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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 62 (1986), S. 250-258 
    ISSN: 1432-1106
    Keywords: Longterm potentiation ; Hippocampus ; Collateral specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Long term potentiation (LTP) in response to brief high frequency trains has been reported for many pathways in the hippocampus. The mechanisms involved are still unclear. The present experiments set out to confirm reports in the literature that LTP of output from CA3 neurons can be specific to particular collaterals. Single pulses delivered to area CA3 produced field responses nearly simultaneously in area CA1 and in the lateral septum (LS). High frequency stimulation of CA3 produced long term potentiation of CA1 but not LS responses. The CA1 response to stimulation of the contralateral hippocampus did not potentiate when the CA1 response to CA3 stimulation showed long term potentiation. The CA1 and LS responses to CA3 stimulation showed similar strength-duration, strength-amplitude and frequency following characteristics. Their latencies were comparable to the latencies of antidromic activation of CA3 cells from CA1 and LS. Movement of stimulating electrodes to the region of the Schaffer collaterals increased the latency of the LS response and decreased the latency of the CA1 response but left the sum of these latencies unchanged. It was concluded that the CA3 and Schaffer stimulation were activating LS and CA1 collaterals of the same CA3 neurons. CA1 and LS responses to CA3 stimulation showed somewhat different paired pulse and frequency potentiation characteristics. These data confirm reports in the literature that long term potentiation is both input-specific and collateral-specific. The mechanisms of long term potentiation are likely, therefore, to be limited to changes at specific synaptic junctions, e.g. changes in sensitivity of specific postsynaptic receptor sites or changes in transmitter release, which can depend on functional or organisational differences between two collaterals of the same neuron.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 54 (1984), S. 567-570 
    ISSN: 1432-1106
    Keywords: Hippocampus ; Frequency potentiation ; Transmembrane potential ; Ephaptic transmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The contribution of ephaptic interactions to potentiation of the hippocampal CA1 extracellular population spike during paired pulse or frequency stimulation of stratum radiatum (SR) inputs was investigated using the in vitro hippocampal slice preparation. Records of the transmembrane potential revealed a depolarizing wave with an amplitude and latency that varied directly with that of the extracellular population spike. Paired pulse or repetitive stimulation of SR resulted in a potentiation of the population spike amplitude and a corresponding increase in the amplitude of the TMP depolarizing wave. Action potentials generated during the stimulus train consistently arose from the peak of the depolarizing wave. It is proposed that ephaptic interactions contribute to potentiation of the extracellular population spike through recruitment of subthreshold neurons within the population during repetitive afferent stimulation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 56 (1984), S. 243-256 
    ISSN: 1432-1106
    Keywords: Medial septum ; Hippocampus ; Dentate gyrus ; Evoked potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous electrophysiological experiments in rabbits have suggested that medial septal stimulation activates dentate granule cells and evokes an associated negative field response at the granule cell layer, without an associated “dendritic” response. Anatomical studies have suggested that septal input to the granule cells may be to stratum moleculare, or close to the cell layer, or may not exist at all. The present experiments confirmed in rats anaesthetised with urethane that medial septal stimulation elicits single action potentials from cells in the granule layer. The associated negative field potential was maximal in the granule cell layer and there was no sign of a separate dendritic potential. The fibres responsible for this potential travel to the dorsal hippocampus in the fornix superior rather than the fimbria, taking the same course as the fibres which contribute to the dense cholinesterase staining just above the granule cell layer. Stimulation at 100 Hz for 1 s of either medial septal, or perforant path, input to the dentate granule cell layer produced long term potentiation of the subsequent evoked field responses to the stimulated pathway. The responses to the non-stimulated pathway were unchanged. Paired pulse stimulation produced both homosynaptic and heterosynaptic potentiation. These data suggest that medial septal input synapses close to granule cell bodies and produces a negative field potential which is a combination of dendritic and population spike potentials. Medial septal input also appeared to produce direct activation of hilar neurones, some of which may be basket cells or other interneurones. The data also show that long term potentiation is specific to this input, perhaps dependent on presynaptic mechanisms. Paired pulse potentiation, at least in the heterosynaptic case appears to depend on postsynaptic mechanisms.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 57 (1985), S. 443-447 
