摘要:

AbstractRecombinant rat CNTF (ciliary neurotrophic factor) at picomolar concentration prevents the death of P19 murine embryonic carcinoma cells that usually follows upon withdrawal of serum from the culture medium. For prolonged survival of P19 cells in serum‐free medium, insulin must also be present. In the presence or absence of serum, CNTF stimulates the differentiation of P19 cells, inducing the formation of neurites and synthesis of neurofilament. The results of radioautographic studies with radioiodinated CNTF indicate the presence of high‐affinity binding sites on P19 cells. Equilibration of P19 cells with [125I]CNTF followed by incubation with cross‐linking reagents reveals evidence for at least two putative receptors of ∼78 and

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00949.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPlatelet‐derived growth factor (PDGF) is a well known mitogen for mesenchyme‐derived cells and glial cells. Its presence in neuronal cells of the central nervous system has only recently been described. We have shown earlier that neurons of newborn rat brains in culture express PDGF β‐receptors and that PDGF‐BB, a homodimer of PDGF B‐chain, increases survival and promotes neurite outgrowth of newborn cerebellar cells (Smitset al., Proc. Natl Acad. Sci. USA,88, 8159 – 8163, 1991). In this study, the effects of PDGF on early postnatal rat cerebellar cells were further explored. By using chemically defined serum‐free medium, we have established primary cell cultures of rat cerebella (postnatal day 4 – 5) containing 70 – 80% neuronal cells. During the first 10 daysin vitro, no difference in total cell number was found between PDGF‐BB‐treated and untreated cultures. After this time period, however, increased survival of the PDGF‐BB‐treated cells was found. Within the first 10 daysin vitro, the addition of PDGF‐BB to the cultures resulted in a relative increase in survival of interneurons expressing glutamic acid decarboxylase (GAD), the GABA biosynthetic enzyme. Moreover, addition of PDGF‐BB in the untreated cell culture resulted in a rapid increase of GAD mRNA. These results show that PDGF‐BB acts as a trophic factor on GABAergic interneurons of the cerebellum by up‐regulating GAD synthesis and prolonging the survival of these cells. Furthermore,in situhybridization revealed that there are scattered cells present in the early postnatal cerebellum that express PDGF β‐receptor mRNA. The localization of these cells in the molecular layer and in the proximity of the internal granular layer corresponds to that of GABAergic inte

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00950.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractVomeronasal receptor cells are differentiated bipolar neurons with a long dendrite bearing numerous microvilli. Isolated cells (with a mean dendritic length of 65 μm) and cells in mucosal slices were studied using whole‐cell and Nystatin‐perforated patch‐clamp recordings. At rest, the membrane potential was −61 ± 13 mV (mean ± SD;n= 61). Sixty‐four per cent of the cells had a resting potential in the range of –60 to –86 mV, with almost no spontaneous action potential. The input resistance was in the GΩ range and overshooting repetitive action potentials were elicited by injecting depolarizing current pulses in the range of 2 – 10 pA. Voltage‐dependent currents were characterized under voltage‐clamp conditions. A transient fast inward current activating near –45 mV was blocked by tetrodotoxin. In isolated cells, it was half‐deactivated at a membrane potential near –75 mV. An outward K+current was blocked by internal Cs+ions or by external tetraethylammonium or Ba2+ions. A calcium‐activated voltage‐dependent potassium current was blocked by external Cd2+ions. A voltage‐dependent Ca2+current was observed in an iso‐osmotic BaCl2solution. Finally, a hyperpolarization‐activated inward current was recorded. Voltage‐dependent currents in these microvillar olfactory receptor neurons appear qualitatively similar to those already described in ciliated olfactory receptor cells loca

