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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 147 (1999), S. 174-181 
    ISSN: 1432-2072
    Keywords: Key words Cat odor ; Predator ; Midazolam ; Anxiety ; Phobia ; Learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale and objectives: Rodents tested in the elevated plus maze model of anxiety only show an anxiolytic response to benzodiazepines on their first exposure to the maze. The present study investigated whether a similar phenomenon occurs with benzodiazepines in a different model of anxiety that involves exposing rats to the odor of a predator. Methods: Testing took place in a rectangular arena containing a cat odor-exuding collar at one end and a small ”hide box” at the opposite end. Rats were initially familiarized with the odor-free apparatus for 20 min and then placed back in the apparatus 24 and 48 h later in the presence of cat odor. Results: Vehicle-treated rats displayed marked avoidance of the cat odor on both first and second exposures, spending most of the session in the hide box and very little time near the odor source. In contrast, rats given a low dose of midazolam (0.375 mg/kg) during first exposure spent considerable time in close proximity to the odor source and much less time in the hide box. Rats given midazolam (0.375 mg/kg) on their second exposure to cat odor displayed no such anxiolytic effect of the drug. Rats given midazolam (0.375 mg/kg) on both exposures showed a potent anxiolytic effect of the drug on each occasion. This pattern of results was replicated with a higher dose of midazolam (0.75 mg/kg). A further experiment showed that rats previously exposed to cat odor showed high levels of hiding in the test environment 24 h later even when the cat odor was no longer present. This conditioned fear was blocked by midazolam (0.75 mg/kg) suggesting that the ineffectiveness of midazolam on second exposure to cat odor is not due to a failure of the drug to affect conditioned fear. Conclusions: The ineffectiveness of midazolam in odor-experienced rats parallels the results obtained with benzodiazepines in the elevated plus maze. Such results may help illuminate the comparative lack of efficacy of benzodiazepines in treating certain types of anxiety disorders in humans.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 142 (1999), S. 302-308 
    ISSN: 1432-2072
    Keywords: Key words Alcohol ; Beer ; Craving ; Rat ; Naloxone ; SR 141716 ; Ritanserin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were given two weeks of home cage access to either “near-beer” (a beverage that tastes like beer but contains 〈0.5% ethanol v/v) or near-beer with added ethanol (4.5% v/v), which is simply referred to as “beer”. The two groups of rats (near-beer and beer) were then trained on a “lick-based progressive ratio paradigm” in operant chambers in which an ever increasing number of licks had to be emitted for each successive fixed unit of near-beer or beer delivered. Break points (the ratio at which responding ceased) for near-beer and beer were approximately equal under baseline conditions. Rats were then tested for the effects of the 5HT2A/2C receptor antagonist ritanserin (0.625, 2.5 or 10 mg/kg), the opioid receptor antagonist naloxone (0.625, 2.5 or 10 mg/kg) or the cannabinoid CB1 receptor antagonist SR 141716 (0.3, 1 or 3 mg/kg). All three drugs caused a dose-dependent reduction of break-points and locomotor activity in both the beer and near-beer groups. However, the effects of SR 141716 and naloxone, but not ritanserin, on break-points were significantly more pronounced on rats drinking beer compared to those drinking near-beer. There were no such differential effects of any of the drugs on locomotor activity across the two groups. These results suggest that both SR 141716 and naloxone differentially affect the motivation to consume alcoholic beverages and may thus have potential as drugs for the treatment of alcohol craving.
    Type of Medium: Electronic Resource
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