摘要:

AbstractSpider venoms are proving to be important sources of specific ion channel toxins. Venom ofAgelenopsis aperta, a funnel web spider, contains a class of polypeptide toxins which blocks neuromuscular synapses at nanomolar concentrations. Detailed physiological analyses of block caused by one of these toxins, ω‐Aga‐I show that it suppresses transmitter release at insect and frog neuromuscular junctions and blocks calcium spikes in insect neuronal cell bodies. ω‐Aga‐I may define a binding site on neuronal calcium channels which is common to both vertebrates and inve

ISSN:0022-3034    

DOI:10.1002/neu.480200402

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe dorsal bulbocavernosus or “levator ani” muscle of the rat is highly responsive to androgens. Both the muscle and the motoneurons which innervate it contain high concentrations of androgen receptors. The neuromuscular synapses in this muscle are also affected by changing androgen levels. In particular, the total number of ACh receptors (AChRs) in the muscle is lower in males that have been castrated, and it increases after treatment with the androgens, testosterone and 5 α‐dihydrotestosterone. An examination of individual endplates using histochemistry and quantitative autoradiography suggested that the reduction in AChR number following castration is caused by reductions in both the size of endplates and in the density of AChRs at each s

ISSN:0022-3034    

DOI:10.1002/neu.480200403

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

年代:1989

数据来源: WILEY

摘要:

AbstractWe have modified the formaldehyde‐glutaraldehyde (FaGlu) histofluorescence method of Furness, Costa, and Blessing (1977a) and Furness, Costa, and Wilson (1977b) to examine wholemounts and sections of both juvenile and adult ganglia as well as peripheral tissues ofAplysia californica. FaGlu fluorescence is the result of a reaction between formaldehyde and tissue catecholamines to produce water‐insoluble (fixed) fluorophores. In serially sectioned cerebral ganglia, 70–80 positive neurons were observed (many in clusters of 10–20 cells), many more than were found using the glyoxylic acid technique. Catecholamine‐containing varicosities were densely packed in localized portions of the neuropil of all central ganglia. Exclusive localization in the neuropil of presumed dopamine release sites is similar to that previously found for the neuropeptide SCP but differs form the widespread ramification of varicose neurites containing 5‐HT, FMRFamide, and ELH. The FaGlu technique also enabled us to study the ultrastructure of catecholamine‐containing neurons. In contrast to the larger vesicles found in serotonergic and histaminergic neurons, these dopaminergic neurons contain 70 nm dense

ISSN:0022-3034    

DOI:10.1002/neu.480200404

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

年代:1989

数据来源: WILEY

摘要:

AbstractChronic treatment of chick embryos with neuromuscular blocking agents, such as curare, rescues motoneurons from naturally occurring cell death. In the present study, embryos treated with curare from E6 to E9 had 35% more motoneurons than controls on E10 and 42% more than controls on E16. Previous studies have shown that several aspects of motoneuron differentiation occur normally in curare‐treated embryos. We report here that dendrite growth and arborization is also unaltered on E10 and E16 following curare treatment. A quantitative analysis of afferent synapses on motoneurons shows that the packing density of both axosomatic and axodendritic synapses is also normal on E10 in curare‐treated embryos, despite the greater number of motoneurons present. This indicates that the interneurons that provide presynaptic input to motoneurons are able to compensate for the increased number of synaptic sites made available by curare treatment. However, by E16 the packing density of synapses is reduced by about half. Because motoneurons and their dendrites continue to grow between E10 and E16, the further increase in synaptic sites made available in curare‐treated embryos apparently exceeds the compensatory capacity of presynaptic interneurons on E16. One can conclude from these results that the increased survival of motoneurons in curare‐treated embryos in not owing to an increase in afferent synapses. Motoneurons in these embryos continue to survive in the face of either no change (E10) or a reduction (E16) in the number of axodendritic and axosomatic synapses. Therefore, increased motoneuron survival in this situation is very likely regulated primarily by motoneuron–target int

ISSN:0022-3034    

DOI:10.1002/neu.480200405

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

年代:1989

数据来源: WILEY

摘要:

AbstractModulation of sensory responses recorded intracellularly in primary sensory afferents of a crustacean proprioceptor is described. The neuropeptide proctolin enhances the sensory response, whereas the bioamines octopamine and serotonin depress it.The lobster oval organ of the second maxilla, a simple stretch receptor lacking centrifugal control, provides a useful model for studies on nonsynaptic modulation at peripheral sensory loci. Its three large afferents, X, Y, and Z, were prepared for intracellular recording and tested under five experimental conditions: (1) when fully rested, (2) when adapted to maintained stretch and firing tonically, (3) when showing reduced responses after habituation to repetitive stimulation, (4) not stretched but depolarized with current injections, (5) after TTX blockade.The results, taken together, indicate that conductances contributing to the overall amplitude of the receptor potential are major targets for modulators. Thus proctolin increased receptor potential amplitudes with consequent augmentation of spiking, whereas serotonin and octopamine depressed the receptor potentials, often to subthreshold levels with loss of spiking. Octopamine was a less potent agent than serotonin and failed to act upon fibers under TTX blockade.Fibers Y and Z consistently showed sensitivity to the modulators tested. The largest fiber, X, typically was resistant to proctolin, octopamine, and serotonin.Threshold concentrations of 10−10−10−11Mdetermined in vitro are well below the circulating levels for serotonin and octopamine found in vivo. Proctolin, however, is usually not detectable in the hemolymph, and it is suggested that a significant site of proctolin release may be the oval organ i

ISSN:0022-3034    

DOI:10.1002/neu.480200406

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

年代:1989

数据来源: WILEY

摘要:

AbstractCells from adultXenopus laevisbrainstem and spinal cord were dissociated with mild enzymatic treatment and grown in long‐term cell culture. These cells had specific attachment/substrate and medium/serum requirements. Cells with bipolar and multipolar morphology were positively identified as neurons using immunohistochemistry with monoclonal antibodies to rat and bovine neurofilament proteins which we show here cross‐react with similar amphibian proteins. Patch clamp recordings demonstrated that these neurons have populations of ionic channels which are activated by L‐glutamate or γ‐aminobutyric acid (GABA).Abbreviations: ABC, avidin‐biotin‐complex; dHnO, distilled water; GABA, γ‐aminohutyric acid; L‐15, Leibovitz's 15 medium; NCM, zero calcium zero magnesium Ringers' solution; NF, neurofilament; NFRS, normal frog Ringers' solution; PAP, peroxidase antiperoxidase.The characteristics of these channels were similar to those previously described for GABA‐ and glutamate‐activated channels in embryonic mammalian neurons isolated in culture. Cell cultures of neurons isolated from adultXenopus laevisbrain may be a useful and simple preparation with which to examine the modulation of neuronal properties by various agents over longer time intervals then has bee

ISSN:0022-3034    

DOI:10.1002/neu.480200407

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

年代:1989

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480200401

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

年代:1989

数据来源: WILEY