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  • Amphetamine  (2)
  • Exploration  (2)
  • 1
    ISSN: 1432-2072
    Keywords: Psychostimulant ; Amphetamine ; Stress ; Long-term sensitization ; Social isolation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to assess the influence of experimential factors on the vulnerability of rats to develop amphetamine (AMPH)- and stressor-induced behavioral sensitization. Young male Wistar rats with previous social experience were isolated from their peers for 2 weeks. 1) The effect of this short-lasting social deprivation were: a) a reduced tendency to explore a fearful environment; b) a prolonged exploratory activity in response to a novel but little fearful environment; and c) a dose-dependent increase in the psychomotor stimulation induced by systemic AMPH injection. 2) After repeated AMPH injections (injection every other day for 10 days), isolated rats exhibited behavioral sensitization at lower doses (0.5 and 0.75 mg/kg) than those required for group-housed rats (1 mg/kg). 3) After being submitted to a repeated stressor (3, 7 or 14 footshock sessions, with 2 days between sessions), the isolated rats exhibited a greater increase in the behavioral responsivity to a subsequent AMPH challenge (1 mg/kg) than did the group-housed rats regardless of the number of stress sessions. In conclusion, these results suggest that experiential factors such as privation of contact with peers (social isolation) may make rats more vulnerable to the long-term repercussions of chronic environmental and pharmacological challenges.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Arginine vasotocin ; Melatonin ; Exploration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Synthetic arginine vasotocin (AVT) was infused into rat brains either by intraventricular administration or by local infusion on the pineal body. Subsequently, exploratory behavior was analyzed in a hole board. The behavioral effects induced by this peptide were dependent on the time of day, i. e. the light or the dark phase. High intraventricular doses (0.4 μg) administered during the light phase altered exploratory activity such that the number of hole visits was increased, while the duration of each visit was decreased; lower doses producted no effect. In contrast, during the dark phase, peripineal infusion of AVT (10-4 pg) attenuated the number of hole visits and increased the mean duration of the visits. The strongest effects were obtained with peripineal applications during the dark phase. This treatment also resulted in significantly lowered levels of pineal melatonin.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Amphetamine ; Apomorphine ; Dopamine ; Exploration ; Locomotor activity ; Hole-board ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the present experiments, the effects of a wide range of doses of d-amphetamine and apomorphine were studied on investigatory behavior in an automated eight-hole box. Amphetamine (0.125, 0.25, 0.5, 1.0, 3.0, 5.0 mg/kg) increased frequency and total duration of responses, and decreased mean duration in a dose-dependent manner. The strategy and organization of responses, as measured by the order of hole-visits and hole-switching, were unchanged at lower doses of amphetamine but were altered at higher doses. Perseverative hole-poking was observed at the highest dose (5.0) as indicated by increased number of hole-pokes per hole-visit. Apomorphine (0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 mg/kg) decreased mean duration of responses, but in contrast to amphetamine markedly diminished frequency. Locomotor activity was also measured at all doses of both drugs. Our observations indicate that these two stimulant drugs both of which increase motor activity, have markedly different effects on investigatory responses. It is likely that amphetamine increases prepotent response tendencies (i.e., hole-poking), although this does not necessarily reflect enhanced exploration. Further, the results obtained with amphetamine support predictions made by the Lyon-Robbins behavioral theory of amphetamine effects.
    Type of Medium: Electronic Resource
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