    ISSN: 1432-1106
    Keywords: Epilepsy ; GABA ; Hippocampus ; Inhibition ; Kindling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In vitro hippocampal slices were prepared from control and commissural-kindled rats and the inhibitory processes of the dentate granule cells were assessed using paired perforant path stimulation. An early (20 ms) Cl--dependent and a late (200 ms-8 s) Cl--independent inhibition were shown to be present in the dentate. Enhancement of the late Cl--insensitive inhibition was observed following the establishment of commissural kindling and persisted for periods of up to eight weeks following the last seizure.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of insect behavior 4 (1991), S. 773-792 
    ISSN: 1572-8889
    Keywords: Delia antiqua ; Anthomyiidae ; Diptera ; herbivore ; egg-laying ; host-finding ; sensory systems ; chemoreception ; n-dipropyl disulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Behavioral responses of female onion flies, Delia antiqua (Meigen), to hostplant cues were quantified during encounters of individual flies with onion plants and onion foliar surrogates. The behavioral repertoire of such females included sitting, grooming, running up and down foliar surfaces, extension of the proboscis such that the labellum contacted foliar and soil surfaces, movements of the tip of the abdomen over surfaces (surface probing), subsurface probing of soil crevices with the ovipositor, and oviposition. Sequences of behaviors preceding oviposition were probabilistic rather than highly stereotyped but generally followed the order given above. Foliar surrogates were used to determine the effects of n-dipropyl disulfide (Pr2S2) on the sequence of behaviors leading up to oviposition. The addition of a Pr2S2-treated surrogate to a cage increased the frequency of alighting on that surrogate but also increased alighting on a nearby foliar surrogate without Pr2S2. After alighting, females encountering surrogates treated with Pr2S2 had shorter latencies to proboscis extension and surface probing, spent less time sitting and grooming, and had runs of shorter duration. These females were also more likely to make the transition from probing of surfaces of foliage and soil to subsurface probing of soil crevices and oviposition. Thus, rather than mediating a particular step in the behavioral sequence, Pr2S2 played a role throughout the sequence leading up to oviposition. Collectively, these data and past studies on the onion fly support the hypothesis that egglaying is triggered by a temporal summation of inputs to the central nervous system from various sensory modalities rather than strict behavioral chaining, with each transition effected by some unique cue.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 13 (1987), S. 1261-1277 
    ISSN: 1573-1561
    Keywords: Onion fly ; onion maggot ; Delia antiqua ; Hylemya antiqua ; Diptera ; Anthomyiidae ; host selection ; oviposition ; dipropyl disulfide ; behavior ; herbivore ; plant-insect interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Onion fly females,Delia antiqua (Diptera: Anthomyiidae) laid the most eggs on ovipositional dishes havingn-dipropyl disulfide (Pr2S2) release rates of 1–6 ng/sec from polyethylene capsules placed beneath a sand substrate. When dipropyl disulfide was released from the wax coating of surrogate foliage rather than from the substrate, ovipositing females again responded differentially to various concentrations, laying more eggs around stems containing 0.075 and 0.089 mg/stem. Factorial combinations of several concentrations released from surrogate foliage and substrate showed that releases from surrogate foliage stimulated four times more egg-laying than releases from the substrate. Females tended to lay more eggs around surrogate stems having Pr2S2 at the base rather than on the upper half of foliage. Observations of individual females performing preovipositional examining behaviors on Pr2S2-treated surrogate stems indicated that females tended to land on the upper portions of the foliage, but after landing, spent most of their time examining areas of soil and surrogate within 1 cm of the soil-surrogate foliage interface. Surrogate stems provide a realistic context for investigating effects of plant chemicals on host-acceptance behaviors.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 15 (1989), S. 905-916 
