摘要:

AbstractDuring early postnatal development of the kitten visual cortex the ectoenzyme 5′‐nucleotidase undergoes a characteristic redistribution. Until about postnatal week 6 it is essentially confined to synaptic contacts in input layer IV and its expression is related to the use‐dependent segregation of thalamic afferents into ocular dominance columns. Subsequently, 5′‐nucleotidase becomes distributed uniformly throughout all layers and is then associated selectively with glial cells. Here we describe an age‐dependent alteration in the expression of a carbohydrate epitope of 5′‐nucleotidase which correlates with the developmental change of the enzyme's localization. We have isolated 5′‐nucleotidase from the occipital cortex of kittens of varying age and from adult cats and investigated by immunoblotting the association of the HNK‐1 carbohydrate epitope with the protein. 5′‐Nucleotidase carries the HNK‐1 epitope in kittens of 3–9 weeks but the epitope is absent from 12‐week‐old kittens or adult cats. Thus, the appearance of the HNK‐1 epitope correlates with the transient localization of the enzyme at synapses. The HNK‐1 carrying 5′‐nucleotidase may be involved in synaptogenesis and use‐depe

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe distribution of interleukin 6 (IL‐6) mRNA and IL‐6 receptor (IL‐6R) mRNA in the brain of adult male rats was studied at the light microscope level byin situhybridization histochemistry using35S‐labelled oligonucleotides. The transcripts of both genes were localized in the pyramidal neurons and in the granular neurons of the hippocampus, in neurons of the habenular nucleus as well as in the dorsomedial and ventromedial hypothalamus, in the piriform cortex, in scattered neurons of the cortex and in granular cells of the cerebellum. The medial preoptic nucleus and the anterior tip of the lateral ventricle contained mRNA encoding IL‐6 and its receptor. Moreover, white matter areas, such as the internal capsule, which consist of only fibres and glial cells, were found to have autoradiographic signals above background. The mRNAs for IL‐6 and IL‐6R in hippocampus and cerebellum are not different, as shown by Northern blot analyses of RNA isolated from these tissues. We postulate that the cytokine IL‐6 is expressed constitutively in discrete regions of the CNS and that it is involved in the mechanisms coordinating metabolic, behavioural and neuroendocrine changes not only during illness but also under normal physiological conditions. Our results suggest that IL‐6 mRNA and IL‐6R mRNA are colocalized, thus supporting a role of the cytokine in autocrine and para

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractHistamine releases catecholamines and opioids in primary cultured bovine adrenal medullary (BAM) chromaffin cells. We have studied whether histamine is synthesized and localized in BAM cells, and whether it can be released upon activation with secretagogues. In BAM cells histamine is immunohistochemically co‐localized with tyrosine hydroxylase in 45 ± 8% of all cells. Only histamine immunoreactivity was observed in 8 ± 2% of all BAM cells. No mast‐cell‐like cells were observed in our system. Histamine can be released from BAM cells by high potassium (56 mM K+) in a calcium‐dependent manner. Compound 48/80 did not release histamine from BAM cells but nicotine caused a dose‐dependent liberation of the amine. Cultured BAM cells have histidine decarboxylase activity which is inhibited by α‐fluoromethylhistidine. These results indicate that endogenous histamine is synthesized, stored and released in BAM chromaffin

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractUsingin situhybridization histochemistry with [32P]oligonucleotide probes, we studied the cellular localization of RNA transcripts for amyloidβ‐protein precursor (βAPP), growth‐associated phosphoprotein‐43 (GAP‐43) and microtubule‐associated protein 2 (MAP2) in the mesostriatal system of normal (+/+) and weaver(wv/wv)mutant mice, which lose mesencephalic dopamine neurons. In addition, expression of the same messages was studied in ventral mesencephalic cell suspensions transplanted to the weaver striatum. Transcripts encoding GAP‐43, MAP2 and isoformsβAPP695,βAPP714andβAPP751were present in normal substantia nigra and progressively reduced in weaver substantia nigra; such a reduction was correlated with dopamine neuron loss. The survival of dopamine neurons in unilateral intrastriatal grafts was documented by methamphetamine‐induced rotational asymmetry tests and by tyrosine hydroxylase immunocytochemistry. High hybridization signals were obtained for GAP‐43, MAP2,βAPP695,βAPP714andβAPP751RNA transcripts in the grafted tissue; theβAPP770species‐normally seen in striatum and not substantia nigra‐was not expressed in the grafts, but it was present in the recipient striatum. Following immunocytochemical labelling with antibodies, GAP‐43 and MAP2 immunoreactivities were seen in cell processes in the grafts and surrounding tissue, whereasβAPP immunoreactivity was mainly found in grafted cell bodies. These results suggest that the transplanted mesencephalic cells mature very similarly to those in the normal substantia nigra, expressing different mRNAs that are normally present in the ventral midbrain and which are reduced in the weaver mutant as a cons

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00212.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have studied the effects of different neurotrophins on the survival and proliferation of rat cerebellar granule cells in culture. These neurons express trkB and trkC, the putative neuronal receptors for brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3) respectively. Binding studies using iodinated BDNF and NT‐3 demonstrated that both BDNF and NT‐3 bind to the cerebellar granule neurons with a similar affinity of ˜ 2x10‐9M. The number of receptors per granule cell was surprisingly high, ∼30x10‐4and 2x 105for BDNF and NT‐3, respectively. Both NT‐3 and BDNF elevated c‐fos mRNA in the granule neurons, but only BDNF up‐regulated the mRNA encoding the low‐affinity neurotrophin receptor (p75). In contrast to NT‐3, BDNF acted as a survival factor for the granule neurons. BDNF also induced sprouting of the granule neurons and significantly protected them against neurotoxicity induced by high (1 mM) glutamate concentrations. Cultured granule neurons also expressed low levels of BDNF mRNA which were increased by kainic acid, a glutamate receptor agonist. Thus, BDNF, but not NT‐3, is a survival factor for cultured cerebellar granule neurons and activation of glutamate receptor(s) up‐regulate

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00213.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractCallosal connections were studied with tracers (horseradish peroxidase (HRP) and wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP)) in normal rats and rats deprived of thyroid hormones with methimazole (Sigma) since embryonic day 14 and thyroidectomized at postnatal day 6. In hypothyroid rats, the auditory areas, in particular the primary auditory area, showed cytoarchitectonic changes including blurred lamination and decrease in the size of layer V pyramidal neurons. In control rats, callosally‐projecting neurons were found between layers II and VI with a peak in layer III and upper layer IV. In hypothyroid rats, labelled neurons were found between layers IV and VI with two peaks corresponding to layer IV and upper layer V, and in upper layer VI. Quantitative analysis of radial distribution of callosally‐projecting neurons confirmed their shift to infragranular layers in hypothyroid rats. Three‐dimensional reconstructions showed a more continuous tangential distribution of callosally‐projecting neurons in hypothyroid rats which may be due to the maintenance of a juvenile ‘exuberant’ pattern of projections. These changes in cortical connectivity may be relevant for understanding epilepsy and mental retardation associated with early hypothyroidism in humans and to clarify basic mechanisms of corti

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00214.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWhole‐cell, patch‐clamp recordings were used to study voltage‐gated currents generated by cerebellar granule cells that were cultured in medium containing either 10% fetal calf serum (hereafter termed S + granules) or neurite outgrowth and adhesion complex (NOAC, hereafter called NOAC granules). NOAC is a protein complex found in rabbit serum that renders granules resistant to the excitotoxic action of excitatory amino acids. During depolarizing commands both S+ and NOAC granules generated Na+and Ca2+inward currents and an early and a late K+outward currents. However, Na+and Ca2+Inward currents and late outward K+currents recorded in NOAC granules were smaller than those seen in S+ granules. Furthermore, although of similar amplitude, early K+currents displayed different kinetics in the two types of neurons. Thus, these data demonstrate that the electrophysiological properties of cerebellar granules, and probably of other neuronal populations, depend upon serum components and raise the possibility that an analogous modulation might be operativein vivo,and play a role in development, synaptic plasticity or neuropathological proc

