Differential susceptibility to anterograde and retrograde amnesia treatments in preweanling rats.

Although there have been several reports that preweanling rats and mice are relatively resistant to experimentally induced retrograde amnesia, there is virtually no information concerning susceptibility to anterograde amnesia in subjects of this age. Therefore, in the present experiment, 23-day-old rats received hypothermia either prior to, or immediately after, punishment training in an attempt to induce anterograde and retrograde amnesia, respectively. When tested 24 hr later, only those subjects given hypothermia prior to training exhibited any loss of retention. Thus these results confirmed previous evidence of resistance to retrograde amnesia in preweanling rats and further demonstrated that substantial anterograde amnesia could be obtained in these subjects. Performance of subjects tested after a 5-min retention interval revealed that the poor retention performance in subjects cooled prior to training and tested 24 hr later was not due to a learning deficit. These results are also discussed with respect to the issue of the independence of anterograde and retrograde amnesia.