    ISSN: 1573-1561
    Keywords: Onion fly ; Delia antiqua ; Diptera ; Anthomyiidae ; Erwinia carotovora varcarotovora ; Klebsiella pneumoniae ; food attractant ; ovipositional stimulant ; dipropyl disulfide ; 2-phenylethanol ; pentanoic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Decomposing onions at certain microbial successional stages produce potent volatile attractants and ovipositional stimulants of the onion fly,Delia antiqua (Diptera: Anthomyiidae). A reproducible source of these compounds was obtained by culturingErwinia carotovora var.carotovora (EC) on sterile onion tissue. In laboratory choice tests, EC-inoculated onion was more attractive thanKlebsiella pneumoniae (KP) cultured on onion, EC cultured on potato (a nonhost of onion fly), or the chemical synthetic baits dipropyl disulfide and an aqueous solution of 2-phenylethanol and pentanoic acid. Onion flies were mildly attracted to potato after inoculation with EC, but females did not accept EC-inoculated potato for oviposition. This work emphasizes that sources of semiochemicals may need to be defined microbiologically as well as physically and chemically.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 10 (1984), S. 1477-1488 
    ISSN: 1573-1561
    Keywords: Delia antiqua ; onion fly ; Diptera ; Anthomyiidae ; food attractants ; host attractants ; microbial attractants ; Klebsiella pneumoniae ; bacteria ; Allium ; onion ; garlic ; chive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Of various chopped vegetables tested,Allium spp. high in propyl-containing alkyl sulfides (e.g.,cepa group) caught the most onion flies in trapping tests in the field. Fly catches to chopped onion increased with bait quantity. Attractancy of chopped onion changed dramatically during aging in the field; catch increased over the first few days, peaked at ca. fivefold over fresh material by 3–5 days, and then declined sharply. This age-dependent increase in attraction was not seen for garlic (known to have antimicrobial properties) nor with chopped onion mixed with chopped garlic. These data suggested that attraction of onion flies to onions was strongly influenced by microbial activity associated with decomposing onions. The bacteriumKlebsiella pneumoniae was identified as a major colonizer of onions maximally attractive to onion flies. This increased attraction is not due to the previously reported microbially produced volatiles ethyl acetate and tetramethyl pyrazine.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 15 (1989), S. 719-730 
    ISSN: 1573-1561
    Keywords: Onion fly ; Delia antiqua ; Diptera ; Anthomyiidae ; oviposition ; deterrent ; capsaicin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In laboratory choice experiments, the spices dill, paprika, black pepper, chili powder, ginger, and red pepper deterredDelia antiqua oviposition by 88–100%. Dose-response choice tests demonstrated that 1 mg of ground cayenne pepper (GCP) placed within 1 cm of artificial onion foliage reduced oviposition by 78%. A synthetic analog of capsaicin, the principal flavor ingredient of red peppers, deterred oviposition by 95% when present at 320 ppm in the top centimeter of sand (the ovipositional substrate). However, in no-choice conditions 10 mg GCP was not an effective deterrent. Sevana Bird Repellent and Agrigard Insect Repellent both use red pepper as a principal ingredient; at recommended field rates, neither of these materials was an effective ovipositional deterrent either in laboratory or field. Capsaicin-based materials do not appear to be candidates for onion maggot control via behavioral modification.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 11 (1985), S. 435-440 
    ISSN: 1573-1561
    Keywords: Delia (Hylemya) antiqua ; Diptera ; Anthomyiidae ; onion fly ; onion maggot ; tube trap ; insect attractants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Responses of onion flies,Delia antiqua, to known attractants were measured in the laboratory with a novel tube-trap bioassay. The relative numbers of flies caught in tube traps baited with enzymatic yeast hydrolysate, brewer's yeast, andn-dipropyl disulfide were similar to those obtained previously with cone traps in the field. Changing the shape of the bioassay cage from a cuboid to a cylinder decreased the experimental error obtained from analysis of variance, as did rotating the floor of the circular cage. This bioassay should be useful in evaluating attractants for other insects that orient along the substrate.
    Type of Medium: Electronic Resource
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