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00215.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWe describe how the stochastic geometry of dendritic arborization of a single identified motoneuron of the rat affects the local details of its electrotonic structure. After describing the 3D dendritic geometry at high spatial resolution, we simulate the distribution of voltage gradients along dendritic branches under steady‐state and transient conditions. We show that local variations in diameters along branches and asymmetric branchings determine the non‐monotonous features of the heterogeneous electrotonic structure. This is defined by the voltage decay expressed as a function of the somatofugal paths in physical distances (voltage gradient). The fan‐shaped electrotonic structure demonstrates differences between branches which are preserved when simulations are computed from different values of specific membrane resistivity although the absolute value of their voltages is changed. At given distances from soma and over long paths, some branches display similar voltages resulting in their grouping which is also preserved when specific membrane resistivity is changed. However, the mutual relation between branches inside the group is respecified when different values of specific membrane resistivity are used in the simulations. We find that there are some invariant features of the electrotonic structure which are related to the geometry and not to the electrical parameters, while other features are changed by altering the electrical parameters. Under transient conditions, the somatofugal invasion of the dendritic tree by a somatic action potential shifts membrane potentials (above 10 mV) of dendritic paths for unequal distances from the soma during several milliseconds. Electrotonic reconfigurations and membrane shifts might be a mechanism for postsynaptic plast

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00216.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects of noradrenaline on pyramidal cells of layer V of the prefrontal cortex were examined in rat brain slicesin vitro.Bath administration of noradrenaline (10 μM) reduced synaptic transmission of afferent inputs from layer 1. The decrease affected all the components of the evoked response and particularly the monosynaptic excitatory postsynaptic potential (EPSP) as evidenced by a reduction of its initial rising slope (mean slope: 71 ± 11% of its control). Pharmacological dissociation of the NMDA‐ and non‐NMDA‐receptor components of the EPSP showed that noradrenaline reduced both (mean EPSP slopes were 71 ± 8% and 73 ± 10% of their control, respectively). Alpha1‐, but notα‐2‐ orβ‐adrenoceptor antagonists prevented the noradrenaline‐induced decrease in synaptic efficacy. However, the effect of noradrenaline was not reproduced byα1‐adrenoceptor agonists. Lastly, noradrenaline acting throughβ‐adrenoceptors reduced the slow hyperpolarization that follows a

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00217.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSingle unit response latencies in striate cortex after visual stimulation with stationary flashed bars were measured and interocularly compared in anaesthetized cats with surgically induced strabismus, in order to elucidate the neural basis of strabismic amblyopia. Four unilateral esotropic and two exotropic cats were studied. The visual onset latencies of cortical neurons ranged from 30 to 170 ms after stimulation of the non‐deviating eye at a contrast of 82%. Responses after visual stimulation of the deviating eye were consistently delayed by ∼10 ms. The latency increase was independent of the direction and absolute angle of squint in the different animals. Peak latencies of cortical neurons ranged from 43 to 245 ms. Median peak latency was 85 ms for the non‐deviating and 95 ms for the deviating eye. The rise time of cortical flash responses, as determined from onset ‐ peak differences, ranged between 2 and 170 ms. Direct interocular comparison of response latencies in the remaining binocular neurons revealed an invariable advantage for the non‐deviating eye. Supragranular neurons showed a greater interocular latency difference than neurons in layer IV. Visual latencies were contrast‐dependent. However, the latency reduction with increasing contrast was less pronounced for the deviating eye. We discuss the possibility that central integration times, especially within cortex, are prolonged in strabismic cats, affecting temporal coincidence of signal processing in the visual cortex. The resulting disturbance of spatio‐temporal integration, as caused by a scrambling of geniculo‐striate and intracortical connections, may be the substrate of binocular suppression and strab

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00218.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY