Brain structures implicated in the four-plate test in naive and experienced Swiss mice using injection of diazepam and the 5-HT2A agonist DOI

Four-plate test-retest (FPT-R) is a useful tool to study aversive memory and abolishment of benzodiazepine effects in experienced mice to four-plate test (FPT), namely one-trial tolerance. In the present study, we have used local injections paradigm, in order to localize structures implied in anxiolytic-like effects of two drugs in naive and experienced mice: a benzodiazepine, diazepam that is only active in naive mice; and a 5-HT2A/2C agonist, DOI that exert its anxiolytic-like effect both in naive and experienced mice. Periacqueductal grey substance, three sub-regions of hippocampus (CA1, CA2 and CA3) and two nuclei of amygdala (BLA and LA) have been studied. Local injections did not cause any modifications of ambulatory activity. DOI injections elicit anxiolytic-like effects only when injected into CA2, in naive and experienced mice. Diazepam had an anxiolytic-like effect in naive mice, only when injected into lateral nucleus of annygdala; and in experienced mice when injected into PAG. These results help us to better understand the way of action of these two compounds and the structures functionally involved in their effects and in one-trial tolerance (OTT). (C) 2009 Elsevier B.V. All rights reserved.