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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Peptides 2 (1981), S. 227-229 
    ISSN: 0196-9781
    Keywords: Behaviorally active peptides ; Dopamine neurons ; Stress ; Substantia nigra ; α-Melanotropin (α-MSH) antiserum
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: α-melantropin (α-MSH) ; Dopamine neurons ; Stress ; Substantia nigra ; Tubero-infun-dibular dopamine neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The response of central dopamine (DA) systems to physical stress (10 s footshock, 0.5 mA, to naive rats) or psychological stress (10 s stay in experimental chamber 1 day after footshock) was studied in male rats in view of possible interactions between these neuron groups and endogenous α-MSH. Three hours before stress, part of the animals were injected i.v. or intraventricularly with antiserum against α-MSH or with inactivated normal rabbit serum (NRS). Characteristic response patterns were observed in different DA neuron groups by histochemical microfluorimetry: In substantia nigra, increased fluorescence intensity of DA neurons indicating increased neuronal activity, was seen on the first day (1) 5 min after physical stress or (2) 30 min after a first transfer to the experimental chamber without footshock, and on the second day (3) immediately after the psychological stress in rats given a footshock on the previous day, or (4) 5 min after the second stay in the experimental chamber in animals previously exposed to the chamber without shock. Hence, the reaction appears to occur faster the second day. No significant intensity changes were detected in the ventromedial tegmental DA neurons (A10). The arcuate DA neurons which i.a. control α-MSH secretion, responded to physical stress or control manipulations in a complex way, while no significant reaction was seen after psychological stress. Differences between physical and psychological stress were also seen in serum levels of α-MSH (determined by RIA). Intravenous antiserum against α-MSH enhanced the response of nigral DA neurons to physical stress and led to elevated intensity levels 5 min after psychological stress when values were again decreasing in uninjected rats. Moreover, a marked rise in intensity was elicited after psychological stress in the A10 DA neurons where no change was detected in the absence of antiserum. Anti-α-MSH also affected the arcuate DA neurons in psychological stress. Intraventricular antiserum did not display any specific effects. These data point to a modulatory influence of circulating α-MSH on the functional state of central DA systems. They further reveal different temporal response patterns of nigral and also arcuate DA neurons in relation to the two stress situations and to other types of manipulations considered to be less stressful.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-9058
    Keywords: endophyte ; Lolium perenne ; Neotyphodium lolii ; photosynthesis ; stomatal conductance ; transpiration rate ; water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The symbiotic association of endophyte fungus, Neotyphodium lolii, and ryegrass improves the ryegrass resistance to drought. This is shown by a 30 % increase in the number of suckers in infected plants (E+), compared to plants lacking endophyte (E−), and by a higher water potential in the E+ than E− plants. The E+ plants have higher stomatal conductance (g s), transpiration rate, net photosynthetic rate (P N), and photorespiratory electron transport rate than the E− plants. The maximal photochemical efficiency (Fv/Fm) and the actual photochemical efficiency (ΦPS2) are not affected by the endophyte fungus. The increase in P N of the E+ plants subjected to water stress was independent from internal CO2 concentration. An increased P N was observed in E+ plants also in optimal water supply. Hence the drought resistance of E+ plants results in increased g s, P N, and photorespiratory electron transport rate.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It has recently been proposed that neurosteroids, such as dehydroepiandrosterone sulphate and pregnenolone sulphate, interfere with the dopamine system in the central nervous system. According to our previous report showing that the butyrophenone, spiperone, slightly enhances the evoked release of [3H]-noradrenaline ([3H]NA) in the presence of these sulphated steroids, the present study was carried out to document the putative interplay between steroids and spiperone, which is known to be a prototypic D2 dopamine antagonist and also a 5-HT2 serotonin antagonist. For this purpose, the paradigm of KCl-evoked [3H]NA release from preloaded rat hippocampal slices was used to investigate the interactions between neurosteroids, spiperone and the voltage-sensitive calcium channels (VSCCs). The selective 5-HT2 serotonin antagonist ritanserine was ineffective, whereas sulpiride, a selective D2 dopamine antagonist mimicked the action of spiperone, thus suggesting that the blockade of D2 dopamine receptors accounted for the modulatory effect of spiperone on neurosteroid-induced modulation of evoked [3H]NA release. In addition, this facilitation of KCl-evoked [3H]NA release by the combination of a steroid and a D2 dopamine antagonist was partially inhibited by the L- and N-type VSCC blockers nifedipine and ω-conotoxin GVIA, respectively. The present results provide in-vitro functional evidence for the putative role of VSCCs in the interplay between steroids and D2 dopamine receptors.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 14 (2002), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Serotonin (5-HT) participates as a neurotransmitter in the control of the circadian sleep/wake rhythm, feeding and sexual behaviours, and emotional and affective states. The present study investigated whether melatonin affects the circadian rhythm of 5-HT neurotransmission in the hippocampus, a major target for serotoninergic antidepressants. The present results show a daytime dependency of [3H]5-HT uptake insensitive to melatonin, with a peak from 14.00 h to 22.00 h and a trough from 02.00 h to 06.00 h. They also indicate that melatonin reduced the spontaneous efflux of [3H]5-HT as well as KCl-evoked release of [3H]5-HT during the dark phase, while it increased the evoked release during the light phase. Both effects were concentration-dependent; the facilitatory effect was maximum at high nanomolar concentrations of melatonin, whereas the inhibition preferentially occurred at low concentrations. Finally, nifedipine, an effective antagonist of l-type voltage-sensitive calcium channels, prevented the effects of melatonin on KCl-evoked [3H]5-HT release during the light but not the dark phase. Together, these data suggest the involvement of two distinct mechanisms by which melatonin might regulate both spontaneous efflux and evoked release of 5-HT in the hippocampus.
    Type of Medium: Electronic Resource
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