0092-7317    

DOI:10.1002/cne.903420304

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

年代:1994

数据来源: WILEY

摘要:

AbstractOrganotypic cerebellar cultures derived from newborn mice were continuously exposed to medium containing tetrodotoxin and elevated levels of magnesium to block all electrical activity. After 2 weeks in vitro, no activity was evident during the first 15–20 minutes following transfer to a recording medium without blocking agents. Thereafter, cortical discharge rates increased until a state of sustained hyperactivity was reached. Ultrastructural examination of such cultures revealed a reduction of inhibitory Purkinje cell somatic synapses to half the control value along with an even greater reduction of axodendritic synapses (largely inhibitory) in the cortical neuropil. No loss of axospinous synapses (excitatory) was evident. These results support the concept that spontaneous neuronal activity is necessary for the full development of inhibitory circuitry. © 1994 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903420305

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn the present study, double‐label immunoelectron microscopy was used to examine the synaptic relationships between amacrine cell populations in the chicken retina that contain either enkephalin or γ‐aminobutyric acid (GABA) or both enkephalin and GABA. The objectives of the present study were twofold. First, the ultrastructural features and synaptic organization of enkephalin and enkephalin/GABA amacrine cells were compared. Second, the synaptic interactions between these populations and the population of GABA amacrine cells were examined.A total of 475 synaptic arrangements were observed to involve enkephalin or enkephalin/GABA amacrine cell processes. The synaptic relationships of enkephalin and enkephalin/GABA amacrine cells were quite similar. Each population was pre‐ and postsynaptic to amacrine cells, postsynaptic to bipolar cells, and presynaptic to processes possibly originating from ganglion cells. A substantial percentage of each population's pre‐ and postsynaptic relationships were with the processes of GABAergic amacrine cells. Moreover, when enkephalin and enkephalin/ GABA amacrine cell processes were postsynaptic to bipolar cells, their dyadic partner was observed frequently to be a GABA amacrine cell process.The present study suggests a diversity in the population of chicken enkephalin amacrine cells with respect to their expression of the classical inhibitory transmitter GABA. Moreover, a functional relationship between enkephalinergic and GABAergic pathways is indicated by studies showing that both enkephalin and enkephalin/GABA amacrine cells exhibit substantial synaptic interaction with GABA amacrine cells. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903420306

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

年代:1994

数据来源: WILEY

摘要:

AbstractImmunocytochemical studies in the primate neocortex have shown that particular populations of pyramidal cells can be identified by antibody SMI 32 that recognizes a nonphosphorylated epitope of neurofilament protein, while chandelier cells (a powerful type of cortical inhibitory interneuron) and presumptive thalamocortical axons can be identified by antibodies directed against the calcium‐binding protein parvalbumin (PV). We used these antibodies in correlative light and electron microscopic immunocytochemical studies to analyze certain aspects of the synaptic circuitry of human temporal neocortex. In sections cut in the tangential plane, many PV‐immunoreactive chandelier cell axon terminals and apical dendrites of SMI 32‐stained pyramidal cells were distributed in small clusters. Combination of immunocytochemistry for PV and SMI 32 revealed four subpopulations of pyramidal cells with regard to the immunocytochemical staining by SMI 32 and the innervation of their axon initial segments by PV‐positive or ‐negative chandelier cell axon terminals, but there were differences in the concentration and proportion of these subpopulations by layers. Furthermore, we present electron microscopic evidence suggesting that the characteristic layer III dense band of PV‐immunoreactive puncta is made up mainly of presumptive thalamocortical axon terminals. Besides, coincidence was found between the dense PV‐immunoreactive band and the dendritic plexus formed by the SMI 32‐stained pyramidal cells in the lower half of layer III, which leads us to think that they are probably a major target of PV‐immunoreactive thalamic terminations. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903420307

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe present study reports the existence of projection fibers from the entopeduncular nucleus to the superior colliculus and lateral parts of the pontobulbar tegmental regions (so‐called lateral tegmental field) in the rat, suggesting that the entopeduncular nucleus may control eye‐head and orofacial movements via these projection fibers. The anterograde axonal tracing withPhaseolus vulgaris‐leucoagglutinin has revealed that the entopedunculotectal fibers terminate, bilaterally, with an ipsilateral predominance, in the deep layers of the superior colliculus through its rostral one‐third level and that the entopedunculotegmental fibers terminate, bilaterally, with an ipsilateral predominance, in the parabrachial area, reticular formation surrounding the trigeminal motor nucleus, and parvicellular, dorsal, and ventral reticular nuclei. The cells of origin of the entopedunculotectal and entopedunculotegmental projections have been identified by retrograde axonal tracing with Fluoro‐Gold and cholera toxin B subunit. The entopedunculotectal or entopedunculotegmental fibers originate, respectively, from the dorsal or ventral part of the entopeduncular nucleus. Additionally, a series of fluorescent retrograde double‐labeling experiments with Fast Blue and Diamidino Yellow have indicated that single entopeduncular nucleus neurons projecting to the superior colliculus or lateral tegmental field often send their axon collaterals to the lateral habenular nucleus.The entopedunculotectal fibers are assumed to control head movements, which may be provoked via the tectospinal fibers, and further to participate in eye movements as the nigrotectal fibers that have been known to arise from the substantia nigra pars reticulata to end in the deep layers of the superior colliculus primarily through its caudal two‐thirds level. The entopedunculotegmental fibers are presumed to be involved in control of orofacial movements, because the sites of termination of the entopedunculotegmental fibers correspond well with the reported areas of distribution of premotor interneurons for the trigeminal motor, facial, and hypoglossal nuclei. © 1994 W

ISSN:0092-7317    

DOI:10.1002/cne.903420308

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

年代:1994

数据来源: WILEY

摘要:

AbstractAs an animal grows, its sensory systems face the task of maintaining sensitivity and discrimination in peripheral fields that are continually enlarging. Without the addition of neurons, existing cells would have to innervate a wider skin area, leading to a decrease in the precision with which stimuli are localized. Neurons were counted in the three dorsal root ganglia (DRGs) that innervate the hindlimb of the bullfrog (Rana catesbeiana). Profiles of neuronal nuclei containing the single nucleolus found in these cells were counted in every third section of serially cut ganglia. This means of assessing neuron number was validated by comparing these profile counts with three‐dimensional reconstructions of sensory neurons. Large frogs (10–17 cm) had more than twice as many DRG neurons as small frogs (3.3–5 cm). The rate of increase was greatest between 3 and 8 cm, when over 1,300 hindlimb sensory neurons were added for each 1 cm increase in body length. The possibility that selective survival of frogs with many neurons biases estimates of mean neuron number was ruled out by the finding that frogs drawn from the same closed population, half of which were sacrificed immediately and half of which were sacrificed after 1 year's survival, showed expected differences in neuron number. Horseradish peroxidase applied to particular hindlimb nerves retrogradely labeled more neurons in large frogs than small frogs, supporting the hypothesis that added neurons extend their axons to the periphery.No evidence of tritium labeling was found following injection of3H‐thymidine (a marker of DNA synthesis) every third day for 20–22 weeks, a period over which, on the basis of changes in body length, substantial numbers of neurons were likely added. These results, combined with previous studies of motoneuron addition in the lumbar lateral motor column, are consistent with the hypothesis that the population of sensory neurons is augmented by late differentiation of existing precursor cells. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903420309

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

年代:1994

数据来源: WILEY

摘要:

AbstractAlthough elevations in cerebral metabolic demand during development may induce angiogenesis, the correlation among ontogenic changes in local cerebral blood flow, cytochrome oxidase activity (an index of oxidative capacity) and capillary density have not been examined previously. We measured these parameters in selected regions of the brains of anesthetized rabbits of various ages. Increases in all three parameters occurred postnatally within the cerebral cortex and striatum, whereas in the medulla, values at birth were similar to those in adults. In newborns, the pattern of distribution of blood flow within the parietal cortex was such that levels were maximal in the outer layers and declined in deeper layers. This distribution correlated closely with that of capillary density, whereas cytochrome oxidase activity was maximal at levels deeper in the cortex. By postnatal day 17, the distribution for all three parameters was similar to that of cytochrome oxidase activity in young animals. A regression analysis of the regional values demonstrated a positive correlation between capillary density and blood flow in young (≤ postnatal day 8) and old (≥ postnatal day 17) animals. In contrast, cytochrome oxidase activity and capillary density were poorly correlated in young animals but positively correlated in older animals, with the slopes being markedly different (P<0.005). The results suggest that early in postnatal development, the pattern of cytochrome oxidase activity is relatively mature compared with that of capillary density. By postnatal day 17, microvascular anatomy is closely associated to oxidative capacity, likely reflecting a steady state regulation of capillary density to metabolic requirements. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903420310

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

年代:1994

数据来源: WILEY

摘要:

AbstractSynapsin I is the best characterized member of a family of nerve terminal‐specific phosphoproteins implicated in the regulation of neurotransmitter release. During development, the expression of synapsin I correlates temporally and topographically with synapse formation, and recent physiological studies (Lu et al. [1992] Neuron 8:521–529.) have suggested that synapsin I may participate in the functional maturation of synapses. To better understand the temporal relationship between synapsin I gene expression and particular cellular events during neuronal development, we have used in situ hybridization histochemistry to localize synapsin I mRNA throughout the rat central and peripheral nervous systems during embryonic and postnatal development. From the earliest embryonic time points assayed (E12), the expression of the synapsin I gene was detectable in both the central and peripheral nervous systems. While, in general, levels of synapsin I mRNAs were high in utero, synapsin I cDNA probes revealed specific patterns of hybridization in different regions of the embryonic nervous system. To determine precisely the temporal onset of expression of the synapsin I gene during neuronal development, we examined in detail the appearance of synapsin I mRNA during the well characterized postnatal development of granule cells of the rat cerebellum and hippocampus. In both regions, the onset of synapsin I gene expression correlated with the period of stem cell commitment to terminal differentiation. Finally, our data demonstrate that, in a second phase, synapsin I gene expression increases to a maximum for a given neuronal population during a particular phase of differentiation, i.e., synaptogenesis. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903420311

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

年代:1994

数据来源: WILEY