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  • Electronic Resource  (3)
  • 1990-1994  (3)
  • 1975-1979
  • Alpha-1-adrenoceptor  (1)
  • Attention  (1)
  • Australia  (1)
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  • Electronic Resource  (3)
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  • 1990-1994  (3)
  • 1975-1979
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  • 1
    ISSN: 1435-1463
    Keywords: Alpha-1-adrenoceptor ; prazosin ; single cell recording ; substantia nigra ; ventral tegmental area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electrical stimulation techniques were employed in the chloral hydrate anaesthetized male rat to evaluate if the pontine noradrenergic nucleus locus coeruleus can influence the activity of midbrain dopamine neurons in the ventral tegmental area and zona compacta, substantia nigra. Single-pulse locus coeruleus stimulation evoked an excitation, followed by an inhibition, of the electrical activity of single midbrain dopamine neurons. Neither of these responses were observed in animals pretreated with reserpine, implicating noradrenaline as a mediator. The α1-adrenoceptor antagonist prazosin decreased the excitation, while other adrenoceptor antagonists were without general effect. Burst-type stimulation produced only a more long-lasting inhibition. The influence from the locus coeruleus on midbrain dopamine neurons could be important in behavioural situations involving novelty and reward, and might also be of importance for the actions of psychotropic drugs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 85 (1990), S. 57-68 
    ISSN: 1432-1939
    Keywords: Herbivory ; Fish ; Odax cyanomelas ; Ecklonia radiata ; Australia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The odacid fish Odax cyanomelas feeds on the kelp Ecklonia radiata, an important component of subtidal reef habitats on the central coast of New South Wales, Australia. Herbivory by Odax has a major impact on the structure and dynamics of discrete patches within larger stands of kelp at Cape Banks. This three-year study showed that each year, between August and October, approximately the same patches of kelp were denuded by preferential feeding on the meristem and primary laminae. This coincided with a variable pulse of Ecklonia recruits to the cleared patches, thereby generating patches of a single age-class of plants. Neighbouring areas of Ecklonia forest, non cleared by Odax, consisted of larger, perennial plants, which exhibited more gradual changes in abundance. The seasonal impact of Odax appeared to be due to a change in the behaviour of female Odax during their spawning period. Observations suggested that females aggregate at traditional sites prior to spawning with territorial males in adjacent areas of kelp forest. An alternative hypothesis, that Odax preferentially attacked stands of one-year old Ecklonia plants, was rejected by a field experiment; the establishment of experimental stands of one-year old plants did not lead to increased damage due to Odax or any change in the use of space by the fish. The generality of this effect of fish herbivory is unknown, but this and other Odax species are widely distributed throughout temperate Australia, where Ecklonia is the dominant laminarian alga. The effects of pulsed herbivory by Odax is contrasted to the more continuous grazing by sea urchins in the same system. The latter herbivore has been shown to maintain areas free of Ecklonia, the long-term effects of herbivory by Odax remain unclear.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Nicotine ; Alzheimer's disease ; Attention ; Information processing ; Short-term memory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This single-blind, placebo controlled study reports on the effects of administering three acute doses of nicotine (0.4, 0.6 and 0.8 mg) subcutaneously to a group of Alzheimer's disease (DAT) patients (n=22), young adult controls (n=24), and normal aged controls (n=24). The study extends our previous findings obtained using smaller groups of subjects. Drug effects were examined on three computerised tests: the first measuring rapid visual information processing, sustained visual attention and reaction time (RVIP task); a delayed response matching to location-order task measuring sustained visual attention and visual short-term memory (DRMLO task); and a finger tapping test measuring simple reaction time (FT task). The critical flicker fusion test (CFF) was used as a measure of perception and the WAIS digit span forwards (DS), of auditory short-term memory. Tests were graded in difficulty, titrated to avoid floor and ceiling effects so that meaningful, direct comparisons between groups could be made. Nicotine significantly improved sustained visual attention (in both RVIP and DRMLO tasks), reaction time (in both FT and RVIP tasks), and perception (CFF task — both ascending and descending thresholds). Nicotine administration did not improve auditory and visual short-term memory. There were no consistent, overall patterns of difference in performance between smokers and non-smokers in the control groups, or between males and females in any group. Despite the absence of change in memory functioning, these results demonstrate that DAT patients have significant perceptual and visual attention deficits which are improved by nicotine administration. The importance of measuring multiple abilities in future drug studies is emphasized and results are discussed in terms of nicotine's actions on attention, information processing and short-term memory.
    Type of Medium: Electronic Resource
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