INFLUENCE OF PRIOR EXPERIENCE ON MICE BEHAVIOR USING THE 4-PLATE TEST

A single prior undrugged exposure to the four-plate test reduces punis hed responding on retest at intervals ranging from 24 h to 42 days. Fu rthermore, prior experience attenuates the anxiolytic response to the benzodiazepines diazepam (0.25 to 2 mg/kg) and lorazepam (0.5 to 4 mg/ kg). The result was first discussed in term of ''one trial tolerance.' ' The anxiety baseline was increased during the retest, which countera cted the anxiolytic action of benzodiazepines. To ascertain if memory processes are also implicated, the cholinergic drugs scopolamine and o xotremorine were used. Additional experiments with the GABAergic inver se agonist FG7142 and with the 5-HT(1)A receptor agonist 8-OH-DPAT wer e also performed. Administration of scopolamine and 8-OH-DPAT-induced weak impairment of memory, when administered before the second trial, but no effect was seen with cognition enhancing agents. (C) 1997 Elsev ier Science Inc.