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00951.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the pulmonate snailLymnaea stagnalis, FMRFamide‐like neuropeptides are encoded by a multi‐exon genomic locus which is subject to regulation at the level of mRNA splicing. We aim to understand the post‐translational processing of one resulting protein precursor encoding the tetrapeptide FMRFamide and a number of other putative peptides, and determine the distribution of the final peptide products in the central nervous system (CNS) and periphery ofLymnaea.We focused on two previously unknown peptide sequences predicted by molecular cloning to be encoded in the tetrapeptide protein precursor consecutively, separated by the tetrabasic cleavage site RKRR. Here we report the isolation and structural characterization of a novel non‐FMRFamide‐like peptide, the 22 amino acid peptide SEQPDVDDYLRDWLQSEEPLY. The novel peptide is colocalized with FMRFamide in the CNS in a number of identified neuronal systems and their peripheral motor targets, as determined byin situhybridization and immunocytochemistry. Its detection in heart excitatory motoneurons and in nerve fibres of the heart indicated that the novel peptide may play a role, together with FMRFamide, in heart regulation in the snail. The second predicted peptide, STEAGGQSEEMTHRTA (16 amino acids), was at very low abundance in the CNS and was only occasionally detected. Our current findings, suggestive of a distinct pattern of post‐translational processing, allowed the reassessment of a previously proposed hypothesis that the two equivalent sequences in theAplysiaFMRFamide gene constitute a molluscan homologue of vertebrate corticotrophin releasing factor‐

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00952.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThis study reports the existence of a purine analogue‐sensitive protein kinase in adult frog sciatic nerves. Cell‐free supernatants of homogenized regenerating sclatic nerves were found to contain a phosphoprotein (MW 90 kDa, referred to as PP90), that was phosphorylated to a much higher degree than in normal, uninjured nerves. The spatial and temporal characteristics of PP90 phosphorylation suggested a relationship with the injury‐induced proliferation of support cells of the regenerating nerve, i.e. its appearance and increment over time correlated with that of [3H]thymidine incorporation in the nerve. PP90 was phosphorylated under conditions that excluded enzyme activities due to Ca2+/calmodulin kinases, cyclic nucleotide‐dependent kinases or protein kinase C. On the other hand, the phosphorylation could be selectively inhibited by the purine analogues adenosine, 2‐aminopurine and 6‐thioguanine (6‐TG). The latter was the most potent and gave complete inhibition at 50 μM. Addition of histone H1 to the cell‐free assay stimulated the phosphorylation of several proteins in both normal and regenerating nerves. The stimulation could be blocked by 6‐TG, indicating the presence of a purine‐sensitive kinase also in uninjured nerves. Separate experiments showed thatin vitroregeneration of the frog sciatic sensory axons, as well as the proliferation of the support cells, was inhi

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00953.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractMicroiontophoretic application of selective agonists for the three major excitatory amino acid receptors,N‐methyl‐d‐aspartate (NMDA), quisqualate and kainate, increased the discharge rate of noradrenergic locus coeruleus (LC) neuronsin vivo.NMDA activation was selectively attenuated by iontophoretic application of 2‐amino‐5‐phosphonopentanoate (AP5), an antagonist at NMDA receptors, whereas kainate‐ and quisqualate‐evoked responses were attenuated by both NMDA and non‐NMDA antagonists iontophoresis. NMDA‐ and quisqualate‐evoked responses were significantly decreased by co‐iontophoresis of serotonin (5‐HT). When the NMDA receptor‐mediated component of the response to kainate was blocked with AP5 iontophoresis, 5‐HT increased the response of LC neurons to kainate. These results revealed that 5‐HT differentially modulates the responsiveness of LC neurons to excitatory amino acids, depending on the receptor subtypes responsi

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00954.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe toxicity of the 1‐methyl‐4‐phenylpyridinium ion (MPP+), an inhibitor of complex I of the respiratory chain, on nigrostriatal dopaminergic neurons contrasts with its relative inefficiency towards other catecholaminergic cell populations in spite of their ability to accumulate this neurotoxin through their high‐affinity uptake system. A constitutive metabolic deficiency of the nigrostriatal dopaminergic neurons could account for their particular vulnerability to MPP+. In order to substantiate this hypothesis, we compared the inhibitory effects of rotenone, an inhibitor of mitochondrial oxidative phosphorylation, on the uptake of dopamine, serotonin, noradrenaline and GABA in mouse striatal synaptosomes, and of dopamine, serotonin and GABA in cultured mesencephalic neurons. In both preparations, the uptake of dopamine was much more affected than that of other neurotransmitters by rotenone. This result was confirmed using two other unrelated inhibitors of oxidative phosphorylation. Moreover, dopamine uptake in synaptosomes from the dorsolateral striatum was more sensitive to rotenone than uptake in synaptosomes from the nucleus accumbens. This indicates that intrinsic metabolic properties of the nigrostriatal dopaminergic neurons may explain the strong inhibition by rotenone of striatal dopamine uptake. Altogether, these results suggest that a constitutive metabolic deficiency could account, at least in part, for the selective vulnerability of the nigrostriatal dopaminergic pathway to the action of the neurotox

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00955.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractUsing the phosphatase inhibitor calyculin A, we have examined the influence of phosphorylation on synaptic transmission and plasticity in rat CA1 hippocampal slices. Bath application of 0.5 – 1 μM of calyculin A resulted in an increase of 42.6 ±2.9% in synaptic responses. The effect produced by calyculin A was not accompanied by changes in fibre volley, was not associated with changes in paired‐pulse facilitation, and could be reproduced by intracellular injection of the compound, thereby indicating a postsynaptic action. Also, the synaptic enhancement produced by calyculin A was expressed only by potentials mediated by amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors, but not by the NMDA responses recorded in the presence of the AMPA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and low magnesium. The effect of calyculin A could be prevented by KN‐62, an inhibitor of calcium/calmodulin‐dependent protein kinase II. Long‐term potentiation could still be induced in the presence of calyculin A, but the effect of the compound was slightly reduced on potentiated compared with control pathways. These results indicate that calyculin A can selectively increase the efficacy of AMPA receptor‐mediated synaptic

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00956.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstractγ‐Aminobutyric acid type A (GABAA) receptors were studied in cultured neurons taken from rat hippocampus at early postnatal stages. GABA‐induced whole‐cell currents showed a broad range of peak amplitudes and time‐courses of desensitization. Dose – response curves of rapidly and slowly desensitizing cells revealed EC50values of 8.5 and 37.3 μM GABA, respectively, with the Hill coefficient being greater than unity. The main‐state conductance of GABAAreceptor channels was 28 – 31 pS in all cells. GABA responses of low‐affinity cells were more strongly affected by benzodiazepine receptor agonists (e.g. flunitrazepam, clonazepam) and inverse agonists (e.g. methyl‐6,7‐dimethoxy‐4‐ethyl‐β‐carboline‐3‐carboxylate), as compared to cells exhibiting high‐affinity GABA responses. Currents were also potentiated by zolpidem, but were little affected by Ro 15‐4513 and Zn2+. These data suggest the presence of physiologically and pharmacologically distinct GABAAreceptor isoforms in neurons of the early postnatal hippocampus, which may subserve different inhibitory c

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00957.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAlthough several lines of evidence indicate that glutamate is a neurotransmitter in primary afferent terminals, controversies exist on the proportion and types of such terminals that release glutamate. In the present study quantitative analysis of immunogold labelling was used to assess the presence of glutamate‐like immunoreactivity in primary afferent terminals in laminae I – V of the rat spinal cord dorsal horn. Anterograde transport of choleragenoid – horseradish peroxidase from a spinal ganglion and tetramethyl benzidine histochemistry were used to identify primary afferent terminals in laminae I and III – V. Presumed C‐fibre terminals in lamina II were identified on morphological criteria (dense sinusoid axon terminals). Primary afferent terminals in all dorsal horn laminae displayed significantly higher levels of glutamate‐like immunoreactivity than pleomorphic vesicle‐containing profiles in laminae III – IV and large neuronal cell bodies in laminae III – V. The density of gold particles over primary afferent terminals also significantly exceeded the average density of gold particles over laminae II and III – IV. The highest densities of gold particles were present over dense sinusoid axon terminals in lamina II. These findings suggest that glutamate, alone or in combination with other neuroactive compounds, is involved in the transfer of all sensory modalities from primary afferent fibres to

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00958.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY