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  • Rat  (2)
  • Amphetamine  (1)
  • Autoradiography
  • 1995-1999  (2)
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  • 1
    ISSN: 1432-2072
    Keywords: Behaviour ; Morphine ; Naloxone ; Withdrawal syndrome ; Ethopharmacology ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The intensity of opiate withdrawal syndrome in rats is usually quantified on the basis of selected physical signs or global scores. However, the selection criteria of signs and scores have not been subjected to an ethological discussion, hence they appear to be somewhat arbitrary. The objectives of this study were thus: i) to analyse the rat's behaviour during the nalox-one-precipitated morphine withdrawal syndrome, ii) to evaluate the validity of classic methods, and iii) to design a new “etho-score”. Ten rats were implanted with morphine pellets (75 mg×2, SC), all receiving different naloxone doses following a within-subject design (0, 0.01, 0.05, 0.1, 0.5, 1 mg/kg SC). Twenty unexperienced rats and 20 with placebo pellets were injected with either saline or naloxone. Behaviour was videotaped and later analysed by computer-based ethological techniques. The ethogram encompassed 16 patterns displayed by rats during morphine withdrawal. Frequency, duration and latency of each pattern was measured, and a cluster analysis allowed discerning the structure of behaviour. Several physical signs and the Gellert-Holtzman score were also evaluated. The data revealed that writhing responses linearly changed in a dose-related fashion, and mastication was also enhanced after naloxone. Wet-dog shakes and jumping changed following an U-shaped curve. Significant changes in weight loss were found to be dose-dependent, and highly correlated to diarrhea. Learning effects were found to reliably affect exploration, writhing responses and some physical signs. The Gellert-Holtzman score was gradually enhanced after naloxone, being affected by learning as well. Naloxone affected lying and self-care responses in placebo rats. To sum up, the data indicated that: i) classic signs are useful, although most of them are disrupted by high naloxone or affected by learning effects, ii) the Gellert-Holtzman score was validated in this study, and iii) mastication and weight loss are good indicators of naloxone-precipitated morphine withdrawal, representing the basis of an “etho-score” which is herein proposed.
    Type of Medium: Electronic Resource
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  • 2
    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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