Progress in neuro-psychopharmacology & biological psychiatry
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Prog. Neuropsychopharmacol. Biol. Psychiatry · May 2005
Comparative StudyA comparative study with two types of elevated plus-maze (transparent vs. opaque walls) on the anxiolytic effects of midazolam, one-trial tolerance and fear-induced analgesia.
The phenomenon known as one-trial tolerance (OTT) to the anxiolytic effects of benzodiazepines observed in rats submitted to the elevated plus-maze test (EPM) is considered to be due to the emergence of phobic states across the test/retest sessions. Antinociception is a usual component of the defense reaction. Until now, no study has examined antinociception and OTT together in freely behaving rats in the EPM. ⋯ These findings show that animals tested in the modified EPM showed higher sensitivity to the anxiolytic effects of midazolam than the standard EPM. Antinociception was not a concomitant of the shift in the emotional state present in the retest sessions of the EPM. These results are in agreement with the premises that repeated stressful experience leads to anxiolytic-insensitive fear state different from anxiety.